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Dispersal patterns can dictate genetic population structure and, ultimately, population resilience, through maintaining gene flow and genetic diversity. However, geographical landforms, such as peninsulas, can impact dispersal patterns and thus be a barrier to gene flow. Here, we use 13 375 genome‐wide single‐nucleotide polymorphisms (SNPs) to evaluate genetic population structure and infer dispersal patterns of the Western Grasswren Amytornis textilis textilis (WGW, n = 140) in the Shark Bay region of Western Australia. We found high levels of genetic divergence between subpopulations on the mainland (Hamelin) and narrow peninsula (Peron). In addition, we found evidence of further genetic sub‐structuring within the Hamelin subpopulation, with individuals collected from the western and eastern regions of a conservation reserve forming separate genetic clusters. Spatial autocorrelation analysis within each subpopulation revealed significant local‐scale genetic structure up to 35 km at Hamelin and 20 km at Peron. In addition, there was evidence of male philopatry in both subpopulations. Our results suggest a narrow strip of land may be acting as a geographical barrier in the WGW, limiting dispersal between a peninsula and mainland subpopulation. In addition, heterogeneous habitat within Hamelin may be restricting dispersal at the local scale. Furthermore, there is evidence to suggest that the limited gene flow is asymmetrical, with directional dispersal occurring from the bounded peninsula subpopulation to the mainland. This study highlights the genetic structure existing within and between some of the few remaining WGW subpopulations, and shows a need to place equal importance on conservation efforts to maintain them in the future. [ABSTRACT FROM AUTHOR]

Associations between genotypes for inversions and quantitative traits have been reported in several organisms, but little has been done to localize regions within inversions controlling variation in these traits. Here, we use an association mapping technique to identify genomic regions controlling variation in wing size within the cosmopolitan inversion In(3R)Payne in Drosophila melanogaster Previous studies have shown that this inversion strongly influences variation in wing size, a trait highly correlated with body size. We found three alleles from two separate regions within In(3R)Payne with significant additive effects on wing size after the additional effect of the inversion itself had been taken into account. There were also several alleles with significant genotype-by-inversion interaction effects on wing size. None of the alleles tested had a significant additive effect on development time, suggesting different genes control these traits and that clinal patterns in them have therefore arisen independently. The presence of multiple regions within In(3R)Payne controlling size is consistent with the idea that inversions persist in populations because they contain multiple sets of locally adapted alleles, but more work needs to be done to test if they are indeed coadapted.

The cosmopolitan inversion In(3R)Payne in Drosophila melanogaster decreases in frequency with increasing distance from the equator on three continents, indicating it is subject to strong natural selection. We investigated patterns of genetic variation and linkage disequilibrium (LD) in 24 molecular markers located within and near In(3R)Payne to determine if different parts of the inversion responded to selection the same way. We found reduced variation in the markers we used compared to others distributed throughout the genome, consistent with the inversion having a relatively recent origin (

Asymmetrical gene flow is an important, but rarely examined genetic parameter. Here, we develop a new method for detecting departures from symmetrical migration between two populations using microsatellite data that are based on the difference in the proportion of private alleles. Application of this approach to data collected from wild-caught Drosophila melanogaster along a latitudinal body-size cline in eastern Australia revealed that asymmetrical gene flow could be detected, but was uncommon, nonlocalized, and occurred in both directions. We also show that, in contrast to the findings of a previous study, there is good evidence to suggest that the cline experiences significant levels of gene flow between populations.

Anthropogenic agents of ocean change such as biological invasions, overfishing, habitat destruction, pollution and ocean acidification and warming are known to have a dramatic impact on marine ecosystems worldwide. They are also intrinsically connected. In Western Australia, a "hot-plate" settlement panel system aimed at investigating the effect of ocean warming on fouling communities led to the first report of a notorious worldwide invasive ascidian species Didemnum perlucidum. This species was subsequently recorded from numerous locations along the coast and included in the Western Australia Prevention List for Introduced Marine Pests. In the present study we used microsatellite markers to determine whether these populations are the result of single or multiple introductions to Australia and if anthropogenic vectors might have facilitated its spread. By including samples collected worldwide, we further aimed to evaluate broad-scale patterns of variation and ascertain whether regional differences could be used to determine the source of introductions of D. perlucidum to Australia. Our results report an extended geographic range for D. perlucidum in Australia and worldwide, in what is the most comprehensive genetic study of this species. Our data further supports the introduced status of D. perlucidum in Australia, an introduction that our results suggest having occurred most likely as a result of multiple events with subsequent admixture. The similarity between genotypes at locations in Western Australia suggests that domestic transport plays a crucial role in shaping these populations, most likely enhanced by climatic anomalies such as heat waves. The identification of the D. perlucidum native range and sourcing of international samples from potential sites of introduction to Australia, particularly south-east Asia, remains essential to understand the presence of this species in the country. Nevertheless, during this study we were able to increase our understanding of D. perlucidum populations in Western Australia. This work provides an important baseline for D. perlucidum management and protection of high value marine areas, in Australia and worldwide. [ABSTRACT FROM AUTHOR]