Genetic consequences of human management in an introduced island population of red deer (Cervus elaphus)

We investigated phylogeography and spatial genetic structure in an introduced island population of red deer (Cervus elaphus) on the Isle of Rum, Scotland, experiencing spatial variation in management regime. Five different mitochondrial DNA (mtDNA) haplotypes were present among female red deer on Rum. These comprised two phylogenetically divergent groups, one of which clustered with red deer from Sardinia and North Africa, while the other four grouped with other Western European red deer. Recent and historical red deer management practices explain this result. The Rum population is descended from recent introductions from at least four different UK mainland populations, and translocation of red deer within the UK and across Europe is well documented. We found significant spatial genetic structure across Rum in both mtDNA haplotypes and microsatellite markers. Mitochondrial spatial structure was over an order of magnitude greater than structure in nuclear markers. This extreme difference is explained by the fact that the Rum population was introduced from different source populations, the highly male-biased dispersal patterns of red deer and the much smaller effective population size of mitochondrial compared to nuclear markers. Spatial structure in mtDNA conformed to a pattern of isolation by distance, while nuclear DNA did not. Apparent structure in the nuclear markers was driven by differences between the North Block and the rest of the island. We suggest that recent differences in the management regimes in different parts of the island have led to differences in effective male migration that would account for this observation.     

Re‐colonization by common eiders Somateria mollissima in the Aleutian Archipelago following removal of introduced arctic foxes Vulpes lagopus

Islands provide refuges for populations of many species where they find safety from predators, but the introduction of predators frequently results in elimination or dramatic reductions in island‐dwelling organisms. When predators are removed, re‐colonization for some species occurs naturally, and inter‐island phylogeographic relationships and current movement patterns can illuminate processes of colonization. We studied a case of re‐colonization of common eiders Somateria mollissima following removal of introduced arctic foxes Vulpes lagopus in the Aleutian Archipelago, Alaska. We expected common eiders to resume nesting on islands cleared of foxes and to re‐colonize from nearby islets, islands, and island groups. We thus expected common eiders to show limited genetic structure indicative of extensive mixing among island populations. Satellite telemetry was used to record current movement patterns of female common eiders from six islands across three island groups. We collected genetic data from these and other nesting common eiders at 14 microsatellite loci and the mitochondrial DNA control region to examine population genetic structure, historical fluctuations in population demography, and gene flow. Our results suggest recent interchange among islands. Analysis of microsatellite data supports satellite telemetry data of increased dispersal of common eiders to nearby areas and little between island groups. Although evidence from mtDNA is suggestive of female dispersal among island groups, gene flow is insufficient to account for recolonization and rapid population growth. Instead, near‐by remnant populations of common eiders contributed substantially to population expansion, without which re‐colonization would have likely occurred at a much lower rate. Genetic and morphometric data of common eiders within one island group two and three decades after re‐colonization suggests reduced movement of eiders among islands and little movement between island groups after populations were re‐established. We predict that re‐colonization of an island group where all common eiders are extirpated could take decades.     

Conserving the endangered Mexican fishing bat (<Emphasis Type="Italic">Myotis vivesi</Emphasis>): genetic variation indicates extensive gene flow among islands in the Gulf of California

The endangered Mexican fishing bat, Myotis vivesi, appears to have suffered widespread extinction and population decline on islands throughout the Gulf of California, largely due to predation by introduced cats and rats. To restore populations of fishing bats and other native species, conservation efforts have focused on eradicating introduced vertebrates from several Gulf islands. These efforts assume that individuals from existing populations will recolonize islands and that continued dispersal will help sustain vulnerable populations thereafter. However, the extent of inter-island dispersal in fishing bats is unknown. In this study we analyzed patterns of genetic variation to gauge the extent of gene flow and, thus, potential dispersal among islands. DNA was sampled from 257 fishing bats on 11 Gulf islands (separated by ca. 6–685 km of open water), and individuals were genotyped at six microsatellite loci and haplotyped at a 282 bp fragment of the mtDNA control region. With microsatellites, we found weak population genetic structure and a pattern of isolation by distance, while with mtDNA we found strong structure but no isolation by distance. Our results indicate that island subpopulations separated by large expanses of open water are nonetheless capable of maintaining high genetic diversity and high rates of gene flow. Unfortunately, little is known about the spatial patterns of dispersal or mating system of fishing bats, and these behavioral factors, in particular female philopatry, might reduce the probability of the species recolonizing Gulf islands.     

The microevolution of the Galápagos marine iguana Amblyrhynchus cristatus assessed by nuclear and mitochondrial genetic analyses

Marine iguanas may have inhabited the Galápagos archipelago and its former, now sunken islands for more than 10 million years (Myr). It is therefore surprising that morphological and immunological data indicate little evolutionary divergence within the genus. We utilized mitochondrial DNA (mtDNA) sequence analyses and nuclear DNA fingerprinting to re-evaluate the level and pattern of genetic differentiation among 22 marine iguana populations from throughout the archipelago. Both genetic marker systems detect a low level of within-genus divergence, but they show contrasting levels of geographical subdivision among the populations. The mitochondrial gene pools of populations from different regions of the archipelago are isolated, and the mtDNA pattern appears to follow the sequence in which the islands were colonized by marine iguanas. Conversely, the nuclear DNA study indicates substantial interpopulational gene exchange, and the geographical distribution of the nuclear markers seems to be determined by isolation by distance among the populations. The natural history of marine iguanas suggests that the contrasting nuclear and mitochondrial DNA patterns result from an asymmetric migration behaviour of the two sexes, with higher (active and passive) interisland dispersal for males than females. Separate genetic analyses for the sexes appear to support this hypophesis. Based on these findings, a scenario is proposed that explains the marine iguanas' low genetic divergence, notwithstanding their long evolutionary history in the Galápagos archipelago.     

Cryptic diversity within the endemic prehensile‐tailed gecko Urocotyledon inexpectata across the Seychelles Islands: patterns of phylogeographical structure and isolation at the multilocus level

The deciphering of the process of genetic differentiation of species with insular distributions is relevant for biogeographical and conservation reasons. Despite their importance as old gondwanic islands and part of the western Indian Ocean biodiversity hotspot, little is known about the genetic structure of taxa from the Seychelles Islands. We have examined the patterns of structure and isolation within Urocotyledon inexpectata (Reptilia: Geckkonidae), an endemic species from this archipelago. Genetic diversity was screened from populations across the archipelago for both mitochondrial and nuclear genes. Gene genealogies and model‐based inference were used to explore patterns and timings of isolation between the main lineages. High levels of genetic diversity were found for the mitochondrial and some of the nuclear markers. This species harbours at least two highly differentiated lineages, exclusively distributed across the northern and southern groups of the islands. The main split between these was dated back to the Miocene–late Pliocene, but isolation events throughout the Pliocene and Pleistocene were also inferred. Migration between groups of islands was apparently nonexistent, except for one case. The low dispersal capabilities of this species, together with the intrinsic fragmented nature of its geographical distribution, seem to have resulted in highly structured populations, despite the cyclic periods of contact between the different island groups. These populations may currently represent more than one species, making U. inexpectata another example of a morphologically cryptic lineage with deep genetic divergence within gekkonids. The observed patterns suggest a hypothetical biogeographic scenario (of a main north–south phylogeographic break) for the Seychelles that can be further tested with the exploration of the phylogeographic structure of other Seychellois taxa. © 2011 The Linnean Society of London, Biological Journal of the Linnean Society, 2011, 104 , 177–191.     

Spatial structure of lemming populations (Dicrostonyx groenlandicus) fluctuating in density

The pattern and scale of the genetic structure of populations provides valuable information for the understanding of the spatial ecology of populations, including the spatial aspects of density fluctuations. In the present paper, the genetic structure of periodically fluctuating lemmings (Dicrostonyx groenlandicus) in the Canadian Arctic was analysed using mitochondrial DNA (mtDNA) control region sequences and four nuclear microsatellite loci. Low genetic variability was found in mtDNA, while microsatellite loci were highly variable in all localities, including localities on isolated small islands. For both genetic markers the genetic differentiation was clear among geographical regions but weaker among localities within regions. Such a pattern implies gene flow within regions. Based on theoretical calculations and population census data from a snap-trapping survey, we argue that the observed genetic variability on small islands and the low level of differentiation among these islands cannot be explained without invoking long distance dispersal of lemmings over the sea ice. Such dispersal is unlikely to occur only during population density peaks.     

Phylogeography of the pine processionary moth Thaumetopoea wilkinsoni in the Near East

Phylogeographic structure of the eastern pine processionary moth Thaumetopoea wilkinsoni was explored in this study by means of nested clade phylogeographic analyses of COI and COII sequences of mitochondrial DNA and Bayesian estimates of divergence times. Intraspecific relationships were inferred and hypotheses tested to understand historical spread patterns and spatial distribution of genetic variation. Analyses revealed that all T. wilkinsoni sequences were structured in three clades, which were associated with two major biogeographic events, the colonization of the island of Cyprus and the separation of southwestern and southeastern Anatolia during the Pleistocene. Genetic variation in populations of T. wilkinsoni was also investigated using amplified fragment length polymorphisms and four microsatellite loci. Contrasting nuclear with mitochondrial data revealed recurrent gene flow between Cyprus and the mainland, related to the long-distance male dispersal. In addition, a reduction in genetic variability was observed at both mitochondrial and nuclear markers at the expanding boundary of the range, consistent with a recent origin of these populations, founded by few individuals expanding from nearby localities. In contrast, several populations fixed for one single mitochondrial haplotype showed no reduction in nuclear variability, a pattern that can be explained by recurrent male gene flow or selective sweeps at the mitochondrial level. The use of both mitochondrial and nuclear markers was essential in understanding the spread patterns and the population genetic structure of T. wilkinsoni, and is recommended to study colonizing species characterized by sex-biased dispersal.     

High similarity of genetic population structure in the false clown anemonefish (<Emphasis Type="Italic">Amphiprion ocellaris</Emphasis>) found in microsatellite and mitochondrial control region analysis

Many studies, using various marker systems, have been conducted on the genetic population structure of marine organisms to reveal connectivity among locations and dispersal capabilities. Although mitochondrial sequence markers are widely used, their accuracy is controversially discussed in the context of small scale population genetic discrimination. In the present study, the genetic population structure of the False Clown Anemonefish (Amphiprion ocellaris) in the Indo-Malay Archipelago was revealed by screening six microsatellite loci. Results were congruent to previous mitochondrial control region results, with three major genetic breaks within the Indo-Malay Archipelago. Similar to the mitochondrial DNA (mtDNA) analysis, microsatellite data showed a correlation of genetic structure to historical ocean basin separation during Pleistocene sea level low stands, geographic distance, and dominant current patterns. However, microsatellite divergences are not as deep as the mtDNA divergence, suggesting either that admixture of mtDNA lineages is slower than that of nuclear microsatellites, providing a rather historic picture of separation, or the stronger differentiation signal is due to lower effective population sizes presented by mtDNA. As well, the microsatellite analysis did not give a better resolution on the small scale as expected. This study showed that depending on the genetic markers used, different stages of population separation might be illuminated.     

Massive genetic introgression in threatened northern crested newts (<Emphasis Type="Italic">Triturus cristatus</Emphasis>) by an invasive congener (<Emphasis Type="Italic">T. carnifex</Emphasis>) in Western Switzerland

Genetic pollution through introgressive hybridization of local species by exotic relatives is a major, yet neglected aspect of biological invasions, particularly in amphibians where human introductions are frequent. In Western Switzerland, crested newts make an interesting case: the Italian species Triturus carnifex was introduced at least a century ago within the range of the native and threatened T. cristatus. To understand the genetic consequences of this introduction and inform wildlife management authorities, we conducted a genetic survey on the remaining northern crested newt populations known in the area, using newly-developed species-diagnostic nuclear (microsatellites) and mitochondrial (control region) DNA markers. We documented massive nuclear introgression by the T. carnifex genome, which has completely replaced T. cristatus in most populations, especially in the Geneva area where the introduction was originally reported. However, many of these individuals retained the ancestral T. cristatus mtDNA, which could be explained by asymmetric introgression between the two species, stemming from demographic and/or selective processes. Analyses of genetic diversity support multiple events of T. carnifex releases, most-likely of proximate North Italian origin. We pinpointed the last indigenous populations in the region and recommend to prioritize their protection. Our study demonstrates the invasive potential of introduced taxa through introgressive hybridization, alerts about the underestimated rate of illegal amphibian translocations, and emphasizes the need for genetic analyses to monitor such invasions.     

Contemporary genetic structure of Xantus's Hummingbird (Basilinna xantusii) in the Baja California peninsula

Genetic structure and phylogeographic patterns of natural populations are of great importance in assessing the conservation status of species. These population properties can be estimated using molecular markers of either mitochondrial DNA (mtDNA) or nuclear DNA (nDNA) to understand the historical, ecological and dispersal patterns that influence genetic exchange within and between populations. Basilinna xantusii is a sexually dimorphic hummingbird endemic to the Baja California Peninsula (BCP). It comprises three ancestral mitochondrial lineages linked to vicariant events, late Pleistocene climate changes and the geographical distribution of oases. This study aimed to determine and understand the current population genetic structure of this hummingbird. The genotypes of 16 microsatellite loci from 100 individuals collected across the geographical range of this species were compared with mtDNA sequences previously published. Cluster analyses identified five populations, two with almost no genetic admixture in the northern part of the BCP and three others with varying levels of admixed ancestry across the BCP. In San José de Magdalena, at the northernmost end of the range of Xantus's Hummingbird, 40% of individuals collected belong to one genetic cluster and the remaining 60% to another, both genetic clusters showing very little admixed ancestry. We hypothesize that, despite being in sympatry, these individuals do not interbreed, unlike the other populations where individuals showed ancestry coefficients of the other genetic groups. The philopatric behaviour of males and the long-range dispersal capacity of females probably determine the observed genetic differentiation pattern. The mito-nuclear discordance detected could be due to the molecular markers used and to female-biased dispersal. Gene flow is asymmetric in this species, being greater from north to south than vice versa, which is probably related to differences in the seasonality of precipitation across the BCP and to urbanization of the oases.     

Population genetic structure,diversity and stocking effect of the oriental weatherloach (<Emphasis Type="Italic">Misgurnus anguillicaudatus</Emphasis>) in an isolated island

Genetic endemism of island organisms and the threat to such organisms provided by artificially introduced genes are aspects of major interest in evolutionary and conservation studies of fishes. In this paper the genetic population structure of the oriental weatherloach, Misgurnus anguillicaudatus, in Sado Island of Japan was elucidated by phylogeographic analysis based on partial mitochondrial control region sequences. The specimens were sampled at 62 sites in Sado Island and 14 sites on the mainland close to the island. We found various haplotypes of different origins, most of which had already been reported from the mainland and other places of Japan. This suggests that the loach has been historically introduced to the island from various regions of Japan. Of the 62 sites on the island, cultured/nonnative individuals were confirmed to have been stocked at eight specific sites for feeding of re-introduced Japanese crested ibis (Nipponia nippon). By a Mantel test, geographical and genetic distances were not significantly correlated among the local populations in Sado Island. However a significant correlation was found when the eight stocked local populations were excluded from the analysis. This implied that the genetic distribution pattern of the loach on the island has been disturbed by the stocking. In addition, the nucleotide diversity values of stocked local populations were significantly higher than those of other local populations, also a likely outcome of the stocking. In conclusion, the loach on the island likely had their origins in multiple historical introductions and colonizations, where more recent stocking for the ibis has caused further genetic disturbance to their local populations.     

Very low genetic variability in the Indian queenless ant Diacamma indicum

Abstract We developed microsatellite markers and combined them with mitochondrial markers to analyse the population genetic structure of the queenless ant Diacamma indicum. This species, lacking winged queens, is likely to have a restricted female dispersal but exhibits various life history traits suggesting higher dispersal abilities than the other Diacamma species. Only 4 of 11 microsatellites were polymorphic and only 1 had more than 4 alleles over 166 individuals originating from 7 populations from the south of India. Only one mitochondrial DNA (mtDNA) haplotype was detected throughout India (including one population in the north) and Sri Lanka. Such a level of polymorphism is particularly low compared with other Diacamma species having much smaller ranges in the south of India. A strong genetic differentiation was observed between populations separated by more than a few kilometres. We also analysed the genetic differentiation between the Indian populations and two populations from the Japanese island of Okinawa, which are morphologically similar and might belong to the same species. The genetic differentiation was high for both markers, suggesting an absence of ongoing gene flow between these populations.     

North‐facing slopes and elevation shape asymmetric genetic structure in the range‐restricted salamander Plethodon shenandoah

Species with narrow environmental tolerances are often distributed within fragmented patches of suitable habitat, and dispersal among these subpopulations can be difficult to directly observe. Genetic data can help quantify gene flow between localities, which is especially important for vulnerable species with a disjunct range. The Shenandoah salamander (Plethodon shenandoah) is a federally endangered species known only from three mountaintops in Virginia, USA. To reconstruct the evolutionary history and population connectivity of this species, we generated both mitochondrial and nuclear data using sequence capture from individuals collected across all three mountaintops. Applying population and landscape genetic methods, we found strong population structure that was independent of geographic distance. Both the nuclear markers and mitochondrial genomes indicated a deep split between the most southern population and the genetically similar central and northern populations. Although there was some mitochondrial haplotype‐splitting between the central and northern populations, there was admixture in nuclear markers. This is indicative of either a recent split or current male‐biased dispersal among mountain isolates. Models of landscape resistance found that dispersal across north‐facing slopes at mid‐elevation levels best explain the observed genetic structure among populations. These unexpected results highlight the importance of incorporating landscape features in understanding and predicting the movement and fragmentation of this range‐restricted salamander species across space.     

Scale-specific sex-biased dispersal in the Valais shrew unveiled by genetic variation on the Y chromosome, autosomes, and mitochondrial DNA

We investigated sex specificities in the evolutionary processes shaping Y chromosome, autosomes, and mitochondrial DNA patterns of genetic structure in the Valais shrew (Sorex antinorii), a mountain dwelling species with a hierarchical distribution. Both hierarchical analyses of variance and isolation-by-distance analyses revealed patterns of population structure that were not consistent across maternal, paternal, and biparentally inherited markers. Differentiation on a Y microsatellite was lower than expected from the comparison with autosomal microsatellites and mtDNA, and it was mostly due to genetic variance among populations within valleys, whereas the opposite was observed on other markers. In addition, there was no pattern of isolation by distance for the Y, whereas there was strong isolation by distance on mtDNA and autosomes. We use a hierarchical island model of coancestry dynamics to discuss the relative roles of the microevolutionary forces that may induce such patterns. We conclude that sex-biased dispersal is the most important driver of the observed genetic structure, but with an intriguing twist: it seems that dispersal is strongly male biased at large spatial scale, whereas it is mildly biased in favor of females at local scale. These results add to recent reports of scale-specific sex-biased dispersal patterns, and emphasize the usefulness of the Y chromosome in conjunction with mtDNA and autosomes to infer sex specificities.     

Historic speciation and recent colonization of Eurasian monkey gobies (Neogobius fluviatilis and N. pallasi) revealed by DNA sequences,microsatellites, and morphology

Aim Hidden diversity within an invasive ‘species’ can mask both invasion pathways and confound management goals. We assessed taxonomic status and population structure of the monkey goby Neogobius fluviatilis across Eurasia, comparing genetic variation across its native and invasive ranges. Location Native populations were analysed within the Black and Caspian Sea basins, including major river drainages (Dnieper, Dniester, Danube, Don and Volga rivers), along with introduced locations within the upper Danube and Vistula river systems. Methods DNA sequences and 10 nuclear microsatellite loci were analysed to test genetic diversity and divergence patterns of native and introduced populations; phylogenetic analysis of mtDNA cytochrome b and nuclear RAG‐1 sequences assessed taxonomic status of Black and Caspian Sea lineages. Multivariate analysis of morphology was used to corroborate phylogenetic patterns. Population genetic structure within each basin was evaluated with mtDNA and microsatellite data using F_ST analogues and Bayesian assignment tests. Results Phylogenetic analysis of mitochondrial and nuclear sequences discerned a pronounced genetic break between monkey gobies in the Black and Caspian Seas, indicating a long‐term species‐level separation dating to c. 3 million years. This pronounced separation further was confirmed from morphological and population genetic divergence. Bayesian inference showed congruent patterns of population structure within the Black Sea basin. Introduced populations in the Danube and Vistula River basins traced to north‐west Black Sea origins, a genetic expansion pattern matching that of other introduced Ponto‐Caspian gobiids. Main conclusions Both genetic and morphological data strongly supported two species of monkey gobies that were formerly identified as subspecies: N. fluviatilis in the Black Sea basin, Don and Volga Rivers, and the Kumo‐Manych Depression, and Neogobius pallasi in the Caspian Sea and Volga River delta. Genetic origins of introduced N. fluviatilis populations indicated a common invasion pathway shared with other introduced Ponto‐Caspian fishes and invertebrates.     

Persistent inter‐ and intraspecific gene exchange within a parallel radiation of caterpillar hunter beetles (Calosoma sp.) from the Galápagos

When environmental gradients are repeated on different islands within an archipelago, similar selection pressures may act within each island, resulting in the repeated occurrence of ecologically similar species on each island. The evolution of ecotypes within such radiations may either result from dispersal, that is each ecotype evolved once and dispersed to different islands where it colonized its habitat, or through repeated and parallel speciation within each island. However, it remains poorly understood how gene flow during the divergence process may shape such patterns. In the Galápagos islands, three phenotypically similar species of the beetle genus Calosoma occur at higher elevations of different islands, while lowlands are occupied by a fourth species. By genotyping all major populations within this radiation for two nuclear and three mitochondrial gene fragments and seven microsatellite markers, we found strong support that the oldest divergence separates the highland species of the oldest island from the remaining species. Despite their morphological distinctness, highland species of the remaining islands were genetically closely related to the lowland population on each island and within the same magnitude as lowland populations sampled at different islands. Repeated evolution of highland ecotypes out of the lowland species appears the most likely scenario and estimates of geneflow rates revealed extensive admixture among ecotypes within islands, as well as between islands. These findings indicate that gene exchange among the different populations and species may have shaped the phylogenetic relationships and the repeated evolution of these ecotypes.     

Hierarchical Analysis of Genetic Structure in Native Fire Ant Populations: Results from Three Classes of Molecular Markers

We describe genetic structure at various scales in native populations of the fire ant Solenopsis invicta using two classes of nuclear markers, allozymes and microsatellites, and markers of the mitochondrial genome. Strong structure was found at the nest level in both the monogyne (single queen) and polygyne (multiple queen) social forms using allozymes. Weak but significant microgeographic structure was detected above the nest level in polygyne populations but not in monogyne populations using both classes of nuclear markers. Pronounced mitochondrial DNA (mtDNA) differentiation was evident also at this level in the polygyne form only. These microgeographic patterns are expected because polygyny in ants is associated with restricted local gene flow due mainly to limited vagility of queens. Weak but significant nuclear differentiation was detected between sympatric social forms, and strong mtDNA differentiation also was found at this level. Thus, queens of each form seem unable to establish themselves in nests of the alternate type, and some degree of assortative mating by form may exist as well. Strong differentiation was found between the two study regions using all three sets of markers. Phylogeographic analyses of the mtDNA suggest that recent limitations on gene flow rather than longstanding barriers to dispersal are responsible for this large-scale structure.     

High gene flow on a continental scale in the polyandrous Kentish plover Charadrius alexandrinus

Gene flow promotes genetic homogeneity of species in time and space. Gene flow can be modulated by sex‐biased dispersal that links population genetics to mating systems. We investigated the phylogeography of the widely distributed Kentish plover Charadrius alexandrinus. This small shorebird has a large breeding range spanning from Western Europe to Japan and exhibits an unusually flexible mating system with high female breeding dispersal. We analysed genetic structure and gene flow using a 427‐bp fragment of the mitochondrial (mtDNA) control region, 21 autosomal microsatellite markers and a Z microsatellite marker in 397 unrelated individuals from 21 locations. We found no structure or isolation‐by‐distance over the continental range. However, island populations had low genetic diversity and were moderately differentiated from mainland locations. Genetic differentiation based on autosomal markers was positively correlated with distance between mainland and each island. Comparisons of uniparentally and biparentally inherited markers were consistent with female‐biased gene flow. Maternally inherited mtDNA was less structured, whereas the Z‐chromosomal marker was more structured than autosomal microsatellites. Adult males were more related than females within genetic clusters. Taken together, our results suggest a prominent role for polyandrous females in maintaining genetic homogeneity across large geographic distances.     

Relative information content of polymorphic microsatellites and mitochondrial DNA for inferring dispersal and population genetic structure in the olive sea snake, Aipysurus laevis

Polymorphic microsatellites are widely considered more powerful for resolving population structure than mitochondrial DNA (mtDNA) markers, particularly for recently diverged lineages or geographically proximate populations. Weaker population subdivision for biparentally inherited nuclear markers than maternally inherited mtDNA may signal male-biased dispersal but can also be attributed to marker-specific evolutionary characteristics and sampling properties. We discriminated between these competing explanations with a population genetic study on olive sea snakes, Aipysurus laevis. A previous mtDNA study revealed strong regional population structure for A. laevis around northern Australia, where Pleistocene sea-level fluctuations have influenced the genetic signatures of shallow-water marine species. Divergences among phylogroups dated to the Late Pleistocene, suggesting recent range expansions by previously isolated matrilines. Fine-scale population structure within regions was, however, poorly resolved for mtDNA. In order to improve estimates of fine-scale genetic divergence and to compare population structure between nuclear and mtDNA, 354 olive sea snakes (previously sequenced for mtDNA) were genotyped for five microsatellite loci. F statistics and Bayesian multilocus genotype clustering analyses found similar regional population structure as mtDNA and, after standardizing microsatellite F statistics for high heterozygosities, regional divergence estimates were quantitatively congruent between marker classes. Over small spatial scales, however, microsatellites recovered almost no genetic structure and standardized F statistics were orders of magnitude smaller than for mtDNA. Three tests for male-biased dispersal were not significant, suggesting that recent demographic expansions to the typically large population sizes of A. laevis have prevented microsatellites from reaching mutation-drift equilibrium and local populations may still be diverging.     

Hierarchical analysis of population genetic structure in the monogynous ant Cataglyphis cursor using microsatellite and mitochondrial DNA markers

Despite having winged queens, female dispersal in the monogynous ant Cataglyphis cursor is likely to be restricted because colonies reproduce by fission. We investigated the pattern of population genetic structure of this species using eight microsatellite markers and a mitochondrial DNA (mtDNA) sequence, in order to examine the extent of female and nuclear gene flow in two types of habitat. Sampling was carried out at a large spatial scale (16 sites from 2.5 to 120 km apart) as well as at a fine spatial scale (two 4.5-km transects, one in each habitat type). The strong spatial clustering of mtDNA observed at the fine spatial scale strongly supported a restricted effective female dispersal. In agreement, patterns of the mtDNA haplotypes observed at large and fine spatial scales suggested that new sites are colonized by nearby sites. Isolation by distance and significant nuclear genetic structure have been detected at all the spatial scales investigated. The level of local genetic differentiation for mitochondrial marker was 15 times higher than for the nuclear markers, suggesting differences in dispersal pattern between the two sexes. However, male gene flow was not sufficient to prevent significant nuclear genetic differentiation even at short distances (500 m). Isolation-by-distance patterns differed between the two habitat types, with a linear decrease of genetic similarities with distance observed only in the more continuous of the two habitats. Finally, despite these low dispersal capacities and the potential use of parthenogenesis to produce new queens, no signs of reduction of nuclear genetic diversity was detected in C. cursor populations.