Ghazi Bitar

A A Ramos-Espla

O Ocaña

Y R Sghaier

A Forcada

C Valle

H El Shaer

Marc Verlaque

A A Ramos-Esplá

The introduced marine macroflora of Lebanon and its distribution on the Levantine coast

Keywords: Marine macroflora, introduced species, invasive species, Lessepsian species, Lebanon, Eastern Mediterranean

établissements d'enseignement et de recherche français ou étrangers, des laboratoires publics ou privés.

Introduction

With nearly 1000 marine introduced taxa identified (excluding microalgae), the Mediterranean Sea is one of the regions of the world most severely impacted by the introduction of species [START_REF] Zenetos | Alien species in the Mediterranean Sea by 2010. A contribution to the application of European Union's Marine Strategy Framework Directive (MSFD). Part I. Spatial distribution[END_REF][START_REF] Zenetos | Alien species in the Mediterranean Sea by 2012. A contribution to the application of European Union's Marine Strategy Framework Directive (MSFD). Part 2. Patterns in introduction trends and pathways[END_REF]. In 2017, the number of introduced marine macrophytes would be around 120-130 taxa [START_REF] Verlaque | Macrophytes[END_REF]M. Verlaque, unpub. data). Among the major pathways of introduction, the Suez Canal ranks ahead. Since its opening in 1869, the flow of Lessepsian species, i.e. Indo-Pacific species introduced into the Mediterranean Sea via the Suez Canal, has never stopped [START_REF] Nunes | Gateways to alien invasions in the European seas[END_REF].

Few studies have dealt with the marine flora of Lebanon. [START_REF] Basson | Ecology of marine macroalgae in relation to pollution along the coast of Lebanon[END_REF] listed 190 taxa of macrophytes (including Cyanobacteria). In 1999, 18 taxa were added to the Lebanese marine flora, including 4 introduced Indo-Pacific species [START_REF] Bitar | Sur les Caulerpa de la côte libanaise (Méditerranée orientale)[END_REF]. In 2000, the checklist of marine macrophytes (including Cyanobacteria) amounted to 243 taxa [START_REF] Lakkis | Distribution of phytobenthos along the coast of Lebanon (Levantine Basin, East Mediterranean)[END_REF][START_REF] Einav | Seaweeds of the eastern Mediterranean coast. Ruggell, Liechtenstein[END_REF]. Since then, the number has been steadily increasing (Abboud-Abi [START_REF] Saab | Environnement côtier et biodiversité marine sur les côtes libanaises; inventaire et mise en place d'un ensemble matériel et humain d'observation et d'analyse de leur évolution, degré d'altération des communautés benthiques littorales. Rapport final Franco-Lebanese Cooperation Program CEDRE[END_REF]Bitar, 2010b;Belous & Kanaan, 2015;[START_REF] Kanaan | Diversity investigation of the seaweeds growing on the Lebanese coast[END_REF]. The aim of our work was to draw up a list of exotic marine macrophytes introduced into Lebanon, and to discuss their distribution, their dynamics and the current status of their populations.

Materials and Μethods

The historical data (publications and technical reports) have been exhaustively looked for. Specimens corresponding to these data have not been re-studied; the same applies for the Lebanese herbaria deposited in Institutions. The field survey covers a 25 year-period and the whole Lebanese coast. Field data were collected by one of us (G.B.) from 1991 to 1999. In October 1999 and May-June 2000, two field surveys were conducted within the framework of the Franco-Lebanese research program CEDRE (Abboud-Abi [START_REF] Saab | Environnement côtier et biodiversité marine sur les côtes libanaises; inventaire et mise en place d'un ensemble matériel et humain d'observation et d'analyse de leur évolution, degré d'altération des communautés benthiques littorales. Rapport final Franco-Lebanese Cooperation Program CEDRE[END_REF]. In September 2005, a field survey was carried out for the EU projet Grundtvig [START_REF] Bitar | Contribution of the Red sea alien species to structuring some benthic biocenosis in the Lebanon coast (Eastern Mediterranean)[END_REF]. In 2012, 2013 and 2016, several Lebanese localities were prospected (Enfeh, Ras Chekaa, Batroun, El Madfoun, Byblos, Raoucheh, Saida, Tyre and Nakoura) within the framework of the interna-tional MedMPAnet Program for the establishment of an effective Mediterranean network of marine protected areas (RAC/SPA -UNEP/MAP, 2014). Finally, a constant monitoring was provided by one of us (G.B.) to detect new introductions.

Surveys were carried out along the complete Lebanese coast (Fig. 1, Table 1), covering from the sea-surface, especially on vermetid reefs, down to 50 m depth, involving different methods (hydroplane transects, snorkelling and SCU-BA diving). Only the large taxa (> 1-2 cm high) were considered. The species were identified in situ, on photographs or in the laboratory after hand sampling or scraping with chisel and hammer. The taxonomic nomenclature of species follows the Algaebase database [START_REF] Guiry | AlgaeBase.World-wide electronic publication[END_REF].

For each species, the date, the locality, and the reference of the first record in Lebanon have been looked for, as well as its alien status and its possible origins, putative pathways of first introduction into the Mediterranean Sea and its establishment success in Lebanon according to the following nomenclature:

Alien status: Al = Alien; Cr = Cryptogenic; Qu = Questionable.

Origins Establishment success in Lebanon: E = established; Inv = invasive; C = casual; E? = establishment to precise by further investigation.

Results

The analysis of historical data revealed a list of 26 taxa of marine macrophytes introduced to Lebanon [START_REF] Hamel | Les Caulerpes méditerranéennes[END_REF][START_REF] Hamel | Sur le Cladostephus dubius Bory. Travaux cryptogamiques dédiés à Louis Mangin. Laboratoire Cryptogamique[END_REF][START_REF] Rayss | Sur les Caulerpes de la côte palestinienne[END_REF][START_REF] Rayss | Les algues marines des côtes palestiniennes. I. Chlorophyceae[END_REF][START_REF] Lipkin | Halophila stipulacea, a review of a successful immigration[END_REF][START_REF] Basson | Ecology of marine macroalgae in relation to pollution along the coast of Lebanon[END_REF]Bitar & Bitar-Kouli, 1995a,b;[START_REF] Bitar | Sur les Caulerpa de la côte libanaise (Méditerranée orientale)[END_REF][START_REF] Bitar | National overview on vulnerability and impacts of climate change on marine and coastal biodiversity in Lebanon[END_REF]Bitar, , 2010aBitar, ,b, 2011Bitar, , 2014;;[START_REF] Bitar | Sur la flore marine benthique supposée Lessepsienne de la côte libanaise. Cas particulier de Stypopodium schimperi[END_REF][START_REF] Bitar | Contribution of the Red sea alien species to structuring some benthic biocenosis in the Lebanon coast (Eastern Mediterranean)[END_REF][START_REF] Lakkis | Distribution of phytobenthos along the coast of Lebanon (Levantine Basin, East Mediterranean)[END_REF], 2001;[START_REF] Bitar | Nouvelles données sur la faune et la flore benthiques de la côte libanaise. Migration lessepsienne[END_REF][START_REF] Saab | Environnement côtier et biodiversité marine sur les côtes libanaises; inventaire et mise en place d'un ensemble matériel et humain d'observation et d'analyse de leur évolution, degré d'altération des communautés benthiques littorales. Rapport final Franco-Lebanese Cooperation Program CEDRE[END_REF][START_REF] Lakkis | Flore et faune marines du Liban (Méditerranée Orientale)[END_REF][START_REF] Verlaque | Macrophytes[END_REF]. On the basis of the field surveys along the Lebanese coasts, this total was increased to 29 taxa, namely 3 brown algae (Chromobionta), 13 red algae (Rhodobionta), 12 green algae (Chlorobionta) and one seagrass (Streptobionta) (Table 1). land;3. Tripoli and El Mina;4. Enfeh;5. El Heri;6. Ras Chekaa;7. Hannouch;8. Selaata;9. Batroun;10. Kfar Abida and El Madfoun;11. Barbara;12. Amchit and Byblos;13. Tabarja;14. Zouk Mkayel;15. Beirut,El Manara and Raoucheh;16. Ouzai; 1. Padina boergesenii Allender & Kraft (Fig. 2) Described from the western Atlantic (Virgin Islands) and present in the Indian Ocean, this species was first found in the Mediterranean Sea in the 1960s along the South Levantine coast [Ramon & Friedmann, 1966, misidentified as P. gymnospora (Kützing) Vickers]. Padina boergesenii was identified in Syria in 1997 [START_REF] Verlaque | Macrophytes[END_REF].

In Lebanon, P. boergesenii was first found in May 1992 at Tripoli -El Mina (Bitar, 1999, as Padina sp.). Currently, P. boergesenii is present at numerous localities along the coast, from sea level down to 15 m depth, especially on vermetid reefs (Bitar, 2010b; present study).

The Padina sp. observed in August 2010 at Ramkine Island, between 4 and 5 m depth (Bitar, 2010b), might be either P. boergesenii or P. tetrastromatica Hauck, another Indo-Pacific species discovered in Syria [START_REF] Mayhoub | Sur la présence de l'algue tropicale Padina tetrastromatica Hauck aux environs de Lattaquié (Syrie)[END_REF], and is not yet reported from Lebanon. Padina boergesenii is well established along the Levantine coasts.

Spatoglossum variabile

Figari & De Notaris (Fig. 3) Described from the Red Sea, this species was first found in the Mediterranean Sea in 1944, in Egypt (Aleem, 1950). The exotic Dictyotale Spatoglossum asperum J. Agardh, regularly recorded from the South Levantine coast [START_REF] Lundberg | Selectivity of food algae by the herbivorous fish Siganus rivulatus in the marine vegetation at Mikhmoret (the Mediterranean coast of Israel)[END_REF][START_REF] Lundberg | Food habits of Siganus rivulatus, a Lessepsian migrant, as adapted to algal resources at the coast of Israel[END_REF][START_REF] Lundberg | Composition of the seaweed vegetation along the Mediterranean coast of Israel[END_REF][START_REF] Lundberg | Diet adaptations of Lessepsian migrant Rabbitfishes, Siganus luridus and S. rivulatus, to the algal resources of the Mediterranean coast of Israel. PSZNI[END_REF] is a probable misidentification of S. variabile, which was later recorded and illustrated from the same region [Einav, 2007, misidentified as Spatoglossum solieri (Chauvin ex Montagne) Kützing].

In Lebanon, S. variabile was first found in July 2009 at Tabarja. Subsequently, it was observed in June 2010 at Enfeh, and in June 2015 at Beirut and Raoucheh, where it constituted a subtidal belt close to the sea-surface. Lebanese specimens were well characterized by (i) the thallus complanate and subdichotomously to irregularly branched in one plane, (ii) the growth from a flat terminal marginal row of apical cells, (iii) the segments cuneate with lateral margins entire, (iv) the apices obtuse, and (v) the scattered hair tufts arising from a pit within the thallus. This is the first time that this species has been recorded in Lebanon. This late discovery probably results from previous confusions with other Dictyotales. The species is probably well established in Lebanon.

Stypopodium schimperi (Kützing) Verlaque

& Boudouresque (Fig. 4) Described from the Red Sea, this species was probably first observed in the Mediterranean Sea in Syria in 1979 [START_REF] Mayhoub | Envahissement de la côte Syrienne par une algue brune de mer Rouge[END_REF] Stypopodium fuliginosum (Martius) Kützing; [START_REF] Mayhoub | Contribution à la connaissance d'un Stypopodium (Dictyotales, Phaeophyceae) installé récemment sur les côtes syriennes[END_REF], as S. zon- ale (J.V. Lamouroux) Papenfuss; [START_REF] Verlaque | Stypopodium schimperi (Buchinger ex Kutzing) Verlaque et Boudouresque comb. nov. (Dictyotales, Fucophyceae), algue de Mer Rouge récemment apparue en Méditerranée[END_REF]]. We found it in 1999 and 2003 at several Syrian localities where it was abundant from the sea surface down to 25 m depth (Bitar, 2010b). The species is also present and invasive in Haifa Bay and the surrounding area (Lundberg, 1996, as S. zonale;Hoffman, 2014a).

In Lebanon, S. schimperi was first found in May 1991 at [START_REF] Schembri | It was only a matter of time: occurrence of Caulerpa taxifolia (Vahl) C. Agardh var. distichophylla (Sonder) Verlaque, Huisman and Procaccini in the Maltese Islands (Chlorophyta, Ulvophyceae, Caulerpaceae)[END_REF]subsequently, in 1995, at Hannouch (Bitar, 1999;Bitar & Bitar-Kouli, 1995a, misidentified as S. zonale;[START_REF] Bitar | Sur la flore marine benthique supposée Lessepsienne de la côte libanaise. Cas particulier de Stypopodium schimperi[END_REF]. [START_REF] Lakkis | Distribution of phytobenthos along the coast of Lebanon (Levantine Basin, East Mediterranean)[END_REF], 2001) recorded S. schimperi from Tripoli to Beirut in 1996-1997. Since 2000, it has become very abundant along the whole Lebanese coast, from the sea surface down to 45 m depth, at the expense of native benthic assemblages [START_REF] Bitar | Sur la flore marine benthique supposée Lessepsienne de la côte libanaise. Cas particulier de Stypopodium schimperi[END_REF]Bitar, 2010b; RAC/SPA -UNEP/MAP, 2014). [START_REF] Kanaan | Diversity investigation of the seaweeds growing on the Lebanese coast[END_REF] recorded the species from Tyre and Barbara. Stypopodium schimperi was the second invasive marine macrophyte to be identified in Lebanon, after Ulva lactuca.

4.

Acanthophora nayadiformis (Delile) Papenfuss (Fig. 5) Although described from both the Red Sea and the Mediterranean Sea (Alexandria) before the opening of the Suez Canal, the chronology of Mediterranean records suggests an introduction or the co-occurrence of introduced and native populations [START_REF] Verlaque | Macrophytes[END_REF]. According to [START_REF] Aleem | The recent migration of certain Indo-Pacific algae from the Red Sea into the Mediterranean[END_REF], the first migration into the Mediterranean Sea could have taken place through the old intermittent canal, which was established by the Ancient Egyptians. However, modern introductions through the Suez Canal cannot be excluded [START_REF] Verlaque | Macrophytes[END_REF]. In 1908, A. nayadiformis was recorded from Syria (Preda, 1908, as A. delilei).The species is also common along the South Levantine coast (Nemlich & Danin, 1964, as A. delilei;[START_REF] Lundberg | Composition of the seaweed vegetation along the Mediterranean coast of Israel[END_REF].

In Lebanon, we first found A. nayadiformis in November 1991 at Tabarja (Bitar, 2010b). Currently, the species is common in shallow habitats, intertidal rock pools and on vermetid reefs [START_REF] Lakkis | Distribution of phytobenthos along the coast of Lebanon (Levantine Basin, East Mediterranean)[END_REF], 2001, 2007, as A. delilei;Bitar, 2010b;Kanaan et al., 2015).

Asparagopsis taxiformis is (Delile) Trevisan de

Saint-Léon (Fig. 6) Described from Alexandria, in 1813, before the opening of the Suez Canal, this taxon corresponds to a complex of species worldwide distributed in temperate and warm seas [START_REF] Andreakis | Phylogeography of the invasive seaweed Asparagopsis (Bonnemaisoniales, Rhodophyta) reveals cryptic diversity[END_REF]. Among these cryptic species, two of them occur in the Mediterranean Sea: a taxon mainly distributed in the Atlantic Ocean and the eastern Mediterranean basin and an Indo-Pacific taxon, which is invasive in the western basin. In 1883, A. taxiformis was recorded from Syria [START_REF] Ardissone | Phycologia mediterranea. Parte prima, Floridee[END_REF]. Gametophytes are rare along the South Levantine coast [START_REF] Lundberg | Composition of the seaweed vegetation along the Mediterranean coast of Israel[END_REF][START_REF] Einav | Seaweeds of the eastern Mediterranean coast. Ruggell, Liechtenstein[END_REF].

In Lebanon, the tetrasporophytic phase described as 'Falkenbergia hillenbrandii' was first found in 1973 at Selaata, Barbara, Zouk Mkayel and Khalde [START_REF] Basson | Ecology of marine macroalgae in relation to pollution along the coast of Lebanon[END_REF], while gametophytes were only found in 1993 at Barbara and Batroun, near the sea-surface (Bitar etal., 2000). The species is common but not invasive on the whole Lebanese coast, down to 5 m depth [START_REF] Lakkis | Distribution of phytobenthos along the coast of Lebanon (Levantine Basin, East Mediterranean)[END_REF], 2001;present study). Records of Asparagopsis armata / Falkenbergia rufolanosa from Batroun, El Manara, Tyre, Barbara and Beirut (Military Club) in 2014 [START_REF] Kanaan | Diversity investigation of the seaweeds growing on the Lebanese coast[END_REF] are probably misidentifications of A. taxiformis / F. hillenbrandii. Molecular studies showed that the species occurring in Lebanon belongs to the taxon distributed in the Atlantic Ocean and the eastern Mediterranean basin [START_REF] Andreakis | Phylogeography of the invasive seaweed Asparagopsis (Bonnemaisoniales, Rhodophyta) reveals cryptic diversity[END_REF], so its alien status in the Mediterranean Sea requires confirmation (Cryptogenic taxon).

Chondria coerulescens (J. Agardh) Falkenberg (not illustrated)

Described from the northeastern Atlantic (Brittany, France), this taxon was widely recorded from the Mediterranean Sea, where introduced and possibly also native populations co-occur [START_REF] Verlaque | Macrophytes[END_REF].

In Lebanon, C. coerulescens was first found in 1973 [START_REF] Basson | Ecology of marine macroalgae in relation to pollution along the coast of Lebanon[END_REF]. Subsequently, it was recorded from Batroun, [START_REF] Schembri | It was only a matter of time: occurrence of Caulerpa taxifolia (Vahl) C. Agardh var. distichophylla (Sonder) Verlaque, Huisman and Procaccini in the Maltese Islands (Chlorophyta, Ulvophyceae, Caulerpaceae)[END_REF]Zouk Mkayel in 1996-1997, in the intertidal and the upper subtidal zones [START_REF] Lakkis | Distribution of phytobenthos along the coast of Lebanon (Levantine Basin, East Mediterranean)[END_REF]. The alga is established in Lebanon, but its identity and the origin of Lebanese populations should be confirmed by molecular studies. Confusion with an unidentified Indo-Pacific taxon introduced through the Suez Canal cannot be excluded.

7.

Galaxaura rugosa (J. Ellis & Solander) J.V. Lamouroux (Fig. 7) Described from Jamaica and Bahamas and widespread in warm seas, this species was first recorded in the Mediterranean Sea from Syria (Mayhoub, 1990, as G. lapidescens). In Syria, we found G. rugosa in June 1999 at Lattakieh, in the Ras Ibn Hani region, in shallow habitats. We observed it again in the same locality in August 2000 and especially in May 2003 when it became invasive on rocky substrates, from the sea-surface down to 10-12m depth. Associated to Stypopodium schimperi, it replaced native species, especially Halopteris scoparia (Linnaeus) Sauvageau (Bitar, 2010b). In August 2003, several Syrian localities, from Tartous to Ras El Samra, were invaded by these two exotic species [START_REF] Bitar | Report of the second mission relating to the Development of Marine Protected Areas on Syrian coasts, 1-18[END_REF]. Galaxaura rugosa was found in 2003 in Haifa Bay, where it has become invasive since 2006 [START_REF] Hoffman | A new Lessepsian macroalga, Galaxaura rugosa, gain control on underwater rocks in the western edges of Haifa bay infralittoral zone[END_REF][START_REF] Hoffman | Invasive and Alien Rhodophyta in the Mediterranean and along the Israeli shores[END_REF]Hoffman, 2014a).

In Lebanon, G. rugosa was first found in May 1995 at Kfar Abida, at 7 m depth, before to become invasive between 3 and 8 m depth in August 2007 (Bitar, 1999, as Galaxaura sp.;[START_REF] Bitar | Sur la flore marine benthique supposée Lessepsienne de la côte libanaise. Cas particulier de Stypopodium schimperi[END_REF]Bitar, 2010b). Subsequently, it was observed down to 35 m depth (RAC/SPA -UNEP/MAP, 2014). [START_REF] Kanaan | Diversity investigation of the seaweeds growing on the Lebanese coast[END_REF] recorded the species from Batroun, El Manara, Saida, Tyre and Barbara in 2014. Galaxaura rugosa was the third invasive marine macrophyte to be identified in Lebanon after Ulva lactuca and Stypopodium schimperi. Described from the Red Sea and widespread in warm seas, G. farinosum was collected for the first time in the Mediterranean Sea in Egypt (Alexandria), before the opening of the Suez Canal (see Hamel, 1931, as Liagora farinosa). However, the chronology of Mediterranean records suggests an introduction or the co-occurrence of introduced and native populations [START_REF] Verlaque | Macrophytes[END_REF]. Ganonema farinosum was recorded, as Liagora farinosa, from the South Levantine coast [START_REF] Nemlich | Marine algae of the coast of Israel[END_REF] and from Syria [START_REF] Mayhoub | Recherches sur la végétation marine de la côte syrienne. Etude expérimentale sur la morphogénèse et le développement de quelques espèces peu connues[END_REF].

In Lebanon, G. farinosum was first found in April 1993 at El Heri (Bitar et al., 2000, as L. farinosa;Bitar, 2010b). Subsequently, it was observed in 1996-1997, forming a G. farinosum facies along the coast, mainly in shallow habitats (2-3 m depth) [START_REF] Lakkis | Distribution of phytobenthos along the coast of Lebanon (Levantine Basin, East Mediterranean)[END_REF], 2001[START_REF] Einav | Seaweeds of the eastern Mediterranean coast. Ruggell, Liechtenstein[END_REF] Liagora farinosa; present study). Ganonema farinosum is established in Lebanon.

9.

Hypnea cornuta (Kützing) J. Agardh (Fig. 9)

The Mediterranean reports of Hypnea spp. must be considered with caution because of frequent confusions in taxonomic identifications [START_REF] Verlaque | Macrophytes[END_REF]. Described from the eastern Atlantic (Guinea) and wide- spread in warm seas, H. cornuta was first collected in 1894 at Rodos Island, Greece [START_REF] Reinbold | Meeresalgen von der Insel Rhodos[END_REF] misidentified as H. valentiae (Turner) Montagne]. Hypnea cornuta was recorded from the South Levantine coast [START_REF] Nemlich | Marine algae of the coast of Israel[END_REF][START_REF] Lundberg | Composition of the seaweed vegetation along the Mediterranean coast of Israel[END_REF][START_REF] Einav | Seaweeds of the eastern Mediterranean coast. Ruggell, Liechtenstein[END_REF]Hoffman, 2014a) and from Syria [Mayhoub, 1976, misidentified as

H. hamulosa (Esper) J.V. Lamouroux].
In Lebanon, H. cornuta was first found in 1973 (Basson et al., 1976, as H. hamulosa). Subsequently, it was recorded from Aramane, Selaata, Barbara and Zouk Mkayel in 1996-1997 (Lakkis & Novel-Lakkis, 2000, misidentified as H. hamulosa;[START_REF] Lakkis | Importance des Caulerpes dans les peuplements algaux de la côte libanaise (Méditerranée Orientale)[END_REF]. We observed it in abundance in shallow pools of Vermetid reefs, especially at Beirut and at Tyre. Hypnea cornuta is established in Lebanon.

Hypnea spinella (C. Agardh) Kützing (not illustrated)

Described from the Caribbean Sea and widespread in warm seas, Hypnea spinella was probably first found in the Mediterranean Sea in 1926 in Greece (Symi Island, Dodecanese) [START_REF] Forti | Nuove segnalazioni di alghe passivamente transportate a traverso al canale di Suez, poi naturalizzate[END_REF]; misidentified as H. nidifica J. Agardh). The species is present along the South Levantine coast (Lundberg, 1996, as H. cervicornis;Hoffman, 2014a).

In Lebanon, we first found H. spinella in August 1998 at Beirut, off the American University, in shallow pools of Vermetid reefs and below their outer margins. Subsequently it was recorded from Aramane, [START_REF] Schembri | It was only a matter of time: occurrence of Caulerpa taxifolia (Vahl) C. Agardh var. distichophylla (Sonder) Verlaque, Huisman and Procaccini in the Maltese Islands (Chlorophyta, Ulvophyceae, Caulerpaceae)[END_REF]Zouk Mkayel in 1996-1997, in mediolittoral and infralittoral zones [START_REF] Lakkis | Distribution of phytobenthos along the coast of Lebanon (Levantine Basin, East Mediterranean)[END_REF], as H. cervicornis J. Agardh). Subsequently, the species was identified at Enfeh, Ras Chekaa, Saida and Tyre in 2012-2013, on Vermetid reefs (RAC/SPA -UNEP/MAP, 2014). [START_REF] Kanaan | Diversity investigation of the seaweeds growing on the Lebanese coast[END_REF] recorded the species from Batroun, Barbara and Nakoura in 2014. Hypnea spinella is established in Lebanon.

11. Hypnea valentiae (Turner) Montagne (Fig. 10) Since its description from the Red Sea, H. valentiae has been reported worldwide in warm seas and in the Mediterranean Sea. However the first illustrated Mediterranean record dates only from 1996 in France [START_REF] Verlaque | Macrophytes[END_REF]. In the eastern Mediterranean basin, it was first collected in the south-eastern Aegean Sea at Rodos Island, Greece [START_REF] Tsiamis | A new contribution to the alien red macroalgal flora of Greece (Eastern Mediterranean) with emphasis on Hypnea species[END_REF].

In Lebanon, H. valentiae was only found at Batroun in 2014, in the lower intertidal zone (Belous & Kanaan, 2015), but the description and the illustration (Fig. 3E) given by the authors do not allow to warrant the identification. The occurrence of this casual species in Lebanon should be confirmed by further studies.

12. Laurencia cf. chondrioides Børgesen (Fig. 11) Described from the Caribbean Sea, L. chondrioides was first recorded in the Mediterranean Sea from the Balearic Islands, the Aeolian Islands and from Lachea Island [START_REF] Boisset | First record of Laurencia chondroides (Ceramiales, Rhodophyta) from the Mediterranean Sea[END_REF]. Subsequently, the species was reported throughout the Mediterranean Sea, without mention of any pullulation, until late October 2007, when [START_REF] Hoffman | First report of Laurencia chondrioides (Ceramiales, Rhodophyta) and its potential to be an invasive in the eastern Mediterranean Sea[END_REF] discovered large quantities of a species of Laurencia, referred to as L. chondrioides, in the algal drift on the shore at Haifa.

In Lebanon, we found large quantities of this Laurencia in October 2009 at El Baiada and between Tyre and Nakoura. In December 2010, we identified Saadiyat as its northern limit of distribution. To date, it has never been observed between Beirut and Tripoli. In 2013, we confirmed the invasion at Saida and the Tyre -Nakoura region, where the species was abundant from the sea-surface down to 23 m depth (RAC/SPA -UNEP/MAP, 2014). Both its recent arrival and its invasive behaviour argue in favour of an introduction on the Levantine coasts. However, the natural presence of L. chondrioides in the Canary Islands, where many Mediterranean taxa are native, makes a recent introduction of the species into the Mediterranean Sea unlikely [START_REF] Boisset | First record of Laurencia chondroides (Ceramiales, Rhodophyta) from the Mediterranean Sea[END_REF]. Consequently, the origin and the identity of this invasive Laurencia should be confirmed by molecular study because the possibility of an introduction through the Suez Canal of another Indo-Pacific species must be considered.

This Laurencia was the fifth invasive marine macrophyte to be identified in Lebanon, after Ulva lactuca, Stypopodium schimperi, Galaxaura rugosa and Codium parvulum. At several Lebanese localities, it competes with the other invasive species.

13. Lophocladia lallemandii (Montagne) F. Schmitz (Fig. 12) Described from the Red Sea, this species was first recorded in the Mediterranean Sea from Greece (Piraeus) and from Libya [START_REF] Petersen | Report on the Danish Oceanographical Expeditions 1908-1910 to the Mediterranean and adjacent seas[END_REF]. In Syria, it was recorded by [START_REF] Mayhoub | Recherches sur la végétation marine de la côte syrienne. Etude expérimentale sur la morphogénèse et le développement de quelques espèces peu connues[END_REF].

Lophocladia lallemandii was first found in Lebanon in 1973 (Basson etal., 1976). Subsequently, it was observed at Batroun and Barbara, in 1996-1997[START_REF] Lakkis | Distribution of phytobenthos along the coast of Lebanon (Levantine Basin, East Mediterranean)[END_REF], 2001). The species is qualified as 'dominant upper infralittoral species' [START_REF] Lakkis | Diversity and distribution of macrophytes along the coast of Lebanon (Levantine Basin, Eastern Mediterranean)[END_REF][START_REF] Lakkis | Flore et faune marines du Liban (Méditerranée Orientale)[END_REF]. We found it in August 1993 drifting in the port of Barbara, at Amchit on Vermetid reefs in 2000, and at Ras Chekaa and Hannouch in 2012, in the infralittoral zone, from the sea-surface down to 25 m depth (Bitar, 2010b; RAC/SPA -UNEP/MAP, 2014). Lophocladia lallemandii is well established in Lebanon.

14.

Polysiphonia atlantica Kapraun & J.N. Norris (Fig. 13) Described from the northeastern Atlantic (Ireland) and reported worldwide in temperate and warm seas, P. atlantica was first found in the Mediterranean Sea in 1969 in France [START_REF] Verlaque | Macrophytes[END_REF]. In the Eastern Mediterranean, it was recorded from Cyprus [START_REF] Taşkin | Alien and invasive marine plants in North Cyprus[END_REF] and Greece [START_REF] Tsiamis | Seaweeds of the Greek coasts. Rhodophyta: Ceramiales[END_REF].

In Lebanon, P. atlantica was only found in 2014 at Batroun (Belous & Kanaan, 2015;[START_REF] Kanaan | Diversity investigation of the seaweeds growing on the Lebanese coast[END_REF]. The occurrence of this casual species in Lebanon should be confirmed through further study. 15. Sarconema filiforme (Sonder) Kylin (Fig. 14)

Described from Western Australia, this species of the Red Sea and the Indian Ocean was first found in the Mediterranean Sea in 1944 in Egypt (Aleem, 1948, as Sarconema furcellatum). Subsequently, it was recorded from the South Levantine coast [START_REF] Rayss | Sur la présence dans la Méditerranée orientale des algues tropicales de la famille des Solieriacées[END_REF], as S. filiforme f. gracillima; Einav, 2007, misidentified as Solieria filiformis) and from Syria, in lower sciaphilic infralittoral assemblages [START_REF] Mayhoub | Recherches sur la végétation marine de la côte syrienne. Etude expérimentale sur la morphogénèse et le développement de quelques espèces peu connues[END_REF].

In Lebanon, S. filiforme was first found in April 2001 at Beirut, in shallow pools of Vermetid reefs and between the sea-surface and 1m depth (Bitar, 2010b). Sarconema filiforme is established in Lebanon.

16. Womersleyella setacea (Hollenberg) R. E. Norris (Fig. 15) Described from Hawaii and widespread in the Tropical Pacific and Atlantic Oceans, this species was first found in the Mediterranean Sea in 1986 in Italy (Livorno) [START_REF] Verlaque | Macrophytes[END_REF]. Invasive in the western Mediterranean basin and the Adriatic Sea, W. setacea was recorded in the eastern Mediterranean basin from Cyprus (Taskin et al., 2008) and Rodos Island, Greece (Zenetos et al, 2015).

In Lebanon, W. setacea was found in October 2016 at Batroun, between 40 and 50 m depth. Lebanese specimens were well characterized by (i) the thallus filamentous without percurrent axis, up to 100 µm in diameter, (ii) the four periaxial cells, and (iii) the rhizoids cut off from periaxial cells and forming terminally a multicellular disc. It is the first time that this highly invasive species has been recorded from Lebanon. 17. Bryopsis pennata J.V. Lamouroux? (Fig. 16) Described from the Caribbean Sea [START_REF] Lamouroux | Observations sur la physiologie des algues marines, et description de cinq nouveaux genres de cette famille[END_REF] and reported worldwide in warm seas, this species was first observed in the Mediterranean Sea in France [START_REF] Feldmann | Les algues marines de la côte des Albères. I-III. Cyanophycées, Chlorophycées, Phéophycées[END_REF]. In the eastern Mediterranean Sea, B. pennata was recorded from Syria [START_REF] Mayhoub | Recherches sur la végétation marine de la côte syrienne. Etude expérimentale sur la morphogénèse et le développement de quelques espèces peu connues[END_REF], from Turkey [START_REF] Cirik | Recherches sur la végétation marine des côtes Turques de la mer Egée. Etude particulière des Peyssonneliacées de Turquie[END_REF][START_REF] Çinar | Alien Species on the coasts of Turkey[END_REF], and from Greece [START_REF] Tsiamis | Seaweeds of the Greek coasts. II. Ulvophyceae[END_REF].

Bryopsis pennata has been excluded of the CIESM Atlas of exotic species of the Mediterranean Sea [START_REF] Verlaque | Macrophytes[END_REF]. However, the Lebanese specimens agree well with descriptions and illustrations of Red Sea and Indo-Pacific algae attributed to B. pennata. Bryopsis pennata is morphologically very close to the Indo-Pacific species B. indica A. Gepp & E.S. Gepp. Consequently, the probability that the Lebanese alga be introduced is high, but its identity and origin should be tested through molecular studies.

In Lebanon, B. pennata was first recorded in 1973 from Khalde [START_REF] Basson | Ecology of marine macroalgae in relation to pollution along the coast of Lebanon[END_REF]. Subsequently, it was found at Batroun and Barbarain 1996-1997and 2014[START_REF] Lakkis | Distribution of phytobenthos along the coast of Lebanon (Levantine Basin, East Mediterranean)[END_REF], 2001;Belous & Kanaan, 2015).We first observed B. pennata in 1991 at Barbara, and subsequently at Ramkine Island, Enfeh, El Heri, Kfar Abida, Tabarja, Beirut and El Baiada. Bryopsis pennata is well established in Lebanon.

18. Caulerpa chemnitzia (Esper) J.V. Lamouroux (Fig. 17) Described from India and widespread in warm seas, this species was first recorded in the Mediterranean Sea from Tunisia (Hamel, 1926, misidentified as C. racemosa). Caulerpa chemnitzia was recorded from Syria (Mayhoub, 1976, as C. racemosa) and from the South Levantine coast [START_REF] Lundberg | Composition of the seaweed vegetation along the Mediterranean coast of Israel[END_REF]Einav, 2007, as C. racemosa).

In Lebanon, C. chemnitzia was first recorded from Beirut [START_REF] Hamel | Sur le Cladostephus dubius Bory. Travaux cryptogamiques dédiés à Louis Mangin. Laboratoire Cryptogamique[END_REF], misidentified as C. racemosa). Subsequently, the species was recorded from Aramane, Batroun, Barbara, Zouk Mkayel and Khalde in 1996-1997 [START_REF] Lakkis | Distribution of phytobenthos along the coast of Lebanon (Levantine Basin, East Mediterranean)[END_REF], 2001, 2007, as C. racemosa). We found C. chemnitzia in 1993 and 2002, at Tripoli, in the area of El Mina and in the commercial port, between the sea-surface and 2m depth [START_REF] Bitar | Sur les Caulerpa de la côte libanaise (Méditerranée orientale)[END_REF](Bitar, , 2010b)). Recently, it has disappeared from El Mina following the economic development of the area. Although uncommon, C. chemnitzia is established in Lebanon.

19. Caulerpa mexicana Sonder ex Kützing (Fig. 18) Described from the Mexico Gulf and widespread in warm seas, this species was first found in the Mediterranean Sea in 1939 in Palestine and in Lebanon (Beirut) [START_REF] Rayss | Sur les Caulerpes de la côte palestinienne[END_REF](Rayss, , 1955, as C. crassifolia), as C. crassifolia). Subsequently, it was recorded from Syria [START_REF] Mayhoub | Recherches sur la végétation marine de la côte syrienne. Etude expérimentale sur la morphogénèse et le développement de quelques espèces peu connues[END_REF] where we observed it in the shallow pools of Vermetid reefs of the Arwad Island [START_REF] Bitar | Report of the second mission relating to the Development of Marine Protected Areas on Syrian coasts, 1-18[END_REF]. The species is common on the South Levantine coast [START_REF] Lundberg | Composition of the seaweed vegetation along the Mediterranean coast of Israel[END_REF][START_REF] Einav | Seaweeds of the eastern Mediterranean coast. Ruggell, Liechtenstein[END_REF] In Lebanon, we found an individual of C. mexicana in 1991 off the Riviera Hotel at El Manara (Beirut), on a sandy-rocky substrate, around 3 m depth. In 1992, it had disappeared and no other specimen was found [START_REF] Bitar | Sur les Caulerpa de la côte libanaise (Méditerranée orientale)[END_REF](Bitar, , 2010b)). It was not until July 2016 that several small individuals were found off the American University of Beirut, in a large pool of the Vermetid reef, at 1m depth. The species was also reported as rare by [START_REF] Lakkis | Etude de la diversité biologique au Liban: faune et flore marines et côtières[END_REF] and [START_REF] Lakkis | Importance des Caulerpes dans les peuplements algaux de la côte libanaise (Méditerranée Orientale)[END_REF]. Although uncommon, C. mexicana is established in Lebanon. Levantine coast (Rayss & Edelstein, 1960, as C. feldmannii). Subsequently, it was recorded from Syria [START_REF] Huvé | Sur une variété nouvelle pour la Méditerranée du Caulerpa racemosa (Forsskål) Agardh[END_REF] where it has become common [START_REF] Bitar | Report of the second mission relating to the Development of Marine Protected Areas on Syrian coasts, 1-18[END_REF].

In Lebanon, our first observation dates from August 1991 at Beirut. From north to south, C. racemosa var. lamourouxii f. requienii was found in 1994[START_REF] Bitar | Sur les Caulerpa de la côte libanaise (Méditerranée orientale)[END_REF], 2001and 2016at Ramkine Island, Tripoli, Hannouch, El Heri, Ras Chekaa, Selaata, Batroun, Beirut, Saadiyat and Saida. (Bitar et al., 2000;Bitar, 2010b;present study). The taxon is established in Lebanon, without any detectable impact on benthic assemblages.

Caulerpa scalpelliformis (R. Brown ex Turner)

C. Agardh (Fig. 20) Described from South Australia and widespread in warm seas, this species was first found in the Mediterranean Sea in 1929 along the South Levantine coast [START_REF] Carmin | Algae of Palestinian shores[END_REF]. In Syria, C. scalpelliformis was recorded by [START_REF] Mayhoub | Recherches sur la végétation marine de la côte syrienne. Etude expérimentale sur la morphogénèse et le développement de quelques espèces peu connues[END_REF], and we found it in 2003 off Arwad Island, at 34 m depth, and at the seaside resort of Lattakieh, around 30 m depth, on a soft bottom, associated with Penicillus capitatus Lamarck and Caulerpa racemosa var. lamourouxii f. requienii [START_REF] Bitar | Report of the second mission relating to the Development of Marine Protected Areas on Syrian coasts, 1-18[END_REF]. The species is common on the South Levantine coast [START_REF] Lundberg | Composition of the seaweed vegetation along the Mediterranean coast of Israel[END_REF].

In Lebanon, C. scalpelliformis was first found at Beirut, close to the sea-surface, where it was abundant, and at 30 m depth [START_REF] Hamel | Les Caulerpes méditerranéennes[END_REF]. Subsequently, the species was recorded from Batroun and Barbara in 1996-1997[START_REF] Lakkis | Etude de la diversité biologique au Liban: faune et flore marines et côtières[END_REF][START_REF] Lakkis | Distribution of phytobenthos along the coast of Lebanon (Levantine Basin, East Mediterranean)[END_REF], 2001[START_REF] Einav | Seaweeds of the eastern Mediterranean coast. Ruggell, Liechtenstein[END_REF]. We found two varieties of C. scalpelliformis (Bitar, 2010b):

-C. scalpelliformis var. scalpelliformis in 1994 at Hannouch, on a rocky substrate, at 1 m depth.

-C. scalpelliformis var. intermedia Weber-van Bosse in June 2000 at Khalde, in the Villamar Marina where it was well established [START_REF] Bitar | Sur la flore marine benthique supposée Lessepsienne de la côte libanaise. Cas particulier de Stypopodium schimperi[END_REF], and in April 2001 at Batroun.

We observed C. scalpelliformis in September 2005 off Selaata, at around 30 m depth, on a muddy substrate [START_REF] Bitar | Contribution of the Red sea alien species to structuring some benthic biocenosis in the Lebanon coast (Eastern Mediterranean)[END_REF]Bitar, 2010b), and in June 2012 at Ras Chekaa, at 44 m depth on a muddy maerl assemblage associated with Flabellia petiolata (Turra) Nizamuddin (RAC/SPA -UNEP/MAP, 2014). The species is well established in Lebanon, without being invasive. (Cevik et al., 2007, as C. taxifolia), Sicily [START_REF] Jongma | Identity and origin of a slender Caulerpa taxifolia strain introduced into the Mediterranean Sea[END_REF], Cyprus (Çiçek et al., 2013), Malta [START_REF] Schembri | It was only a matter of time: occurrence of Caulerpa taxifolia (Vahl) C. Agardh var. distichophylla (Sonder) Verlaque, Huisman and Procaccini in the Maltese Islands (Chlorophyta, Ulvophyceae, Caulerpaceae)[END_REF], and Rodos Island [START_REF] Aplikioti | Further expansion of the alien seaweed Caulerpa taxifolia var. distichophylla (Sonder) Verlaque, Huisman & Procacini (Ulvophyceae, Bryopsidales) in the Eastern Mediterranean Sea[END_REF].

In Lebanon, C. taxifolia var. distichophylla was first found in October 2016 at El Madfoun and Byblos, between 16 and 48 m depth, where it constituted small patches (10-40 cm in diameter) on sand and gravels. Lebanese specimens were well characterized by (i) the thallus tiny with fronds, up to 3.5 mm broad and 10 cm high, bearing distichously arranged pinnules, and (ii) the pinnules closely adjacent, compressed, slightly upwardly curved, broadest just above the base, and tapering to a distinct spinous tip. Caulerpa taxifolia var. distichophylla, which is invasive in the Central Mediterranean basin (Sicily; [START_REF] Jongma | Identity and origin of a slender Caulerpa taxifolia strain introduced into the Mediterranean Sea[END_REF], is recorded for the first time from Lebanon.

Cladophora herpestica (Montagne) Kützing

(Fig. 22) Described from New Zealand and widespread in the Indo-Pacific Ocean, this species was first recorded in the Mediterranean Sea from Egypt (Aleem, 1948, as Cladophoropsis zollingeri). All the other Levantine records of Cladophoropsis spp. [START_REF] Rayss | Les algues marines des côtes palestiniennes. I. Chlorophyceae[END_REF][START_REF] Mayhoub | Recherches sur la végétation marine de la côte syrienne. Etude expérimentale sur la morphogénèse et le développement de quelques espèces peu connues[END_REF][START_REF] Lundberg | Composition of the seaweed vegetation along the Mediterranean coast of Israel[END_REF][START_REF] Einav | Seaweeds of the eastern Mediterranean coast. Ruggell, Liechtenstein[END_REF] have been attributed to C. herpestica [START_REF] Verlaque | Macrophytes[END_REF].

In Lebanon, C. herpestica was first found in 1973 at Barbara, Zouk Mkayel, Khalde and Doha (Basson et al., 1976, misidentified as Cladophoropsis modonensis).

Subsequently it was found at Aramane and Batroun in 1996-1997 [START_REF] Lakkis | Distribution of phytobenthos along the coast of Lebanon (Levantine Basin, East Mediterranean)[END_REF]. We observed C. herpestica, in October 1991 at Saadiyat and May 2016 at Tyre. Cladophora herpestica is well established on the outer margins of Vermetid reefs of the Lebanese coast.

Cladophora patentiramea (Montagne) Kützing

(Fig. 23) Described from Tahiti and widespread in the Indo-Pacific Ocean, this species was first found in the Mediterranean Sea in 1991 at Cyprus [START_REF] Verlaque | Macrophytes[END_REF].

In Lebanon, we found C. patentiramea at Selaata and Tyre in September 2005 (Bitar etal., 2007). Subsequently, it was observed at several other localities, especially in May 2010 and May 2016 at El Jamal (Tyre), on extended surfaces sheltered by small islets, at 2-3 m depth. The species is very similar to several native species of Cladophora, so the identity and origin of Mediterranean populations should be tested through molecular studies. Cladophora patentiramea requires special attention be-cause it was invasive on shallow sandy localities in Cyprus.

25.

Codium arabicumKützing (Fig. 24) Described from the Red Sea and widespread in the Indo-Pacific Ocean, this species was first found in the Mediterranean Sea in 2007 at Haifa [START_REF] Hoffman | First record of the IndoPacific seaweed Codium arabicum Kütz. (Bryopsidales, Chlorophyta) in the Mediterranean Sea[END_REF]. In Syria, it was found in April 2013 [START_REF] Abbas | Three new records of marine green algae (Bryopsidales, Chlorophyta) from the Syrian coast[END_REF]. According to Hoffman (2014a), C. arabicum should be regarded and treated as an invasive species.

In Lebanon, we found some individuals of C. arabicum at Hannouch in August 2007. Subsequently, we found it on a cliff, between 1 and 4 m depth, at Ramkine Island in August 2010, at Barbara in October 2011, close to the Sea Star Hotel, at 2 m depth, and at Enfehin June 2012 (Bitar, 2014;present study). Although uncommon, C. arabicum seems to be established in Lebanon.

26.

Codium parvulum (Bory ex Audouin) P.C. Silva (Fig. 25) Described from the Red Sea and present in the Indian Ocean, this species was first found in the Mediterranean Sea in 2004 at Haifa [START_REF] Israel | First report of the seaweed Codium parvulum (Chlorophyta) in Mediterranean waters: recent blooms on the northern shores of Israel[END_REF]. In Syria, it was found in April 2013 [START_REF] Abbas | Three new records of marine green algae (Bryopsidales, Chlorophyta) from the Syrian coast[END_REF].

In Lebanon, we first found C. parvulum at Nakourain June 2008, where it occupied extensive areas at 30 m depth (Bitar, 2010b). Currently, C. parvulum is invasive along the whole Lebanese coast, between 1 and 35 m depth. Codium parvulum was the fourth invasive marine macrophyte to be identified in Lebanon, after Ulva lactuca, Stypopodium schimperi and Galaxaura rugosa.

27. Codium taylorii P.C. Silva (Fig. 26)

Described from Florida and widespread in the Atlantic and the Indian Oceans, C. taylorii was first recorded in the Mediterranean Sea from Palestine [START_REF] Rayss | Les algues marines des côtes palestiniennes. I. Chlorophyceae[END_REF]misidentified as C. dichotomum). In Syria, it was found in 1973 (Mayhoub, 1976, as C. decorticatum) and April 2013 [START_REF] Abbas | Three new records of marine green algae (Bryopsidales, Chlorophyta) from the Syrian coast[END_REF].

In Lebanon, we first found C. taylorii in September 2002 at Ouzai, on the breakwater close to Beirut Airport (Abboud-Abi [START_REF] Saab | Environnement côtier et biodiversité marine sur les côtes libanaises; inventaire et mise en place d'un ensemble matériel et humain d'observation et d'analyse de leur évolution, degré d'altération des communautés benthiques littorales. Rapport final Franco-Lebanese Cooperation Program CEDRE[END_REF][START_REF] Bitar | Contribution of the Red sea alien species to structuring some benthic biocenosis in the Lebanon coast (Eastern Mediterranean)[END_REF], Bitar, 2010b). Currently, C. taylorii is well established along the whole Lebanese coast, without being invasive.

28. Ulva lactuca Linnaeus (Fig. 27) All the European records of U. lactuca over the past 200 years correspond to another species referable as 'U. lactuca auctores' [START_REF] Verlaque | Macrophytes[END_REF]. The genuine U. lactuca is an alga widespread in warm seas and usually known as U. fasciata Delile (1813), a taxon described from the Mediterranean Sea (Egypt, Alexandria), before the opening of the Suez Canal. However, the chronology of Mediterranean records suggests multiple introductions via different vectors or co-occurrence of introduced and native populations [START_REF] Verlaque | Macrophytes[END_REF]. Ulva lactuca was recorded along the whole Levantine coast [START_REF] Mayhoub | Recherches sur la végétation marine de la côte syrienne. Etude expérimentale sur la morphogénèse et le développement de quelques espèces peu connues[END_REF]Hoffman, 2014a; both as U. fasciata). In Lebanon, we first found U. lactuca in April 1991 at Beirut (Bitar, 1999, as U. fasciata). [START_REF] Kanaan | Diversity investigation of the seaweeds growing on the Lebanese coast[END_REF] recorded the species from Batroun, El Manara, Saida, Tyre and Barbara in 2014. The species is invasive along the whole Lebanese coast on Vermetid reefs and in shallow habitats. Ulva lactuca was the first invasive exotic marine macrophyte to be identified in Lebanon.

29.

Halophila stipulacea (Forsskål) Ascherson (Fig. 28) Described from the Red Sea and present in the Indian Ocean, H. stipulacea was first found in the Mediterranean Sea in 1894 at Rodos Island, Greece [START_REF] Verlaque | Macrophytes[END_REF]. In Syria, dense seagrass beds were observed at Ras El Bassit (Abboud-Abi [START_REF] Saab | Environnement côtier et biodiversité marine sur les côtes libanaises; inventaire et mise en place d'un ensemble matériel et humain d'observation et d'analyse de leur évolution, degré d'altération des communautés benthiques littorales. Rapport final Franco-Lebanese Cooperation Program CEDRE[END_REF][START_REF] Bitar | Report of the second mission relating to the Development of Marine Protected Areas on Syrian coasts, 1-18[END_REF][START_REF] Bitar | Contribution of the Red sea alien species to structuring some benthic biocenosis in the Lebanon coast (Eastern Mediterranean)[END_REF]. The species has not yet been detected along the South Levantine coast (Hoffman, 2014a).

In Lebanon, it was first collected in 1966, off Saida, by Dr J. H. Powell [START_REF] Lipkin | Halophila stipulacea, a review of a successful immigration[END_REF]. We found it in July 1993 in the Beaulieu tourism complex at El Heri, at 2m depth, then in 1999 at Selaata [START_REF] Bitar | Sur la flore marine benthique supposée Lessepsienne de la côte libanaise. Cas particulier de Stypopodium schimperi[END_REF]Bitar, 2010b). The species was also recorded from Aramane, Batroun, Barbara, Enfeh and Zouk Mkayel in 1996-1997[START_REF] Lakkis | Distribution of phytobenthos along the coast of Lebanon (Levantine Basin, East Mediterranean)[END_REF], 2001[START_REF] Einav | Seaweeds of the eastern Mediterranean coast. Ruggell, Liechtenstein[END_REF]present study). Halophila stipulacea is mainly distributed in the northern part of Lebanon, between 1 and 40 m depth. No dense meadow shave been found in Lebanon.

Discussion and conclusion

The analysis of historical and field data provided the basis for drawing up a list of 29 exotic macrophytes for the marine flora of Lebanon. The major origin and pathway of introduction are the Indo-Pacific Ocean and the Suez Canal, respectively (Table 1), namely the Lessepsian or Erythraean invasion. Caulerpa taxifolia var. disticho-phylla, Spatoglossum variabile and Womersleyella setacea are recorded for the first time from Lebanon. Among the invasive or potentially invasive species listed in the Mediterranean Sea [START_REF] Verlaque | Macrophytes[END_REF], thirteen occur in Lebanon: Asparagopsis taxiformis, Caulerpa taxifolia var. distichophylla, Cladophora patentiramea, Codium arabicum, C. parvulum, Galaxaura rugosa, Halophila stipulacea, Hypnea cornuta, Laurencia cf. chondrioides, Lophocladia lallemandii, Stypopodium schimperi, Ulva lactuca and Womersleyella setacea, and five of them, namely Codium parvulum, Galaxaura rugosa, Laurencia cf. chondrioides, Stypopodium schimperi and Ulva lactuca, already occupy extensive stretches of the coast, more or less replacing the native benthic assemblages.

Neomeris annulata Dickie and Solieria dura (Zanardini) F. Schmitz, two Indo-Pacific species respectively first recorded from Syria [START_REF] Bitar | Neomeris annulata Dickie (Dasycladales, Chlorophyceae): a potential new invader from the Red Sea to the Mediterranean Sea[END_REF] and from the South Levantine coast [START_REF] Rayss | Sur la présence dans la Méditerranée orientale des algues tropicales de la famille des Solieriacées[END_REF], have not yet been found in Lebanon contrary to what is stated in [START_REF] Verlaque | Macrophytes[END_REF]. The identity and the origin of several exotic species, namely Bryopsis pennata, Chondria coerulescens, Cladophora patentiramea, Hypnea valentiae, Laurencia cf. chondrioides and Polysiphonia atlantica, should be confirmed by further studies (Questionable species). Acanthophora nayadiformis, A. taxiformis, G. farinosum and U. lactuca are considered to be cryptogenic (Table 2).

The total number of exotic macrophytes listed in the marine flora of Lebanon is probably under-estimated because, in addition to Neomeris annulata and Solieria dura, several other large exotic species recorded from the other Levantine countries have not yet been found in Lebanon, namely Dichotomaria cf. obtusata (J.Ellis & Solander) Lamarck, Gracilaria arcuata Zanardini, Grateloupia turuturu (identification to be confirmed by molecular studies), Hypnea flagelliformis Greville ex J. Agardh (misidentified as H. spicifera), Padina boryana Thivy, Rhodymenia erythraea Zanardini and Sarconema scinaioides Børgesen (Hoffman, 2014b;Hoffman et al., 2015;[START_REF] Verlaque | Macrophytes[END_REF][START_REF] Arraj | First records of two Padina species (Dictyotales, Phaeophyceae) from the Syrian coast (eastern Mediterranean)[END_REF], as well as Palisada maris-rubri (K.W. Nam & Saito) K.W. Nam, a species recorded from Rodos Island, Greece [START_REF] Tsiamis | First report of the red alga Palisada maris-rubri (Ceramiales, Florideophyceae) from the Eastern Mediterranean Sea[END_REF] and Tunisia [START_REF] Boudouresque | The Red Sea macroalga Palisada maris-rubri (Rhodobionta, Archaeplastida): first record in Tunisia[END_REF]. Likewise, we did not look for the small exotic species (< 1-2 cm high) such as Acrochaetium spp., Antithamnionella elegans (Berthold) [START_REF] Einav | Two observations of seaweeds from the Israeli coast: Boodleopsis pusilla and Caulerpa prolifera (Forsskål) Lamouroux (Chlorophyta, Caulerpales)[END_REF][START_REF] Einav | Seaweeds of the eastern Mediterranean coast. Ruggell, Liechtenstein[END_REF][START_REF] Verlaque | Macrophytes[END_REF]Hoffman, 2014a[START_REF] Hoffman | [END_REF][START_REF] Hoffman | First reports of the red alga Hypoglossum caloglossoides from the Mediterranean and the Red Sea[END_REF], 2016). As far as the ecological and economic impact is concerned, the introduction of species constitutes biological pollution and is one of major constituents of Global Change. In the eastern Mediterranean basin, the negative impact of the arrival of Indo-Pacific species is on the increase, and this phenomenon will likely be intensified with the doubling of the Suez Canal [START_REF] Galil | Double trouble': the expansion of the Suez Canaland marine bioinvasions in the Mediterranean Sea[END_REF]. Consequently, the Mediterranean nations must be made fully aware and international collaboration must be developed between all stakeholders (national and international organisations, governmental and non-governmental organisations, research institutes, etc.) to attempt to slow down the phenomenon and mitigate the consequences.

  : A = Atlantic; IP= Red Sea / Indo-Pacific. Pathways: Categories / Subcategories according to the CBD (2014) classification: C/CAE = Corridor / Canal of Ancient Egyptians; C/SC = Corridor / Suez Canal; R/Aq = Release in nature / Aquarium species; T-C/A = Transport-Contaminant / Aquaculture; T-S/Sh = Transport-Stowaway / Ship hull fouling or ballast water.

Fig. 1 :

 1 Fig. 1: Study localities in Lebanon: 1. Aramane; 2. Ramkine Is-land; 3. Tripoli and El Mina; 4. Enfeh; 5. El Heri; 7. Hannouch; 8. Selaata; 9. Batroun; 10. Kfar Abida and El Madfoun; 11. Barbara; 12. Amchit and Byblos; 13. Tabarja; 14. Zouk Mkayel; 15. Beirut, El Manara and Raoucheh; 16. Ouzai; 17. Khalde; 18. Doha; 19. Saadiyat; 20. Saida; 21. Tyre and El Jamal; 22. El Baiada; 23. Nakoura.

Fig. 2 :

 2 Fig. 2: Padina boergesenii, Tyre, August 2013.

Fig. 3 :

 3 Fig. 3: Spatoglossum variabile, Raoucheh, June 2015.

Fig. 4 :

 4 Fig. 4: Stypopodium schimperi, Nakoura, March 2008.

Fig. 5 : 6 :

 56 Fig. 5: Acanthophora nayadiformis, Tyre, May 2016. Fig. 6: Asparagopsis taxiformis, Beirut, April 2008.

Fig. 7 :

 7 Fig. 7: Galaxaura rugosa, Batroun, May 2008.

Fig. 8 :

 8 Fig. 8: Ganonema farinosum, Barbara, June 2008.

Fig. 9 :

 9 Fig. 9: Hypnea cornuta, Tyre, May 2016.

Fig. 10 :

 10 Fig. 10: Hypnea valentiae, Lebanon, with the permission of Prof. Oksana Belous.

Fig. 11 :Fig. 13 :

 1113 Fig. 11: Laurencia cf. chondrioides, Saadiyat, April 2013. Fig. 12: Lophocladia lallemandii, Lebanon, August 2015.

Fig. 14 :

 14 Fig. 14: Sarconema filiforme, Beirut, June 2010.

Fig. 15 :

 15 Fig. 15: Womersleyella setacea, Batroun, October 2016.

Fig. 16 :

 16 Fig. 16: Bryopsis pennata, Kfar Abida, August 2012.

20.

  Caulerpa racemosa (Forsskål) J. Agardh var. lamourouxii (Turner) Weber-van Bosse f. requienii (Montagne) Weber-van Bosse (Fig.19) Described from the Red Sea, this species was first foundin the Mediterranean Sea in 1951 along the South

Fig. 17 :

 17 Fig. 17: Caulerpa chemnitzia, Tripoli, September 2002.

Fig. 18 :

 18 Fig. 18: Caulerpa mexicana, Beirut, July 2016.

Fig. 19 :

 19 Fig. 19: Caulerpa racemosa var. lamourouxii f. requienii, Batroun, September 2016.

22.

  Caulerpa taxifolia var. distichophylla (Sonder) Verlaque, Huisman & Procaccini (Fig. 21) Described from south-western Australia and recorded from Torres Strait and Central Polynesia, this Indo-Pacific species was first found in the Mediterranean Sea by one of us (G.B.) in August 2003 in Syria (RAC/SPA -UNEP/MAP, 2003, misidentified as a dwarf form of C. mexicana; Bitar, 2010b, as a dwarf form of C. mexicana or C. taxifolia). Subsequently, it was recorded from Turkey (Gulf of Iskenderun)

Fig. 20 :

 20 Fig. 20: Caulerpa scalpelliformis, Chekaa, June 2012.

Fig. 21 :

 21 Fig. 21: Caulerpa taxifolia var. distichophylla, El Madfoun, October 2016.

Fig. 22 :

 22 Fig. 22: Cladophora herpestica, Tyre, May 2016.

Fig. 23 :

 23 Fig. 23: Cladophora patentiramea, Tyre, May 2016.

Fig. 24 :

 24 Fig. 24: Codium arabicum, Enfeh, June 2012.

Fig. 25 :

 25 Fig. 25: Codium parvulum, Kfar Abida, August 2012.

Fig. 26 :

 26 Fig. 26: Codium taylorii, Hannouch, August 2012.

Fig. 27 :

 27 Fig. 27: Ulva lactuca, Beirut, June 2010.

  J.H. Price & D.M. John, Boodlea composita (Harvey) F.Brand (record requiring confirmation), Boodleopsis pusilla (Collins) Taylor (Identification requiring confirmation), Chondria pygmaea Garbary & Vandermeulen, a common epiphytic species of Halophila stipulacea, Derbesia boergesenii (Iyengar & Ramanathan) Mayhoub, Hypnea anastomosans Papenfuss, Lipkin & P.C. Silva, Hypoglossum caloglossoides M.J.Wynne & Kraft, Monosporus indicus Børgesen

Fig. 28 :

 28 Fig. 28: Halophila stipulacea, Enfeh, October 1999.

  Lastly, it is worth noting the absence of Caulerpa cylindracea Sonder, which is probably the most aggressive invasive species of the Mediterranean Sea. All these exotic species need to be looked for in Lebanon. On the other hand, the Lebanese record of Solieria filiformis (RAC/ SPA -UNEP/MAP, 2014) is a misidentification of Sarconema filiformis.

	SPECIES	STATUS	DATE LOCALITY	SOURCE	ORIGINS	PATHWAYS	SUCCESS
	CHROMOBIONTA
	Padina boergesenii Allender & Kraft	Al	1992	Tripoli	Bitar, 1999	IP	C/SC	E
	Spatoglossum variabile Figari & De Notaris	Al	2009	Tabarja	Present study	IP	C/SC	E
	Stypopodium schimperi (Kützing) Verlaque &	Al	1991	Barbara	Bitar, 1999	IP	C/SC	Inv
	Boudouresque
	RHODOBIONTA
	Acanthophora nayadiformis (Delile) Papenfuss Cr	1991	Tabarja	Bitar, 2010b	IP	C/CAE	E
							C/SC
							T-S/Sh
	Asparagopsis taxiformis (Delile) Trevisan de	Cr	1973	Selaata, Barbara,	Basson et al., 1976 A/IP?	C/CAE	E
	Saint-Léon (Tetrasporophyte)			Zouk Mkayel			C/SC
				Khalde			T-S/Sh
	Asparagopsis taxiformis (Delile) Trevisan de	Cr	1993	Barbara, Batroun Bitar etal., 2000	A/IP ?	C/CAE	E
	Saint-Léon (Gametophyte)						C/SC
							T-S/Sh
	Chondria coerulescens (J. Agardh) Falkenberg* Qu	1973	North Lebanon Basson etal., 1976 A	T-C/A	E
	Galaxaura rugosa (J. Ellis & Solander) J.V.	Al	1995	Kfar Abida	Bitar et al., 2000	IP	C/SC	Inv
	Lamouroux
	Ganonema farinosum (J.V. Lamouroux) K.C.	Cr	1993	El Heri	Bitar et al., 2000,	IP	C/SC	E
	Fan & Y.C. Wang				as Liagora farinosa		T-S/Sh
	Hypnea cornuta (Kützing) J. Agardh	Al	1973	North Lebanon Basson etal., 1976,	IP	C/SC	E
					as H. hamulosa		T-S/Sh
	Hypnea spinella (C. Agardh) Kützing	Al	1998	Beirut,	Present study	A/IP	C/SC	E
							T-S/Sh
	Hypnea valentiae (Turner) Montagne*	Qu	2014	Batroun	Belous & Kanaan,	IP	C/SC	C
					2015		T-C/A
	Laurencia cf. chondrioides Børgesen*	Qu	2009	El Baiada, Tyr,	Present study	A	T-S/Sh	Inv
				Nakoura
	Lophocladia lallemandii (Montagne) F. Schmitz Al	1973	North Lebanon Basson etal., 1976 IP	C/SC	E
							T-S/Sh
	Polysiphonia atlantica Kapraun & J.N. Norris*	Qu	2014	Batroun	Bellous & Kanaan,	A/P	T-S/Sh	C
					2015
	Sarconema filiforme (Sonder) Kylin	Al	2001	Beirut	Bitar, 2010b	IP	C/SC	E
	Womersleyella setacea (Hollenberg) R.E.Norris	Al	2016	Batroun	Present study	IP	R/Aq	E?
							T-S/Sh
	CHLOROBIONTA
	Bryopsis pennata J.V. Lamouroux*	Qu	1973	Khalde	Basson et al., 1976 IP	C/SC	E
							T-S/Sh
	Caulerpa chemnitzia (Esper) J.V. Lamouroux	Al	1931	Beirut	Hamel, 1931, as C.	IP	C/SC	E
					racemosa;
	C. mexicana Sonder ex Kützing	Al	1941	Beirut	Rayss, 1941, as C.	IP	C/SC	E
					crassifolia
	C. racemosa var. lamourouxii f. requienii (Mon-	Al	1991	Beirut	Present study	IP	C/SC	E
	tagne) Weber-van Bosse
	C. scalpelliformis (R.Brown ex Turner) C. Agardh Al	1930	Beirut	Hamel, 1930	IP	C/SC	E
	Caulerpa taxifolia var. distichophylla (Sonder)	Al	2016	El Madfoun,	Present study	IP	R/Aq	E
	Verlaque, Huisman & Procaccini			Byblos			T-S/Sh
	Cladophora herpestica (Montagne) Kützing	Al	1973	Barbara, Zouk	Basson et al., 1976,	IP	C/SC	E
				Mkayel, Khalde,	as Cladophoropsis
				Doha	modonensis
	Cladophora patentiramea (Montagne) Kützing* Qu	2005	Selaata, Tyr	Bitar etal., 2007	IP	C/SC	E
	Codium arabicum Kützing	Al	2007	Hannouch	Present study	IP	C/SC	E
	C. parvulum (Bory ex Audouin) P.C.Silva	Al	2008	Nakoura	Bitar, 2010b	IP	C/SC	Inv
	C. taylorii P.C. Silva	Al	2002	Ouzai, Beirut	Abboud-Abi Saab	IP/A	T-C/A	E
					et al., 2003		T-S/Sh
	Ulva lactuca Linnaeus	Cr	1991	Beirut	Bitar, 1999, as U.	IP	C/CAE	Inv
					fasciata		T-S/Sh
	STREPTOBIONTA
	Halophila stipulacea (Forsskål) Ascherson	Al	1966	Saida	Lipkin, 1975	IP	C/SC	E
	* Identification requiring confirmation

Acknowledgements

The surveys in 2012, 2013 and 2016 were conducted within the framework of the MedMPAnet Project, implemented by UNEP/MAP-RAC/SPA and funded by RAC/SPA, the European Commission (EC), the Spanish Agency for International Cooperation for Development (AECID), and the French Global Environment Facility (FFEM). We thank the Ministry of Environment of Lebanon and the Lebanese National Council for Scientific Research for their invaluable help in field studies, Prof. Oksana Belous for kind permission to reproduce her illustrations, Michèle Perret-Boudouresque for documentation assistance and Michael Paul for revising the English text. Many thanks are due to the anonymous reviewers for their comments and constructive criticism of the manuscript.


Eiichi Yoshida

Mathieu Poirier

Jean-Paul Laumond

Oussama Kanoun

Florent Lamiraux

Rachid Alami

Kazuhito Yokoi

Regrasp Planning for Pivoting Manipulation by a Humanoid Robot

A method of regrasp planning for humanoid robot manipulation is proposed. We adopt pivoting manipulation for the humanoid robot to move a bulky object without lifting in a stable and dexterous manner. In order to carry the object to a desired place, the humanoid should sometimes move through narrow areas surrounded by obstacles. We propose a roadmap multiplexing planning to allow the robot to leave the object near narrow places and to regrasp it from another position to continue carrying. We utilize visibility probabilistic roadmap (PRM) method as a preprocessing to capture the critical configurations for regrasping. Then a diffusion method is employed to plan the overall manipulation path including regrasping. The proposed method is verified through planning simulation including whole-body motions.

I. INTRODUCTION

Manipulation requiring whole-body motion is one of the tasks that are appropriate for humanoid robots. Currently whole-body humanoid tasks are actively being studied: for instance, pushing [START_REF] Hwang | Whole body cooperative tasks and static stability evaluations for a humanoid r obot[END_REF], [START_REF] Harada | Real-Time Planning of Humanoid Robot's Gait for Force Controlled Manipulation[END_REF] or lifting [START_REF] Harada | A Humanoid robot carrying a heavy object[END_REF], [START_REF] Arisumi | Dynamic Lifting Motion of Humanoid Robots[END_REF]. We have been studying on pivoting [START_REF] Aiyama | Pivoting: A new method of graspless manipulation of object by robot fingers[END_REF] that consists of manipulating a bulky object by inclining and rotating. It is advantageous for the humanoid robot in terms of dexterity, stability and security since the robot does not need to lift the object [START_REF] Yoshida | Pivoting a large object: whole-body manipulation by a humanoid robot[END_REF]. We have proposed collision-free whole-body motion planning for pivoting in our previous work [START_REF] Yoshida | Pivoting Based Manipulation by Humanoids: a Controllability Analysis[END_REF], [START_REF] Yoshida | Whole-Body Motion Planning for Pivoting Based Manipulation by Humanoids[END_REF]. Fig. 1 shows an example of whole-body manipulation including coordinated arm and leg motions also by keeping dynamic balance. The manipulated object is carried to the goal position several meters away along the planned curve.

However, the planner proposed in [START_REF] Yoshida | Whole-Body Motion Planning for Pivoting Based Manipulation by Humanoids[END_REF] does not allow the robot to change the grasping point: it may be blocked if there are places where the robot and the object cannot pass through together. When we humans transport a bulky object in a cluttered environment, we sometimes release the object and hold it with another position according to the situation.

In this work, we provide a humanoid robot with more flexibility in whole-body pivoting manipulation by including regrasp planning. The robot releases the object when it cannot go further towards the goal position and grasp it again to continue manipulation.

The difficulty resides in finding narrow passages for the robot and object together and in combining the paths with different grasping positions to plan a manipulation motion to achieve the goal.

Movable objects have been dealt with using classical motion planners [START_REF] Wilfong | Motion panning in the presence of movable obstacles[END_REF], [START_REF] Chen | Pracitcal path planning among movable obstacles[END_REF], [START_REF] Latombe | Robot Motion Planning[END_REF] before the introduction of randomized motion planners where different configuration spaces are addressed depending on the relative position of the robot to the movable objects. Simeon et al. [START_REF] Simeon | Manipulation planning with probabilistic roadmaps[END_REF] proposed a theoretical basis of manipulation planning including "transit" path without the object and "transfer" with it, which allows the manipulation plan with regrasping. In the humanoid related research, Stilman et al. [START_REF] Stilman | Navigation among movable obstacles: Realtime reasoning in complex environments[END_REF], [START_REF] Stilman | Planning and executing navigation among movable obstacles[END_REF] addressed "navigation among movable objects" and Okada et al. [START_REF] Okada | Environment Manipulatio Planner for Humaonid Robots Using Task Graph That Generates Action Sequence[END_REF] proposed an "environment planner" respectively, to allow the humanoid robot to navigate by displacing movable obstacles. Both methods focus on navigation based on search in the graph that represents the structure of the environment.

We here address the regrasp planning problem for pivoting manipulation through a roadmap-multiplexing approach. First, we plan an object-only roadmap to identify "critical configurations" by capturing the global view of the environment based on visibility roadmap planning method [START_REF] Simeon | Visibility-based probabilistic roadmaps for motion planning[END_REF]. From the obtained object visibility roadmap, multiple "manipulation roadmaps" are constructed for the combined robot-object system for different grasping positions. Those roadmaps are interconnected by a "regrasping roadmap" for free robot walking. A collision-free manipulation path including regrasping is searched by applying randomized diffusion planning method to the whole set of those roadmaps. Finally the whole-body motions are generated based on the method proposed in [START_REF] Yoshida | Whole-Body Motion Planning for Pivoting Based Manipulation by Humanoids[END_REF].

The contribution of this work is reinforcement of the flexibility for humanoid manipulation by allowing regrasping and also the integration of visibility roadmap, diffusion planning and whole-body motion generation of humanoid motion.

II. PIVOTING MANIPULATION BY HUMANOID ROBOT So far we have been investigating the whole-body manipulation of a polyhedral object by a humanoid robot [START_REF] Yoshida | Pivoting a large object: whole-body manipulation by a humanoid robot[END_REF], [START_REF] Yoshida | Pivoting Based Manipulation by Humanoids: a Controllability Analysis[END_REF], [START_REF] Yoshida | Whole-Body Motion Planning for Pivoting Based Manipulation by Humanoids[END_REF]. It is useful when the object is bulky or heavy since the robot does not lift the object but manipulates it by using the contact support from the floor. We can also expect a dexterous manipulation by using point contacts of the object vertices. As shown in Fig. 2, the 3D pivoting motion of the object is modeled by a 2D segment of which two endpoints are used as a center of horizontal rotation. We have shown a property that any collision-free path is transformed into pivoting sequence based on small-time controllability [START_REF] Yoshida | Pivoting Based Manipulation by Humanoids: a Controllability Analysis[END_REF].

The pivoting sequence planning proposed in [START_REF] Yoshida | Whole-Body Motion Planning for Pivoting Based Manipulation by Humanoids[END_REF] takes two steps. A supporting collision-free path for the edge is first planned. While manipulating, it is easier for the humanoid to move in the forward direction than sidestepping. By taking this in account as nonholonomic constraints [START_REF]Robot Motion Planning and Control[END_REF], we applied a local steering method called Reeds and Shepp curves [START_REF] Reeds | Optimal paths for a car that goes both forwards and backwards[END_REF], composed of line segment and arc of circles allowing backward motions. This steering method enables the robot to go backwards to manipulation the object near a wall.

Once a basic collision-free path is planned, it is transformed into a pivoting sequence of the object. Finally, the whole-body humanoid motion is generated to achieve the hand trajectory that achieves the planned sequence.

With those results at hand, we are now ready to investigate roadmap multiplexing to handle more complex situations.

III. IDENTIFYING CRITICAL CONFIGURATIONS

We employ the "visibility" Probabilistic Roadmap (PRM) [START_REF] Simeon | Visibility-based probabilistic roadmaps for motion planning[END_REF], [START_REF] Lavalle | Planning Algorithms[END_REF] to help the planner identify the critical configurations. Two types of nodes are considered in visibility roadmap.

1) Guards: To become a guard, a node in the roadmap q must not be able to see other guards. Thus, the visibility region, V (q) , must be empty of other guards. 2) Connectors: To become a connector, a node q , must see at least two guards. Thus, there exist guards q 1 and q 2 , such that q ∈ V (q 1 ) ∩ V (q 2 ) . Fig. 3 shows the way it works. The black circles are the guards already included in the roadmap G. There are three cases when a new configuration q new is sampled. First, if q new cannot be connected to any guards, q new becomes a guard and is inserted into the roadmap (Fig. 3a). The second case is that q new can be connected to at least two different connected components of G. In this case, q new becomes a connector that adds associated edges in G to connect the different connected components (Fig. 3b). If q new does not satisfy any of those two conditions, it is discarded (Fig. 3c).

Supporting edge

The visibility PRM has characteristics to keep the roadmap compact. Since it attempts to connect separate connected components, it helps identifying narrow passages more efficiently than plain PRM.

For those reasons, we adopt this Visibility PRM to capture the global view of the environment. When the humanoid robot carries the object by pivoting manipulation in an environment with obstacles, it may often be blocked by narrow spaces where it cannot go through by holding the object. The Visibility PRM serves as a preprocessing procedure that helps the planner identify possible regrasping points of manipulation.

This preprocessing is illustrated in Fig. 4. First, the visibility PRM is executed with the carried object alone to capture the passages where the object can pass through. Suppose that a new node q obj new that is judged to be added to the "object roadmap" G obj (Fig. 4a). Before the addition, collisions are checked by attaching the approximated robot bounding volume along the new edges e obj new to be added to connect to other connected components. If e obj new is collisionfree, insert it in G obj .

On the other hand, if e obj new induces collisions between the robot and the obstacles, the collision-free portions e rob free are extracted (Fig. 4b). Then e rob free are added in G obj instead of e obj new .

The newly inserted nodes q rob free are considered to represent critical configurations that are the candidates of the regrasping points. Fig. 5 shows an example of object roadmap. We can observe that the narrow areas are roughly covered by the roadmap. Note that the links between the nodes are symbolic to represent the connectivity and their actual motions are subject to nonholonomic constraints of Reeds and Shepp curves for car-like robots. Notice also that the edges between the nodes do not have much importance because we will use only the nodes in construction of roadmap for the combined robot-object system in the next section.

IV. REGRASP PLANNING BY MULTIPLEXING ROADMAPS

In this section we describe a method of regrasp planning using roadmap multiplexing to combine different grasping positions. Fig. 6 illustrates the overview of the planning scheme. Several grasping positions are possible for a given object position. The roadmaps are built for the combined bounding volumes of both the robot and the object. There Object size Fig. 5. An example of resulting object roadmap. The link between nodes represents symbolic connections by nonholonomic local steering method. The absence of connection between two nodes apparently close means that the shortest Reeds and Shepp path is not collision-free. are two types of roadmap: the first is the "manipulation roadmap" G i manip for i-th grasping position r i grasp expressed as the relative robot position with respect to object. In this roadmap, the robot and the object move together. The second type of roadmap is the "regrasping roadmap" G reg where the robot moves alone between different grasping positions.

As can be seen in the figure, manipulation roadmaps G 1 manip and G 2 manip for different grasping positions are interconnected via the regrasping roadmap G reg . For instance, the path from A to B is possible only by alternating the different grasping positions.

We first use the visibility roadmap of the object G obj introduced in Section III to construct those roadmap. The objective of this operation is to allow the roadmaps to cover the areas around the critical configurations. Since the manipulation roadmaps generated from the object roadmap are only rough capture of the narrow passages, a fine path search is usually necessary to find the precise regrasping positions. If no solutions are found after this roadmap building operation, we adopt a diffusing roadmap exploration to grow the roadmap in narrow spaces.

The detailed procedure to research a manipulation path for the combined robot-object system is shown in Fig. 7. Since there are multiple grasping positions for the robot, the start and goal configurations are not unique. The path planning problem has then multiple start and goal sets S start and S goal . The subroutine PlanWithObjectConfig(q obj , S start , S goal ) makes a path search between start and goal node sets in the whole set of the roadmaps by adding a new node generated from the object configuration q obj . Fig. 8 shows an example of roadmap generated from the multiplexing method. The thick line segments with black circle nodes are the roadmap built from the object roadmap and the thin line with square nodes are the result of the diffusion. We adopted a diffusion method with self parameter-tuning [START_REF] Ferre | An iterative diffusion algorithm for part disassembly[END_REF]. In this figure, roadmaps for different grasping positions PlanManipulation(q start obj , q goal obj ) 1: G i manip ← ∅, G reg ← ∅ n 2: // Set of start and goal nodes: S start and S goal 3: S start ← ∅, S goal ← ∅ 4: // Add start and goal nodes to the roadmaps 5: for i-th grasping position r i grasp do 6:

q start rob ← CalcRobConfigFromObj(q start obj , r i grasp )

7:

q goal rob ← CalcRobConfigFromObj(q goal obj , r i grasp )

8:

AddNode(G i manip , q start rob ), AddNode(G i manip , q goal rob )

9:

AddNode(G reg , q start rob ), AddNode(G reg , q goal rob )

10:

AddNodeSet(S start , q goal rob ), AddNodeSet(S goal , q goal rob ) 11: end for 12: // Search with the object roadmap G obj 13: Path P ← ∅ 14: for all node q obj in G obj do q obj ← RandomObjConfig() 23:

q near obj ← NearestNode(q random obj , G obj ) 24:
q new obj ← Extend(q near obj , )

P ← PlanWithObjectConfig(q new obj , S start , S goal )

if P = ∅ then 27:

Return solution path P 28:

end if 29: end for PlanWithObjectConfig(q obj , S start , S goal ) 1: for i-th grasping position r i grasp do 2:

q i rob ← CalcRobConfigFromObj(q obj , r i grasp )

3:

if q i rob is collision-free then 4:

AddNodeAndLink(G i manip , q i rob )

AddNodeAndLink(G reg , q i rob )

6:

return FindPath(S start , S goal , ({ i G i manip }∩G reg ))

7:

end if 8: end for are merged. We can observe that the rough coverage from the object roadmap serves as a guide for diffusion process to find a path including regrasping.

In this framework, any local steering method that connects two configurations can be used. As mentioned earlier, we apply Reeds and Shepp curves for the object trajectory. To allow the robot to move freely to change the grasping configuration, we employ a method combining a smooth carlike robot path for forward walking and linear interpolation for sideways or backward walking in short distances.

V. IMPLEMENTATION ISSUES

We have implemented the proposed method in a shared software development called humanoid path planner (HPP) [START_REF] Yoshida | Give me the Purple Ball --he said to HRP-2 N.14[END_REF], based on a motion planning library KineoWorks TM [START_REF] Laumond | Kineo CAM: a success story of motion planning algorithms[END_REF]. In this framework, the software components are developed in a modular manner for the sake of reusability and easy maintenance. Thanks to the object-oriented modular architecture and common interface definitions, the developers can implement the components necessary for their own planning problem by using inherited classes of various basic libraries of motion planning.

In this research we have implemented a planning system for the proposed method of whole-body pivoting motion as shown in Fig. 9. The planner interacts with basic functions such as roadmap builders, path optimizers and collision checkers. We also implemented the steering methods specific to the pivoting planning problem.

We have developed such local steering methods as Reeds and Shepp curves for pivoting basic path, pivoting sequence generation, and path planner for free walking. We also implemented the visibility PRM builder and the multiplexed roadmap builder with combined structure of the humanoid and the object. The generalized inverse kinematics (IK) module [START_REF] Yoshida | Task-driven Support Polygon Reshaping for Humanoids[END_REF] takes care of the dynamic and stable whole-body motion including the coordinated hands and legs motions.

VI. SIMULATION RESULTS

The proposed method has been verified to an environment including obstacles with narrow areas. The humanoid robot HRP-2 [START_REF] Kaneko | The Humanoid Robot HRP-2[END_REF] should carry a box-share object from the initial position (Fig. 10a) to its goal (Fig. 10h). First, the basic path for pivoting is planned by using the proposed method. As the resulting collision-free regrasping path is not always optimal, a path optimizer has been applied to remove redundant path components. It is then transformed to a pivoting sequence of the box and finally to the whole-body motion. The humanoid robot displaces the object at the entry of a narrow passage (Fig. 10b,c). Then it releases the object and walk to the other side of the wall (Fig. 10d). By combining backward and forward manipulation, the humanoid goes to another narrow passage (Fig. 10e,f). After another regrasping, the object is carried to the goal position (Fig. 10g,h).

The proposed method needs improvements to find a good mixture between the Visibility PRM and the diffusion algorithm. When the exploration by PRM is insufficient, the diffusion planner takes more search time. Moreover, in our example with many narrow passages, nonholonomic constraints make it difficult to connect the valid configurations. As a result, the average computation time for the example was 263.7sec by a PC with 2.16 GHz Intel Centrino Duo CPU and 2GB memory. The failure ratio was 10 %, mainly due to the difficulty in identification of critical configurations of the object and the robot that has nonholonomic constraints.

From a theoretical point of view, the proposed multiplexing method inherits the probabilistic completeness of the PRM and the diffusion algorithms (as in [START_REF] Simeon | Manipulation planning with probabilistic roadmaps[END_REF]).

VII. CONCLUSIONS

In this paper we have presented a method for regrasp planning for manipulation of a humanoid robot. To address this complex planning problem including manipulation and regrasping, we benefit from well-developed randomized sampling-based motion planning method. First, Visibility PRM is utilized as a preprocessing to capture the critical configurations and then roadmap multiplexing has been introduced. Manipulation roadmaps are built for each of different grasping positions whereas a regrasping roadmap interconnects them to allow the robot to change the grasping position. The set of those roadmaps are explored to find a path including regrasping that is finally transformed into a whole-body motion. A simulation result has demonstrated the validity of the proposed method.

Future work includes extension of the method to integrate different types of manipulation (lifting, pushing, etc) to reinforce the capacity of manipulation, and also improvement of the roadmap search for efficient planning. Reactive regrasp planning using sensor data to implement the proposed method with real hardware is another aspect of future development.

Fig. 1 .

 1 Fig. 1. An experiment of whole-body pivoting manipulation.

Fig. 2 .Fig. 3 .

 23 Fig. 2. Supporting edge. The pivoting sequence is planned using rotation of the endpoints of this edge.

Fig. 4 .

 4 Fig. 4. Preprocessing of Visibility roadmap for object to identify critical configurations with the robot.

Fig. 6 .

 6 Fig. 6. Roadmap multiplexing. Different manipulation roadmaps G 1 manip and G 1 manip are connected by way of the regrasping roadmap Greg.

15 :P

 15 ← PlanWithObjectConfig(q obj , S start , S goal ) 16: if P = ∅ then 17: Return solution path P 18: end if 19: end for 20: // Search with diffusion process: cf. [20], [21] 21: for n < Ntry do 22:

Fig. 7 .

 7 Fig. 7. Algorithm for roadmap multiplexing.

Fig. 8 .

 8 Fig. 8. Generated manipulation roadmap by the proposed method. The thick links with circle denote the roadmap derived from the object visibility-based roadmap. The thin links with squares are additional diffused roadmap.

Fig. 9 .

 9 Fig. 9. Software implementation based on humanoid path planner (HPP)

Fig. 10 .

 10 Fig. 10. Simulation result of regrasp planning. Starting from initial position (a), the humanoid robot makes pivoting sequences (b) first puts the object to the entry of passage (c). It leaves the object and walks freely by combining forward and sideways walking (d) to regrasp the object on the other side (e). Then the robot goes towards another narrow passage (f) and make another regrasp sequence (g) to arrive at the goal (h).

ACKNOWLEDGMENTS

This research was partially supported by Japan Society for the Promotion of Science (JSPS) Grant-in-Aid for Scientific Research (B), 18300070, 2006.