Historical range contraction,and not taxonomy,explains the contemporary genetic structure of the Australian tree <Emphasis Type="Italic">Acacia dealbata</Emphasis> Link

Irrespective of its causes, strong population genetic structure indicates a lack of gene flow. Understanding the processes that underlie such structure, and the spatial patterns it causes, is valuable for conservation efforts such as restoration. On the other hand, when a species is invasive outside its native range, such information can aid management in the non-native range. Here we explored the genetic characteristics of the Australian tree Acacia dealbata in its native range. Two subspecies of A. dealbata have previously been described based on morphology and environmental requirements, but recent phylogeographic data raised questions regarding the validity of this taxonomic subdivision. The species has been widely planted within and outside its native Australian range and is also a highly successful invasive species in many parts of the world. We employed microsatellite markers to investigate the population genetic diversity and structure among 42 A. dealbata populations from across the species’ native range. We also tested whether environmental variables purportedly relevant for the putative separation of subspecies are linked with population genetic differentiation. We found no relationship between population genetic structure of A. dealbata in Australia and these environmental features. Rather, we identified two geographically distinct genetic clusters that corresponded with populations in the northeastern part of mainland Australia, and the southern mainland and Tasmanian range of the species. Our results do not support the taxonomic subdivision of the species into two distinct subspecies based on environmental features. We therefore assume that the observed morphological differences between the putative subspecies are plastic phenotypic responses. This study provides population genetic information that will be useful for the conservation of the species within Australia as well as to better understand the invasion dynamics of A. dealbata.     

Genetic distinctiveness of brown pelicans (<Emphasis Type="Italic">Pelecanus occidentalis</Emphasis>) from the Galápagos Islands compared to continental North America

We examined population differentiation across a substantial portion of the range of the brown pelican (Pelecanus occidentalis) to assess (1) the genetic distinctness of the Galápagos subspecies (P. o. urinator) and (2) genetic differentiation between subspecies that inhabit the coasts of North and Central America (P. o. californicus and P. o. carolinensis). Birds were sampled from coastal California, coastal Florida, and the Galápagos Islands. Using a 957 bp (bp) fragment of the NADH dehydrogenase subunit 2 (ND2) gene, 661 bp of the mitochondrial control region, and eleven microsatellite loci we characterize population genetic differentiation among 158 brown pelicans. The Galápagos subspecies is genetically distinct from the sampled continental subspecies, possessing a unique ND2 haplotype and unique mitochondrial control region haplotypes. Samples from the two continental subspecies all possessed the same ND2 haplotype and shared four mitochondrial control region haplotypes. Bayesian clustering in STRUCTURE placed the Galápagos subspecies in a distinct genetic group with high probability, but could not differentiate the continental subspecies from one another. Estimates of migration rates from BayesAss indicated substantial migration between continental subspecies, but no migration between the Galápagos subspecies and either continental subspecies. There are clearly two Evolutionarily Significant Units within the range of the brown pelican, which warrants conservation attention. Further investigation should determine how the un-sampled subspecies (P. o. murphyi and P. o. occidentalis) fit into the broader picture.     

Population and Conservation Genetics in an Endangered Lemur, <Emphasis Type="Italic">Indri indri</Emphasis>, Across Three Forest Reserves in Madagascar

Population decline and fragmentation often lead to reduced genetic diversity and population differentiation. Habitat destruction throughout Madagascar has caused population decline and extinction of many endemic species. Lemur populations, including those of the largest extant lemur, Indri indri, have been fragmented into remaining forest patches. We assessed the level of genetic diversity in indri populations in three protected reserves by genotyping a total of 43 individuals at 17 microsatellite loci. Genetic diversity in terms of heterozygosity was high in all three reserves, with no differences between reserves. Population structure and F _ST analyses revealed Analamazaotra Forest Station and the Torotorofotsy Conservation Area, which are separated by ca. 18 km to be genetically differentiated from each other with some admixture. Betampona Strict Nature Reserve, which is separated from the other reserves by ca. 130 km, exhibited clear population genetic differentiation, with no signs of admixture with the other reserves. Our genetic diversity estimates are similar to those for other Indridae in similar habitats and may reflect past rather than current population processes, given that populations have declined recently. Our results suggest that Betampona may be genetically isolated and that it is important to maintain gene flow between remaining populations to prevent loss of genetic diversity for the future conservation of Indri indri.     

Microsatellite analysis supports the existence of three cryptic species within the bumble bee <Emphasis Type="Italic">Bombus lucorum sensu lato</Emphasis>

Mitochondrial cytochrome oxidase I (COI) partial sequences are widely used in taxonomy for species identification. Increasingly, these sequence identities are combined with modelling approaches to delineate species. Yet the validity of species delineation based on such DNA ‘barcodes’ is rarely tested and may be called into question by phenomena such as ancestral polymorphisms in DNA sequences, phylogeographic divergence, mitochondrial introgression and hybridization, or distortion of mitochondrial inheritance through such factors as Wolbachia infection. The common and widespread European bumble bee Bombus lucorum s. lato contains three distinct mitochondrial DNA lineages that are assumed to represent three cryptic species, namely Bombus cryptarum, B. lucorum s. str. and B. magnus. To test whether nuclear gene pools of the three putative species were differentiated, we genotyped 304 sympatric members of the lucorum complex (54 B. cryptarum females, 168 B. lucorum s. str. females and 82 B. magnus females, as defined using mtDNA COI haplotypes) from 11 localities spread across the island of Ireland at seven nuclear microsatellite loci. Multilocus genotypes clustered into three discrete groups that largely corresponded to the three mtDNA lineages: B. cryptarum, B. lucorum s. str. and B. magnus. The good fit of mitochondrial haplotype to nuclear (microsatellite) genotypic data supports the view that these three bumble bee taxa are reproductively isolated species, as well as providing a vindication of species identity using so-called DNA barcodes.     

Genetic structure of Sakhalin spruce (<Emphasis Type="Italic">Picea glehnii</Emphasis>) in northern Japan and adjacent regions revealed by nuclear microsatellites and mitochondrial gene sequences

The genetic structure of Sakhalin spruce (Picea glehnii) was studied across the natural range of the species, including two small isolated populations in south Sakhalin and Hayachine, by using six microsatellite loci and maternally inherited mitochondrial gene sequences. We also analyzed P. jezoensis, a sympatric spruce in the range. Genetic diversity of P. glehnii was higher in central Hokkaido and the lowest in the Hayachine. Bayesian clustering and principal coordinate analysis by using the microsatellites indicated that the Hayachine was clearly distinct from other populations, implying that it had undergone strong genetic drift since the last glacial period. P. glehnii harbored four mitochondrial haplotypes, two of which were shared with P. jezoensis. One of the two was observed without geographical concentration, suggesting its derivation from ancestral polymorphism. Another was observed in south Sakhalin and in P. jezoensis across Sakhalin. The Bayesian clustering—by using four microsatellite loci, including P. jezoensis populations—indicated unambiguous species delimitation, but with possible admixture of P. jezoensis genes into P. glehnii in south Sakhalin, where P. glehnii is abundantly overwhelmed by P. jezoensis; this might explain the occurrence of introgression of the haplotype of P. jezoensis into P. glehnii.     

Conservation genetics of redside dace (<Emphasis Type="Italic">Clinostomus elongatus</Emphasis>): phylogeography and contemporary spatial structure

Redside dace Clinostomus elongatus (Teleostei: Cyprinidae) is a species of conservation concern that is declining throughout its range as a result of habitat fragmentation, degradation and loss. We characterized the genetic structure and diversity of redside dace populations across the species range using mitochondrial and microsatellite data to inform conservation efforts and assess how historical and recent events have shaped genetic structure and diversity within and among populations. Phylogeographic structure among 28 redside dace populations throughout southern Ontario (Canada) and the United States was assessed by sequence analysis of the mitochondrial cytochrome b and ATPase 6 and 8 genes. Populations were also genotyped using ten microsatellite loci to examine genetic diversity within and among populations as well as contemporary spatial structuring. Mitochondrial DNA sequence data revealed three geographically distinct lineages, which were highly concordant with groupings identified by microsatellite analysis. The combined genetic data refute published glacial refugia hypotheses of a single Mississippian refugium or of two lineages associated with Mississippian and Atlantic refugia. Secondary contact between the two eastern groups was documented in the Allegheny River drainage and tributaries to Lake Ontario. With the exception of several allopatric populations within the Allegheny watershed, high genetic structuring among populations suggests their isolation, indicating that recovery efforts should be population-based.     

Existence of two strains of <Emphasis Type="Italic">Habrobracon hebetor</Emphasis> (Hymenoptera: Braconidae): a complex in Thailand and Japan

Habrobracon hebetor Say (Hymenoptera: Braconidae) is a cosmopolitan gregarious ectoparasitoid that attacks larvae of several species of Lepidoptera. Although there are two genetically different strains within H. hebetor, distribution of the strains has been poorly understood. In 2010, in Thailand, where H. hebetor has been known as a parasitoid of stored grain pests, it was found that H. hebetor attacked Opisina arenosella Walker (Lepidoptera: Oecophoridae), which is an invasive pest of coconut palm. For correct identification of this H. hebetor, we conducted DNA analysis and cross tests using populations collected from O. arenosella and stored grain pests in Thailand and populations in Japan known as H. hebetor. We obtained 413 bp of mitochondrial cytochrome oxidase I (COI) sequences and 414 bp of 16S rRNA gene sequences, and both indicated that there are two distinct clades within H. hebetor: one contains insects from Thailand, Spain, India, and Barbados; the other contains insects from Japan and the USA. There were no genetic differences or sexual isolation between Thai populations from different hosts. Our results also showed that populations in Thailand were sexually isolated from a H. hebetor population in Japan.     

Evidence of multiple introductions and genetic admixture of the Asian brush-clawed shore crab <Emphasis Type="Italic">Hemigrapsus takanoi</Emphasis> (Decapoda: Brachyura: Varunidae) along the Northern European coast

The Asian brush-clawed shore crab Hemigrapsus takanoi is a non-indigenous species along the Northern European coast. Although the history of range expansion of European H. takanoi has been well-documented, little is known about the genetic compositions of either the introduced European populations or the native Asian ones. We therefore collected H. takanoi broadly from their native Asian sites and introduced European ranges, and genotyped them by sequencing the mitochondrial 16S RNA gene and by analyzing nuclear microsatellite loci. Our results revealed that the H. takanoi Bay of Seine (France) populations consisted of a genetic admixture between populations in Japan and those in the Yellow Sea region. These French populations should be carefully monitored in the future, since the genetic admixture of multiple source populations may accelerate range expansion in non-indigenous organisms. Our results also suggested that shipping lines from East Asia were more probable vectors than historical juvenile oyster transportations from Japan for the foundation of present European H. takanoi populations. Interestingly, gene flow between populations in Japan and those in the Yellow Sea region (i.e., domestic invasion) was not observed despite the higher potential for artificial translocations via shipping lines in the native Asian range compared with those from Asia to Europe. The lack of domestic invasions implied that intra-specific priority effects of the resident H. takanoi populations played an important role in preventing the successful colonization of artificially-transferred individuals.     

Biogeography and designatable units of <Emphasis Type="Italic">Bombus occidentalis</Emphasis> Greene and <Emphasis Type="Italic">B. terricola</Emphasis> Kirby (Hymenoptera: Apidae) with implications for conservation status assessments

Conservation action for species of concern requires that “designatable units” (e.g., species, subspecies, geographic races, genetically distinct forms) are clearly defined, or that the species complex is treated as a whole. Several species of bumble bee are currently threatened, and some of these have cryptic colouration (resembling other species), or form complexes that vary considerably in colour patterning. Here we address the taxonomy and distribution of Bombus occidentalis Greene and B. terricola Kirby, both of which are currently of conservation concern in North America. Bombus occidentalis includes two apparently monophyletic groups of COI barcode haplotypes (recently considered as subspecies) with ranges mostly separated by that of their sister species, B. terricola. The southern B. o. occidentalis ranges throughout the western United States and into western Canada from southern Saskatchewan and Alberta, and throughout British Columbia north to ca. 55°N; the northern B. o. mckayi Ashmead, is restricted to north of this in British Columbia, westernmost Northwest Territories, Yukon Territory and Alaska. Bombus o. mckayi exists, as far as is known, only with a “banded” colour pattern. By contrast, B. o. occidentalis occurs in both banded and non-banded colour patterns, although the southern banded colour pattern is geographically isolated from the northern subspecies. Bombus o. occidentalis has declined throughout its range, perhaps due in part to exposure to novel parasites. Despite having similar levels of parasitism (ca. 40 %) as the southern subspecies, B. o. mckayi appears to have stable populations at present. There is therefore compelling evidence that the two subspecies should be distinguished for conservation and management purposes. We present the evidence for their distinction and provide tools for subspecies recognition.     

Chemical and molecular identification of the invasive termite <Emphasis Type="Italic">Zootermopsis nevadensis</Emphasis> (Isoptera: Archotermopsidae) in Japan

Numerous termite species have been introduced outside their native ranges by human transport, and some have become invasive. The dampwood termite Zootermopsis nevadensis (Hagen), which is native to western North America, has been introduced to and become established in Kawanishi City, Hyogo Prefecture, Japan. Zootermopsis nevadensis is subdivided into two subspecies based on cuticular hydrocarbon (CHC) phenotypes: Z. nevadensis nevadensis and Z. nevadensis nuttingi (Haverty and Thorne). Here, we identified Z. nevadensis in Japan as hybrids between the two subspecies. Chemical analysis showed the presence of 7,15-dimethylhenicosane and 5,17-dimethylhenicosane in the CHCs of Z. nevadensis in Japan, corresponding to the CHC phenotype of Z. n. nevadensis. Conversely, all mitochondrial cytochrome c oxidase subunit I sequences of Z. nevadensis in Japan were identical to sequences from Z. n. nuttingi and hybrids between the two subspecies from a native hybrid zone in California, USA. In addition, phylogenetic analysis showed that Z. nevadensis in Japan formed a clade with Z. n. nuttingi and hybrids between the two subspecies. Our results show discordance between the chemical and genetic features of Z. nevadensis in Japan, indicating that individuals of Z. nevadensis in Japan are hybrids between the two subspecies.     

Isolation and Characterization of Microsatellite Markers for <Emphasis Type="Italic">Viola websteri</Emphasis> (Violaceae) and Cross-Species Amplification within the Genus <Emphasis Type="Italic">Viola</Emphasis>

We isolated and characterized microsatellite loci in Viola websteri (Violaceae), an endangered species from Korea and endemic to Northeast Asia. A total of 27 microsatellite loci were developed and tested in Korean and Chinese populations. The number of alleles per locus varied from two to eight. The observed and expected heterozygosities within two populations were 0.000 to 1.000 and 0.080 to 0.816, respectively. Korean and Chinese populations were clearly distinguished by the private alleles from 16 loci. A total of 21 loci out of the 27 developed loci were successfully cross-amplified in 39 other Viola species. We believe that these microsatellite loci will be useful for future studies on genetic diversity and population structure of V. websteri, as well as other Viola species.     

Evaluation of phylogenetic relationships in the genus <Emphasis Type="Italic">Mus</Emphasis> using <Emphasis Type="Italic">t</Emphasis>-specific microsatellite DNA markers

The t-complex includes a complex system of genes localized in the proximal region of chromosome 17 of house mouse Mus musculus. The results of microsatellite analysis of laboratory stocks of house mice carrying t ¹², t ^w5, t ^w12, and t ^w73 haplotypes and wild mice from natural populations of Russia (Volgograd, Rostov, Saratov oblasts, and Kalmykia), Armenia, Bulgaria, Iran, and Mongolia performed by the PCR method with the use of eight pairs of D17Mit primers (16, 21, 23, 28, 32, 57, 63, 78) are presented. These pairs of primers amplify microsatellite DNA sequences on mouse chromosome 17 in the region from 7.6 to 18.8 cM that correspond to inversions (In (17) 3.4). Each pair of primers recognized three to six variants of nucleotide sequences ranging in size from 90–120 bp (D17Mit 16) to 300–330 bp (D17Mit 57). In most cases, two variants of nucleotide sequences were detected in each individual, i. e., most individuals were heterozygous for the microsatellite loci under study. The highest similarity of the spectra of microsatellite DNA fragments was revealed in laboratory stocks of house mice carrying the t ^w5 and t ^w73 haplotypes. The spectra of animals from the Rostov and Volgograd oblasts appeard to be most similar to them. The microsatellite spectra of individuals from Iran closely resemble the spectrum of an individual from Armenia. It was demonstrated that amplified microsatellite fragments localized in the region of the t-complex can be used to identify representatives of the Mus genus from wild populations.     

Complete mitochondrial genome sequence of <Emphasis Type="Italic">Cucullaea labiata</Emphasis> (Arcoida: Cucullaeidae) and phylogenetic implications

The complete mitochondrial genome of Cucullaea labiata (Arcoida: Cucullaeidae) was firstly determined in this study in order to better understand the phylogenetic relationship between Cucullaeidae and Arcidae. The C. labiata mitochondrial genome was 25,845 bp in size and contained 12 protein-coding genes, 2 rRNA and 22 tRNA genes. The number and the location of the tRNA genes were different from three Arcidae species (Scapharca broughtonii, Scapharca kagoshimensis and Tegillarca granosa). Gene arrangement also differed dramatically. The length of the non-coding regions was 10,559 bp, in which the largest one (6057 bp) included eight point nine copies of a 659 bp repeat motif. The number of repeated sequences was different in different individuals, similar to the findings from the mitochondrial genome of S. broughtonii and Placopecten magellanicus. One intron was found in cox1 gene both in CL_98 and in CL_99 individuals of C. labiata. The reason why mitochondrial introns are retained so scarcely in bivalve taxa needs further research. Phylogenetic analyses based on 12 concatenated amino acid sequences of protein-coding genes supported Cucullaeidae was the sister group of Arcidae.     

Nuclear mtDNA pseudogenes as a source of new variants of the mtDNA cytochrome <Emphasis Type="Italic">b</Emphasis> haplotypes: A case study of Siberian rubythroat <Emphasis Type="Italic">Luscinia calliope</Emphasis> (Muscicapidae,Aves)

Sequence polymorphism of the mitochondrial DNA cytochrome b gene fragment was analyzed in 21 specimens of subspecies Luscinia calliope calliope (Pallas, 1776) and two specimens of L. c. anadyrensis (Portenko, 1939). On sequence chromatograms, in 19 specimens of L. c. calliope, double peaks of heteroplasmy type in the taxon-specific positions were revealed. Moreover, two clone variants were identified. The first variant was the calliope mitochondrial cyt b gene and the second was the nuclear cyt b pseudogene, similar to the mitochondrial haplotype anadyrensis-camtschatkensis. In L. c. anadyrensis, four clone variants, represented by the mitochondrial calliope and anadyrensis-camtschatkensis cyt b genes and nuclear calliope and sachalinensis cyt b pseudogenes, were identified. Some nuclear cyt b pseudogenes were highly similar (98–99%) to the mitochondrial genes of the subspecies L. c. anadyrensis, L. c. camtschatkensis, and L. c. sachalinensis. In the same time, the majority of nuclear pseudogene sequences were characterized by a high level of polymorphism, caused by nonsynonymous substitutions (up to five substitutions per sequence), the presence of indels in some of the clones, and TAA and TGA stop codons. In our opinion, the mitochondrial haplotypes anadyrensis-camtschatkensis and sachalinensis occurred as a result of intergenomic homologous recombination. This finding provides a new insight into the colonization history of the northeastern part of the range by L. calliope, according to which populating the territory of Chukotka, Kamchatka, and Sakhalin took place at different times and along the independent pathways.     

Phylogenetic relationships in southern African Bryde’s whales inferred from mitochondrial DNA: further support for subspecies delineation between the two allopatric populations

Bryde’s whales (Balaenoptera edeni) are medium-sized balaenopterids with tropical and subtropical distribution. There is confusion about the number of species, subspecies and populations of Bryde’s whale found globally. Two eco-types occur off South Africa, the inshore and offshore forms, but with unknown relationship between them. Using the mtDNA control region we investigated the phylogenetic relationship of these populations to each other and other Bryde’s whale populations. Skin, baleen and bone samples were collected from biopsy-sampled individuals, strandings and museum collections. 97 sequences of 674 bp (bp) length were compared with published sequences of Bryde’s whales (n?=?6) and two similar species, Omura’s (B. omurai) and sei (B. borealis) whales (n?=?3). We found eight haplotypes from the study samples: H1–H4 formed a distinct, sister clade to pelagic populations of Bryde’s whales (B. brydei) from the South Pacific, North Pacific and Eastern Indian Ocean. H5–H8 were included in the pelagic clade. H1–H4 represented samples from within the distributional range of the inshore form. Pairwise comparisons of the percentage of nucleotide differences between sequences revealed that inshore haplotypes differed from published sequences of B. edeni by 4.7–5.5% and from B. brydei by 1.8–2.1%. Ten fixed differences between inshore and offshore sequences supported 100% diagnosability as subspecies. Phylogenetic analyses grouped the South African populations within the Bryde’s-sei whale clade and excluded B. edeni. Our data, combined with morphological and ecological evidence from previous studies, support subspecific classification of both South African forms under B. brydei and complete separation from B. edeni.     

Phenotypic variability of eye-spots in natural populations of <Emphasis Type="Italic">Coenonympha pamphilus</Emphasis> L. (Lepidoptera,Satyridae)

Variation of eye-spots in the wing pattern of Coenonympha pamphilus (Linnaeus, 1758) was studied in the Urals with adjacent territories and in Dzhelal-Abad Province of Kyrgyzstan. Discriminant analysis of the wing length and eye-spot diameter and the phenetic distances calculated by the Hartman’s method revealed clinal variation of the characters. The butterflies in the northern parts of the range (Sverdlovsk and Kurgan Provinces) are smaller than those in the south (Orenburg and Chelyabinsk Provinces) and have fewer eye-spots which themselves are smaller. The Kyrgyzstan specimens differ significantly from the Ural ones (the nominotypical subspecies) in both quantitative and qualitative characteristics of the wing pattern, and should probably be assigned to the subspecies C. pamphilus marginata Heyne, 1894. As in most Satyridae, females of C. pamphilus are larger than males and on the average possess more eye-spots on the wings. The degree of phenotypic variation in natural populations was studied using the method of variation spectra (Kovalenko, 1996a, 1996b, 2007, etc.). The arrangement of phenotypic combinations within the theoretical spectrum (St) matrix allows one to describe the actual (Sr) and potential (Sp) spectra for either sex and for the species as a whole. The actual spectrum was found to be considerably broader in males than in females. With minor variations, Sr and Sp showed the same general trends in different samples of both sexes. In all the samples, phenetic combinations with one spot on the fore wing (in cell M ₁-M ₂) were predominant. The hind wing had either no spots (which was typical of males, especially in the northern parts of the range) or the maximum possible number, six (mostly in females, more often in the southern parts of the range). The phenetic combinations with the maximum (4) number of spots on the fore wing and the minimum number (0) on the hind wing are prohibited for C. pamphilus.     

Nucleotide polymorphisms of candidate genes of adaptive significance in the ural populations of <Emphasis Type="Italic">Larix sibirica</Emphasis> Ledeb.

The objectives of conservation and sustainable forest management require in depth study of genomes of woody plants and definition of their intraspecific genetic diversity. In recent years, an approach was developed based on the study of “candidate genes” that can potentially be involved in the formation of adaptive traits. In this study, we investigated nucleotide polymorphism of several adaptive candidate genes in the populations of Siberian larch (Larix sibirica Ledeb.) in the Urals. Representatives of this genus are among the most valuable and widely distributed forest tree species in Russia. From ten selected gene loci in the genome of L. sibirica, we isolated and investigated three loci, one of which (ABA-WDS) was sequenced in L. sibirica for the first time. The total length of the analyzed sequence in each individual amounted to 2865 bp. The length of locus alignment was from 360 bp to 1395 bp. In total, we identified 200 polymorphic positions. The most conservative is locus 4CL1-363, and the most polymorphic is locus sSPcDFD040B03103-274. The studied populations of L. sibirica are characterized by a high level of nucleotide polymorphism in comparison with other species and genuses (Picea, Pinus, Pseudotsuga, Abies) conifers plants (Hd = 0.896; π = 0.007; θ_W = 0.015). The most selectively neutral polymorphism (D _T =–0.997) was attributed to locus 4CL1-363, and polymorphism with high probability of adaptability (D _T =–1.807) was determined for the ABA-WDS locus. We identified 54 SNP markers, only five of which were nonsynonymous (9.26%) replacements. The average frequency of SNPs in the three studied loci of L. sibirica was one SNP in 53 bp. We detected unique SNP markers for eight populations, which could potentially be used to identify populations. Populations that are characterized by the highest number of unique SNP markers can be recommended for selection in order to preserve the gene pool of the species.     

The role of ecological factors in determining phylogeographic and population genetic structure of two sympatric island skinks (<Emphasis Type="Italic">Plestiodon kishinouyei</Emphasis> and <Emphasis Type="Italic">P. stimpsonii</Emphasis>)

We conducted comparative phylogeographic and population genetic analyses of Plestiodon kishinouyei and P. stimpsonii, two sympatric skinks endemic to islands in the southern Ryukyus, to explore different factors that have influenced population structure. Previous phylogenetic studies using partial mitochondrial DNA indicate similar divergence times from their respective closest relatives, suggesting that differences in population structure are driven by intrinsic attributes of either species rather than the common set of extrinsic factors that both presumably have been exposed to throughout their history. In this study, analysis of mtDNA sequences and microsatellite polymorphism demonstrate contrasting patterns of phylogeography and population structure: P. kishinouyei exhibits a lower genetic variability and lower genetic differentiation among islands than P. stimpsonii, consistent with recent population expansion. However, historical demographic analyses indicate that the relatively high genetic uniformity in P. kishinouyei is not attributable to recent expansion. We detected significant isolation-by-distance patterns among P. kishinouyei populations on the land bridge islands, but not among P. stimpsonii populations occurring on those same islands. Our results suggest that P. kishinouyei populations have maintained gene flows across islands until recently, probably via ephemeral Quaternary land bridges. The lower genetic variability in P. kishinouyei may also indicate smaller effective population sizes on average than that of P. stimpsonii. We interpret these differences as a consequence of ecological divergence between the two species, primarily in trophic level and habitat preference.