M Reverter
email: mirireverter@gmail.com

T H Cribb

S C C Cutmore

R A D Bray

V Parravicini

P Sasal

Did biogeographical processes shape the monogenean community of butterflyfishes in the tropical Indo-west Pacific region?

Keywords: Butterflyfish, Community nestedness, Community turnover, Dactylogyrids, 43 Ectoparasites, Host specificity, Indo-Pacific, Parasite biogeography 44

Geographical distribution of parasite species can provide insights into the evolution and diversity of parasitic communities. Biogeography of marine parasites is poorly known, especially because it requires an understanding of host-parasite interactions, information that is rare, especially over large spatial scales. Here, we have studied the biogeographical patterns of dactylogyrid parasites of chaetodontids, one of the most well-studied fish families, in the tropical Indo-west Pacific region. Dactylogyrid parasites were collected from gills of 34 butterflyfish species (n = 560) at nine localities within an approximate area of 62 million km 2 . Thirteen dactylogyrid species were identified, with richness ranging from 6-12 species at individual localities. Most dactylogyrid communities were dominated by Haliotrema angelopterum or Haliotrema aurigae, for which relative abundance was negatively correlated (ρ = -0.59). Parasite richness and diversity were highest in French Polynesia and the Great Barrier Reef (Australia) and lowest in Palau. Three biogeographic regions were identified based on dactylogyrid dissimilarities: French Polynesia, characterized by the dominance of H. angelopterum, the western Pacific region dominated by H. aurigae, and Ningaloo Reef (Australia), dominated by Euryhaliotrema berenguelae. Structure of host assemblages was the main factor explaining the dissimilarity (turnover and nestedness components of the Bray-Curtis dissimilarity and overall Bray-Curtis dissimilarity) of parasite communities between localities, while environment was only significant in the turnover of parasite communities and overall dissimilarity. Spatial structure of localities explained only 10% of the turnover of parasite communities. The interaction of the three factors (host assemblages, environment and spatial structure), however, explained the highest amounts of variance of the dactylogyrid communities, indicating a strong colinearity between the factors. Our findings show that spatial arrangement of chaetodontid dactylogyrids in the tropical Indo-west Pacific is primarily characterised by the turnover of the main Haliotrema spp., which is mainly explained by the structure of host assemblages.

Introduction

The biogeography of free-living marine taxa (e.g. corals, fish, bacteria) has been the focus of much research in recent decades [START_REF] Tittensor | Global patterns and predictors of marine biodiversity across taxa[END_REF][START_REF] Briggs | A realignment of marine biogeographic provinces with particular reference to fish distributions[END_REF][START_REF] Ghiglione | Pole-to-pole biogeography of surface and deep marine bacterial communities[END_REF]. The mechanisms that underpin their biogeographical patterns are relatively well understood [START_REF] Leprieur | Partitioning global patterns of freshwater fish beta diversity reveals contrasting signatures of past climate changes[END_REF][START_REF] Rombouts | Marine copepod diversity patterns and the metabolic theory of ecology[END_REF][START_REF] Chust | Latitudinal phytoplankton distribution and the neutral theory of biodiversity[END_REF]. In contrast, the biogeography of marine parasites is virtually unknown, especially because evaluating their large-scale distribution implies an understanding of their host-parasite interactions, information that is very rare, especially over large spatial scales [START_REF] Rohde | Ecology and biogeography of marine parasites[END_REF]Poulin et al., 2011b;[START_REF] Cribb | Trematodes of fishes of the Indo-west Pacific: told and untold richness[END_REF].

Parasites are strictly dependent on their hosts for essential resources (nutrients and physical attachment); thus, their geographical distribution, biodiversity and evolutionary history must, in some part, be influenced by that of their hosts (Poulin et al., 2011b). Host-parasite interactions may lead to the development of strict host specificity and subsequently to tight host-parasite coevolution [START_REF] Klein | Seoul virus infection increases aggressive behaviour in male Norway rats[END_REF]. Therefore, the study of the biogeography of parasite communities, coupled with the study of their hosts and parasite specificities, can provide insights into the evolution of parasitic communities and diversity over large spatial scales.

The analysis of beta-diversity, the extent of change in community structure among sites [START_REF] Whittaker | Vegetation of the Siskiyou Mountains, Oregon and California[END_REF], has recently been shown to be a powerful tool in the analysis of biogeographical patterns [START_REF] Leprieur | Partitioning global patterns of freshwater fish beta diversity reveals contrasting signatures of past climate changes[END_REF][START_REF] Baselga | The relationship between species replacement, dissimilarity derived from nestedness, and nestedness[END_REF]. One of the most widely used relationships in biogeography to evaluate beta-diversity is distance decay of similarity, which describes how similarity in community structure varies with increasing distance between localities (McNight et al., 2007;[START_REF] Soininen | The Distance decay of similarity in ecological communities[END_REF][START_REF] Morlon | A general framework for the distance-decay of similarity in ecological communities[END_REF]. Numerous studies have shown that the similarity of parasite communities decreases with increasing distance (e.g. Oliva and Gonzalez, 2005;[START_REF] Pérez-Del-Olmo | Not everything is everywhere: the distance decay of similarity in a marine host-parasite system[END_REF][START_REF] Timi | Host ontogeny and the temporal decay of similarity in parasite communities of marine fish[END_REF]. However, some studies have shown that other parameters such as host phylogenetic distance or environmental conditions may play a more important role in driving similarity of parasite communities than geographical distance [START_REF] Vinarski | Decay of similarity of gamasid mite assemblages parasitic on Palaearctic small mammals: geographic distance, host-species composition or environment[END_REF][START_REF] Thieltges | Salinity gradient shapes distance decay of similarity among parasite communities in three marine fishes[END_REF][START_REF] Warburton | Patterns of parasite community dissimilarity: the significant role of land use and lack of distance-decay in a bat-helminth system[END_REF].

In a recent study, [START_REF] Locke | The decay of parasite community similarity in ring-billed gulls Larus delawarensis and other hosts[END_REF] showed that distance decay depends upon the geographic scale of the study and latitude, being more significant further from the Equator. However, [START_REF] Vignon | Multiscale determinants of parasite abundance: A quantitative hierarchical approach for coral reef fishes[END_REF] found that fish parasite abundances at a global scale were determined by the site sampled, host species and host size. To date, most studies of parasite communities have used either presence/absence or abundance data to analyse variation in the overall similarity in structures of communities (e.g. Jaccard, Sørensen, Bray-Curtis algorithms).

However, recent studies have shown that incidence-based measures of dissimilarities reflect two different components of dissimilarity, namely turnover and nestedness, turnover being the replacement of some species, while nestedness reflects the dissimilarity due to variation in the absence of turnover [START_REF] Baselga | Partitioning the turnover and nestedness components of beta diversity[END_REF][START_REF] Baselga | The relationship between species replacement, dissimilarity derived from nestedness, and nestedness[END_REF]. Disentangling the relative contribution of spatial turnover and nestedness components to the overall dissimilarity among communities is crucial to understand biogeographic patterns, since they can be generated from different underlying processes [START_REF] Williams | Interpreting biogeographical boundaries among Afrotropical birds: spatial patterns in richness gradients and species replacement[END_REF]. For example, spatial turnover patterns may suggest the existence of spatial and historical constraints, whereas nestedness mainly reflects processes related to variation in species richness [START_REF] Baselga | Partitioning the turnover and nestedness components of beta diversity[END_REF].

In terms of biogeographical delineation, one of the best known and most well-studied fish families is the Chaetodontidae (butterflyfishes) [START_REF] Blum | Biogeography of the Chaetodontidae: an analysis of allopatry among closely related species[END_REF][START_REF] Fessler | Molecular phylogenetics of the butterflyfishes (Chaetodontidae): taxonomy and biogeography of a global coral reef fish family[END_REF][START_REF] Kulbicki | Global biogeography of reef fishes: A hierarchical quantitative delineation of regions[END_REF]. Butterflyfishes are a diverse and emblematic family of coral reef fishes, and some butterflyfish species are among the most broadly distributed reef fishes [START_REF] Dibattista | Blinded by the bright: a lack of congruence between colour morphs, phylogeography and taxonomy for a cosmopolitan Indo-Pacific butterflyfish, Chaetodon auriga[END_REF].

Their ecology has been studied extensively [START_REF] Pratchett | Gill monogenean communities (Platyhelminthes, Monogenea, Dactylogyridae) of butterflyfishes from tropical Indo-West Pacific Islands[END_REF] and they are known to harbour a diverse array of parasites [START_REF] Morand | Endoparasite species richness of New Caledonian butterfly fishes: host density and diet matter[END_REF][START_REF] Mcnamara | Monorchiids (Platyhelminthes: Digenea) of chaetodontid fishes (Perciformes): Biogeographical patterns in the tropical Indo-West Pacific[END_REF][START_REF] Mcnamara | Evidence for extensive cryptic speciation in trematodes of butterflyfishes (Chaetodontidae) of the tropical Indo-West Pacific[END_REF][START_REF] Yong | The ghost of[END_REF]. Thus, the Chaetodontidae represent an ideal host group to study spatial distribution and biogeography of parasite species. Butterflyfishes are regularly and reliably parasitized by gill monogeneans belonging to the family Dactylogyridae. Dactylogyrids are the primary monogenean group found on this fish family; a few capsalids are the only other monogeneans known to infect chaetodontids [START_REF] Bullard | Six new host records and an updated list of wild hosts for Neobenedenia melleni (MacCallum) (Monogenea: Capsalidae)[END_REF]. Fifteen dactylogyrid species have been reported from chaetodontids to date [START_REF] Plaisance | Dactylogyrids (Platyhelminthes: Monogenoidea) parasitizing butterfly fishes (Teleostei: Chaetodontidae) from the coral reefs of Palau, Moorea, Wallis, New Caledonia, and Australia: species of Euryhaliotrematoides n. gen. and Aliatrema n[END_REF]Plaisance et al., 2004). In a recent study, we found that prevalence, intensity and taxonomic composition of butterflyfish dactylogyrid communities differed significantly between butterflyfish species (Reverter et al., 2016). However, in contrast to most monogeneans, which are typically reported as having strict (species-specific or oioxenous) specificity, dactylogyrids of chaetodontids display an unusually low specificity, allowing the exploration of their biogeography as a special case. The wide distribution of the hosts and the broad overlap in host specificity of the parasite species means that suitable hosts are available for each dactylogyrid species across much of the tropical Indo-west Pacific region.

This study aims to investigate biogeographical patterns of dactylogyrid parasites of butterflyfishes in the tropical Indo-west Pacific region. We studied the area of distribution, prevalence and intensity of 13 dactylogyrids species from butterflyfishes at nine localities and identified distinct bioregions in the tropical Indo-west Pacific on the basis of dactylogyrid communities. Most parasite community studies consider one host species. Here, we studied 34 host species belonging to the same family, Chaetodontidae, which allows a deeper understanding of the spatial arrangement of dactylogyrids and which factors shape parasite communities. We have evaluated the relative contribution of geographic distance, similarity in host communities and environmental similarities on both components of parasite community dissimilarity, turnover and nestedness, on what it is possibly the largest marine spatial scale to date. The purity of our dataset, which was comprised of only one group of parasites (dactylogyrids), limited other types of variability (e.g. parasite dispersal, longevity, life cycle complexity) that can introduce extra noise into distance decay studies.

Materials and methods

Sampling

Thirty-four species of butterflyfish (n = 560) were examined from eight localities in the Pacific region: Palau, Wallis and Futuna, Lizard Island (Great Barrier Reef (GBR), Australia), and the five archipelagos in French Polynesia (Society Archipelago, Tuamotu Archipelago, Austral Archipelago, Gambier Archipelago and Marquesas Archipelago). Butterflyfish were also sampled from a single locality in the Indian Ocean, Ningaloo Reef on the western Australian coast (Supplementary Table S1).

Adult butterflyfish were spear-fished and killed immediately by cranial pithing, put in individual plastic bags with seawater and transported to a laboratory, where the gills were dissected and fixed in 70% ethanol. Dactylogyrids were removed from the gills using a stereo microscope and mounted on glass slides in Malmberg's ammonium picrate-glycerine.

All dactylogyrid specimens from each individual fish were observed under a compound microscope, and parasite species and numbers were recorded. Dactylogyrid species were identified using the published taxonomic literature (Plaisance et al., 2004;[START_REF] Plaisance | Dactylogyrids (Platyhelminthes: Monogenoidea) parasitizing butterfly fishes (Teleostei: Chaetodontidae) from the coral reefs of Palau, Moorea, Wallis, New Caledonia, and Australia: species of Euryhaliotrematoides n. gen. and Aliatrema n[END_REF][START_REF] Kritsky | Dactylogyrids (Monogenoidea: Polyonchoinea) parasitizing the gills of snappers (Perciformes: Lutjanidae): Revision of Euryhaliotrema with new and previously described species from the Red Sea, Persian Gulf, the eastern and Indo-west Pacific Ocean, and the Gulf of Mexico[END_REF], which is based on the morphological characters of the sclerotised structures of the haptor and reproductive organs. As reported by Reverter et al., (2016), two of the dactylogyrid species encountered are undescribed. These species are identified here as Haliotrema sp. A and Haliotrema sp. B and will be formally characterised elsewhere.

Sampling of hosts was performed in order to be as representative as possible of the butterflyfish community for each of the localities, thus differential sampling of butterflyfish species reflects differences in butterflyfish presence among localities (Supplementary Table S1).

Data analysis

Dactylogyrid prevalence (percentage of parasitized fish) and mean intensity (the number of parasites on parasitized fish) were determined for each dactylogyrid species at each geographic site surveyed during this study. The effect of host size on dactylogyrid prevalence, intensity and taxonomic composition was evaluated in a previous work and it was found non-significant (Reverter et al., 2016). Areas of dactylogyrid distribution were determined using presence-absence of the dactylogyrid species at the nine studied geographic locations. Previous records found in the literature [START_REF] Yamaguti | Monogenetic Trematodes of Hawaiian Fishes[END_REF][START_REF] Dyer | Monogeneans from marine fishes of Okinawa, Japan[END_REF]Zhang et al., 2001;Plaisance et al., 2004;[START_REF] Plaisance | Dactylogyrids (Platyhelminthes: Monogenoidea) parasitizing butterfly fishes (Teleostei: Chaetodontidae) from the coral reefs of Palau, Moorea, Wallis, New Caledonia, and Australia: species of Euryhaliotrematoides n. gen. and Aliatrema n[END_REF] were also taken into account only for the distribution, in order not to limit the area of distribution to our sampling sites. Pearson correlation was used to test correlations between dactylogyrid species prevalences.

The relative abundance of dactylogyrid species (contribution of a dactylogyrid species to the overall dactylogyrid community expressed as a percentage) and the weighted parasite intensity were calculated for each site. The weighted parasite intensity at each geographic site (Iw site ) was computed in order to correct for the effect of differential parasite intensities from different butterflyfish species sampled at different geographic locations (Reverter et al., 2016). Weighted parasite (Iw) intensity was calculated according to the following equation:

where Isp site is the mean parasite intensity of a fish species (sp 1,2,x ) at one geographic site, Isp is the global mean parasite intensity of that fish species and n° sp site is the number of fish species sampled at that geographic site.

Parasite diversity at each geographic site was computed using the Shannon diversity index (H) and parasite richness was also determined. A hierarchical cluster analysis («hclust » package for R) using the Bray-Curtis distance was used to identify geographic regions with similar monogenean assemblages. The Unweighted Pair Group Method with Arithmetic Mean (UPMGA) agglomerative algorithm was chosen after analysis of the cophenetic correlation coefficients (Pearson correlation between the cophenetic distances calculated on cluster branches and the parasite dissimilarity matrix). The Kelley-Gardner-Sutcliffe (KGS) penalty function was used to define the optimal number of clusters [START_REF] Bottegoni | AClAP, Autonomous hierarchical agglomerative Cluster Analysis based protocol to partition conformational datasets[END_REF].

The function "bray.part" from the package betapart (R Software, www.r-project.org) was used to obtain three distance matrices of the parasite communities at different locations, accounting for the balanced variation (dBC-bal), the abundance gradient (dBC-gra) components of Bray-Curtis dissimilarity, and the sum of both values (Bray-Curtis dissimilarity, dBC) [START_REF] Baselga | Separating the two components of abundance-based dissimilarity: balanced changes in abundance vs. abundance gradients[END_REF]. These are an extension of the turnover and nestedness concepts to the case of an abundance matrix instead of a presence/absence matrix.

We used redundancy analysis (RDA) with variation partitioning [START_REF] Borcard | Partialling out the spatial component of ecological variation[END_REF] in order to assess the relative contribution of environmental conditions, spatial structure and the structure of hosts assemblages in explaining the dissimilarity in parasite communities among locations (dBC-gra and dBC-bal). Environmental conditions of our locations were characterised according to chlorophyll concentration, cloud cover, photosynthetically available radiation, dissolved oxygen, nitrate concentration, phosphate concentration, silicate concentration, salinity and sea surface temperature, extracted from the Bio-Oracle database [START_REF] Tyberghein | Bio-ORACLE: a global environmental dataset for marine species distribution modelling[END_REF], a global database successfully employed in various biogeographical applications [START_REF] Parravicini | Global patterns and predictors of tropical reef fish species richness[END_REF][START_REF] Parravicini | Niche shift can impair the ability to predict invasion risk in the marine realm: an illustration using Mediterranean fish invaders[END_REF]. Linear geographic distances between pairs of geographic locations were obtained from the Latitude/Longitude Distance Calculator of the National Hurricane Center from the National Oceanic and Atmospheric Administration (http://www.nhc.noaa.gov/gccalc.shtml). In order to characterise the spatial structure of the locations, we generated a set of multiscale principal coordinates of neighbour matrices (PCNM) from the geographic distance matrix [START_REF] Dray | Spatial modelling: a comprehensive framework for principal coordinate analysis of neighbour matrices (PCNM)[END_REF].

PCNM eigenfunctions consist of the spectral decomposition of the spatial relationships among locations. The structures of the host assemblages at our locations were assessed according to a Bray-Curtis dissimilarity matrix on species abundance at each location. The procedure involved the partitioning of the global variation into distinct components: a pure environmental component, a pure spatial component, a pure host assemblage component, their interaction and the residual component. First, forward selection was used for each set of variables separately in order to select only those variables that explained a significant proportion of the variation (P < 0.05, after 999 random permutations). The retained variables were then used in the variation partitioning using adjusted-R 2 values that correct for the variation jointly explained by multiple variables [START_REF] Peres-Neto | Variation partitioning of species data matrices: estimation and comparison of fractions[END_REF]. Prior to the analysis, dissimilarity matrices were transformed into data frames by conducting a principal coordinate analysis according to [START_REF] Legendre | Distance-based redundancy analysis: testing multispecies responses in multifactorial ecological experiments[END_REF].

Results

Dactylogyrid area of distribution

Thirteen dactylogyrid species were detected infecting the 34 species of chaetodontids examined (Supplementary Table S2). Overwhelmingly the dactylogyrid species were found to be widely distributed throughout the tropical Indo-west Pacific region, from Ningaloo Reef in the Indian Ocean to the most easterly Polynesian archipelago, the Gambiers (Fig. 1). Six species were found at all nine locations explored by us, and a further four were found at six or more sites (Fig. 1, Supplementary Fig. S1). Three species were each found at only two localities. Haliotrema sp. A and Haliotrema sp. B were both found at Lizard Island and French Polynesia (Australs and Tuamotus, respectively). Haliotrema scyphovagina [START_REF] Yamaguti | Monogenetic Trematodes of Hawaiian Fishes[END_REF] was found only at the Tuamotus, having been originally described from Hawaii [START_REF] Yamaguti | Monogenetic Trematodes of Hawaiian Fishes[END_REF]) (Supplementary Table S2).

Although the dactylogyrid species were generally widespread, their prevalences and intensities varied strikingly between host species and locations. Between them, Haliotrema angelopterum Plaisance, Bouamer and Morand 2004 and Haliotrema aurigae Plaisance, Bouamer and Morand 2004 comprised 55.2% of all individual dactylogyrids counted. In contrast, the combination of the seven least abundant species comprised just 4.2% of all individuals (Supplementary Table S2). Euryhaliotrema pirulum [START_REF] Plaisance | Dactylogyrids (Platyhelminthes: Monogenoidea) parasitizing butterfly fishes (Teleostei: Chaetodontidae) from the coral reefs of Palau, Moorea, Wallis, New Caledonia, and Australia: species of Euryhaliotrematoides n. gen. and Aliatrema n[END_REF] was especially striking in terms of low abundance, being represented by single specimens at four localities, and just two, five and 15 at the other three localities for which counts were available (Supplementary Table S2). In terms of contrasts for individual species (Fig. 1), H. angelopterum had its highest prevalences and abundances in French Polynesia (all five sites), whereas the highest prevalences of H. aurigae were found at Ningaloo Reef (80%) and Lizard Island (57%). Euryhaliotrema berenguelae [START_REF] Plaisance | Dactylogyrids (Platyhelminthes: Monogenoidea) parasitizing butterfly fishes (Teleostei: Chaetodontidae) from the coral reefs of Palau, Moorea, Wallis, New Caledonia, and Australia: species of Euryhaliotrematoides n. gen. and Aliatrema n[END_REF]) was a relatively rare species at most sites (total prevalence < 15%), however, 73% of fish from Ningaloo Reef were parasitized by this species, often in high numbers (Fig. 1). Euryhaliotrema grandis (Mizelle & Kritsky 1969) was most prevalent in the Tuamotus (48%), but the highest intensities were observed on fish from Ningaloo Reef.

Euryhaliotrema microphallus [START_REF] Yamaguti | Monogenetic Trematodes of Hawaiian Fishes[END_REF]) was most prevalent on fish from Lizard Island (44%), but its greatest mean abundance per fish was observed in the Marquesas (Fig. 1). For Euryhaliotrema triangulovagina [START_REF] Yamaguti | Monogenetic Trematodes of Hawaiian Fishes[END_REF]) the highest prevalence was observed in the Marquesas (40%).

Pearson correlation was used to study the interspecific interactions between the parasite species. Results showed that H. angelopterum is negatively correlated with H. aurigae (-0.59, P value < 0.05) and Euryhaliotrema cribbi [START_REF] Plaisance | Dactylogyrids (Platyhelminthes: Monogenoidea) parasitizing butterfly fishes (Teleostei: Chaetodontidae) from the coral reefs of Palau, Moorea, Wallis, New Caledonia, and Australia: species of Euryhaliotrematoides n. gen. and Aliatrema n[END_REF]) (-0.69, P value < 0.05), and H. aurigae is positively correlated with E. berenguelae (0.79, P value < 0.05) and E. grandis (0.63, P value < 0.05). Euryhaliotrema microphallus is also strongly positively correlated with Euryhaliotrema annulocirrus (0.73) (Fig. 2).

Biogeographic structure of dactylogyrid communities

Weighted intensity, that is, dactylogyrid intensity corrected for the effect of differential host species intensities, showed striking differences among geographic locations. Fish from the Marquesas Archipelago presented the lowest intensity of parasites (Iw Marquesas = 0.57), followed by Palau (Iw Palau = 0.65) and the Gambier Archipelago (Iw Gambiers = 0.67). Fish from the Tuamotu Archipelago had the highest intensity of dactylogyrid parasites (Iw Tuamotu = 1.49) followed by the Society Archipelago (Iw Society = 1.12) and Ningaloo Reef (Iw NR = 1.09) (Fig. 3, Table 1).

Twelve out of the 13 identified dactylogyrid species were found at the Tuamotu Archipelago and Lizard Island, while the Marquesas had the lowest number of dactylogyrid species (n=6) (Table 1). Dactylogyrid diversity (Shannon diversity index (H)) varied between geographic locations (Table 1). The highest diversity was found at Lizard Island (1.96) on the Great Barrier Reef, followed by the Gambier Archipelago (1.74) and the Tuamotus (1.64). The lowest dactylogyrid diversity was observed in the Society Archipelago (1.12), where the community was strongly dominated by H. angelopterum (65%). Palau and the Marquesas also presented notably low dactylogyrid diversity (1.22). Palau dactylogyrid assemblages were dominated mostly by H. aurigae (66%), while H. angelopterum (46%) and E. triangulovagina (36%) were the most abundant parasites in the Marquesas (Table 1, Fig. 3).

A hierarchical cluster analysis identified three distinct biogeographic regions based on dissimilarities among their dactylogyrid communities: the eastern Pacific region containing five sites from French Polynesia; the western Pacific containing Lizard Island, Palau, and Wallis and Futuna; and Ningaloo Reef in the Indian Ocean (Fig. 4). Localities in French Polynesia were united especially by a high abundance of H. angelopterum, whereas those in the western Pacific region exhibited higher abundances of H. aurigae. Ningaloo Reef was distinguished by the high abundance of E. berenguelae (Figs. 3,4).

Factors shaping biogeographic differences in dactylogyrid communities

The structure of host assemblages was identified as the factor that explained the highest variance in dactylogyrid communities among geographic sites (Fig. 5). The pure host assemblage component explained 20% of the balanced variation (dBC-bal, turnover) of the dactylogyrid communities, 21% of the abundance gradient (dBC-gra, nestedness) and 15% of the overall Bray-Curtis dissimilarity of the dactylogyrid communities. The pure environmental component explained 18% of the balanced variation and 4% of the overall Bray-Curtis dissimilarity of the dactylogyrid communities (Fig. 5A,C). The pure spatial component only accounted for 10% of the balanced variation of the dactylogyrid communities (Fig. 5A). However, most of the variation was explained by the interaction between the three components (spatial structure, environment and host assemblages), which explained 42% of the balanced variation, 38% of the abundance gradient and 16% of the overall Bray-Curtis dissimilarity of the dactylogyrid communities; indicating an interaction between environment and host assemblage sructure (Fig. 5). Finally, a considerable amount of variance remained unexplained by the components that were studied (residual variance) (Fig. 5).

Discussion

Most dactylogyrid species from butterflyfishes were broadly distributed throughout the study locations in the tropical Indo-west Pacific region. There were three exceptions, Haliotrema sp. A and sp. B. and H. scyphovagina. Haliotrema sp. A and sp. B were both found at Lizard Island on the GBR and at single, separate sites within French Polynesia. Given that both species were relatively rare (just 0.8% and 0.4% of all dactylogyrids collected, respectively), it seems likely, or at least plausible, that these species were simply missed at other sites between the GBR and French Polynesia. In contrast, H. scyphovagina was found only at the Tuamotus in French Polynesia, having been described originally from Hawaii by [START_REF] Yamaguti | Monogenetic Trematodes of Hawaiian Fishes[END_REF]. In Hawaii the species has been reported from Chaetodon miliaris Quoy and Gaimard, 1825 and Chaetodon multicinctus Garrett, 1863, whereas in the Tuamotus it was only found on Chaetodon unimaculatus Bloch, 1787, and Chaetodon vagabundus Linnaeus, 1758, two species sampled at the other locations in this study. Thus, it seems at least possible that this species is restricted to Hawaii and parts of French Polynesia. Overall, however, the broad distributions reported here suggest that, despite the possible distinct origins and evolutionary ages of the dactylogyrid species as proposed by Plaisance et al., (2007), these species share similar dispersal strategies that enable similar geographic ranges.

The Coral Triangle, which encompasses the Philippines, Indonesia and New Guinea, is the area of highest marine biodiversity in the world, with marine richness decreasing radially from it [START_REF] Bellwood | Regional-scale assembly rules and biodiversity of coral reefs[END_REF][START_REF] Carpenter | The center of the center of marine shore fish biodiversity: the Philippine Islands[END_REF]. For example, richness of shore fishes declines from 1693 at the centre of the Coral Triangle in the Philippines to 1579 in the main island of New Caledonia, to 702 fish species in the Society Archipelago and just 245 fish species in the Gambier Archipelago [START_REF] Kulbicki | Biogeography of reef fishes of the French Territories in the South Pacific[END_REF]. Changes in biodiversity of parasitic organisms, with increasing distance from the Coral Triangle, have been much less studied. A few studies have shown that some heteroxenous helminths follow the same trend as free-living species, showing a west-to-east reduction in diversity in the Pacific region (e.g. [START_REF] Rigby | Patterns of species diversity in the gastrointestinal helminths of a coral reef fish, Epinephelus merra (Serranidae), from French Polynesia and the South Pacific Ocean[END_REF][START_REF] Mcnamara | Monorchiids (Platyhelminthes: Digenea) of chaetodontid fishes (Perciformes): Biogeographical patterns in the tropical Indo-West Pacific[END_REF][START_REF] Cribb | Biogeography of tropical Indo-West Pacific parasites: a cryptic species of Transversotrema and evidence for rarity of Transversotrematidae (Trematoda) in French Polynesia[END_REF]. In contrast, previous studies on butterflyfish dactylogyrids suggested that their greatest richness is actually in French Polynesia and that there is an east-to-west reduction towards the GBR (Plaisance et al., 2004, Plaisance and[START_REF] Plaisance | Dactylogyrids (Platyhelminthes: Monogenoidea) parasitizing butterfly fishes (Teleostei: Chaetodontidae) from the coral reefs of Palau, Moorea, Wallis, New Caledonia, and Australia: species of Euryhaliotrematoides n. gen. and Aliatrema n[END_REF]. However, our study does not support that finding; we discovered equal parasite richness and diversity in French Polynesia and the GBR. The lowest parasite richness, in the Marquesas Archipelago, is potentially explained by the isolation of this archipelago coupled with the absence of lagoons and the very low coral cover there. As a result, there are relatively fewer susceptible host species and individuals in the Marquesas than in other nearby archipelagos [START_REF] Kulbicki | Biogeography of reef fishes of the French Territories in the South Pacific[END_REF]. In contrast, the relatively close Tuamotu Archipelago is characterised by enormous lagoons and rich coral growth and is exceedingly rich in dactylogyrids.

Although we have demonstrated that most dactylogyrid species occur in all or nearly all localities, there are clear differences in the structure of the dactylogyrid communities at different localities. The cluster analysis, based on differences in the dactylogyrid communities of butterflyfishes, showed that three distinct biogeographic regions can be recognised: French Polynesia, the western Pacific (Palau, Lizard Island, and Wallis and Futuna) and Ningaloo Reef. Thus, our results show that the two bioregions in the western Pacific region (the southwestern Pacific and French Polynesia), support quantitatively different monogenean assemblages.

The key basis of this difference is that Pacific communities tend to be dominated by two Haliotrema spp. (H. angelopterum and H. aurigae) throughout the whole studied geographical range, but that they are negatively correlated; H. angelopterum was more abundant than H. aurigae in French Polynesia by a factor of three, whereas H. aurigae was nearly five times more abundant than H. angelopterum in the western Pacific region. These data indicate a significant but incomplete species turnover in the dactylogyrid community between French Polynesia and the western Pacific region. The phylogeography of two dactylogyrid parasites from butterflyfishes was studied by [START_REF] Plaisance | Colonization of Pacific islands by parasites of low dispersal ability: phylogeography of two monogenean species parasitizing butterflyfishes in the South Pacific Ocean[END_REF], who found clear genetic differentiation of E. grandis between the population in Moorea (French Polynesia) and all the other populations (western Pacific), but, perhaps surprisingly, no such biogeographical structuring in H. aurigae. They suggested that differentiation of E. grandis could have been driven by isolation of French Polynesia during Pleistocene sea-level fluctuation. It seems plausible that such fluctuation might have driven the overall differences in the dactylogyrid communities between the eastern and western Pacific regions. [START_REF] Macpherson | Biogeography of the deep-sea galatheid squat lobsters of the Pacific Ocean[END_REF] also found different communities of galatheid squat lobsters between French Polynesia and the rest of the western Pacific region with a high proportion of endemism, suggesting French Polynesia as a centre of diversity.

Our results show, contrary to expectations, that geographic distance between host populations is not the most significant factor in either the turnover or nestedness of the parasite community. Instead, structure of host populations between sites was identified as the main driver responsible for the dissimilarity in parasite communities (turnover, nestedness and overall dissimilarity). Similarly, [START_REF] Locke | Predicting the similarity of parasite communities in freshwater fishes using the phylogeny, ecology and proximity of hosts[END_REF] found that parasite community similarity was mostly associated with host phylogeny while distance decay was mainly a within-host species phenomenon. In a previous study, sympatric butterflyfish species were shown to harbour welldelineated communities of dactylogyrids, and six clusters consisting of chaetodontid species infected by similar dactylogyrid assemblages were identified (Reverter et al., 2016). The two main clusters of butterflyfish species based on similarity of their dactylogyrid parasites were characterized by the dominance of H. aurigae (cluster 1) and H. angelopterum (cluster 2). Most of the species from cluster 1 were found most frequently in the western Pacific region (e.g. Chaetodon baronessa Cuvier, 1829, Chaetodon speculum Cuvier, 1831, Chaetodon semeion Bleeker, 1855, Chaetodon lineolatus Cuvier, 1831) and species from cluster 2 were found most frequently in French Polynesia (e.g. Chaetodon reticulatus Cuvier 1831, Chaetodon trichrous Günther, 1874, Chaetodon ornatissimus Cuvier 1831) (Reverter et al., 2016). Plaisance et al. (2007) found that H. aurigae showed little biogeographical genetic structure in the tropical Indo-west Pacific region, suggesting its recent evolutionary age compared with other dactylogyrid species. Haliotrema aurigae and H. angelopterum are phylogenetically close [START_REF] Plaisance | Molecular phylogeny of gill monogeneans (Platyhelminthes, Monogenea, Dactylogyridae) and colonization of Indo-West Pacific butterflyfish hosts (Perciformes, Chaetodontidae)[END_REF], and we hypothesise that H. aurigae and H. angelopterum diverged from a common ancestor during the French Polynesia Pleistocene isolation from the western Pacific region, and that these past biogeographical processes might have shaped the observed parasite specificity among the different butterflyfish species. It is noteworthy that H. aurigae and H. angelopterum are also among the biggest species of dactylogyrid parasites found on butterflyfishes (Plaisance et al., 2004); their size may thus be important as a basis of their numerical dominance on individual fishes.

Recent studies have shown that environmental factors such as salinity and temperature are important in driving the compositions of parasite communities [START_REF] Thieltges | Salinity gradient shapes distance decay of similarity among parasite communities in three marine fishes[END_REF]Poulin et al., 2011a;[START_REF] Blasco-Costa | Biogeography of parasitism in freshwater fish: spatial patterns in hot spots of infection[END_REF]. For example, [START_REF] Campiao | The effect of local environmental variables on the helminth parasite communities of the pointedbelly frog Leptodactylus podicipinus from ponds in the Pantanal wetlands[END_REF] found that change in parasite composition of the frog Leptodactylus podicipinus Cope, 1862, was mainly related to variation in environmental conditions rather than to species distribution. [START_REF] Warburton | Patterns of parasite community dissimilarity: the significant role of land use and lack of distance-decay in a bat-helminth system[END_REF] also observed that environmental variables, rather than spatial variables, explained variation in helminth community similarities of big brown bats (Eptesicus fuscus, Palisot de Beauvois 1796). In our study, the environment was a significant factor in the turnover and overall dissimilarity of dactylogyrid communities. Since chaetodontid larvae, the only planktonic phase of butterflyfishes, are not parasitized by monogenean parasites [START_REF] Peyrusse | Parasite acquisition by larval coral-reef fishes[END_REF] and dactylogyrid oncomiracidia live only a few hours without a host [START_REF] Whittington | Reproduction and host-location among the parasitic Platyhelminthes[END_REF], it has been proposed that dactylogyrid dispersal takes place through the passive dispersion of their eggs by oceanic currents (Ganicott and Tinsley, 1998;[START_REF] Plaisance | Colonization of Pacific islands by parasites of low dispersal ability: phylogeography of two monogenean species parasitizing butterflyfishes in the South Pacific Ocean[END_REF]. Previous studies have shown that monogenean egg hatching and larval infection processes are highly dependent on environmental parameters such as water temperature [START_REF] Cecchini | Influence of temperature on the life cycle of Diplectanum aequans (Monogenea, Diplectanidae), parasitic on sea bass, Dicentrarchus labrax (L.)[END_REF][START_REF] Pietrock | Free-living endohelminth stages: at the mercy of environmental conditions[END_REF][START_REF] Tubbs | Effects of temperature on fecundity in vitro, egg hatching and reproductive development of Benedenia seriolae and Zeuxapta seriolae (Monogenea) parasitic on yellowtail kingfish Seriola lalandi[END_REF]. Our results are thus consistent with the idea that environmental parameters can affect the turnover of parasite species, suggesting the importance of suitable environmental conditions for larval development, egg hatching, and successful infection of fishes.

Interestingly, the interaction of the three factors studied (host assemblage, environment and spatial structure) explained an important part of the parasite dissimilarity, indicating a strong colinearity between them. This finding may indicate that both host assemblage and environment dissimilarity are important factors underlying the commonly observed distance decay. Finally, a significant amount of variance remained unexplained by the study of these three factors, suggesting that other factors (e.g. host phylogeny) might affect parasite dissimilarity.

We have observed two main biogeographic regions in the Pacific Ocean that can be differentiated mainly by a partial turnover in two species of Haliotrema. To the best of our knowledge, this is the first study on the biogeography of parasite communities that distinguishes between the balanced variation (turnover) and abundance gradient (nestedness) components of dissimilarity. Differences between chaetodontid assemblages are the main factor influencing parasite community turnover. Coupled with the results from previous work (Reverter et al. 2016), this finding suggests that biogeographical processes shaped parasite specificity through a tight but not species-specific host-parasite coevolutionary process. Environmental dissimilarity is also identified as an important factor explaining the turnover of dactylogyrid communities, indicating the importance of favourable environmental conditions for dactylogyrid egg hatching and successful host infection.

This study dramatically increases knowledge of communities of dactylogyrid monogeneans of butterflyfishes and their distribution in the tropical Indo-west Pacific region. However, more study is needed to determine the complete distribution of these parasite species, which might include other oceans (e.g. E. annulocirrus has been recorded in the Red Sea) [START_REF] Paperna | Monogenea of Red Sea fishes: III. Dactylogyridae from littoral and reef fishes[END_REF]. The Indian Ocean in general remains poorly studied for ectoparasites and much could be learned from focused surveys in this region. Butterflyfishes are well known for their propensity to hybridize [START_REF] Montanari | Does genetic distance between parental species influence outcomes of hybridization among coral reef butterflyfishes?[END_REF]. The study of dactylogyrid communities of hybrids and closely related sister species from the Indian Ocean might also provide further insight into the biogeography and evolutionary history of dactylogyrids. Similarly, the integrated study of the biogeography of direct cycle parasites (monogeneans) and complex cycle parasites (digeneans) might provide new insight into the biogeography of coral reef parasites.  Three biogeographic regions were identified based on dactylogyrid dissimilarities.

 The two main Haliotrema species were negatively correlated.

 Structure of hosts' assemblage was the main factor explaining parasite dissimilarity.

  parasites past: eggs of the blood fluke Cardicola chaetodontis (Aporocotylidae) trapped in the heart and gills of butterflyfishes (Perciformes: Chaetodontidae) of the Great Barrier Reef. Parasitology 140, 1186-1194. Zhang, J., Yang, T., Liu, L.,, 2001. Monogeneans of Chinese Marine Fishes. Agriculture Press, Beijing, People's Republic of China.

Fig. 1 .

 1 Fig. 1. Areas of distribution (blue shadow), prevalence (circle colour) and abundance (mean

Fig. 2 .

 2 Fig. 2. Correlation matrix between dactylogyrid species (Pearson correlation) of the tropical Indo-

Fig. 3 .

 3 Fig. 3. Structure of dactylogyrid communities at nine locations in the tropical Indo-west Pacific

Fig. 4 .

 4 Fig. 4. Cluster analysis of the dissimilarities in parasite communities (Bray-Curtis distance,

  Figure 1



  Figure 3

Table 1 .

 1 Dactylogyrid diversity index (Shannon index (H)), richness, intensity and weighted intensity at nine geographic locations in the tropical Indo-west Pacific region. Indian Ocean, off the western Australian coast.

	Site	Richness	Shannon index (H)	Intensity	Weighted intensity
	Society a,b Palau a Marquesas a,b Australs a,b Ningaloo Reef c	9 8 6 11 7	1.12 1.22 1.22 1.24 1.25	111.3 24.4 60.7 79.8 132.4	1.12 0.65 0.57 0.99 1.09
	Wallis and Futuna a Tuamotus a,b Gambiers a,b Lizard Island a	6 12 9 12	1.45 1.65 1.74 1.96	19.7 126.5 26.5 56.5	0.90 1.49 0.67 0.86

a Pacific location. b Archipelago in French Polynesia. c

Acknowledgements

The authors would like to thank Serge Planes and Matt Nolan for their help in the collection of butterflyfish and the staff from the various field stations where sampling was conducted. We would also like to thank Guillaume Iwankow for his help with the cartography. This work was supported by the labex Corail project (MECANO, Mise en évidence des mécanismes chimiques et biochimiques permettant aux poissons de lutter contre les parasites à cycle direct, France). This research is part of an Ecole Pratique des Hautes Etudes (EPHE, France) PhD thesis supported by a labex "Corail" doctoral grant awarded to Miriam Reverter.


Pr. Mohamed Lakhdar X Sahli
email: mohamed.sahli@femto-st.fr

M Roizard

G Assoul

S Colas

J P Giampiccolo

Barbe

X Roizard

M Assoul

G Colas

S Giampiccolo

J P Barbe

the effect of clearance on the forming quality in the fine blanking process

Keywords: Metal blanking, plasticity, numerical simulation, steel sheet Metal blanking, plasticity, numerical simulation, steel sheet

Finite element simulation and experimental investigation of

Introduction

The fine blanking is a forming process characterized by effective precision. It is playing an increasingly important role in the industry [START_REF] Rafsanjani | Investigation of the viscous and thermal effects on ductile fracture in sheet metal blanking process[END_REF][START_REF] Cao | Flange forming with combined blanking and extrusion process on sheet metals by FEM and experiments[END_REF][START_REF] Liu | Finite Element Simulation of Effect of Part Shape on Forming Quality in Fine-blanking Process[END_REF][START_REF] Yu | Ductile fracture modeling of initiation and propagation in sheet-metal blanking processes[END_REF]. The parts with a smooth cutting surface can be obtained using this process type [START_REF] Shim | Investigation on blanking of thin sheet metal using the ductile fracture criterion and its experimental verification[END_REF][START_REF] Hou | Effect of technological parameters on microstructure and accuracy of B1500HS steel parts in the hot blanking[END_REF]. This process is often used to mass-produce metal components used for industries such as aerospace and automotive. The fine blanking process consists in separating a blank from a sheet by means of a high-localized shear deformation due to the action of a punch (Fig. 1a). The quality of sheared edge after blanking process depends not only on the material used, but also many process parameters such as the blank holding force, the sharpness of the edge of punch and die, blanking speed, lubrification, temperature and clearance between the punch and the die [START_REF] Hatanaka | Simulation of Sheared Edge Formation Process in Blanking of Sheet Metals[END_REF][START_REF] Penalva | Effect of tool wear on roughness in hard turning[END_REF].

Numerical simulations offer an efficient way not only to save manufacturing costs and to speed up production, but essentially to predict the final quality of the edge profile of the pieces with adequate precision. However, for a realistic modelisation of the fine blanking process, the identification of the laws of behaviour adapted according to the deformation generated, the strain rate imposed, the temperature produced and the final behaviour to the damage is essential.

Several numerical studies were conducted to understand the effect of process parameters on the geometry of the blanked edge including burr, fracture zone, shear surface and rollover. [START_REF] Faura | Finite element analysis of optimum clearance in the blanking process[END_REF], tried to determine optimum clearance by presenting crack propagation angles throughout the sheared edge [START_REF] Faura | Finite element analysis of optimum clearance in the blanking process[END_REF]. [START_REF] Fang | Finite element simulation of the effect of clearance on the forming quality in blanking process[END_REF] examined the forming quality of the blanking process and concluded substantial effect of punch/die clearance on the shape of the blanked edge [START_REF] Fang | Finite element simulation of the effect of clearance on the forming quality in blanking process[END_REF]. Hambli et al, (2001) studied the same concept and also integrated neural networks to predict burr heights and to optimize the blanking process [START_REF] Hambli | Finite element model fracture prediction during sheet-metal blanking process[END_REF]. [START_REF] Husson | Finite element analysis simulations of thin copper sheets blanking: study of blanking parameters on shear ededge quality[END_REF] found that the quality of the sheared edges is lower for greater punch/die clearances and/or tool wear [START_REF] Husson | Finite element analysis simulations of thin copper sheets blanking: study of blanking parameters on shear ededge quality[END_REF]. As shown by [START_REF] Bratus | Determination of optimal cutting edge geometry on a stamped orthotropic circular electrical steel sheet[END_REF], optimisation of the punch shape and clearance leads to a better geometrical accuracy of the blanked part [START_REF] Bratus | Determination of optimal cutting edge geometry on a stamped orthotropic circular electrical steel sheet[END_REF].

Morever, [START_REF] Uemori | Simulation of Springback in V-bending Process by Elasto-Plastic Finite Element Method with Consideration of Bauschinger Effect[END_REF] examined the linear kinematic hardening and it is concluded that the results of simulation in combined model is very similar to reality [START_REF] Uemori | Simulation of Springback in V-bending Process by Elasto-Plastic Finite Element Method with Consideration of Bauschinger Effect[END_REF]. [START_REF] Liu | Eliminating springback error in U-shaped part forming by variable blankholder force[END_REF] were minimized the percentage of elastic return by varying the holding load imposed on the blank support [START_REF] Liu | Eliminating springback error in U-shaped part forming by variable blankholder force[END_REF]. [START_REF] Padmanabhan | Influence of draw restraining force on the springback in advanced high strength steels[END_REF] analyzed the effect of the return load applied to the metal sheet on the elastic return. They observed that increasing the applied force can lead to reduce in the elastic return angle [START_REF] Padmanabhan | Influence of draw restraining force on the springback in advanced high strength steels[END_REF]. Huang et al. (2014) were studied the shear-zone length in fine hydromechanical blanking and the effect of the hydraulic pressure in the V-ring cavity. The results indicate the significance of the hydraulic pressure in the V-ring cavity and ejector chamber [START_REF] Huang | Optimal design for the fluid cavity shape in hydromechanical fine blanking[END_REF]. [START_REF] Achouri | Influence of the edge rounding process on the behaviour of blanked parts: numerical predictions with experimental correlation[END_REF] were studied influence of the edge rounding process on the behaviour of blanked parts. It is shown that edge rounding by punching improves the component resistance. The punching results also in work hardening of the material in the rounded zones which results in an increase in the local resistance [START_REF] Achouri | Influence of the edge rounding process on the behaviour of blanked parts: numerical predictions with experimental correlation[END_REF]. Gustafsson and al. (2016) were conducted the experimental study of strain fields during shearing of medium and high-strength steel sheet. They showed that the fracture strain was larger for the medium strength material compared with the high strength material and increased with increasing clearance [START_REF] Gustafsson | Experimental study of strain fields during shearing of medium and high-strength steel sheet[END_REF]. [START_REF] Wang | A novel fine-blanking approach[END_REF] were proposed a novel fine-blanking approach. The burnished surface obtained from this approach can nearly achieve the complete thickness of the blank in one operation, suggesting that the fracture zone can be nearly eliminated [START_REF] Wang | A novel fine-blanking approach[END_REF]. [START_REF] Zheng | Investigation on wear-induced edge passivation of fine-blanking punch[END_REF] were investegated on wear-induced edge passivation of fine-blanking punch. They shows that reducing the length of straight lines and radius of arcs results in a large relative sliding distance of material at the punch edge [START_REF] Zheng | Investigation on wear-induced edge passivation of fine-blanking punch[END_REF].

The aim of this paper is to predict the shear stress and plastic strain distribution in shearing zone during blanking versus punch-die clearance (J) and their effect on the cut edge quality. The results of simulated blanking process were compared with experimental results.

Fig. 1. Schematic of the blanking process and typical defects in the blank′s sheared edge [START_REF] Monteil | In situ punch wear measurement in a blanking tool, by means of thin layer activation[END_REF][START_REF] Falconnet | Prediction of abrasive punch wear in copper alloy thin sheet blanking[END_REF].

Materials and sample preparation

Blanking experiments

The parts were cut in a sheet made of 16MnCr5 with a thickness of 4.6 mm, was a commonly used, raw material quality in blanking process. Table 1 shows the chemical composition and Table 2 shows the associated mechanical properties of metallic materials.

To obtain the hardening parameters, tensile tests were conducted using specimens designed according to standards. The tensile test was performed using a servo-electric Instron machine with a maximum load capacity of 100 kN, an accuracy of the load cell of 0.2% with a resolution of 0.01 N and an accuracy of the displacement cell of 0.06% with a resolution of 0.001 mm. Tensile test setup with online strain measurement unit was shown in Fig. 2. Flat tensile specimens were cuted in such a manner that specimen loading axis lies in the rolling of the sheet or in perpendicular direction. A constant strain rate of 1mm/s was used for conducting the tensile test. All tests were continued until fracture of the sample. The stress-strain curves of samples with different loading angles, i.e. the angle of the loading directions with respect to the rolling and transverse direction, were shown in Fig. 3. Figure 3, the rolling direction develops a preferred crystallographic orientation in the microstructure that results in an higher strength. [START_REF] Kuwabara | Difference in tensile and compressive flow stresses in austenitic stainless steel alloys and its effect on springback behavior[END_REF] investigated the effect of the rolled direction on the spring back. They found that the effect of spring back in the tangential direction of rolling always is less than the perpendicular direction [START_REF] Kuwabara | Difference in tensile and compressive flow stresses in austenitic stainless steel alloys and its effect on springback behavior[END_REF].

In this regard, mechanical properties tend to be lower in the transverse direction which is perpendicular. All of these experimental data was implemented in simulation codes to describe the constitutive model of the steel sheet (see Table 2). All tests were continued until fracture of the sample. Microscopic observations at higher magnification carried out on fractured tensile specimens to reveal the mode of fracture, as shown in Fig. 4. The fracture fully ductile with a dull appearance were observed.

Blanking test description

The blanking tool consists of a moving upper part and a fixed lower part. The upper part was instrumented with a displacement, force and thermals sensors, placed close to the punch. The microstructural analysis was done with a digital microscope from Keyence Co., Ltd., Japan. Microstructural analysis of blanked edges were conducted on a routine basis to assess the edge condition.

Finite Element Model

Finite element analyser Lsdyna/Explicit were employed for the numerical simulation of the finite element model. The lower die and blank holder were considered as rigid bodies and assumed to be non-deformable while the sheet blanking was supposed to be deformable isotropic elasto-plastic material of 4.6 mm thickness. In order to study the effect of deformability or not of the punch on the quality of sheared edge after blanking process, in our simulation, we have taken into account this parameter. The exponential hardening law of sheet blanking was identified using tensile tests. Poisson's ratio was 0.3 and Young's modulus was 210 GPa for all materials. The numerical simulations were carried-out for different values of punching clearance (clearance/sheet thickness). The coulomb friction values fitting equal to 0.1 was used in all contacts.

The blanking workpiece was meshed with with PLANE183 elements with reduced integration. The total number of elements in the workpiece was about 6653 elements with 25 elements through the sheet thickness. Lagrangian-Eulerian (ALE) adaptive meshing technique in Lsdyna/Explicit was employed to avoid element distortion in the large plastic deformation of necking localization in the in-situ tensile tests. The displacement was implemented on the punch and fixed constraint was imposed at the bottom of the die. The axisymetric view of the designed tool and its components were given in Fig. 8.

Table 3 present the data concerning the properties of the components of a physical model, such as the numbers of nodes and finite elements, into which the individual components of the physical model are divided (see Fig. 8).

Numerical results and discussion

A comparison of shear stress distribution between blanking with reduced clearance of 0.01 mm (case 1) and blanking with 10% or 15% clearance (cases 2&3) was shown in Fig. 9. The decrease in clearance limits bending moment acting on the blank due to the lateral displacement between cutting edges. It is also showed the essential influence of clearance on stress values in the shearing zone and consequently on the cut-surface shape. A method in which the metal flow line tilting angle was measured and converted to local shear strain, was used by [START_REF] Wu | Characterization of mechanically sheared edges of dual phase steels[END_REF] to characterise the strain distribution within mechanically sheared edges of dual phase steels [START_REF] Wu | Characterization of mechanically sheared edges of dual phase steels[END_REF].

The plastic strains distribution evolution obtained through FEM in shearing zone during blanking process (case 2) with sheet compression is shown in the Fig. 10. During blanking plasticized zones spreading from the cutting edges of the die and punch, where the plastic deformations initiate, join earlier. Clearance reduction leads to the delay of fracture initiation. All these give smoother cut-surface. As a result, a high quality cut-surface is produced. It should be noted, however, that there is likely to be a minimum clearance limit below which cutting conditions may deteriorate [START_REF] Subramonian | Optimum selection of variable punch-die clearance to improve tool life in blanking non-symmetric shapes[END_REF]. E. Gustafsson and al. (2016) showed that most of the deformation in the sheet during shearing was concentrated to a band between the tools. The strain band was most straight at 0.15h clearance [START_REF] Gustafsson | Experimental study of forces and energies during shearing of steel sheet with angled tools[END_REF]. The blanking clearance can have a great influence upon the surface quality and the shape of the workpiece. For a better understanding of blanking clearance effect on sheared edge different shear ededges, achieved by FE simulations, have been plotted in Fig. 11.

Calculation results showed the essential influence of clearance on strain values in the shearing zone and consequently on the blanking course and cut-surface shape. The decrease in clearance limits bending moment acting on the blank due to the lateral displacement between cutting edges. Bending moment is responsible for the tensile stresses in shearing zone. It is largely due clear that plastic strains are less intensive for the blanking process when an higher clearance. In the literature, it is related that, on the one hand, tool wear therefore can be affects sheared edge, so does blanking clearance. On the other hand, tools with dull edges promote material flow instead of allowing shearing deformation [START_REF] Kwak | Finite element analysis on the effect of die clearance on shear planes in fine blanking[END_REF][START_REF] Samuel | FEM simulations and experimental analysis of parameters of influence in the blanking process[END_REF].

Experimental validation

The comparison on simulation and experiment results of burr height is shown in Fig. 13. The simulation results indicate that shape of blanked product can be predicted. As can be expected in the case of a large clearance, the profile of the workpiece boundary causes a bad quality due to the presence of large rollover and longer fractured zone. This result is in agreement with the literature [START_REF] Samuel | FEM simulations and experimental analysis of parameters of influence in the blanking process[END_REF][START_REF] Zhang | Numerical Study of the Effect of Tool Wear on Burr Formation in Blanking Process[END_REF][33]. The rollover depth is over estimated by our simulations with an approximate error margin of 31%, since the springback phenomena after unloading and tools warming up during the cutting procedure have not been considered. Nevertheless, the predicted sheared edge is a little in agreement with the sheared edge obtained experimentally. To conclude, the presented model predictions are moderately in agreement with the experimental data.

Conclusions

This paper presents numerical simulation of blanking process for coldrolled steel sheet metal. The problem was modeled using axial symmetry in commercial finite element software Lsdyna ® . Data obtained by experimental measurement were used to create adapted elasto-plastic material model for blanking simulation. Based on the results achieved, the following conclusions can be formulated:

• During of numerical simulations of the blanking process was observed elongation in shear surface and simultaneous reduction in fracture zone versus clearance punch/die and also that punch is be considered deformable or not.

• The blanking course and cut-surface shape quality dependent among others of clearance punch/die. Generally, clearance reduction leads to the delay of fracture initiation, and consequently, all these give smoother cut-surface.

• Tools with high blanking clearance it may deteriorate a little sheared edge quality.

• Results from the numerical model correctly agrees with the experimentally obtained results in terms the punched edge profiles. However, the model less specific about the size of each area, Numerical simulation can be used to find optimal parameters for the blanking process and it is also more cost efficient than using physical prototypes. Further work is still required to introduce other effects concerning the behaviour of the rolled metal sheets, such as sheet anisotropy, temperature effect and spring-back effects. This FE model will also extended to investigate the tribological behaviour between a punch with nano-structured surface and a blank under full or severe tribological conditions. Necessary conditions for functionalization surface such as arrangement, coverage, and depth will be experimentally and numerical studied to extend the tool life in precision blanking.

Fig. 2 .

 2 Fig. 2. Experimental setup for tensile testing using servo-electric Instron test.

Fig. 3 .

 3 Fig. 3. Stress-strain relationship of 16MnCr5.

Fig. 4 .

 4 Fig. 4. Optical microscopic structure of necking.

  The instrumented tool was designed to cut a mechanical component from a 4.6 mm thick sheet metal band. The blanking tests were performed on a mechanical press with a speed of 30 strokes/min. For this part, a cycle time of 1.5 s was used, whereby the actual cut requires approximately 0.4 s. The stroke of the punch (Ø) was set so as to obtain a penetration depth of 5.8 mm. Four clearance of parameters have been used of punch/stripper (J1) and punch/die (J2): (J1/J2) equals to (0.1/0.01), (0.1/0.1), (0.3/0.01) and (0.3/0.1).

Fig. 5 .

 5 Fig. 5. Geometry of punch, die, stripper, metal sheet and clearance.

Fig. 6 .

 6 Fig.6. Signals measured during blanking test.

Figure 7

 7 shows macro photograph of sections of a cut-out zone made with the use of a cylindrical punch. It show the presence of different edge zones: rollover, sheared, fracture and burr zones. The magnification of the zone near the shear cut edge illustrates the degree of deformation of the microstructure. The depth of the shear affected zone was approximately 3.6±0.2 mm, which corresponds to more than one half of the sheet metal thickness. According to[START_REF] Dalloz | Effect of shear cutting on ductility of a dual phase steel[END_REF], the depth of a heavily deformed zone is 0.2 mm when shearing a 1.5 mm thick sheet. The effective measurement length of this zone equal to 0.12 mm on 4.6 mm thick sheet. This is in good agreement with the experimental observation[START_REF] Dalloz | Effect of shear cutting on ductility of a dual phase steel[END_REF]. Micro-hardness testing of sheared samples was used by[START_REF] Weaver | A study of edge characteristics of sheared and bent steel plate[END_REF] to study the deformation hardening in this region, and Dalloz et al.(2009) showed that a heavily deformed sub-surface region contains crack initiating voids[START_REF] Dalloz | Effect of shear cutting on ductility of a dual phase steel[END_REF][START_REF] Weaver | A study of edge characteristics of sheared and bent steel plate[END_REF].

Fig. 7 .

 7 Fig. 7. (a) Blanking process of sheet metal: (a) sheet metal with cylindrical hole, and (b) cross-sections of sample.

Fig. 8 .

 8 Fig. 8. Geometry and FE mesh used in the numerical simulations of the blanking process.

Fig. 9 .

 9 Fig. 9. Shear stress distribution in shearing zone (at 73ms).

Fig. 10 .

 10 Fig. 10. Plastic strain distribution vs. times during blanking process (case 2).

Fig. 11 .Fig. 12 .

 1112 Fig.11. Sheared edges predicted by FE simulations for different blanking clearances.

Fig. 13 .

 13 Fig. 13. Characteristic features of sheared edge achieved by optical microscopy analysis and of sheared edge predicted by FE simulations.

Table 1 .

 1 Chemical composition (average), [%].

	Tensile strength Rm	Yield strength R0.2	Young's modulus	Poisson's ratio
	450 MPa	344 MPa	210 GPa	0.3

Table2. Material properties of the 16MnCr5 sheet.

Table 3 .

 3 Juxtaposition of data concerning the components of a physical model.

	N°	Name of the part	Kind of Part	Number of Nodes	Number of Elements
	1	Punch	Rigid or Deformable	1209	1140
	2	Stipper	Deformable	4576	4375
	3	Workpiece	Rigid	616	569
	4	Die	Rigid	616	569
			Total Number : 7017/6653

Acknowledgement

This work has been supported by the EIPHI Graduate School (contract ANR-17-EURE-0002) and the French "Investissements d'Avenir" program, project ISITE-BFC (contract ANR-15-IDEX-0003).

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