Phylogeographic Break Research Articles

Repeated expansions and fragmentations linked to Pleistocene climate changes shaped the genetic structure of a woody climber,Actinidia arguta(Actinidiaceae)

The genetic structure of temperate plants was extremely affected by climate changes during the Pleistocene. In East Asia, however, there are a limited number of phylogeography studies of widely distributed species. Actinidia arguta (Sieb. & Zucc.) Planch. ex Miq. (Actinidiaceae), a widely distributed woody climber, was chosen for this study. Twelve haplotypes were obtained using five chloroplast fragments. No haplotypes were shared on two sides of the Qinling–Dabie mountain ranges, indicating a phylogeographic break. The break was further revealed by analysis of molecular variance, spatial analysis of molecular variance, and ecological niche modelling. The most recent common ancestor of all haplotypes showed that global cooling and aridity of the Asian interior at the Pliocene–Pleistocene boundary may triggered this divergence. Two monophyletic lineages (north and south lineage) were revealed by Bayesian phylogeny and the maximum parsimony network. In the north lineage, mismatch analysis indicated an ancient spatial expansion. Distant distribution of closely related haplotypes indicated subsequent allopatric fragmentation. The widespread haplotype H2 implied another significant range expansion. In the south lineage, a considerable rise in sea level of the East China Sea may have triggered population fragmentation. The nested clade analysis also indicated that expansion and allopatric fragmentation were the main processes shaping the haplotype distributions. So, repeated range expansions and fragmentations have shaped the present genetic structure of A. arguta.

Congruent phylogeographic patterns in a young radiation of live‐bearing marine snakes: Pleistocene vicariance and the conservation implications of cryptic genetic diversity

AbstractAimTo investigate phylogeographic patterns among and within co‐occurring sea snake species from Australia's endemic viviparous Aipysurus lineage, which includes critically endangered species, and evaluate the conservation implications of geographically structured patterns of genetic divergence and diversity.LocationAustralia's tropical shallow water marine environments spanning four regions: Great Barrier Reef (GBR), Gulf of Carpentaria (GoC), Timor Sea (TS) and coastal WA (WAC).MethodsSamples from >550 snakes representing all nine nominal Aipysurus group species were obtained from throughout their known Australian ranges. Coalescent phylogenetic analyses and Bayesian molecular dating of mitochondrial DNA, combined with Bayesian and traditional population genetic analyses of 11 microsatellite loci, were used to evaluate genetic divergence and diversity.ResultsMitochondrial DNA revealed highly congruent phylogeographic breaks among co‐occurring species, largely supported by nuclear microsatellites. For each species, each region was characterized by a unique suite of haplotypes (phylogroups). Divergences between the TS, GoC and/or GBR were invariably shallow and dated as occurring 50,000–130,000 years ago, coinciding with the cyclic Pleistocene emergence of the Torres Strait land bridge. By contrast, sea snakes from coastal WA were consistently highly divergent from other regions and dated as diverging 178,000–526,000 years ago, which was not associated with any known vicariant events.Main ConclusionsPreviously unappreciated highly divergent sea snake lineages in coastal WA potentially represent cryptic species, highlighting this region as a high‐priority area for conservation. The cyclic emergence of the Torres Strait land bridge is consisted with observed divergences between the TS, GoC and/or GBR; however, processes involved in the earlier divergences involving the WAC remain to be determined. The observed strong population genetic structures (as surrogates for dispersal) indicate that sea snakes have limited potential to reverse population declines via replenishment from other sources over time frames relevant to conservation.

Adding loci improves phylogeographic resolution in red mangroves despite increased missing data: comparing microsatellites and RAD-Seq and investigating loci filtering

The widespread adoption of RAD-Seq data in phylogeography means genealogical relationships previously evaluated using relatively few genetic markers can now be addressed with thousands of loci. One challenge, however, is that RAD-Seq generates complete genotypes for only a small subset of loci or individuals. Simulations indicate that loci with missing data can produce biased estimates of key population genetic parameters, although the influence of such biases in empirical studies is not well understood. Here we compare microsatellite data (8 loci) and RAD-Seq data (six datasets ranging from 239 to 25,198 loci) from red mangroves (Rhizophora mangle) in Florida to evaluate how different levels of data filtering influence phylogeographic inferences. For all datasets, we calculated population genetic statistics and evaluated population structure, and for RAD-Seq datasets, we additionally examined population structure using coalescence. We found higher FST using microsatellites, but that RAD-Seq-based estimates approached those based on microsatellites as more loci with more missing data were included. Analyses of RAD-Seq datasets resolved the classic Gulf-Atlantic coastal phylogeographic break, which was not significant in the microsatellite analyses. Applying multiple levels of filtering to RAD-Seq datasets can provide a more complete picture of potential biases in the data and elucidate subtle phylogeographic patterns.

Phylogeography Study of the Siberian Apricot (Prunus sibirica L.) in Northern China Assessed by Chloroplast Microsatellite and DNA Makers.

There is evidence that a band of dry climate separated plants in East Asia into distinct northern and southern groups. However, few studies have focused on the arid belt in this region, especially with regard to plants. We analyzed genetic variation in 22 populations of Siberian apricot (Prunus sibirica L.), a temperate deciduous species distributed in this arid belt, using two chloroplast DNA (cpDNA) sequences, seven chloroplast microsatellite loci (cpSSRs), and 31 nuclear microsatellite loci (nSSRs), to study its phylogeography. Chloroplast data showed the complete fixation of two different genetic groups: the eastern and western groups. Genetic differentiation between the two groups was significant (FST = 0.90925, p < 0.01). This pronounced phylogeographic break was also indicated by nSSR data, but there were disparities regarding individual populations. An asymmetric gene flow via pollen and seeds likely resulted in discordance between the present-day geography of nuclear and chloroplast lineages. There was a distinct boundary between the two large groups, which were fixed for two of the most ancestral chlorotypes. Two populations with the highest chloroplast genetic diversity were located in the Yanshan Mountains and Jinzhou, considered to be the glacial refugia. The split of chloroplasts between the eastern and western groups was estimated to have occurred ~0.1795 Ma, whereas nuclear divergence occurred approximately 13,260 years ago. Linear regression analysis showed that climatic factors (annual precipitation and annual mean temperature) had a significant correlation with mean ancestry value (P < 0.05) indicated that they were potential factors for the formation of the two groups. In addition, this boundary was a contact zone between two groups from different refugia.

Do River Drainage Boundaries Coincide with Phylogeographic Breaks in the Redband Darter?

The Redband Darter, Etheostoma luteovinctum, is a benthic headwater fish species found in the Caney Fork and Stones rivers (Cumberland River) and the Duck and Elk rivers (Tennessee River) of central Tennessee. Phylogenetic analyses of 2601 amplified fragment length polymorphisms (AFLPs) were used to assess the relationships among populations and identified two genetically distinct lineages of Redband Darter. One lineage is comprised of populations in the Duck R., Elk R., Middle Fork Stones R., West Fork Stones R., and Hickory Creek of the Caney Fork River, while the other lineage is confined to the remainder of the known localities in the Cumberland R. drainage. As clades were not restricted to drainage or system boundaries, patterns suggest system and drainage transfers. Additionally, morphological variation was examined among populations using standard meristic data and nuptial male color and pigmentation characteristics. Although some morphological traits varied between the two clades, members were not clearly diagnosable using morphology. Taxonomic recognition is not proposed for the two identified clades; however, each clade should be recognized as an evolutionarily significant unit and regarded as such in future conservation efforts. Furthermore, this study demonstrates the utility of AFLPs to assess genetic variation and phylogenetic relationships for species-level taxonomic or phylogeographic studies.

Pleistocene climatic fluctuations drive isolation and secondary contact in the red diamond rattlesnake (Crotalus ruber) in Baja California

AbstractAimMany studies have investigated the phylogeographic history of species on the Baja California Peninsula, and they often show one or more genetic breaks that are spatially concordant among many taxa. These phylogeographic breaks are commonly attributed to vicariance as a result of geological or climatic changes, followed by secondary contact when barriers are no longer present. We use restriction‐site associated DNA sequence data and a phylogeographic model selection approach to explicitly test the secondary contact hypothesis in the red diamond rattlesnake, Crotalus ruber.LocationBaja California and Southern California.MethodsWe used phylogenetic and population clustering approaches to identify population structure. We then used coalescent methods to simultaneously estimate population parameters and test the fit of phylogeographic models to the data. We used ecological niche models to infer suitable habitat for C. ruber at the Last Glacial Maximum (LGM).ResultsCrotalus ruber is composed of distinct northern and southern populations with a boundary near the town of Loreto in Baja California Sur. A model of isolation followed by secondary contact provides the best fit to the data, with both divergence and contact occurring in the Pleistocene. We also identify a genomic signature of northern range expansion in the northern population, consistent with LGM niche models showing that the northern‐most portion of the range of C. ruber was not suitable habitat during the LGM.Main conclusionsWe provide the first explicitly model‐based test of the secondary contact model in Baja California and show that populations of C. ruber were isolated before coming back into contact near Loreto, a region that shows phylogeographic breaks for other taxa. Given the timing of divergence and contact, we suggest that climatic fluctuations have driven the observed phylogeographic structure observed in C. ruber and that they may have driven similar patterns in other taxa.

Geography and past climate changes have shaped the evolution of a widespread lizard from the Chilean hotspot

The complex orogenic history and structure of Southern South America, coupled with Pleistocene glacial cycles, have generated paleoclimatic and environmental changes that influenced the spatial distribution and genetic composition of natural populations. Despite the increased number of phylogeographic studies in this region and given the frequent idiosyncratic phylogeographic patterns, there is still the need to focus research especially on species that are currently distributed within a wide range of bioclimatic regimes, and that historically have been subject to contrasting scenarios. Liolaemus tenuis is a widely distributed lizard species inhabiting latitudinally in almost 1000km through central and southern Chile. Here we describe the geographical patterns of genetic variation and lineage diversification within L. tenuis, and their association with geography and Pleistocene glaciations, using sequences from one mitochondrial and two nuclear genes, and five microsatellite loci, and covering most of the species distributional range. Our results revealed a high diversity both within and among populations, as well as two phylogeographic breaks, which are consistent with two of the larger rivers of central Chile, the Maipo and Biobío Rivers. Liolaemus tenuis is characterized by several allopatric lineages, especially in its north and central range, which suggest a history of multiple vicariance processes. Conversely, populations found in the southern range, south of the Biobío River, show signatures of recent decreases in effective population sizes, coupled with recent range expansions and secondary contact. Niche “envelope” data are consistent with patterns of genetic variation; both suggest a history of discontinuous areas of relatively stable populations throughout all of the distribution of L. tenuis. These data are also consistent with higher probabilities of habitat suitability north of the Maipo River (ca. 33°S), in both coastal areas and the “Intermediate Depression” between 34° and 37°S, as well as in the southern Coastal Cordillera between the Biobío and Araucanía regions. Interestingly, both molecular and niche envelope modeling data suggest that some populations may have persisted in fragmented refugia in Andean valleys, within the limits of the ice sheet. Finally, our results suggest that several populations of L. tenuis colonized glaciated regions from refugial areas in lowlands and coastal regions, and in the southern distribution, historic migration events would have occurred from refugial areas within the limits of the ice sheet.

Phylogeography of two intertidal seaweeds, Gelidium lingulatum and G. rex (Rhodophyta: Gelidiales), along the South East Pacific: patterns explained by rafting dispersal?

Rafting on floating seaweeds facilitates dispersal of associated organisms, but there is little information on how rafting affects the genetic structure of epiphytic seaweeds. Previous studies indicate a high presence of seaweeds from the genus Gelidium attached to floating bull kelp Durvillaea antarctica (Chamisso) Hariot. Herein, we analyzed the phylogeographic patterns of Gelidium lingulatum (Kutzing 1868) and G. rex (Santelices and Abbott 1985), species that are partially co-distributed along the Chilean coast (28°S–42°S). A total of 319 individuals from G. lingulatum and 179 from G. rex (20 and 11 benthic localities, respectively) were characterized using a mitochondrial marker (COI) and, for a subset, using a chloroplastic marker (rbcL). Gelidium lingulatum had higher genetic diversity, but its genetic structure did not follow a clear geographic pattern, while G. rex had less genetic diversity with a shallow genetic structure and a phylogeographic break coinciding with the phylogeographic discontinuity described for this region (29°S–33°S). In G. lingulatum, no isolation-by-distance was observed, in contrast to G. rex. The phylogeographic pattern of G. lingulatum could be explained mainly by rafting dispersal as an epiphyte of D. antarctica, although other mechanisms cannot be completely ruled out (e.g., human-mediated dispersal). The contrasting pattern observed in G. rex could be attributed to other factors such as intertidal distribution (i.e., G. rex occurs in the lower zone compared to G. lingulatum) or differential efficiency of recruitment after long-distance dispersal. This study indicates that rafting dispersal, in conjunction with the intertidal distribution, can modulate the phylogeographic patterns of seaweeds.

Cryptic genetic divergence in Scolopsis taenioptera (Perciformes: Nemipteridae) in the western Pacific Ocean

We studied the phylogeny, population structure, and demographic history of Scolopsis taenioptera in the western Pacific Ocean. Using the 80 samples collected from four locations, we obtained the nucleotide sequences of mitochondrial cytochrome c oxidase subunit I and cytochrome b genes. We identified two distinct lineages showing a clear phylogeographic break that was possibly due to the Pleistocene sea-level change. One lineage was distributed in Iloilo (Philippines) and the other in Terengganu (Malaysia), Rayong (Thailand), and Ha Long Bay (Vietnam). The Terengganu and Rayong populations showed clear signs of demographic expansion; the Iloilo and Ha Long Bay populations were relatively stable or spatially expanded as geographically subdivided populations.

Phylogeography and Ecological Niche Modeling of the Desert Iguana (Dipsosaurus dorsalis, Baird & Girard 1852) in the Baja California Peninsula.

Understanding the factors that explain the patterns of genetic structure or phylogeographic breaks at an intraspecific level is key to inferring the mechanisms of population differentiation in its early stages. These topics have been well studied in the Baja California region, with vicariance and the dispersal ability of individuals being the prevailing hypothesis for phylogeographic breaks. In this study, we evaluated the phylogeographic patterns in the desert iguana (Dipsosaurus dorsalis), a species with a recent history in the region and spatial variation in life history traits. We analyzed a total of 307 individuals collected throughout 19 localities across the Baja California Peninsula with 15 microsatellite DNA markers. Our data reveal the existence of 3 geographically discrete genetic populations with moderate gene flow and an isolation-by-distance pattern presumably produced by the occurrence of a refugium in the Cape region during the Pleistocene Last Glacial Maximum. Bayesian methods and ecological niche modeling were used to assess the relationship between population genetic structure and present and past climatic preferences of the desert iguana. We found that the present climatic heterogeneity of the Baja California Peninsula has a marked influence on the population genetic structure of the species, suggesting that there are alternative explanations besides vicariance. The information obtained in this study provides data allowing a better understanding of how historical population processes in the Baja California Peninsula can be understood from an ecological perspective.

Cryptic lineages and high population genetic structure in the exploited marine snail Hexaplex trunculus (Gastropoda: Muricidae)

Although the banded murex Hexaplex trunculus (Linnaeus, 1758) has no dispersal stage, it is widely distributed in a relatively broad range of habitats. These features make it a particularly suitable model to reconstruct the history of the fragmentation of its geographical range. We investigated its genetic structure from the eastern Mediterranean to the Atlantic coast, by sequencing a nuclear intron (i29) and a mitochondrial marker (cox1). We found strong genetic differentiation between all population pairs, congruent with the absence of a dispersing larval stage. A deep phylogeographical break separated two parapatric lineages, a western lineage (I) and an eastern one (II). The two lineages were separated by a vicariance event dated to the Pliocene by both markers, analysed independently. They co-occur in southern Italy and in the Siculo-Tunisian straight, where some individuals display recombined genotypes (lineage I for one marker, lineage II for the other), suggesting that introgression occurred in sympatric populations. We were unable to determine whether the vicariance was across the STS or located further east across the Peloponnese Arc, but the presence of lineage I in the northern Adriatic is more parsimoniously explained by a more eastern vicariance. Lineage I displayed a stronger signal of demographic expansion than lineage II, and its expansion was estimated to be more recent. This result, which has been reported in other marine species, suggests less drastic conditions for the eastern (and possibly also the central) Mediterranean benthos than for western populations during past climatic oscillations. The parapatric distribution still observed today suggests that human exploitation of this snail, which dates back to Antiquity, did not result in efficient introductions among basins, although present-day introductions were recently reported in the Bay of Biscay.

A new species of Deltamys Thomas, 1917 (Rodentia: Cricetidae) endemic to the southern Brazilian Araucaria Forest and notes on the expanded phylogeographic scenario of D. kempi

Deltamys is a monotypic sigmodontine rodent from the Pampas of South America. In addition to the formally recognized D. kempi that inhabits lowlands, an undescribed form Deltamys sp. 2n=40 was recently found in the highlands of southeastern Brazil. In the present study, we perform a phylogeographic reassessment of Deltamys and describe a third form of the genus, endemic to the Brazilian Araucaria Forest. We describe this new species based on an integrative analysis, using complete cytochrome b DNA sequences, karyology and morphology. Bayesian tree recovered two allopatric clades (lowlands vs. highlands) and three lineages: (i) the lowland D. kempi, (ii) the highland Deltamys sp. 2n=40, and (iii) Deltamys araucaria sp. n. Deltamys araucaria sp. n. is karyotypically (2n=34) and morphologically distinguishable from D. kempi (2n=37-38), showing a tawnier dorsum/flank pelage, presence of a protostyle, M1 alveolus positioned anteriorly to the posterior margin of the zygomatic plate, and several other distinguishing characteristics. A phylogeographic assessment of D. kempi recovered two haplogroups with significant differences in skull measurements. This phylogeographic break seems to have been shaped by the Patos Lagoon estuarine channel. The diversification in Deltamys might have been triggered by dispersal of older lineages over different altitudinal ranges in the Paraná geological basin.

Genetic differentiation between Mediterranean and Atlantic populations of the common prawn Palaemon serratus (Crustacea: Palaemonidae) reveals uncommon phylogeographic break

The Atlantic–Mediterranean transition zone between the Alborán Sea and the Gulf of Cádiz constitutes the most prominent marine geographic barrier in European waters and includes known phylogeographic breaks such as the Strait of Gibraltar and the Almería-Oran Front. A genetic shift in this area has been previously documented for the European littoral shrimp Palaemon elegans. Here we carried out a phylogeographic analysis with the congeneric and sympatric species Palaemon serratus to test for similar intraspecific genetic differentiation and geographic structure. This littoral prawn is distributed in the Northeastern Atlantic Ocean, the Mediterranean Sea and the Black Sea. We compared DNA sequences from the mitochondrial genes Cox1 and to a lesser extent from 16S rRNA of several Atlantic and Mediterranean populations. Furthermore, sequences from the nuclear gene Enolase were included for corroborating differences between Mediterranean and Atlantic individuals. A pronounced genetic differentiation was detected between the Mediterranean and Atlantic populations, amounting to 10.14% in Cox1 and 2.0% in 16S, indicating the occurrence of two independent evolutionary lineages. Interestingly, specimens from the Atlantic Gulf of Cadiz cluster together with the Mediterranean individuals, indicating that a biogeographic barrier appears to be located west of the Strait of Gibraltar.

Deep Phylogeographic Breaks in Magpie Pica pica Across the Holarctic: Concordance with Bioacoustics and Phenotypes.

We examined sequences of the mitochondrial control region in magpies (Pica pica) from the entire distribution range and found deep genetic splits into four major lineages: (1) group West (Europe-Siberia), (2) group East (southern Far East), (3) P. p. mauritanica (North Africa), and (4) P. p. hudsonia (North America). These lineages show a geographic pattern corresponding to known subspecies or subspecies groups. Genetic variation within the widely-distributed group West is low and neutrality tests supported a recent expansion scenario. The haplotypes from Kamchatka, representing a separated sublineage with clear affinity to the European-Siberian group, are almost identical, implying a recent bottleneck. Group East contained two subclades without clear geographic pattern, presumably due to admixing of populations that had diverged in Pleistocene refuges. The homogeneity of the Kyushu population supports historical reports of introduction of the species from Korea. In contrast, the high variation in the recently established Hokkaido population may reflect an ongoing invasion from several populations of the Far Eastern mainland. Bioacoustic data based on chatter call differentiate groups of subspecies and reflect phylogeographic patterns, i.e., mitochondrial lineages. Furthermore, we report the fast spreading of P. p. jankowskii towards the west along the upper Amur River, and a slower shifting of P. p. leucoptera in the opposite direction thus yielding a new contact zone. Overall, our data support a scenario of divergence in geographic isolation, but the ongoing expansion of distribution ranges may lead to major changes in phylogeographic patterns.

Asymmetrical dispersal and putative isolation-by-distance of an intertidal blenniid across the Atlantic-Mediterranean divide.

Transition zones are of high evolutionary interest because unique patterns of spatial variation are often retained. Here, we investigated the phylogeography of the peacock blenny, Salaria pavo, a small marine intertidal fish that inhabits rocky habitats of the Mediterranean and the adjacent Atlantic Ocean. We screened 170 individuals using mitochondrial and nuclear sequence data from eight locations. Four models of genetic structure were tested: panmixia, isolation-by-distance, secondary contact and phylogeographic break. Results indicated clear asymmetric migration from the Mediterranean to the Atlantic but only marginally supported the isolation-by-distance model. Additionally, the species displays an imprint of demographic expansion compatible with the last glacial maximum. Although the existence of a refugium in the Mediterranean cannot be discarded, the ancestral lineage most likely originated in the Atlantic, where most of the genetic diversity occurs.

Integrative inference of population history in the Ibero-Maghrebian endemic Pleurodeles waltl (Salamandridae)

Inference of population histories from the molecular signatures of past demographic processes is challenging, but recent methodological advances in species distribution models and their integration in time-calibrated phylogeographic studies allow detailed reconstruction of complex biogeographic scenarios. We apply an integrative approach to infer the evolutionary history of the Iberian ribbed newt (Pleurodeles waltl), an Ibero-Maghrebian endemic with populations north and south of the Strait of Gibraltar. We analyzed an extensive multilocus dataset (mitochondrial and nuclear DNA sequences and ten polymorphic microsatellite loci) and found a deep east-west phylogeographic break in Iberian populations dating back to the Plio-Pleistocene. This break is inferred to result from vicariance associated with the formation of the Guadalquivir river basin. In contrast with previous studies, North African populations showed exclusive mtDNA haplotypes, and formed a monophyletic clade within the Eastern Iberian lineage in the mtDNA genealogy. On the other hand, microsatellites failed to recover Moroccan populations as a differentiated genetic cluster. This is interpreted to result from post-divergence gene flow based on the results of IMA2 and Migrate analyses. Thus, Moroccan populations would have originated after overseas dispersal from the Iberian Peninsula in the Pleistocene, with subsequent gene flow in more recent times, implying at least two trans-marine dispersal events. We modeled the distribution of the species and of each lineage, and projected these models back in time to infer climatically favourable areas during the mid-Holocene, the last glacial maximum (LGM) and the last interglacial (LIG), to reconstruct more recent population dynamics. We found minor differences in climatic favourability across lineages, suggesting intraspecific niche conservatism. Genetic diversity was significantly correlated with the intersection of environmental favourability in the LIG and LGM, indicating that populations of P. waltl are genetically more diverse in regions that have remained environmentally favourable through the last glacial cycle, particularly southern Iberia and northern Morocco. This study provides novel insights into the relative roles of geology and climate on the biogeography of a biodiversity hotspot.

Extinction risk or lack of sampling in a threatened species: Genetic structure and environmental suitability of the neotropical frog Pristimantis penelopus (Anura: Craugastoridae)

IUCN Red Lists have been a valuable tool to prioritize conservation plans in endemic neotropical frogs. However, many areas in this region are poorly known in terms of their diversity and endemism. Based on examined museum specimens of the threatened species Pristimantis penelopus we revised its geographic distribution and determined the habitat suitability using niche modeling techniques. Using a mitochondrial fragment of COI gene, we determine the phylogenetic position and the extent of the genetic variation across its distribution in Colombia. We present the first records of P. penelopus for the Cordillera Oriental, the western versant of Cordillera Occidental and the northern portion of the Cauca river basin. Based on the molecular phylogenetic analysis, Pristimantis penelopus belongs to the P. ridens series sensu Padial et al. (2014). The mean of intraspecific genetic variation is 2.1% and the variation among population ranges between 2.3 and 3.5%. The genetic distance between the western populations and the Magdalena Valley populations suggests a potential phylogeographic break in northwestern Antioquia. We expand the realized distribution by 258 kilometers north, 200 km east and 223 km northwest. Based on our results and according to the IUCN criteria we propose a new category for the species and highlight the need to increase the surveys in poorly known regions to better understand the geographic distribution and conservation status of listed species.

Genetic differentiation of European anchovy (Engraulis encrasicolus) along the Moroccan coast reveals a phylogeographic break around the 25th parallel North

ABSTRACTSeven microsatellite markers were used to investigate the population structure of the offshore ecotype of the European anchovy (Engraulis encrasicolus) by comparing 12 marine samples collected off the Moroccan coast with an inshore sample taken as a reference for the lagoonal ecotype. F-statistics, correspondence analysis and Bayesian assignment all concurred to cluster the European anchovy in this region into three groups: (i) one reference lagoonal sample, (ii) samples north of the 25°N latitude and (iii) samples south of it. Moreover, the Bayesian cluster analysis pointed toward the existence of an admixture between the group north of 25°N and the lagoonal ecotype, while this was not detectable with the group south of 25°N. Differential introgression between the two ecotypes could be one of the plausible explanations for the observed genetic structure and reveals the possible existence of a phylogeographic break around the 25th parallel North. Our study illustrates the fact that, for those species that encompass several incompletely isolated ecotypes, the level of gene flow among them may vary in space and serve as a tool for stock identification. This information may be useful to improve fishery management of this important harvested species along the Moroccan coast.

Phylogeographic breaks and the mechanisms of their formation in the Sino-Japanese floristic region

Phylogeographic breaks and the mechanisms of their formation in the Sino-Japanese floristic region

Genetic variability of the banded murex (Hexaplex trunculus) revealed by ND2 and ITS2 sequences

The gastropod Hexaplex trunculus is widely distributed in a relatively large range of habitats, but has no dispersal stage. We investigated its genetic structure across its distribution range, from Mediterranean Sea to adjacent Atlantic coasts, by sequencing mitochondrial DNA portions of the NADH dehydrogenase gene ND2 (420 pb) and the internal transcribed spacer ITS2 (450 pb). Our results suggested a significant genetic variability of ND2 (π = 0.009 and Hd = 0.629) and low variability of the ITS2 sequences. A strong phylogeographic break, separated the Aegean populations from those of Western/Eastern Mediterranean and the Atlantic ones, was founded. The tow lineages may have been separated by vicariance events due to the Peloponnese break that separates the Aegean populations from other populations and was maintained until now by the quasi-circular anticyclonic front associated to the straits of Cretan Arc of the Peloponnesian Peninsula. Tunisian coasts appear particularly diverse since the two divergent lineages co-occured. These results may have management consequences since H. trunculus is a high commercial value harvested species.