Microsatellite variation and significant population genetic structure of endangered finless porpoises (Neophocaena phocaenoides) in Chinese coastal waters and the Yangtze River

The finless porpoise (Neophocaena phocaenoides) inhabits a wide range of tropical and temperate waters of the Indo-Pacific region. Genetic structure of finless porpoises in Chinese waters in three regions (Yangtze River, Yellow Sea, and South China Sea) was analyzed, including the Yangtze finless porpoise which is widely known because of its highly endangered status and unusual adaptation to freshwater. To assist in conservation and management of this species, ten microsatellite loci were used to genotype 125 individuals from the three regions. Contrary to the low genetic diversity revealed in previous mtDNA control region sequence analyses, relatively high levels of genetic variation in microsatellite profiles (H _E = 0.732–0.795) were found. Bayesian clustering analysis suggested that finless porpoises in Chinese waters could be described as three distinct genetic groups, which corresponded well to population “units” (populations, subspecies, or species) delimited in earlier studies, based on morphological variation, distribution, and genetic analyses. Genetic differentiation between regions was significant, with F _ST values ranging from 0.07 to 0.137. Immigration rates estimated using a Bayesian method and population ancestry analyses suggested no or very limited gene flow among regional types, even in the area of overlap between types. These results strongly support the classification of porpoises in these regions into distinct evolutionarily significant units, including at least two separate species, and therefore they should be treated as different management units in the design and implementation of conservation programmes.     

Molecular evidence reveals the distinctiveness of Indo-Pacific finless porpoises (Neophocaena phocaenoides) in the Pearl River Estuary and insights into genus Neophocaena’s origin

Much of the knowledge about the wide-ranging finless porpoise species (Neophocaena phocaenoides) remains limited, as well as its phylogenetic relationship with another taxa (N. asiaeorientalis) in genus Neophocaena. Using 11 microsatellite loci, we first investigated population differentiation of N. phocaenoides within the Pearl River Estuary (PRE). We then used mtDNA control region (CR) and cytochrome b (cyt b) sequences from the PRE population (75) as well as those from other geographic populations to reveal the divergence level and phylogeny of the PRE N. phocaenoides. Pairwise F _ST analysis with mtDNA CR sequences determined that the PRE population was highly differentiated from other putative populations (with the closest population 400-km away in the Taiwan Strait) (F _ST = 0.388–0.764, p < 0.01). The level of genetic divergence between the PRE and its conspecific population was as high as comparisons between the two subspecies under N. asiaeorientalis (F _ST = 0.361, p < 0.01). Our results also revealed contrasting demographic histories between the PRE and the other geographic finless porpoise populations (the Taiwan Strait population, the southern and northern Yellow Sea population and the middle Yangtze River population), which suggested stability in the warmer waters of the Indo-Pacific and expansions in the colder waters of the North Pacific. Phylogenetic trees created using cyt b data indicated that some haplotypes exclusive to the PRE population were basal to the rest of the genus. Based on these results, we argue that the genus Neophocaena originated in tropical waters (because the PRE is the most southern location sampled, i.e., the closest location to tropical waters).     

Disjunct Sea of Cortez–Pacific Ocean Gillichthys mirabilis populations and the evolutionary origin of their Sea of Cortez endemic relative, Gillichthys seta

The shortjaw mudsucker, Gillichthys seta, an intertidal goby endemic to the Sea of Cortez, has been proposed to be the paedomorphic derivative of the longjaw mudsucker, Gillichthys mirabilis. G. mirabilis is a disjunct species, with populations found along the Pacific coast of central California to central Baja California, and with isolated populations found in the northern Sea of Cortez. Previous studies have suggested that the endemic paedomorph form speciated in sympatry with the Sea of Cortez population of G. mirabilis. Alternatively, this speciation event could have occurred before the separation of G. mirabilis populations into two disjunct entities. To test these alternative hypotheses, we collected adult individuals from both species throughout their ranges from December 1997 to November 1998. We amplified and sequenced 142 partial [527 base pairs (bp)] mitochondrial cytochrome b regions and 18 nuclear creatine kinase introns (140 bp). We found that Pacific populations of G. mirabilis separated into two distinct clades, possibly reflecting a phylogeographic break found in other fish species along the Baja California coast at Punta Eugenia. These two Pacific populations were well separated from Sea of Cortez populations. Furthermore, our results indicate that the split between Sea of Cortez and Pacific populations of G. mirabilis occurred well after the speciation event that separated G. mirabilis from its paedomorphic counterpart, G. seta. Received: 30 March 2000 / Accepted: 4 September 2000     

Phylogeography of the Southwestern Atlantic menhaden genus <Emphasis Type="Italic">Brevoortia</Emphasis> (Clupeidae,Alosinae)

Among pelagic fish, the Southwestern Atlantic menhaden genus Brevoortia (Clupeidae, Alosinae) constitutes an important species model to investigate the patterns of genetic differentiation. It is abundant in the Río de la Plata estuary and in the Atlantic coastal lagoons system from Uruguay and Southern Brazil. To access in the taxa discrimination and population structure in Brevoortia we perform a phylogeographic approach based on mitochondrial cytochrome b (cyt-b) sequences including 240 individuals from 16 collecting sites. Among the 720 bp cyt-b sequenced, 199 correspond to variables and 88 to phylogenetically informative sites. High values of haplotype diversity (h = 1.000) and nucleotide diversity (π = 0.061), as well as an average of 0.084 polymorphic segregating sites and 46 different haplotypes were found. Maximum likelihood analysis based on the GTR + I + G model and Bayesian inference strongly support the idea that B. aurea is the only species of the genus inhabiting the Southwestern Atlantic region. Our analyses revealed a complex population pattern characterized by the existence of long-term highly structured genetic assemblages of mixed stocks. Each monophyletic entity included individuals from different collecting sites, different age groups and collected in different years. Our data also suggest that the recruitment of unrelated mtDNA haplotypes carried out by individuals within schools could be occurring in the same nursery areas revealing the existence of many different maternal lineages. A scenario where different simultaneously and successively mixed mtDNA lineages remain historically connected through basal haplotypes among different clades could explains more accurately the complex and ordered metapopulation dynamic found in this pelagic fish.     

Population genetics of the nurse shark (Ginglymostoma cirratum) in the western Atlantic

The nurse shark, Ginglymostoma cirratum, inhabits shallow, tropical, and subtropical waters in the Atlantic and the eastern Pacific. Unlike many other species of sharks, nurse sharks are remarkably sedentary. We assayed the mitochondrial control region and eight microsatellite loci from individuals collected primarily in the western Atlantic to estimate the degree of population subdivision. Two individuals from the eastern Atlantic and one from the Pacific coast of Panama also were genotyped. Overall, the mtDNA haplotype (h = 48 ± 5%) and nucleotide (π = 0.08 ± 0.06%) diversities were low. The microsatellite data mirror the mitochondrial results with the average number of alleles ([`(N)]<sub>A</sub> \bar{N}_{A}  = 9) and observed heterozygosity ([`(H)]_O \bar{H}_{O}  = 0.58) both low. The low levels of diversity seen in both the mtDNA and the microsatellite may be due to historical sea level fluctuations and concomitant loss of shallow water habitat. Eight of the 10 pair-wise western Atlantic F _ST estimates for mtDNA indicated significant genetic subdivision. Pair-wise F _ST values for the microsatellite loci indicated a similar pattern as the mtDNA. The western Atlantic population of nurse sharks is genetically subdivided with the strongest separation seen between the offshore islands and mainland Brazil, likely due to deep water acting as a barrier to dispersal. The eastern and western Atlantic populations were closely related. The eastern Pacific individual is quite different from Atlantic individuals and may be a cryptic, sister species.     

DNA sequence analysis identifies genetically distinguishable populations of harp seals (Pagophilus groenlandicus) in the Northwest and Northeast Atlantic

Harp seals (Pagophilus groenlandicus Erxleben, 1777) comprise three populations based upon whelping areas in the Greenland Sea, White Sea, and Northwest Atlantic. The last comprises two subpopulations, one whelping in the Gulf of St. Lawrence (“Gulf ”) and one on the pack ice of the southern Labrador/northern Newfoundland coastal shelf (“Front”). A total of 40 female seals from the four whelping areas were collected during the 1990 and 1992 whelping seasons. DNA sequence variation was examined in a 307 bp region of the mitochondrial cytochrome b gene. Eleven variable nucleotide positions defined 13 genotypes: a significant fraction of the genotypic variance (F _ST=0.12, or 0.09 as measured by Weir's coancestry coefficient θ) is attributable to differentiation between Northwest and Northeast Atlantic populations. There was no significant differentiation between the two whelping areas in the Northwest Atlantic, or between the Greenland Sea and White Sea. These findings suggest significant reproductive isolation exists between trans-Atlantic breeding populations. Received: 18 January 1999 / Accepted: 22 February 2000     

Multi-marker estimate of genetic connectivity of sole (Solea solea) in the North-East Atlantic Ocean

A thorough knowledge on the genetic connectivity of marine populations is important for fisheries management and conservation. Using a dense population sampling design and two types of neutral molecular markers (10 nuclear microsatellite loci and a mtDNA cytochrome b fragment), we inferred the genetic connectivity among the main known spawning grounds of sole (Solea solea L.) in the North-East Atlantic Ocean. The results revealed a clear genetic structure for sole in the North-East Atlantic Ocean with at least three different populations, namely the Kattegat/Skagerrak region, the North Sea and the Bay of Biscay, and with indications for a fourth population, namely the Irish/Celtic Sea. The lack of genetically meaningful differences between biological populations within the southern North Sea is likely due to a large effective population size and sufficient connection (gene flow) between populations. Nevertheless, an isolation-by-distance pattern was found based on microsatellite genotyping, while no such pattern was observed with the cytochrome b marker, indicating an historical pattern prevailing in the latter marker. Our results demonstrate the importance of a combined multi-marker approach to understand the connectivity among marine populations at region scales.     

Population structure and genetic variation of lane snapper (<Emphasis Type="Italic">Lutjanus synagris</Emphasis>) in the northern Gulf of Mexico

Lane snappers (Lutjanus synagris), sampled from eight localities in the northern Gulf of Mexico (Gulf) and one locality along the Atlantic coast of Florida, were assayed for allelic variation at 14 nuclear-encoded microsatellites and for sequence variation in a 590 base-pair fragment of the mitochondrially encoded ND-4 gene (mtDNA). Significant heterogeneity among the nine localities in both microsatellite allele and genotype distributions and mtDNA haplotype distributions was indicated by exact tests and by analysis of molecular variance (AMOVA). Exact tests between pairs of localities and spatial analysis of molecular variance (SAMOVA) for both microsatellites and mtDNA revealed two genetically distinct groups: a Western Group that included six localities from the northwestern and northcentral Gulf and an Eastern Group that included three localities, one from the west coast of Florida, one from the Florida Keys, and one from the east (Atlantic) coast of Florida. The between-groups component of molecular variance was significant for both microsatellites (Φ _CT = 0.016, P = 0.009) and mtDNA (Φ _CT = 0.208, P = 0.010). Exact tests between pairs of localities within each group and spatial autocorrelation analysis did not reveal genetic heterogeneity or an isolation-by-distance effect among localities within either group. MtDNA haplotype diversity was significantly less (P < 0.0001) in the Western Group than in the Eastern Group; microsatellite allelic richness and gene diversity also were significantly less in the Western Group (P = 0.015 and 0.013, respectively). The difference in genetic variability between the two groups may reflect reduced effective population size in the Western Group and/or asymmetric rates of genetic migration. The relative difference in variability between the two groups was substantially greater in mtDNA and may reflect one or more mtDNA selective sweeps; tests of neutrality of the mtDNA data were consistent with this possibility. Bayesian analysis of genetic demography indicated that both groups have experienced a historical decline in effective population size, with the decline being greater in the Western Group. Maximum-likelihood analysis of microsatellite data indicated significant asymmetry in average, long-term migration rates between the two groups, with roughly twofold greater migration from the Western Group to the Eastern Group. The difference in mtDNA variability and the order-of-magnitude difference in genetic divergence between mtDNA and microsatellites may reflect different demographic events affecting mtDNA disproportionately and/or a sexual and/or spatial bias in gene flow and dispersal. The spatial discontinuity among lane snappers in the region corresponds to a known zone of vicariance in other marine species. The evidence of two genetically distinct groupings (stocks) has implications for management of lane snapper resources in the northern Gulf.     

Complex patterns of population structure and recruitment of <Emphasis Type="Italic">Plectropomus leopardus</Emphasis> (Pisces: Epinephelidae) in the Indo-West Pacific: implications for fisheries management

Here the population genetic structure of an ecologically and economically important coral reef fish, the coral trout Plectropomus leopardus, is investigated in the context of contemporary and historical events. Coral trout were sampled from four regions (six locations) and partial mtDNA D-loop sequences identified six populations (Fst = 0.89209, P < 0.0001): Scott Reef and the Abrolhos Islands in west Australia; the Great Barrier Reef (GBR), represented by northern and southern GBR samples; New Caledonia and Taiwan, with Taiwan containing two genetic lineages. Furthermore, this study identified source and sink populations within and among regions. Specifically, the northern population in west Australia (Scott Reef) was identified, as the source for replenishment of the Abrolhos population, whilst New Caledonia was a source for recruitment to the GBR. Based on these insights from a single mtDNA marker, this study will facilitate the development of rational management plans for the conservation of P. leopardus populations and therefore mitigate the risk of population declines from anthropogenic influences.     

Microsatellite data reveal fine genetic structure in male Guiana dolphins (<Emphasis Type="Italic">Sotalia guianesis)</Emphasis> in two geographically close embayments at south-eastern coast of Brazil

A large macrogeographic differentiation has been observed among Sotalia guianensis populations along the South American coast. However, no genetic structure has been detected so far in closely distributed populations of this species, even though it has been observed in other cetaceans. Here, we examined the fine scale population structure for the largest populations of S. guianensis inhabiting Sepetiba and Paraty embayments at the south-eastern coast of Rio de Janeiro, Brazil. Analysis of mitochondrial DNA (mtDNA) control region sequences failed to detect variability among sequences. Conversely, evidence of significant male population structure was found on the basis of ten nuclear microsatellite loci. Surprisingly, the microsatellite markers were able to distinguish between individuals from the two embayments located 60 km apart. The results suggest that differences in habitat type and behavioral specializations are likely to explain the patterns of genetic structure. These findings should provide baselines for the management of communities exposed to increasing human-driven habitat loss.     

Population structure of the wreckfish Polyprion americanus determined with microsatellite genetic markers

 We examined population structure in the wreckfish, Polyprion americanus, by assaying six microsatellite loci in 422 individuals collected throughout the geographic range. Eighteen hapuku, P. oxygeneios, were assayed at the same loci for use as an outgroup. Expected heterozygosities ranged from 0.49 to 0.88 and averaged 0.66. Allele-frequency distributions at those loci indicated that samples from the eastern North Atlantic, western North Atlantic and the Mediterranean were genetically similar, confirming the pattern seen in a previous analysis of mitochondrial DNA (mtDNA) restriction fragment length polymorphisms (RFLPs). Both mtDNA and microsatellite studies differentiated northern and southern wreckfish stocks. However, in contrast to the mtDNA studies, allelic variation at microsatellite loci clearly differentiated wreckfish from two Southern Hemisphere locations, Brazil and the South Pacific. Far more genetic variation was observed at microsatellite loci than with mtDNA RFLPs (haplotype diversity averaged 0.01), and we saw more evidence of population structure with the microsatellite loci. The differentiation between southern and northern wreckfish supports the distribution records, which indicate that wreckfish do not occur in the tropics. Temperature profiles and current patterns throughout the southern oceans apparently also prevent significant gene flow between the South Pacific and Brazilian samples. Received: 29 January 2000 / Accepted: 27 June 2000     

Microsatellite analysis of albacore tuna (<Emphasis Type="Italic">Thunnus alalunga</Emphasis>): population genetic structure in the North-East Atlantic Ocean and Mediterranean Sea

Stock heterogeneity was investigated in albacore tuna (Thunnus alalunga, Bonnaterre 1788), a commercially important species in the North Atlantic Ocean and Mediterranean Sea. Twelve polymorphic microsatellite loci were examined in 581 albacore tuna from nine locations, four in the north-east Atlantic Ocean (NEA), three in the Mediterranean Sea (MED) and two in the south-western Pacific Ocean (SWP). Maximum numbers of alleles per locus ranged from 9 to 38 (sample mean, 5.2–22.6 per locus; overall mean, 14.2 ± 0.47 SE), and observed heterozygosities per locus ranged from 0.44 to 1.00 (overall mean: 0.79 ± 0.19 SE). Significant deficits of heterozygotes were observed in 20% of tests. Multilocus F _ST values were observed ranging from 0.00 to Θ = 0.036 and Θ′ = 0.253, with a mean of Θ = 0.013 and Θ′ = 0.079. Pairwise F _ST values showed that the SWP, NEA and MED stocks were significantly distinct from one another, thus corroborating findings in previous studies based on mitochondrial DNA, nuclear DNA (other than microsatellites) and allozyme analyses. Heterogeneity was observed for the first time between samples within the Mediterranean Sea. GENELAND indicated the potential presence of three populations across the NEA and two separate populations in the Mediterranean Sea. Observed genetic structure may be related to migration patterns and timing of movements of subpopulations to the feeding grounds in either summer or autumn. We suggest that a more intensive survey be conducted throughout the entire fishing season to ratify or refute the currently accepted genetic homogeneity within the NEA albacore stock.     

Mitochondrial DNA lineages in the European populations of mussels (<Emphasis Type="Italic">Mytilus</Emphasis> spp.)

Marine mussels (Mytilus spp.) belong to a group of benthic species crucial to coastal ecosystems in Europe and are important for the cultivation industry. In the present study, the nuclear adhesive protein marker (Me15/16) was used for identification of Mytilus species in coastal areas, on a large geographic scale in Europe. Pure M. edulis populations were found in the White Sea and Iceland. M. edulis, M. trossulus and their hybrids were found in the Baltic Sea and the North Sea (Oosterschelde, The Netherlands). M. galloprovincialis, M. edulis and their hybrids occurred in Ireland. M. galloprovincialis populations were observed in the Sea of Azov (Black Sea), the Mediterranean and Portugal. The mitochondrial (mt) DNA coding-region ND2-COIII was studied by PCR (polymerase chain reaction) and RFLP (restriction fragment length polymorphism) assay methods. The mtDNA control region was studied by PCR. Substantial differentiation in the frequency of female haplotypes among the studied populations in Europe was observed. Despite isolation between the Mytilus taxa on a macro-geographic scale, considerable mitochondrial gene flow occurred between populations, with introgression in hybrid zones on a more local geographic scale in Europe. MtDNA of the Atlantic Iberian (Portugal) population of M. galloprovincialis was more similar to mtDNA in populations of M. galloprovincialis and M. edulis from the Atlantic coasts of the Ireland and M. edulis from the North Sea, than to M. galloprovincialis from the Mediterranean. Lower polymorphism of mtDNA in populations of the Baltic and Azov Sea mussels in comparison with other European populations was observed and can be explained by the recent history of both seas after the Pleistocene glaciation. In the M. galloprovincialis population from the Azov Sea, the presence of the male-inherited (M) genome was demonstrated for the first time by sequencing the control region and was observed at high frequency. Possible influence of mussel culture on geographic distribution of the Mytilus taxa in Europe is discussed.     

Phylogeographic differentiation of storm petrels (<Emphasis Type="Italic">Hydrobates pelagicus</Emphasis>) based on cytochrome<Emphasis Type="Italic"> b</Emphasis> mitochondrial DNA variation

We evaluated mitochondrial DNA (mtDNA) sequence variation in a 910 bp region of the cytochrome b gene of the storm petrel, Hydrobates pelagicus. Samples from birds collected from five populations in the North Atlantic Ocean and the Mediterranean Sea were investigated. Genetic differentiation within the Mediterranean basin was low but high in the Atlantic. Strong differences were noted between the Atlantic and the Mediterranean populations, confirming the distinction of the subspecies H. p. pelagicus and H. p. melitensis for the Atlantic and Mediterranean seabirds, respectively. Divergence between the two subspecies probably resulted from paleogeographic changes in the Strait of Gibraltar, which was likely the route used by H. pelagicus to invade the Mediterranean Sea. Current and past demography and ecology of the storm petrel is regarded as an explanation for the level of differentiation observed within each oceanic basin. We compare the phylogeographic pattern of the storm petrel to other seabirds that breed in the same regions.Communicated by S. A. Poulet, RoscoffC.C. and L.B. contributed equally to this paper.     

Microsatellite analysis of plaice (Pleuronectes platessa L.) in the NE Atlantic: weak genetic structuring in a milieu of high gene flow

Many species of marine fish are typified by large population sizes, strong migratory behavior, high fecundity, and pelagic eggs and larvae that are passively transported by ocean currents, all features that tend to increase gene flow, and hence reduce genetic partitioning, among localized populations. The plaice, Pleuronectes platessa, is a commercially important demersal species that exhibits all of these characteristics. We analyzed genetic variation at eight microsatellite loci in samples of spawning adults (N = 348) from the coasts of Ireland, Iceland, and, for the first time, from the Baltic Sea. Significant differentiation was observed between Iceland and Irish and Baltic Sea samples. However, there were no genetic differences between Irish and Baltic Sea samples, which contrast with the significant differentiation reported between Baltic Sea and North Sea/Atlantic populations of other flatfish species. To increase the data set, we carried out a cross-calibration exercise, allowing us to perform a joint analysis of data with an earlier study on adult and juvenile plaice (N = 480) collected over a broad geographic range, using six microsatellite loci in common to the two studies. Significant differentiation was observed between fish collected at the northern (Iceland, Faeroes, Norway) and southern (Bay of Biscay) parts of the species range. In contrast, the results showed little evidence of genetic structuring over much of the continental shelf of Europe. We believe that bathymetric and hydrographic barriers are the major factors shaping genetic structure, while lack of structure over much of the European continental shelf may be explained by a combination of past historical events, population structure, and dynamics of the species.     

Evidence for restricted gene flow over small spatial scales in a marine snapping shrimp <Emphasis Type="Italic">Alpheus angulosus</Emphasis>

Despite the apparent absence of geographic barriers, connectivity among marine populations may be restricted by, for example, ecological or behavioral mechanisms. In such cases, populations may show genetic differentiation even over relatively small spatial scales. Here, mitochondrial sequence data from the cytochrome oxidase I (COI) gene and seven polymorphic microsatellite markers were used to investigate fine geographic scale population genetic structure in the snapping shrimp Alpheus angulosus, a member of the A. armillatus species complex, from collections in Florida, Jamaica, and Puerto Rico carried out from 1999 to 2005. The COI data showed a deep divergence that separated these samples into two mitochondrial clades, but this divergence was not supported by the microsatellite data. The COI data reflect past population divergence not reflected in extant population structure on the whole genome level. The microsatellite data also revealed evidence for moderate population structure between populations as close as ∼10 km, and no evidence for isolation by distance, as divergences between near populations were at least as strong as those between more broadly separated populations. Overall, these data suggest a role for restricted gene flow between populations, though the mechanisms that reduce gene flow in this taxon remain unknown.     

Low levels of genetic variation in mtDNA sequences over the western Mediterranean and Atlantic range of the sponge<Emphasis Type="Italic"> Crambe crambe</Emphasis> (Poecilosclerida)

Crambe crambe is a common encrusting sponge found in the Mediterranean and Atlantic littoral. An analysis of a partial sequence (535 bp) of the mitochondrial DNA (mtDNA) gene cytochrome oxidase subunit I (COI) was conducted in an attempt to determine population structure in this species. This is the first study of population genetics using this kind of marker in the phylum. Samples (N=86) were taken in eight populations separated by distances from 20 to 3,000 km, spanning from the western Mediterranean to the Atlantic. Low variability of this gene was found, as only two haplotypes were identified, along with low nucleotide diversity (=0.0006). However, the different frequencies found among populations revealed genetic structure and low gene flow between close populations, as expected from the dispersal biology of the species. The low variability found in sponges is in agreement with reports on cnidarians and points to a high conservation of mtDNA in diploblastic phyla.     

Phylogeography and demographic history of <Emphasis Type="Italic">Atherina presbyter</Emphasis> (Pisces: Atherinidae) in the North-eastern Atlantic based on mitochondrial DNA

A fragment of the mitochondrial control region was used to assess phylogeographic patterns and historical demography of the sand-smelt Atherina presbyter in the North-eastern Atlantic, covering its geographical range. A striking result is the highly marked differentiation between the Canary Islands population and western European ones. A genetic structure among European populations of A. presbyter was revealed, with a pattern of isolation-by-distance or a gradient effect at a scale of hundreds kilometres, an uncommon pattern likely related to the biological and life-history traits of the sand-smelt. The northern European populations present a much lower genetic diversity when compared to southern populations, which is consistent with a recent colonization from southern populations. The results showed signs of Pleistocene signatures, with the population age estimates for the European populations being clearly older than the Last Glacial Maximum (18,000 years bp). Nevertheless, paleotemperature reconstructions show that the sand-smelt could not have inhabited the western European shores during the last glacial phase. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Negligible evidence for regional genetic population structure for two shark species <Emphasis Type="Italic">Rhizoprionodon acutus</Emphasis> (Rüppell, 1837) and <Emphasis Type="Italic">Sphyrna lewini</Emphasis> (Griffith &; Smith, 1834) with contrasting biology

Biodiversity of sharks in the tropical Indo-Pacific is high, but species-specific information to assist sustainable resource exploitation is scarce. The null hypothesis of population genetic homogeneity was tested for scalloped hammerhead shark (Sphyrna lewini, n = 237) and the milk shark (Rhizoprionodon acutus, n = 207) from northern and eastern Australia, using nuclear (S. lewini, eight microsatellite loci; R. acutus, six loci) and mitochondrial gene markers (873 base pairs of NADH dehydrogenase subunit 4). We were unable to reject genetic homogeneity for S. lewini, which was as expected based on previous studies of this species. Less expected were similar results for R. acutus, which is more benthic and less vagile than S. lewini. These features are probably driving the genetic break found between Australian and central Indonesian R. acutus (F-statistics; mtDNA, 0.751–0.903, respectively; microsatellite loci, 0.038–0.047 respectively). Our results support the spatially homogeneous monitoring and management plan for shark species in Queensland, Australia.