Geographic allozyme variation in the Japanese clouded salamander, Hynobius nebulosus (Amphibia: Urodela)

Using starch gel electrophoresis, geographical enzyme variation was surveyed in 46 populations of the Japanese salamander Hynobius nebulosus , which occurs widely in western Japan. This species exhibits substantial local genetic differentiation and is more diverse in inland regions than on small islands. In several different analyses, two groups of populations, one from Kyushu Island to the westernmost part of Chugoku district, Honshu (western group), and another from Shikoku through Kinki to Chubu district, Honshu (eastern group), were consistently recognized. Most of the remaining populations were placed in two less clearly-defined groups: the montane group from the Chugoku Mountains and the Chugoku group from the coastal regions of Chugoku district. The divergence patterns of H. nebulosus are thought to be related to the geological history of its range. The populations near the boundary of the western group were found to share several alleles that were predominant on both sides of the boundary, indicating past secondary contact. Differentiation in the montane group did not follow the isolation by distance model, probably because several populations included were genetically mixed with lowland populations of the Chugoku group.  © 2006 The Linnean Society of London, Biological Journal of the Linnean Society , 2006, 89 , 311–330.     

A new species of salamander of the genus Hynobius from Central Honshu, Japan (Amphibia, Urodela)

We describe a small salamander from south Central Honshu, Japan, as a new species, Hynobius katoi. The genetic distances between this species and several named species, including sympatric H. kimurae, derived from allozyme data from a starch gel electrophoresis, proved to be sufficiently large to differentiate it at a specific rank. Distribution of this species is confined to the montane regions of Shizuoka and Nagano Prefectures, on the Akaishi Mountains of the Chubu District, central Japan. It is regarded as a member of the naevius group of Hynobius, characterized by small number of large, pigmentless ova. The species differs from the other species of the naevius group by the combination of relatively small body size, nearly spotless body, relatively few vomerine teeth forming moderately shallow series, and unique electrophoretic pattern of isozymes.     

The application of RAPD markers in stock discrimination of the four-wing flyingfish, Hirundichthys affinis in the central western Atlantic

The polymerase chain reaction–random amplified polymorphic DNA (PCR–RAPD) technique was used to examine genetic variability and population structuring in the four-wing flyingfish, Hirundichthys affinis within the central western Atlantic. Three random decamer primers and pairs of these primers were used to amplify nuclear DNA from 360 fish sampled from six populations (at five locations) across the region. A total of 58 polymorphic RAPD markers were identified, 20 of which were population-specific and six of which were subregional or stock-specific markers. Cluster analysis of similarity indices indicated the presence of three genetically distinct subregional stocks located in the eastern Caribbean, southern Netherlands Antilles and Brazil, respectively. Estimates of gene diversity (φ) and gene flow ( Nm ) are consistent with this three-stock hypothesis. Furthermore, partially restricted gene flow was apparent among spatially and temporally separate sampled populations within the eastern Caribbean subregional stock, indicating the possible presence of different spawning groups. These results are entirely consistent with those obtained from PCR–RFLP analysis of the mtDNA D-loop in the same fish, indicating the presence of barriers to dispersal and interbreeding in both sexes. We conclude that the PCR–RAPD technique is suitable for determining population stock structure in this species and that a three-stock approach to managing H. affinis within the central western Atlantic would be appropriate.     

中国西南部小鲵属的遗传分化

运用同工酶电泳和DNA测序技术,我们研究了中国东南部两种小鲵的遗传多样性。同工酶数据显示义乌小鲵和安吉小鲵之间存在中等水平的种间差异。而线粒体DNA序列数据则显示两种之间存在较高水平的种间差异。安吉小鲵种群存在明显的近亲繁殖现象;义乌小鲵种群间存在明显的分化。舟山群岛上义乌小鲵种群明显有别于大陆种群。     

Geographic patterns in morphometric and genetic variation for coyote populations with emphasis on southeastern coyotes

Prior to 1900, coyotes (Canis latrans) were restricted to the western and central regions of North America, but by the early 2000s, coyotes became ubiquitous throughout the eastern United States. Information regarding morphological and genetic structure of coyote populations in the southeastern United States is limited, and where data exist, they are rarely compared to those from other regions of North America. We assessed geographic patterns in morphology and genetics of coyotes with special consideration of coyotes in the southeastern United States. Mean body mass of coyote populations increased along a west‐to‐east gradient, with southeastern coyotes being intermediate to western and northeastern coyotes. Similarly, principal component analysis of body mass and linear body measurements suggested that southeastern coyotes were intermediate to western and northeastern coyotes in body size but exhibited shorter tails and ears from other populations. Genetic analyses indicated that southeastern coyotes represented a distinct genetic cluster that differentiated strongly from western and northeastern coyotes. We postulate that southeastern coyotes experienced lower immigration from western populations than did northeastern coyotes, and over time, genetically diverged from both western and northeastern populations. Coyotes colonizing eastern North America experienced different selective pressures than did stable populations in the core range, and we offer that the larger body size of eastern coyotes reflects an adaptation that improved dispersal capabilities of individuals in the expanding range.     

Morphological discrimination of two genetic groups of a Japanese salamander, Hynobius naevius (Amphibia, Caudata)

Hynobius naevius, distributed on western Honshu, Shikoku, and Kyushu Islands of Japan, includes two genetically distinct groups (Groups A and B) that have never been delimited morphologically. Using specimens from the entire species range, we investigated the possibility of distinguishing these groups morphologically. Multivariate analyses of morphometric characters resulted in recognition of two groups that corresponded well to the two genetic groups. One (Group A) was characterized by larger body, compressed tail, shallower vomerine tooth series, bluish- or reddish-purple ground color, and pale-white lateral markings. In contrast, another (Group B) was characterized by smaller body, cylindrical tail, longer vomerine tooth series, reddish-brown ground color, and white lateral markings. Group A was composed of populations from the Chugoku District of Honshu and northern Kyushu, and could not be divided into subgroups, while Group B encompassed populations from the Chubu and Kinki Districts of Honshu, Shikoku and Kyushu, and was subdivided into three local subgroups that are geographically separated by marine straits. Morphometric differentiation in Group A is presumed to have been less affected by genetic factors than by other factors, such as ecological relationships with other, coexisting species. Differentiation in Group B is assumed to have been enhanced not only by genetic but also by climatological factors.     

Genetic differentiation of the marbled white butterfly, Melanargia galathea, accounts for glacial distribution patterns and postglacial range expansion in southeastern Europe

Isolation of Mediterranean species in the southern European peninsulas during the cold glacial phases often resulted in differentiation of several genetic lineages confined to the respective peninsulas. However, whilst there is good genetic evidence for multiple refugia in Iberia, there are only limited data available for the Balkans. Therefore, we wish to examine the hypothesis of a strong genetic structuring within southeastern Europe for the existence of multiple Balkan differentiation centres and/or several leading edges. As a model we use the marbled white butterfly, Melanargia galathea. We studied 18 allozyme loci of 564 individuals from 16 populations distributed over a large part of southeastern Europe. The single populations showed moderately high genetic diversity and no northward decline of genetic diversity was detected. The overall genetic differentiation between populations was considerable (F(ST) 7.0%). Cluster analysis discriminated three genetic groups: (i) a western flank in the former Yugoslavia, parts of eastern Austria and Hungary; (ii) an eastern flank with populations from Bulgaria and Romania (south of the southern Carpathians and eastern Carpathians); and (iii) the eastern Carpathian Basin. Hierarchical variance analysis distributed 53% of the variance among populations between these three groups. One sample from the Greek-Bulgarian border clustered within the eastern flank, but showed some tendency towards the eastern Carpathian Basin populations. Two populations from Carinthia clustered together with the eastern Carpathian Basin ones and a population from Styria showed an intermediate genetic composition between the three groups. Most probably, the eastern and the western flank groups are due to postglacial range expansion from the northeastern and the northwestern edges of the glacial differentiation centre (so-called leading edges). The eastern Carpathian Basin group may have resulted from postglacial expansion from northern Greece through valley systems of the central Balkan peninsula, maybe even expanding westwards north of the Balkan mountains reaching some parts of eastern Austria (e.g. Carinthia). Therefore, the Balkanic refugium of M. galathea may or may not have been continuous along the coastal areas of the Mediterranean, but must have been strongly genetically structured.     

Nesting habits influence population genetic structure of a bee living in anthropogenic disturbance

While most organisms are negatively affected by anthropogenic disturbance, a few species thrive in landscapes altered by humans. Typically, native bees are negatively impacted by anthropogenic environmental change, including habitat alteration and climate change. Here, we investigate the population structure of the eastern carpenter bee Xylocopa virginica, a generalist pollinator with a broad geographic range spanning eastern North America. Eastern carpenter bees now nest almost exclusively in artificial wooden structures, linking their geographic distribution and population structure to human activities and disturbance. To investigate the population structure of these bees, we sampled females from 16 different populations from across their range. Nine species‐specific microsatellite loci showed that almost all populations are genetically distinct, but with high levels of genetic diversity and low levels of inbreeding overall. Broadly speaking, populations clustered into three distinct genetic groups: a northern group, a western group and a core group. The northern group had low effective population sizes, decreased genetic variability and the highest levels of inbreeding in the data set, suggesting that carpenter bees may be expanding their range northward. The western group was genetically distinct, but lacked signals of a recent range expansion. Climatic data showed that summer and winter temperatures explained a significant amount of the genetic differentiation seen among populations, while precipitation did not. Our results indicate that X. virginica may be one of the rare ‘anthrophilic’ species that thrive in the face of anthropogenic disturbance.     

Are solitary and gregarious Mormon crickets (Anabrus simplex, Orthoptera, Tettigoniidae) genetically distinct?

Phase polyphenisms are usually thought to reflect plastic responses of species, independent of genetic differences; however, phase differences could correlate with genetic differentiation for various reasons. Mormon crickets appear to occur in two phases that differ in morphology and behaviour. Solitary individuals are cryptic and sedentary whereas gregarious individuals form bands, migrate, and are aposematically coloured. These traits have been thought to be phenotypically plastic and induced by environmental conditions. However, there has been no previous investigation of the extent of genetic differences between solitary and gregarious populations of this widespread North American species. We sequenced two mitochondrial genes, COII and COIII, in samples of Mormon crickets from gregarious populations west of the continental divide and solitary mountain populations primarily east of the divide. Sequencing revealed two genetically distinct clades that broadly correspond with the solitary eastern populations and the mainly gregarious western populations. We used coalescent modelling to test the hypothesis that the species consists of two deep genetic clades, as opposed to a series of equally distinct populations. Results allowed us to reject the null hypothesis that a radiation independent of phase produced these clades, and molecular clock estimates indicate the time of divergence to be approximately 2 million years ago. This work establishes that the solitary populations found in the mountains on the eastern slope are part of a clade that is genetically distinct from the western populations, which are primarily gregarious, and the implications of this apparent correlation between phase and genetic differentiation are discussed.     

Lack of genetic differentiation between monarch butterflies with divergent migration destinations

Monarch butterflies are best known for their spectacular annual migration from eastern North America to Mexico. Monarchs also occur in the North American states west of the Rocky Mountains, from where they fly shorter distances to the California Coast. Whether eastern and western North American monarchs form one genetic population or are genetically differentiated remains hotly debated, and resolution of this debate is essential to understand monarch migration patterns and to protect this iconic insect species. We studied the genetic structure of North American migratory monarch populations, as well as nonmigratory populations in Hawaii and New Zealand. Our results show that eastern and western migratory monarchs form one admixed population and that monarchs from Hawaii and New Zealand have genetically diverged from North American butterflies. These findings suggest that eastern and western monarch butterflies maintain their divergent migrations despite genetic mixing. The finding that eastern and western monarchs form one genetic population also suggests that the conservation of overwintering sites in Mexico is crucial for the protection of monarchs in both eastern and western North America.     

Genetic variation in Bromus tectorum (Poaceae): differentiation in the eastern United States

Bromus tectorum, a devastating plant invader in western North America, had entered Pennsylvania by 1790. Although rare, or extirpated, in the east until the 1850s, it was collected with increasing frequency after 1859 from Vermont to Virginia. Using enzyme electrophoresis, we analyzed 38 populations of this grass in the eastern U.S. to determine their genetic variation and structure as well as assess their relatedness to populations in the west. Genetic variation among eastern U.S. populations is low: mean number of alleles per locus (A), percent polymorphic loci per population (%P), and expected heterozygosity (H(exp)) are 1.01, 1.05%, and 0.002, respectively. No heterozygotes were detected. The eastern populations are genetically similar: mean genetic identity for all populations was 0.990 with values among population pairs ranged from 0.913 to 1.000. Thirteen populations in eastern and western North America shared Pgm-1a and Pgm-2a, while eight populations shared Mdh-2b and Mdh-3b. Other alleles detected in western North America (Got-4c, Got-4d, and Pgi-2b) were not, however, found in eastern U.S. populations. The invasion of North America by B. tectorum occurred through multiple introductions on both coasts; results from historical and genetic evidence suggest that eastern populations stem from a minimum of two introductions. The 19th century westward spread of B. tectorum from the East appears to be plausible.     

Systematic Relationships of Hynobius okiensis among Japanese Salamanders (Amphibia: Caudata)

We conducted an electrophoretic survey to examine systematic relationships of a lotic-breeding salamander Hynobius okiensis endemic to Dogo Island of the Oki Islands, Japan, with several lentic and lotic-breeding Japanese species. Genetically H. okiensis with 2n=56 chromosomes was closer to the lentic-breeding H. nebulosus group (H. nebulosus and H. dunni) with the same chromosome number than to the lotic-breeding H. naevius group (H. naevius and H. kimurae) and H. boulengeri with 58 chromosomes. Chromosome number reduction from 58 to 56, possibly accompanied with a change in breeding environment from streams to still waters, is estimated to have first occurred in the nebulosus group of Hynobius. A reversal only in breeding habits then seems to have followed in steep, montane environments of the small island of Dogo, resulting in the speciation of H. okiensis.     

Inferring the origin of populations introduced from a genetically structured native range by approximate Bayesian computation: case study of the invasive ladybird Harmonia axyridis

Correct identification of the source population of an invasive species is a prerequisite for testing hypotheses concerning the factors responsible for biological invasions. The native area of invasive species may be large, poorly known and/or genetically structured. Because the actual source population may not have been sampled, studies based on molecular markers may generate incorrect conclusions about the origin of introduced populations. In this study, we characterized the genetic structure of the invasive ladybird Harmonia axyridis in its native area using various population genetic statistics and methods. We found that native area of H. axyridis most probably consisted of two geographically distinct genetic clusters located in eastern and western Asia. We then performed approximate Bayesian computation (ABC) analyses on controlled simulated microsatellite data sets to evaluate (i) the risk of selecting incorrect introduction scenarios, including admixture between sources, when the populations of the native area are genetically structured and sampling is incomplete and (ii) the ability of ABC analysis to minimize such risks by explicitly including unsampled populations in the scenarios compared. Finally, we performed additional ABC analyses on real microsatellite data sets to retrace the origin of biocontrol and invasive populations of H. axyridis, taking into account the possibility that the structured native area may have been incompletely sampled. We found that the invasive population in eastern North America, which has served as the bridgehead for worldwide invasion by H. axyridis, was probably formed by an admixture between the eastern and western native clusters. This admixture may have facilitated adaptation of the bridgehead population.     

Genetic evidence for historical continuity between populations of the Australian freshwater fish Craterocephalus stercusmuscarum (Atherinidae) east and west of the Great Dividing Range

The freshwater Craterocephalus stercusmuscarum (Atherinidae) has a broad northern and south-eastern Australian distribution, and has been divided into two sub-species. Craterocephalus stercusmuscarum fulvus occurs in eastern and western flowing drainages of the southeast, while C. s. stercusmuscarum occurs in north eastern and northern flowing drainages. Four populations of each sub-species were sampled from different river systems to examine if genetic diversity was consistent with this nomenclature or a previously proposed vicariance hypothesis. Allozyme data did not support the notion that the subspecies were genetically distinct, but the mtDNA data showed that haplotypes from one sub-species, regardless of geography, were reciprocally monophyletic to haplotypes of the other subspecies. Thus, mtDNA genetic diversity was partitioned by prevailing taxonomy and the data suggest that C. s. fulvus populations in eastern and western flowing drainages may have had a relatively recent connection subsequently interrupted by geological events.     

Genetic structure of Hypochaeris uniflora (Asteraceae) suggests vicariance in the Carpathians and rapid post-glacial colonization of the Alps from an eastern Alpine refugium

Aim The range of the subalpine species Hypochaeris uniflora covers the Alps, Carpathians and Sudetes Mountains. Whilst the genetic structure and post‐glacial history of many high‐mountain plant taxa of the Alps is relatively well documented, the Carpathian populations have often been neglected in phylogeographical studies. The aim of the present study is to compare the genetic variation of the species in two major European mountain systems – the Alps and the Carpathians. Location Alps and Carpathians. Methods The genetic variation of 77 populations, each consisting of three plants, was studied using amplified fragment length polymorphism (AFLP). Results Neighbour joining and principal coordinate analyses revealed three well‐supported phylogeographical groups of populations corresponding to three disjunct geographical regions – the Alps and the western and south‐eastern Carpathians. Moreover, two further clusters could be distinguished within the latter mountain range, one consisting of populations from the eastern Carpathians and the second consisting of populations from the southern Carpathians. Populations from the Apuseni Mountains had an intermediate position between the eastern and southern Carpathians. The genetic clustering of populations into four groups was also supported by an analysis of molecular variance, which showed that most genetic variation (almost 46%) was found among these four groups. By far the highest within‐population variation was found in the eastern Carpathians, followed by populations from the southern and western Carpathians. Generally, the populations from the Alps were considerably less variable and displayed substantially fewer region‐diagnostic markers than those from the south‐eastern Carpathians. Although no clear geographical structure was found within the Alps, based on neighbour joining or principal coordinate analyses, some trends were obvious: populations from the easternmost part were genetically more variable and, together with those from the south‐western part, exhibited a higher proportion of rare AFLP fragments than populations in other areas. Moreover, the total number of AFLP fragments per population, the percentage of polymorphic loci and the proportion of rare AFLP fragments significantly decreased from east to west. Main conclusions Deep infraspecific phylogeographical gaps between the populations from the Alps and the western and south‐eastern Carpathians suggest the survival of H. uniflora in three separate refugia during the last glaciation. Our AFLP data provide molecular evidence for a long‐term geographical disjunction between the eastern and western Carpathians, previously suggested from the floristic composition at the end of 19th century. It is likely that Alpine populations survived the Last Glacial in the eastern part of the Alps, from where they rapidly colonized the rest of the Alps after the ice sheet retreated. Multiple founder effects may explain a gradual loss of genetic variation during westward colonization of the Alps.     

Biogeography meets conservation: the genetic structure of the endangered lycaenid butterfly Lycaena helle (Denis & Schiffermüller, 1775)

Cold‐adapted species are thought to have had their largest distribution ranges in central Europe during the glacial periods. Postglacial warming caused severe range shifts of such taxa into higher latitudes and altitudes. We selected the boreomontane butterfly Lycaena helle (Denis & Schiffermüller, 1775) as an example to demonstrate the genetic effects of range changes, and to document the recent status of highly fragmented remnant populations. We analysed five polymorphic microsatellite loci in 1059 individuals sampled at 50 different localities scattered over the European distribution area of the species. Genetic differentiation was strong among the mountain ranges of western Europe, but we did not detect similarly distinct genetic groups following a geographical pattern in the more eastern areas. The Fennoscandian populations form a separate genetic group, and provide evidence for a colonization from southern Finland via northern Scandinavia to south‐central Sweden. Species distribution modelling suggests a large extension of the spatial distribution during the last glacial maximum, but highlights strong retractions to a few mountain areas under current conditions. These findings, combined with our genetic data, suggest a more or less continuous distribution of L. helle throughout central Europe at the end of the last ice age. As a consequence of postglacial warming, the species retreated northwards to Fennoscandia and escaped increasing temperatures through altitudinal shifts. Therefore, the species is today restricted to population remnants located at the mountain tops of western Europe, genetically isolated from each other, and evolved into genetically unique entities. Rising temperatures and advancing habitat destruction threaten this wealth of biodiversity. © 2010 The Linnean Society of London, Biological Journal of the Linnean Society, 2010, 101 , 155–168.     

ELECTROPHORETIC ENZYME ANALYSIS OF NORTH AMERICAN AND EASTERN ASIAN POPULATIONS OF AGASTACHE SECT. AGASTACHE (LABIATAE)

Agastache sect. Agastache consists of seven species in North America and one disjunct in eastern Asia. Starch-gel electrophoresis of enzymatic proteins was employed to assess genetic relationships among these species and to estimate the amount of genetic divergence between the North American and Asian populations. Species of the western United States appear to be better adapted for outcrossing than are the others and are much more genetically variable, with higher levels of heterozygosity per individual, more alleles per species, and higher percentages of polymorphic loci per population. Nonmetric multidimensional scaling of Nei's genetic distances among 32 populations partitioned the section into four discrete groups: 1) A. nepetoides (eastern North America), 2) A. scrophulariifolia and A. foeniculum (eastern and central North America), 3) the four species of the western United States (A. urticifolia, A. occidentalis, A. parvifolia and A. cusickii) and 4) A. rugosa (eastern Asia). Asian Agastache, separated from its American congeners for over twelve million years, differed from American populations at two of fifteen loci surveyed. Nei's genetic distances between Asian and North American populations ranged from 0.2877 to 0.6734.     

东亚——北美东部间断透骨草属的扩增片段长度多态性

透骨草属(Phryma)是一个单种属,间断分布于东亚与北美东部.尽管东亚与北美东部居群形态差异非常小,但分子变异却非常明显.本研究进一步运用AFLP两对引物来衡量透骨草属的遗传多样性并评估其形态保守性.结果发现透骨草的遗传差异主要存在于两大洲的居群之间.聚类与PCA分析显示透骨草分成两大支与其地理分布相吻合,一支全部来自东亚,另一支则是北美东部的居群.我们的结果强烈支持透骨草东亚--北美东部居群存在明显的遗传分化和形态保守.     

Phylogeography of the tree Hymenaea stigonocarpa (Fabaceae: Caesalpinioideae) and the influence of quaternary climate changes in the Brazilian cerrado

BACKGROUND AND AIMS: Hymenaea stigonocarpa (Fabaceae: Caesalpinioideae) is an endemic tree from the Brazilian cerrado (savanna vegetation), a biome classified as a hotspot for conservation priority. This study investigates the phylogeographic structure of H. stigonocarpa, in order to understand the processes that have led to its current spatial genetic pattern. METHODS: The polymorphism level and spatial distribution of variants of the plastid non-coding region between the genes psbC and trnS were investigated in 175 individuals from 17 populations, covering the greater part of the total distribution of the species. Molecular diversity indices were calculated and intra-specific relationships were inferred by the construction of haplotype networks using the median-joining method. Genetic differentiation among populations and main geographical groups was evaluated using spatial analysis of molecular variance (SAMOVA). KEY RESULTS: Twenty-three different haplotypes were identified. The level of differentiation among the populations analysed was relatively high (F(ST) = 0.692). Phylogeographic analyses showed a clear association between the haplotype network and geographic distribution of populations, revealing three main geographical groups: western, central and eastern. SAMOVA corroborated this finding, indicating that most of the variation can be attributed to differences among these three groups (58.8 %), with little difference among populations within groups (F(SC) = 0.252). CONCLUSIONS: The subdivision of the geographic distribution of H. stigonocarpa populations into three genetically differentiated groups can be associated with Quaternary climatic changes. The data suggest that during glacial times H. stigonocarpa populations became extinct in most parts of the southern present-day cerrado area. Milder climatic conditions in the north and eastern portions of the cerrado resulted in maintenance of populations in these regions. Thus it is inferred that the most southern part of the present-day cerrado was re-colonized by different lineages from northern parts of this biome, after postglacial climate amelioration.     

Using molecular and ecological data to diagnose endangered populations of the puritan tiger beetle Cicindela puritana

Populations of the puritan tiger beetle Cicindela puritana in the eastern United States were found to be highly threatened at the Connecticut River, whereas several large populations on the western shore and newly discovered populations on the eastern shore of the Chesapeake Bay appeared to be less endangered. We assessed if the disjunct C. puritana subgroups are genetically distinct and therefore should be treated as separate units for conservation purposes. A total of 13 individuals from the Connecticut River and 27 individuals from the Chesapeake Bay were each analysed by sequencing of up to 837 base pairs of mitochondrial DNA per individual. Five different haplotypes could be distinguished. In a phylogenetic analysis of these DNA sequences that included four related Cicindela species as out-groups, haplotypes from the Chesapeake Bay represent a distinct clade. The conservation status of these populations was evaluated using a phylogenetic approach based on cladistic analysis and the framework of the phylogenetic species concept. According to this analysis, beetles from the Connecticut River and the Chesapeake Bay have to be considered as independent units. Populations from the eastern and western shore of Chesapeake Bay are not split in more than one unit using the same criteria, although they exhibited some degree of genetic subdivision. The results from the mtDNA analysis were corroborated by ecological parameters in that the Chesapeake Bay populations can be distinguished from all congeners by their different tat association.