The influence of landscape,climate and history on spatial genetic patterns in keystone plants (Azorella) on sub‐Antarctic islands

The distribution of genetic variation in species is governed by factors that act differently across spatial scales. To tease apart the contribution of different processes, especially at intermediate spatial scales, it is useful to study simple ecosystems such as those on sub‐Antarctic oceanic islands. In this study, we characterize spatial genetic patterns of two keystone plant species, Azorella selago on sub‐Antarctic Marion Island and Azorella macquariensis on sub‐Antarctic Macquarie Island. Although both islands experience a similar climate and have a similar vegetation structure, they differ significantly in topography and geological history. We genotyped six microsatellites for 1,149 individuals from 123 sites across Marion Island and 372 individuals from 42 sites across Macquarie Island. We tested for spatial patterns in genetic diversity, including correlation with elevation and vegetation type, and clines in different directional bearings. We also examined genetic differentiation within islands, isolation‐by‐distance with and without accounting for direction, and signals of demographic change. Marion Island was found to have a distinct northwest–southeast divide, with lower genetic diversity and more sites with a signal of population expansion in the northwest. We attribute this to asymmetric seed dispersal by the dominant northwesterly winds, and to population persistence in a southwestern refugium during the Last Glacial Maximum. No apparent spatial pattern, but greater genetic diversity and differentiation between sites, was found on Macquarie Island, which may be due to the narrow length of the island in the direction of the dominant winds and longer population persistence permitted by the lack of extensive glaciation on the island. Together, our results clearly illustrate the implications of island shape and geography, and the importance of direction‐dependent drivers, in shaping spatial genetic structure.     

Phylogeography of <Emphasis Type="Italic">Eupodes minutus</Emphasis> (Acari: Prostigmata) on sub-Antarctic Marion Island reflects the impact of historical events

Marion Island, situated ∼2,300 km south-east of Cape Town, South Africa, has experienced multiple volcanic and glaciation events during its history. To better understand the impact of these events on species’ genetic structure, we determined the phylogeographic population structure of the mite, Eupodes minutus. We included 57 individuals sampled from 11 localities across the island. Our analyses based on the mitochondrial COI gene suggest a population expansion as would typically be expected when species recover after being confined to refugia. Standard phi (Φ) statistics and a spatial analysis of molecular variance (SAMOVA) identified unique populations on the south-western and south-eastern sides of the island. We argue that multiple volcanic events on the southern side of Marion, in combination with glaciations, effectively isolated these populations from each other.     

Population structure, propagule pressure, and conservation biogeography in the sub-Antarctic: lessons from indigenous and invasive springtails

The patterns in and the processes underlying the distribution of invertebrates among Southern Ocean islands and across vegetation types on these islands are reasonably well understood. However, few studies have examined the extent to which populations are genetically structured. Given that many sub‐Antarctic islands experienced major glaciation and volcanic activity, it might be predicted that substantial population substructure and little genetic isolation‐by‐distance should characterize indigenous species. By contrast, substantially less population structure might be expected for introduced species. Here, we examine these predictions and their consequences for the conservation of diversity in the region. We do so by examining haplotype diversity based on mitochondrial cytochrome c oxidase subunit I sequence data, from two indigenous (Cryptopygus antarcticus travei, Tullbergia bisetosa) and two introduced (Isotomurus cf. palustris, Ceratophysella denticulata) springtail species from Marion Island. We find considerable genetic substructure in the indigenous species that is compatible with the geological and glacialogical history of the island. Moreover, by employing ecological techniques, we show that haplotype diversity is likely much higher than our sequenced samples suggest. No structure is found in the introduced species, with each being represented by a single haplotype only. This indicates that propagule pressure is not significant for these small animals unlike the situation for other, larger invasive species: a few individuals introduced once are likely to have initiated the invasion. These outcomes demonstrate that sampling must be more comprehensive if the population history of indigenous arthropods on these islands is to be comprehended, and that the risks of within‐ and among‐island introductions are substantial. The latter means that, if biogeographical signal is to be retained in the region, great care must be taken to avoid inadvertent movement of indigenous species among and within islands. Thus, quarantine procedures should also focus on among‐island movements.     

Phylogeography of related diadromous species in continental and island settings,and a comparison of their potential and realized dispersal patterns

Aim To compare patterns of potential and realized dispersal in ecologically similar and phylogenetically related amphidromous shrimps (Atyidae) in continental and island‐dominated landscapes. Location Eastern Australia and the Caribbean region. Methods Population genetic and phylogeographic analyses of mitochondrial DNA data for Australatya striolata from eastern Australia (a continental landscape) and Atya scabra from the Caribbean (an island‐dominated landscape). Results Australatya striolata contained two highly divergent genetic lineages in eastern Australia, corresponding to the disjunct northern and southern populations, respectively. These lineages probably represent allopatric cryptic species, both of which were found to have genetically homogeneous population structures within their regions of occurrence. Atya scabra was genetically homogeneous throughout the Caribbean. Recent population expansions were detected for Atya scabra in the Caribbean, but not for northern or southern Australatya striolata. Main conclusions The findings of this study are consistent with previously reported patterns of genetic population structure in amphidromous species in both continental and island‐dominated landscapes, suggesting that potential for widespread dispersal is typically matched by realized patterns of panmixia. We therefore raise the hypothesis that landscape setting (i.e. continent or island‐dominated) does not influence dispersal patterns in amphidromous species. Further studies, especially of population genetic patterns of amphidromous species on continents, are needed to test this idea. Interestingly, results of the genetic neutrality tests led us to hypothesize that demographic and drift‐mutation equilibrium is attainable although not always evident for amphidromous species on continents, but is not attainable for those species distributed across island settings.     

Extinction and recolonization of maritime Antarctica in the limpet Nacella concinna (Strebel, 1908) during the last glacial cycle: toward a model of Quaternary biogeography in shallow Antarctic invertebrates

Quaternary glaciations in Antarctica drastically modified geographical ranges and population sizes of marine benthic invertebrates and thus affected the amount and distribution of intraspecific genetic variation. Here, we present new genetic information in the Antarctic limpet Nacella concinna, a dominant Antarctic benthic species along shallow ice‐free rocky ecosystems. We examined the patterns of genetic diversity and structure in this broadcast spawner along maritime Antarctica and from the peri‐Antarctic island of South Georgia. Genetic analyses showed that N. concinna represents a single panmictic unit in maritime Antarctic. Low levels of genetic diversity characterized this population; its median‐joining haplotype network revealed a typical star‐like topology with a short genealogy and a dominant haplotype broadly distributed. As previously reported with nuclear markers, we detected significant genetic differentiation between South Georgia Island and maritime Antarctica populations. Higher levels of genetic diversity, a more expanded genealogy and the presence of more private haplotypes support the hypothesis of glacial persistence in this peri‐Antarctic island. Bayesian Skyline plot and mismatch distribution analyses recognized an older demographic history in South Georgia. Approximate Bayesian computations did not support the persistence of N. concinna along maritime Antarctica during the last glacial period, but indicated the resilience of the species in peri‐Antarctic refugia (South Georgia Island). We proposed a model of Quaternary Biogeography for Antarctic marine benthic invertebrates with shallow and narrow bathymetric ranges including (i) extinction of maritime Antarctic populations during glacial periods; (ii) persistence of populations in peri‐Antarctic refugia; and (iii) recolonization of maritime Antarctica following the deglaciation process.     

Genetic variation and population structure of the carpet shell clam <Emphasis Type="Italic">Ruditapes decussatus</Emphasis> along the Tunisian coast inferred from mtDNA and ITS1 sequence analysis

Surveys of allozyme polymorphisms in the carpet shell clam Ruditapes decussatus have revealed sharp genetic differentiation of populations. Analysis of population structure in this species has now been extended to include nuclear and mitochondrial genes. A partial sequence of a mitochondrial COI gene and of the internal transcribed spacer region (ITS-1) were used to study haplotype distribution, the pattern of gene flow, and population genetic structure of R. decussatus. The samples were collected from twelve populations from the eastern and western Mediterranean coasts of Tunisia, one from Concarneau and one from Thau. A total of twenty and twenty-one haplotypes were detected in the examined COI and ITS1 regions respectively. The study revealed higher levels of genetic diversity for ITS1 compared to COI. The analysis of haplotype frequency distribution and molecular variation indicated that the majority of the genetic variation was distributed within populations (93% and 86% for COI and ITS1 respectively). No significant differentiation was found among eastern and western groups on either side of the Siculo-Tunisian strait. However, distinct and significant clinal changes in haplotypes frequencies between eastern and western samples were found at the most frequent COI haplotype and at three out of five major ITS1 haplotypes. These results suggest the relative importance of historical processes and contemporary hydrodynamic features on the observed patterns of genetic structure.     

Genetic evidence confirms the origin of the house mouse on sub-Antarctic Marion Island

Biological invasions and climate change are two of the largest threats to biodiversity, and this is especially true for island ecosystems that have largely evolved in isolation. The house mouse is considered to have been introduced to sub-Antarctic Marion Island by sealers in the early 1800s. It is currently widespread across the island and has a large impact on the indigenous biota. To date, little information is available on genetic aspects of biological invasions in the sub-Antarctic. Ten specimens of the house mouse were collected from two geographically separated localities on Marion Island. Sequences of the mitochondrial DNA control region revealed only two haplotypes, separated by a single site change. More importantly, these haplotypes are shared between the eastern and western side of Marion Island. By comparing our sequences to data available on GenBank, we provide evidence that house mice on Marion Island is Mus musculus domesticus (Rutty 1772), and most closely related to haplotypes characterizing this species from Denmark, Sweden, Finland, and northern Germany.     

Reduced genetic variation and strong genetic population structure in the freshwater killifish Valencia letourneuxi (Valenciidae) based on nuclear and mitochondrial markers

The genetic variation of the critically endangered Corfu killifish (Valencia letourneuxi), an endemic freshwater fish species of the western Balkans, was assessed for nine populations sampled in eight water systems in western continental Greece, the Peloponnese and the Ionian Island of Corfu, using mitochondrial and microsatellite markers. The analyses were based on data from three mtDNA regions (D‐loop, COI and 16S rRNA sequences) and 14 microsatellite loci. Samples from the congeneric species Valencia hispanica and the phylogenetically closely related species Aphanius fasciatus were also used in the study as outgroups. Both the mitochondrial and the microsatellite analyses revealed three distinct population groupings associated with the geographical distribution of the populations: one southern group occupying rivers draining to the Patraikos Gulf, the second one including the populations flowing into the Amvrakikos Gulf and the third, more northern group, including the other populations from rivers in Corfu Island and Epirus flowing into the Ionian Sea. Within these groupings there is limited genetic differentiation between populations; in addition, there is reduced intrapopulation genetic variation, evidenced by low heterozygosity values, number of alleles and haplotype diversity. In terms of taxonomic implications and appropriate management actions for conservation, our data suggest that the major population groups should be regarded at least as three distinct conservation units (CUs), with translocation and restocking actions to take place only within the geographical range of the CU concerned. © 2013 The Linnean Society of London, Biological Journal of the Linnean Society, 2014, 111 , 334–349.     

Panmixia on a continental scale in a widely distributed colonial waterbird

Many highly mobile species, such as migratory birds, can move and disperse over long distances, yet exhibit high levels of population genetic structuring. Although movement capabilities may enable dispersal, gene flow may be restricted by behavioural constraints such as philopatry. In the present study, we examined patterns of genetic differentiation across the range of a highly mobile, colonial waterbird. American white pelicans (Pelecanus erythrorhynchos) breed across continental North America and are currently experiencing a range expansion, especially on the eastern range limit. To assess patterns of genetic structuring, we sampled 333 individuals from 19 colonies across their North American range. The use of ten variable microsatellite markers revealed high levels of allelic richness with no population differentiation. Both Bayesian and frequentist approaches to examining genetic structuring revealed a single panmictic population. We found no evidence of genetic structuring across the Continental Divide or between migratory and non‐migratory colonies. The lack of any genetic structure across the range indicates that, unlike other waterbirds with similar life‐history characteristics, extensive gene flow and presumably low philopatry appear to preclude genetic differentiation. The lack of population genetic structure in American white pelicans provides an example of range‐wide panmixia, a rare phenomenon in any terrestrial species. © 2011 The Linnean Society of London, Biological Journal of the Linnean Society, 2011, 102 , 583–592.     

Genetic diversity,genetic structure and phylogeography of the Iberian endemic Gypsophila struthium (Caryophyllaceae) as revealed by AFLP and plastid DNA sequences: connecting habitat fragmentation and diversification

Iberian gypsum outcrops are highly fragmented and ecologically challenging environments for plant colonization. As gypsophytes occur exclusively in such habitats, they are ideal models for the study of both the effects of habitat fragmentation and selection on population genetic diversity and structure. In this study, we used amplified fragment length polymorphism (AFLP) and plastid DNA sequences to investigate the phylogeographical history of the Iberian plant Gypsophila struthium (Caryophyllaceae), a widespread endemic restricted to Iberian gypsum outcrops. Gypsophila struthium consists of two subspecies that differ in the architecture of their inflorescence and have mostly allopatric ranges. Gypsophila struthium subsp. struthium occurs in central, eastern and south‐eastern Iberia, whereas G. struthium subsp. hispanica occurs in northern and eastern areas. AFLPs revealed low but significant genetic differentiation between the subspecies, probably as a result of a recent diversification during the Pliocene–Pleistocene. In the geographical contact zone between the taxa, the Bayesian analyses revealed populations with mixed ancestries and genetic clusters predominantly of one or the other subspecies, indicating incomplete reproductive barriers between them. Plastid DNA haplotypes revealed strong geographical structure and testified to processes of isolation by distance and continuous range expansion for some haplotype clades. The Bayesian analyses of the population structure of AFLP data and nested clade phylogeographical analysis (NCPA) of plastid haplotypes revealed that the putative ancestral range corresponded to central and eastern populations of G. struthium subsp. struthium, with those lineages contributing through more recent expansion to increased genetic diversity and structure of the south‐eastern and eastern ranges of this subspecies and to the diversification of G. struthium subsp. hispanica in northern and eastern gypsum outcrops. © 2013 The Linnean Society of London, Botanical Journal of the Linnean Society, 2013, 173 , 654–675.     

Phylogeography of the Trans‐Volcanic bunchgrass lizard (Sceloporus bicanthalis) across the highlands of south‐eastern Mexico

We quantify the population divergence processes that shaped population genetic structure in the Trans‐Volcanic bunchgrass lizard (Sceloporus bicanthalis) across the highlands of south‐eastern Mexico. Multilocus genetic data from nine nuclear loci and mitochondrial (mt)DNA were used to estimate the population divergence history for 47 samples of S. bicanthalis. Bayesian clustering methods partitioned S. bicanthalis into three populations: (1) a southern population in Oaxaca and southern Puebla; (2) a population in western Puebla; and (3) a northern population with a broad distribution across Hidalgo, Puebla, and Veracruz. The multilocus nuclear data and mtDNA both supported a Late Pleistocene increase in effective population size, and the nuclear data revealed low levels of unidirectional gene flow from the widespread northern population into the southern and western populations. Populations of S. bicanthalis experienced different demographic histories during the Pleistocene, and phylogeographical patterns were similar to those observed in many co‐distributed highland taxa. Although we recommend continuing to recognize S. bicanthalis as a single species, future research on the evolution of viviparity could gain novel insights by contrasting physiological and genomic patterns among the different populations located across the highlands of south‐eastern Mexico. © 2013 The Linnean Society of London, Biological Journal of the Linnean Society, 2013, 110 , 852–865.     

Metabolic rate, genetic and microclimate variation among springtail populations from sub-Antarctic Marion Island

Measurement of metabolic rates (made at 10°C) of individuals of the springtail Cryptopygus antarcticus travei from six geographically distinct populations on sub-Antarctic Marion Island were combined with mitochondrial DNA (COI) haplotype analysis to examine in parallel both physiological and genetic variation of distinct populations. We found evidence of genetic differentiation among populations and a general indication of long-term isolation with limited gene flow. While we found support for an overall pattern of metabolic rate structure among populations from different geographic locations on the island (mean rate = 0.0009–0.0029 μl O₂ μg⁻¹ h⁻¹ for populations of a mean individual mass of 8–26 μg), we were unable to demonstrate a coherent common pattern between this and genetic variation. However, spatial structure in metabolic rate variation was strongly related to the extent of variability in microclimate among sites, and also showed some indication of a phylogeographic signal. Thus, over the relatively short timescale of Marion Island’s history (<1 million years), the periodic geographic barriers that have driven population differentiation from a molecular perspective may also have resulted in some physiological differentiation of populations.     

Phylogeography of Hyalomma (Euhyalomma) lusitanicum (Acarina,Parasitiformes, Ixodidae) in Andalusia based on mitochondrial cytochrome oxidase I gene

The genetic population structure relationships of Hyalomma (Euhyalomma) lusitanicum in Andalusia (the south of the Iberian Peninsula) were examined using mtDNA sequence data from 887 bp of cytochrome oxidase subunit I (COI) gene. The sequence for the COI region was determined for 84 individuals collected in several localities of Andalusia, and 10 for other localities (i.e., five from Toledo, central Iberian Peninsula, four from Sicily (Italy) and one from Canary Island). Seventeen haplotypes were detected, including 27 polymorphic sites. The number of amino acid substitutions per site from mean diversity calculations for the entire population was 0.017. AMOVA analysis revealed a low gene flow that characterises the genetic population structure of this species in South Iberian Peninsula, with a haplotype diversity (h) value of 0.815. No geographically induced differentiation was observed, and separate evolutionary units were not detected. Our results indicate low genetic diversity across the geographical range of H. lusitanicum tick in Andalusia. Our data do not show any genetic discontinuity between the tick populations studied, including specimens from Canary Island and Sicily (Italy).

     

Genetic differentiation,speciation, and phylogeography of cactus flies (Diptera: Neriidae: Odontoloxozus) from Mexico and south‐western USA

Nucleotide sequences from the mitochondrial cytochrome c oxidase subunit I (COI) gene, comprising the standard barcode segment, were used to examine genetic differentiation, systematics, and population structure of cactus flies (Diptera: Neriidae: Odontoloxozus) from Mexico and south‐western USA. Phylogenetic analyses revealed that samples of Odontoloxozus partitioned into two distinct clusters: one comprising the widely distributed Odontoloxozus longicornis (Coquillett) and the other comprising Odontoloxozus pachycericola Mangan & Baldwin, a recently described species from the Cape Region of the Baja California peninsula, which we show is distributed northward to southern California, USA. A mean Kimura two‐parameter genetic distance of 2.8% between O. longicornis and O. pachycericola, and eight diagnostic nucleotide substitutions in the COI gene segment, are consistent with a species‐level separation, thus providing the first independent molecular support for recognizing O. pachycericola as a distinct species. We also show that the only external morphological character considered to separate adults of the two species (number of anepisternal bristles) varies with body size and is therefore uninformative for making species assignments. Analysis of molecular variance indicated significant structure among populations of O. longicornis from three main geographical areas, (1) Arizona, USA and Sonora, Mexico; (2) Santa Catalina Island, California, USA; and (3) central Mexico (Querétaro and Guanajuato), although widely‐separated populations from Arizona and Sonora showed no evidence of structure. A TCS haplotype network showed no shared haplotypes of O. longicornis among the three main regions. The potential roles of vicariance and isolation‐by‐distance in restricting gene flow and promoting genetic differentiation and speciation in Odontoloxozus are discussed. © 2013 The Linnean Society of London, Biological Journal of the Linnean Society, 2013, 110 , 245–256.     

Tracing geographical patterns of population differentiation in a widespread mangrove gastropod: genetic and geometric morphometrics surveys along the eastern African coast

In the present study, we assessed the inter‐ and intrapopulation genetic and morphological variation of Cerithidea decollata along the eastern coast of Africa. The population structure of C. decollata along the latitudinal gradient was examined by sequencing 420 bp of the mitochondrial cytochrome c oxidase I (COI) gene in 172 snails from 29 sites, in a combined analysis with geometric morphometrics in 1799 snails from 32 sites. Analysis of molecular variance and spatial analysis of molecular variance showed a moderate spatial population differentiation from Kenya to the Republic of South Africa, suggesting genetic divergence between the northern, central, and southern regions. This structure appears to be the result of life‐history traits combined with oceanographic features. Haplotype network and mismatch analysis suggest a recent population expansion during the Holsteinian interglacial period in the northern region and several colonization events in the central and southern regions. The morphometric approach suggests that morphological variation in shell shape is somewhat independent of the genetic divergence, revealing an overlap of shape across the latitudinal gradient but significant differences among‐population at a local level. This may indicate that similar ecological pressures are acting along the coast, leading to the occurrence of similar morphological characters. © 2012 The Linnean Society of London, Biological Journal of the Linnean Society, 2012, 107 , 647–663.     

Phylogeography of palo santo trees (Bursera graveolens and Bursera malacophylla; Burseraceae) in the Galápagos archipelago

Two species of palo santo trees are distributed in the Galápagos archipelago, the native Bursera graveolens and the endemic Bursera malacophylla (Burseraceae). However, a zone of individuals morphologically intermediate between the two exists on northern Santa Cruz Island and south‐eastern Santiago Island, suggesting that they may not be reproductively isolated. Here we review the species' distributional and morphological differences and test for evidence of hybridization between the two species using DNA sequence and AFLP data. We find that the species lack distinguishing synapomorphies across the five nuclear and plastid regions examined. Population assignment tests and population genetic analyses of AFLP data indicate that genetically similar palo santo individuals (N = 87), including putative hybrids, partition into two genealogical groups that do not uniformly correspond to island‐ or taxon‐based membership. Furthermore, genotypic admixture levels among morphologically intermediate individuals do not indicate widespread hybridization. Thus, we recommend recognizing the endemic palo santo taxon as B. graveolens subspecies malacophylla (B.L.Rob.) A. Weeks & Tye comb. & stat. nov. in light of its close genetic relationship to B. graveolens subsp. graveolens and its distinctive morphology and distribution. Future research should quantify phenotypic variation in palo santo populations as another means for understanding the basis of morphological differences between the subspecies. © 2009 The Linnean Society of London, Botanical Journal of the Linnean Society, 2009, 161 , 396–410.     

Genetic evaluation of marine biogeographical barriers: perspectives from two widespread Indo-Pacific snappers (Lutjanus kasmira and Lutjanus fulvus)

Aim In the Indo‐Pacific, the mass of islands of the Indonesian archipelago constitute a major biogeographical barrier (the Indo‐Pacific Barrier, IPB) separating the Pacific and Indian oceans. Evidence for other, more localized barriers include high rates of endemism at the Marquesas and other isolated peripheral islands in the Pacific. Here we use mitochondrial‐sequence comparisons to evaluate the efficacy of biogeographical barriers on populations of the snappers Lutjanus kasmira and Lutjanus fulvus across their natural ranges. Location Pacific and Indian oceans. Methods Mitochondrial cytochrome b sequence data were obtained from 370 individuals of L. kasmira and 203 individuals of L. fulvus collected from across each species’ range. Allele frequency data for two nuclear introns were collected from L. kasmira. Phylogenetic and population‐level analyses were used to determine patterns of population structure in these species and to identify barriers to dispersal. Results Lutjanus kasmira lacks genetic structure across the IPB and throughout 12,000 km of its central Indo‐Pacific range. In contrast, L. fulvus demonstrates high levels of population structure at all geographical scales. In both species, highly significant population structure results primarily from the phylogenetic distinctiveness of their Marquesas Islands populations (L. kasmira, d = 0.50–0.53%; L. fulvus, d = 0.87–1.50%). Coalescence analyses of the L. kasmira data indicate that populations at opposite ends of its range (western Indian Ocean and the Marquesas) are the oldest. Coalescence analyses for L. fulvus are less robust but also indicate colonization from the Indian to the Pacific Ocean. Main conclusions The IPB does not act as a biogeographical barrier to L. kasmira, and, in L. fulvus, its effects are no stronger than isolating mechanisms elsewhere. Both species demonstrate a strong genetic break at the Marquesas. Population divergence and high endemism in that archipelago may be a product of geographical isolation enhanced by oceanographic currents that limit gene flow to and from those islands, and adaptation to unusual ecological conditions. Lutjanus kasmira shows evidence of Pleistocene population expansion throughout the Indo‐central Pacific that originated in the western Indian Ocean rather than the Marquesas, further demonstrating a strong barrier at the latter location.     

Conservation genetics of an island-endemic lizard: low Ne and the critical role of intermediate temperatures for genetic connectivity

Island populations are at higher risk of extinction than mainland populations. Therefore, understanding the factors that facilitate connectivity is particularly pressing for the conservation of island taxa. Sceloporus occidentalis becki, the Island Fence Lizard, is an endemic taxon restricted to the Northern Channel Islands, part of a nearshore archipelago in Southern California, USA. Since the Last Glacial Maximum, fence lizard habitat on the Northern Channel Islands has decreased with rising sea levels and increasing temperatures that have reduced the availability of woody vegetation. More recently, the introduction (and subsequent removal) of invasive ungulates over the last 170 years and recovery of vegetation has resulted in further dramatic habitat modification. Given the potential for genetic bottlenecks, the history of habitat alteration, and topographic and landscape complexity, we used landscape and population genetic approaches to characterize patterns of genetic diversity and structure of Island Fence Lizards on Santa Cruz Island, the largest of the Northern Channel Islands. Our analyses revealed shallow population structure across the island, low effective population size (N_e?=??~?200), and evidence for a recent genetic bottleneck. Landscape genetic analyses showed that connectivity is facilitated by tree canopy cover and shrubland, as well as by intermediate temperatures, emphasizing the importance of woody vegetation and habitats with variable thermal regimes as the climate warms. Combined, these population and landscape genetic analyses suggest that the Island Fence Lizard is of greater conservation concern than currently appreciated, and increased conservation management focus is warranted for this island endemic.

     

Phylogeography of the Japanese pipistrelle bat,Pipistrellus abramus,in China: the impact of ancient and recent events on population genetic structure

The influence of Pleistocene climatic oscillations on shaping the genetic structure of Asian biota is poorly known. The Japanese pipistrelle bat occurs over a wide range in eastern Asia, from Siberia to Japan. To test the relative impact of ancient and more recent events on genetic structure in this species, we combined mitochondrial (cytochrome b) and microsatellite markers to reconstruct its phylogeographic and demographic history on continental China and its offshore islands, Hainan Island and the Zhoushan Archipelago. Our mitochondrial DNA tree recovered two divergent geographical clades, indicating multiple glacial refugia in the region. The first clade was mainly confined to Hainan Island, indicating that gene flow between this population and the continent has been restricted, despite being repeatedly connected to the mainland during repeated glacial episodes. By contrast, haplotypes sampled on the Zhoushan Archipelago were mixed with those from the mainland, suggesting a recent shared history of expansion. Although microsatellite allele frequencies showed clear discontinuities across the sampling range, supporting the current isolation of both Hainan Island and the Zhoushan Archipelago, we also found clear evidence of more recent back colonization, probably via post‐glacial expansion or, in the latter case, occasional long distance dispersal. The results obtained highlight the importance of using multiple sets of markers for teasing apart the roles of ancient and more recent events on population genetic structure. © 2010 The Linnean Society of London, Biological Journal of the Linnean Society, 2010, 99 , 582–594.     

Phylogeography of a pearl oyster (Pinctada maxima) across the Indo‐Australian Archipelago: evidence of strong regional structure and population expansions but no phylogenetic breaks

This study investigates the genetic structure and phylogeography of a broadcast spawning bivalve mollusc, Pinctada maxima, throughout the Indo‐West Pacific and northern Australia. DNA sequence variation of the mitochondrial cytochrome oxidase subunit I (COI) gene was analysed in 367 individuals sampled from nine populations across the Indo‐West Pacific. Hierarchical AMOVA indicated strong genetic structuring amongst populations (Φ_ST = 0.372, P < 0.001); however, sequence divergence between the 47 haplotypes detected was low (maximum 1.8% difference) and no deep phylogenetic divergence was observed. Results suggest the presence of genetic barriers isolating populations of the South China Sea and central Indonesian regions, which, in turn, show patterns of historical separation from northern Australian regions. In P. maxima, historical vicariance during Pleistocene low sea levels is likely to have restricted planktonic larval transport, causing genetic differentiation amongst populations. However, low genetic differentiation is observed where strong ocean currents are present and is most likely due to contemporary larval transport along these pathways. Geographical association with haplotype distributions may indicate signs of early lineage sorting arising from historical population separations, yet an absence of divergent phylogenetic clades related to geography could be the consequence of periodic pulses of high genetic exchange. We compare our results with previous microsatellite DNA analysis of these P. maxima populations, and discuss implications for future conservation management of this species. © 2012 The Linnean Society of London, Biological Journal of the Linnean Society, 2012, 107 , 632–646.