Search

Dispersal is a critically important process that dictates population persistence, gene flow, and evolutionary potential, and is an essential element for identifying species conservation risks. This study aims to investigate the contributions of dispersal syndromes and hydrographic barriers on patterns of population connectivity and genetic structure in fishes occupying the particularly rugged and fragmented landscape of the Kimberley Plateau, Western Australia. We assessed population genetic structure between three neighbouring catchments (the Mitchell, King Edward, and Drysdale rivers) in three congeneric groups of freshwater fishes that exhibit varied dispersal syndromes within and among groups: (1) Melanotaenia australis and M. gracilis; (2) Syncomistes trigonicus and S. rastellus; and (3) Hephaestus jenkinsi and H. epirrhinos. Within each species we sampled the upper, middle, and lower reaches of each catchment and assessed patterns of gene flow between and within catchments using microsatellite markers. Our results suggest that contemporary connectivity between catchments is greatly limited or absent in all study species, regardless of their dispersal syndromes. However, gene flow within catchments varied in line with predicted dispersal potential, with poor dispersers exhibiting limited gene flow and significant genetic structuring. We conclude that the rugged landscape and historical habitat isolation has contributed to patterns of population fragmentation among fish populations from different river catchments. However, it appears dispersal syndromes influence connectivity and gene flow within catchments, where landscape constraints are not as pervasive. This study presents a comparative population genetic analysis of freshwater fishes with differing dispersal syndromes and colonisation ability. Our findings provide new insights into factors shaping patterns of biodiversity on the Kimberley Plateau, and the evolutionary uniqueness of fish communities

Infectious diseases are recognized as one of the greatest global threats to biodiversity and ecosystem functioning. Consequently, there is a growing urgency to understand the speed at which adaptive phenotypes can evolve and spread in natural populations to inform future management. Here we provide evidence of rapid genomic changes in wild Australian blacklip abalone (Haliotis rubra) following a major population crash associated with an infectious disease. Genome scans on H. rubra were performed using pooled whole genome resequencing data from commercial fishing stocks varying in historical exposure to haliotid herpesvirus-1 (HaHV-1). Approximately 25,000 single nucleotide polymorphism loci associated with virus exposure were identified, many of which mapped to genes known to contribute to HaHV-1 immunity in the New Zealand pāua (Haliotis iris) and herpesvirus response pathways in haliotids and other animal systems. These findings indicate genetic changes across a single generation in H. rubra fishing stocks decimated by HaHV-1, with stock recovery potentially determined by rapid evolutionary changes leading to virus resistance. This is a novel example of apparently rapid adaptation in natural populations of a nonmodel marine organism, highlighting the pace at which selection can potentially act to counter disease in wildlife communities.

The number of human–shark interactions has increased worldwide during the past decade resulting in injuries and fatalities. In Australia, the white shark (Carcharodon carcharias), tiger shark (Galeocerdo cuvier), and bull shark (Carcharhinus leucas) are responsible for the majority of fatal incidents. On the southeast coast of Australia, monitoring programs currently rely on SMART (Shark‐Management‐Alert‐in‐Real‐Time) drumlines and mesh nets to catch, tag, and monitor shark movement. However, these methods are laborious, costly, and involve the capture of only a fraction of the total shark population. Here, we develop a multiplex environmental DNA assay capable of detecting all three shark species simultaneously from water samples by targeting conserved but specific mitochondrial sequences that are characteristic of each species. The specificity of the assay was validated by testing for cross‐amplification across a range of non‐target but co‐occurring shark species from eastern Australia. We test the sensitivity of the assay on water samples collected from shark capture events and sites where these shark species are known to frequent, and undertake DNA sequencing on positive samples to confirm species haplotype authenticity. Samples collected from one of these sites also demonstrate that eDNA detections are dependent on shark activity in the area. This assay will allow for rapid detection of DNA from each shark species in water samples, providing a cost‐effective alternative for monitoring sharks along the east coast of Australia and potentially elsewhere.

Worldwide, rising ocean temperatures are causing declines and range shifts in marine species. The direct effects of climate change on the biology of marine organisms are often well documented; yet, knowledge on the indirect effects, particularly through trophic interactions, is largely lacking. We provide evidence of ocean warming decoupling critical trophic interactions supporting a commercially important mollusc in a climate change hotspot. Dietary assessments of the Australian blacklip abalone (Haliotis rubra) indicate primary dependency on a widespread macroalgal species (Phyllospora comosa) which we show to be in state of decline due to ocean warming, resulting in abalone biomass reductions. Niche models suggest further declines in P. comosa over the coming decades and ongoing risks to H. rubra. This study highlights the importance of studies from climate change hotspots and understanding the interplay between climate and trophic interactions when determining the likely response of marine species to environmental changes.

Animal and plant species around the world are being challenged by the deleterious effects of inbreeding, loss of genetic diversity, and maladaptation due to widespread habitat destruction and rapid climate change. In many cases, interventions will likely be needed to safeguard populations and species and to maintain functioning ecosystems. Strategies aimed at initiating, reinstating, or enhancing patterns of gene flow via the deliberate movement of genotypes around the environment are generating growing interest with broad applications in conservation and environmental management. These diverse strategies go by various names ranging from genetic or evolutionary rescue to provenancing and genetic resurrection. Our aim here is to provide some clarification around terminology and to how these strategies are connected and linked to underlying genetic processes. We draw on case studies from the literature and outline mechanisms that underlie how the various strategies aim to increase species fitness and impact the wider community. We argue that understanding mechanisms leading to species decline and community impact is a key to successful implementation of these strategies. We emphasize the need to consider the nature of source and recipient populations, as well as associated risks and trade-offs for the various strategies. This overview highlights where strategies are likely to have potential at population, species, and ecosystem scales, but also where they should probably not be attempted depending on the overall aims of the intervention. We advocate an approach where short- and long-term strategies are integrated into a decision framework that also considers nongenetic aspects of management.

Rising ocean temperatures and extreme temperature events have precipitated declines and local extinctions in many marine species globally, but patterns of loss are often uneven across species ranges for reasons that are poorly understood. Knowledge of the extent of local adaptation and gene flow may explain such patterns and help predict future trajectories under scenarios of climate change. We test the extent to which local differentiation in thermal tolerance is influenced by gene flow and local adaptation using a widely distributed intertidal seaweed (Hormosira banksii) from temperate Australia. Population surveys across ~2,000 km of the species range revealed strong genetic structuring at regional and local scales (global F ST = 0.243) reflecting extremely limited gene flow, while common garden experiments (14-day exposures to 15, 18, 21°C) revealed strong site differences in early development and mortality in response to elevated temperature. Embryos from many sites spanning a longitudinal thermal gradient showed suppressed development and increased mortality to elevated water temperatures, but populations originating from warmer and more variable thermal environments tended to be less susceptible to warming. Notably, there was significant local-scale variation in the thermal responses of embryos within regions which was corroborated by the finding of small-scale genetic differences. We expect the observed genetic and phenotypic differentiation to lead to uneven responses to warming sea surface temperatures in this important marine foundation species. The study highlights the challenges of predicting species responses to thermal stress and the importance of management strategies that incorporate evolutionary potential for "climate-proofing" marine ecosystems.

Warming from climate change and resulting increases in energy stored in the oceans is causing changes in the hydrodynamics and biogeochemistry of marine systems, exacerbating current challenges facing marine fisheries. Although studies have evaluated effects of rising temperatures on marine species, few have looked at these impacts along with other environmental drivers over long time periods. In this study, we associate long‐term density of blacklip abalone to changing oceanographic conditions in a climate change ‘hot‐spot’ off southeast Australia. We downscaled and hind‐casted existing hydrodynamic models to provide information on waves and currents over 25 yr and used this information to run biophysical connectivity models. We combined the connectivity models with 21 yr of data on abalone density, temperature, seafloor habitat, and the effects of a disease outbreak in an machine learning modeling approach to develop a spatio‐temporal model of abalone density. We found that the combination of temperature, connectivity, current speed, wave orbital velocity, fishery catch, depth, reef structure and a disease outbreak explain 70% of variation in abalone density and allowed us to create 30 m resolution predictive grids with 75% accuracy. An emerging hotspot analysis run on the individual predictive grids from each year detected a predominance of low‐density grids across the region, with 49.5% of cells classified as cold spots, 14.3% as hotspots and 36.2% with no significant patterns observed. This type of spatio‐temporal analysis provides important insights into how changing environmental conditions are impacting density in an important fishery species, allowing for better adaptive management in the face of future climate change.

Habitat fragmentation imperils the persistence of many functionally important species, with climate change a new threat to local persistence due to climate niche mismatching. Predicting the evolutionary trajectory of species essential to ecosystem function under future climates is challenging but necessary for prioritizing conservation investments. We use a combination of population genetics and niche suitability models to assess the trajectory of a functionally important, but highly fragmented, plant species from south-eastern Australia (Banksia marginata, Proteaceae). We demonstrate significant genetic structuring among, and high level of relatedness within, fragmented remnant populations, highlighting imminent risks of inbreeding. Population simulations, controlling for effective population size (N e), suggest that many remnant populations will suffer rapid declines in genetic diversity due to drift in the absence of intervention. Simulations were used to demonstrate how inbreeding and drift processes might be suppressed by assisted migration and population mixing approaches that enhance the size and connectivity of remnant populations. These analyses were complemented by niche suitability models that predicted substantial reductions of suitable habitat by 2080; ~30% of the current distribution of the species climate niche overlaps with the projected distribution of the species climate niche in the geographic region by the 2080s. Our study highlights the importance of conserving remnant populations and establishing new populations in areas likely to support B. marginata in the future, and adopting seed sourcing strategies that can help populations overcome the risks of inbreeding and maladaptation. We also argue that ecological replacement of B. marginata using climatically suited plant species might be needed in the future to maintain ecosystem processes where B. marginata cannot persist. We recommend the need for progressive revegetation policies and practices

Rising ocean temperatures and extreme temperature events have precipitated declines and local extinctions in many marine species globally, but patterns of loss are often uneven across species ranges for reasons that are poorly understood. Knowledge of the extent of local adaptation and gene flow may explain such patterns and help predict future trajectories under scenarios of climate change. We test the extent to which local differentiation in thermal tolerance is influenced by gene flow and local adaptation using a widely distributed intertidal seaweed (Hormosira banksii) from temperate Australia. Population surveys across ~2,000 km of the species range revealed strong genetic structuring at regional and local scales (global F ST = 0.243) reflecting extremely limited gene flow, while common garden experiments (14-day exposures to 15, 18, 21°C) revealed strong site differences in early development and mortality in response to elevated temperature. Embryos from many sites spanning a longitudinal thermal gradient showed suppressed development and increased mortality to elevated water temperatures, but populations originating from warmer and more variable thermal environments tended to be less susceptible to warming. Notably, there was significant local-scale variation in the thermal responses of embryos within regions which was corroborated by the finding of small-scale genetic differences. We expect the observed genetic and phenotypic differentiation to lead to uneven responses to warming sea surface temperatures in this important marine foundation species. The study highlights the challenges of predicting species responses to thermal stress and the importance of management strategies that incorporate evolutionary potential for "climate-proofing" marine ecosystems.

Characterising adaptive genetic divergence among conspecific populations is often achieved by studying genetic variation across defined environmental gradients. In marine systems this is challenging due to a paucity of information on habitat heterogeneity at local and regional scales and a dependency on sampling regimes that are typically limited to broad longitudinal and latitudinal environmental gradients. As a result, the spatial scales at which selection processes operate and the environmental factors that contribute to genetic adaptation in marine systems are likely to be unclear. In this study we explore patterns of adaptive genetic structuring in a commercially- harvested abalone species (Haliotis rubra) from southeastern Australia, using a panel of genome-wide SNP markers (5,239 SNPs), and a sampling regime informed by marine LiDAR bathymetric imagery and 20-year hindcasted oceanographic models. Despite a lack of overall genetic structure across the sampling distribution, significant genotype associations with heterogeneous habitat features were observed at local and regional spatial scales, including associations with wave energy, ocean current, sea surface temperature, and geology. These findings provide insights into the potential resilience of the species to changing marine climates and the role of migration and selection on recruitment processes, with implications for conservation and fisheries management. This study points to the spatial scales at which selection processes operate in marine systems and highlights the benefits of geospatially-informed sampling regimes for overcoming limitations associated with marine population genomic research.

The emergence of cost-effective and rapid sequencing approaches has resulted in an exponential rise in the number of mitogenomes on public databases in recent years, providing greater opportunity for undertaking large-scale comparative genomic and systematic research. Nonetheless, current datasets predominately come from small and disconnected studies on a limited number of related species, introducing sampling biases and impeding research of broad taxonomic relevance. This study contributes 21 crustacean mitogenomes from several under-represented decapod infraorders including Polychelida and Stenopodidea, which are used in combination with 225 mitogenomes available on NCBI to investigate decapod mitogenome diversity and phylogeny. An overview of mitochondrial gene orders (MGOs) reveals a high level of genomic variability within the Decapoda, with a large number of MGOs deviating from the ancestral arthropod ground pattern and unevenly distributed among infraorders. Despite the substantial morphological and ecological variation among decapods, there was limited evidence for correlations between gene rearrangement events and species ecology or lineage specific nucleotide substitution rates. Within a phylogenetic context, predicted scenarios of rearrangements show some MGOs to be informative synapomorphies for some taxonomic groups providing strong independent support for phylogenetic relationships. Additional comparisons for a range of mitogenomic features including nucleotide composition, strand asymmetry, unassigned regions and codon usage indicate several clade-specific trends that are of evolutionary and ecological interest.

AIM: The alpine region of mainland Australia is one of the world's 187 biodiversity hotspots. Genetic analyses of Australian alpine fauna indicate high levels of endemism on fine spatial scales, unlike Northern Hemisphere alpine systems where shallow genetic differentiation is typically observed among populations. These discrepancies have been attributed to differences in elevation and influence from glacial activity, and point to a unique phylogeographic history affecting Australian alpine biodiversity. To test generality of these findings across Australian alpine biota, we assessed patterns of genetic structure across plant species. LOCATION: The Australian Alps, Victoria, eastern Australia. METHODS: We used an economical pooled genotyping‐by‐sequencing (GBS) approach to examine patterns of genetic diversity among seven widespread species including shrubs and forbs from 16 mountain summits in the Australian Alpine National Park. Patterns of genetic structure among summit populations for each species were inferred from an average of 2,778 independent SNP loci using Bayesian phylogenomic inference and clustering approaches. RESULTS: SNP results were consistent across species in identifying deep evolutionary splits among summit communities from the Northern and Central Victorian Alpine regions. These patterns of genetic structure are also consistent with those previously reported for invertebrate and mammal taxa. However, local genetic structure was less pronounced in the plants, supporting the notion that population connectivity tends to be higher in plant species. MAIN CONCLUSION: There is deep lineage diversification between the North and Central Victorian Alpine regions, reflecting a high level of endemism. These findings differ from those reported for alpine biodiversity from New South Wales and much of the Northern Hemisphere, and support the notion that genetic diversity is typically greatest in areas least affected by historical ice sheet formation. We discus

BACKGROUND: Australian scorpions have received far less attention from researchers than their overseas counterparts. Here we provide the first insight into the molecular variation and evolutionary history of the endemic Australian scorpion Urodacus yaschenkoi. Also known as the inland robust scorpion, it is widely distributed throughout arid zones of the continent and is emerging as a model organism in biomedical research due to the chemical nature of its venom. METHODS: We employed Bayesian Inference (BI) methods for the phylogenetic reconstructions and divergence dating among lineages, using unique haplotype sequences from two mitochondrial loci (COXI, 16S) and one nuclear locus (28S). We also implemented two DNA taxonomy approaches (GMYC and PTP/dPTP) to evaluate the presence of cryptic species. Linear Discriminant Analysis was used to test whether the linear combination of 21 variables (ratios of morphological measurements) can predict individual's membership to a putative species. RESULTS: Genetic and morphological data suggest that U. yaschenkoi is a species complex. High statistical support for the monophyly of several divergent lineages was found both at the mitochondrial loci and at a nuclear locus. The extent of mitochondrial divergence between these lineages exceeds estimates of interspecific divergence reported for other scorpion groups. The GMYC model and the PTP/bPTP approach identified major lineages and several sub-lineages as putative species. Ratios of several traits that approximate body shape had a strong predictive power (83-100%) in discriminating two major molecular lineages. A time-calibrated phylogeny dates the early divergence at the onset of continental-wide aridification in late Miocene and Pliocene, with finer-scale phylogeographic patterns emerging during the Pleistocene. This structuring dynamics is congruent with the diversification history of other fauna of the Australian arid zones. DISCUSSION: Our results indicate that the taxonomi

© 2016, Springer Science+Business Media Dordrecht. The Australasian fucoid, Hormosira banksii, commonly known as ‘Neptune’s necklace’ or ‘bubbleweed’ is regarded as an autogenic ecosystem engineer with no functional equivalents. Population declines resulting from climate change and other anthropogenic disturbances pose significant threats to intertidal biodiversity. For effective conservation strategies, patterns of gene flow and population genetic structure across the species distribution need to be clearly understood. We developed a suite of 15 polymorphic microsatellite markers using next generation sequencing of 53–55 individuals from two sites (south-western Victoria and central New South Wales, Australia) and a replicated spatially hierarchical sampling design. We observed low to moderate genetic variation across most loci (mean number of alleles per locus =3.26; mean expected heterozygosity =0.38) with no evidence of individual loci deviating significantly from Hardy-Weinberg equilibrium. Marker independence was confirmed with tests for linkage disequilibrium, and analyses indicated no evidence of null alleles across loci. Independent spatial autocorrelation analyses were performed for each site using multilocus genotypes and different relatedness measures. Both analyses indicated no significant patterns between relatedness and geographic distance, complemented by non-significant Hardy-Weinberg estimates (P < 0.05), suggesting that individuals from each site represent a randomly mating, outcrossing population. A preliminary investigation of population structure indicates that gene flow among sites is limited (FST = 0.49), however more comprehensive sampling is needed to determine the extent of population structure across the species range (>10,000 km). The genetic markers described provide a valuable resource for future population genetic assessments that will help guide conservation planning for H. banksii and the associated intertidal communities.

Estimating contemporary genetic structure and population connectivity in marine species is challenging, often compromised by genetic markers that lack adequate sensitivity, and unstructured sampling regimes. We show how these limitations can be overcome via the integration of modern genotyping methods and sampling designs guided by LiDAR and SONAR data sets. Here we explore patterns of gene flow and local genetic structure in a commercially harvested abalone species (Haliotis rubra) from southeastern Australia, where the viability of fishing stocks is believed to be dictated by recruitment from local sources. Using a panel of microsatellite and genomewide SNP markers, we compare allele frequencies across a replicated hierarchical sampling area guided by bathymetric LiDAR imagery. Results indicate high levels of gene flow and no significant genetic structure within or between benthic reef habitats across 1400 km of coastline. These findings differ to those reported for other regions of the fishery indicating that larval supply is likely to be spatially variable, with implications for management and long-term recovery from stock depletion. The study highlights the utility of suitably designed genetic markers and spatially informed sampling strategies for gaining insights into recruitment patterns in benthic marine species, assisting in conservation planning and sustainable management of fisheries.

The complete mitochondrial genome and a set of polymorphic microsatellite markers were identified by 454 pyrosequencing (1/16th of a plate) for the New Caledonian rainforest spider-ant Leptomyrmex pallens. De novo genome assembly recovered the entire mitochondrial genome with mean coverage of 8.9-fold (range 1-27). The mitogenome consists of 15,591 base pairs including 13 protein-coding genes, 2 ribosomal subunit genes, 22 transfer RNAs, and a non-coding AT-rich region. The genome arrangement is typical of insect taxa and very similar to the only other published ant mitogenome from the Solenopsis genus, with the main differences consisting of translocations and inversions of tRNAs. A total of 13 polymorphic loci were also characterized using 41 individuals from a single population in the Aoupinié region, corresponding to workers from 21 nests and 16 foraging workers. We observed moderate genetic variation across most loci (mean number of alleles per locus = 4.50; mean expected heterozygosity = 0.53) with evidence of only two loci deviating significantly from Hardy-Weinberg equilibrium due to null alleles. Marker independence was confirmed with tests for linkage disequilibrium. Most loci cross amplified for three additional Leptomyrmex species. The annotation of the mitogenome and characterization of microsatellite markers will provide useful tools for assessing the colony structure, population genetic patterns, and dispersal strategy of L. pallens in the context of rainforest fragmentation in New Caledonia. Furthermore, this paper confirms a recent line of evidence that comprehensive mitochondrial data can be obtained relatively easily from small next-generation sequencing analyses. Greater synthesis of next-generation sequencing data will play a significant role in expanding the taxonomic representation of mitochondrial genome sequences.

BACKGROUND: Mountain landscapes are topographically complex, creating discontinuous 'islands' of alpine and sub-alpine habitat with a dynamic history. Changing climatic conditions drive their expansion and contraction, leaving signatures on the genetic structure of their flora and fauna. Australia's high country covers a small, highly fragmented area. Although the area is thought to have experienced periods of relative continuity during Pleistocene glacial periods, small-scale studies suggest deep lineage divergence across low-elevation gaps. Using both DNA sequence data and microsatellite markers, we tested the hypothesis that genetic partitioning reflects observable geographic structuring across Australia's mainland high country, in the widespread alpine grasshopper Kosciuscola tristis (Sjösted). RESULTS: We found broadly congruent patterns of regional structure between the DNA sequence and microsatellite datasets, corresponding to strong divergence among isolated mountain regions. Small and isolated mountains in the south of the range were particularly distinct, with well-supported divergence corresponding to climate cycles during the late Pliocene and Pleistocene. We found mixed support, however, for divergence among other mountain regions. Interestingly, within areas of largely contiguous alpine and sub-alpine habitat around Mt Kosciuszko, microsatellite data suggested significant population structure, accompanied by a strong signature of isolation-by-distance. CONCLUSIONS: Consistent patterns of strong lineage divergence among different molecular datasets indicate genetic breaks between populations inhabiting geographically distinct mountain regions. Three primary phylogeographic groups were evident in the highly fragmented Victorian high country, while within-region structure detected with microsatellites may reflect more recent population isolation. Despite the small area of Australia's alpine and sub-alpine habitats, their low topographic relief and lack of

A suite of polymorphic microsatellite markers and the complete mitochondrial genome sequence was developed by next generation sequencing (NGS) for the critically endangered orange-bellied parrot, Neophema chrysogaster. A total of 14 polymorphic loci were identified and characterized using DNA extractions representing 40 individuals from Melaleuca, Tasmania, sampled in 2002. We observed moderate genetic variation across most loci (mean number of alleles per locus = 2.79; mean expected heterozygosity = 0.53) with no evidence of individual loci deviating significantly from Hardy-Weinberg equilibrium. Marker independence was confirmed with tests for linkage disequilibrium, and analyses indicated no evidence of null alleles across loci. De novo and reference-based genome assemblies performed using MIRA were used to assemble the N. chrysogaster mitochondrial genome sequence with mean coverage of 116-fold (range 89 to 142-fold). The mitochondrial genome consists of 18,034 base pairs, and a typical metazoan mitochondrial gene content consisting of 13 protein-coding genes, 2 ribosomal subunit genes, 22 transfer RNAs, and a single large non-coding region (control region). The arrangement of mitochondrial genes is also typical of Avian taxa. The annotation of the mitochondrial genome and the characterization of 14 microsatellite markers provide a valuable resource for future genetic monitoring of wild and captive N. chrysogaster populations. As found previously, NGS provides a rapid, low cost and reliable method for polymorphic nuclear genetic marker development and determining complete mitochondrial genome sequences when only a fraction of a genome is sequenced.

The Glenelg spiny crayfish, Euastacus bispinosus, is an iconic freshwater invertebrate of south eastern Australia and listed as 'endangered' under the Environment Protection and Biodiversity Conservation Act 1999, and 'vulnerable' under the International Union for Conservation of Nature's Red List. The species has suffered major population declines as a result of over-fishing, low environmental flows, the introduction of invasive fish species and habitat degradation. In order to develop an effective conservation strategy, patterns of gene flow, genetic structure and genetic diversity across the species distribution need to be clearly understood. In this study we develop a suite of polymorphic microsatellite markers by next generation sequencing. A total of 15 polymorphic loci were identified and 10 characterized using 22 individuals from the lower Glenelg River. We observed low to moderate genetic variation across most loci (mean number of alleles per locus = 2.80; mean expected heterozygosity = 0.36) with no evidence of individual loci deviating significantly from Hardy-Weinberg equilibrium. Marker independence was confirmed with tests for linkage disequilibrium, and analyses indicated no evidence of null alleles across loci. Individuals from two additional sites (Crawford River, Victoria; Ewens Ponds Conservation Park, South Australia) were genotyped at all 10 loci and a preliminary investigation of genetic diversity and population structure was undertaken. Analyses indicate high levels of genetic differentiation among sample locations (F ST = 0.49), while the Ewens Ponds population is genetically homogeneous, indicating a likely small founder group and ongoing inbreeding. Management actions will be needed to restore genetic diversity in this and possibly other at risk populations. These markers will provide a valuable resource for future population genetic assessments so that an effective framework can be developed for implementing conservation strategies for E.

Major disjunctions among marine communities in southeastern Australia have been well documented, although explanations for biogeographic structuring remain uncertain. Converging ocean currents, environmental gradients, and habitat discontinuities have been hypothesized as likely drivers of structuring in many species, although the extent to which species are affected appears largely dependent on specific life histories and ecologies. Understanding these relationships is critical to the management of native and invasive species, and the preservation of evolutionary processes that shape biodiversity in this region. In this study we test the direct influence of ocean currents on the genetic structure of a passive disperser across a major biogeographic barrier. Donax deltoides (Veneroida: Donacidae) is an intertidal, soft-sediment mollusc and an ideal surrogate for testing this relationship, given its lack of habitat constraints in this region, and its immense dispersal potential driven by year-long spawning and long-lived planktonic larvae. We assessed allele frequencies at 10 polymorphic microsatellite loci across 11 sample locations spanning the barrier region and identified genetic structure consistent with the major ocean currents of southeastern Australia. Analysis of mitochondrial DNA sequence data indicated no evidence of genetic structuring, but signatures of a species range expansion corresponding with historical inundations of the Bassian Isthmus. Our results indicate that ocean currents are likely to be the most influential factor affecting the genetic structure of D. deltoides and a likely physical barrier for passive dispersing marine fauna generally in southeastern Australia.