Divergent Selection in Low Recombination Regions Shapes the Genomic Islands in Two Incipient Shorebird Species.

Speciation in the face of gene flow is usually associated with a heterogeneous genomic landscape of divergence in nascent species pairs. However, multiple factors, such as divergent selection and local recombination rate variation, can influence the formation of these genomic islands. Examination of the genomic landscapes of species pairs that are still in the early stages of speciation provides an insight into this conundrum. In this study, population genomic analyses were undertaken using a wide range of sampling and whole-genome resequencing data from 96 unrelated individuals of Kentish plover (Charadrius alexandrinus) and white-faced plover (Charadrius dealbatus). We suggest that the two species exhibit varying levels of population admixture along the Chinese coast and on the Taiwan Island. Genome-wide analyses for introgression indicate that ancient introgression had occurred in Taiwan population, and gene flow is still ongoing in mainland coastal populations. Furthermore, we identified a few genomic regions with significant levels of interspecific differentiation and local recombination suppression, which contain several genes potentially associated with disease resistance, coloration, and regulation of plumage molting and thus may be relevant to the phenotypic and ecological divergence of the two nascent species. Overall, our findings suggest that divergent selection in low recombination regions may be a main force in shaping the genomic islands in two incipient shorebird species.

Running the gauntlet; flyway-wide patterns of pollutant exposure in blood of migratory shorebirds.

Shorebirds (order Charadriiformes) are among the world's most threatened avian taxa. Within the East Asian-Australasian Flyway (EAAF), a major threat to shorebirds' survival may be the gauntlet of pollution along the flyway. Metals, persistent organic pollutants (POPs), and per-/polyfluoroalkyl substances (PFASs) persist in the environment to the detriment of wildlife. In this study, we analysed element and PFAS concentrations in blood from 142 individuals across six species of Arctic-breeding migratory shorebirds with contrasting population trends, to discern species- and site-specific pollution differences, and determine how pollution correlated with population trends of EAAF shorebirds. Potential within-year pollution variations were investigated by blood-sampling birds at two sites, representing different points in the birds' annual migrations: staging in Taiwan on southward migrations and at non-breeding grounds in Western Australia (WA). Species' pollutant concentrations were compared to established population trends. Concentrations of potentially toxic elements were low in most individuals regardless of species. PFASs (range: <0.001-141 ng/g), Hg (<0.001-9910 ng/g) and Pb (<0.01-1210 ng/g) were higher in Taiwan than in WA (PFAS Taiwan median: 14.5 ng/g, WA median: 3.45 ng/g; Hg Taiwan: 338 ng/g, WA: 23.4 ng/g; Pb Taiwan: 36.8 ng/g, WA: 2.26 ng/g). Meanwhile As (range <0.001-8840 ng/g) and Se (290-47600 ng/g) were higher in WA than Taiwan (As Taiwan median: 500 ng/g, WA median: 1660 ng/g; Se Taiwan: 5490 ng/g, Se WA: 23700 ng/g). Nevertheless, pollutant concentrations in a subset of individuals may exceed sublethal effect thresholds (As, Se and PFASs). Finally, we found no consistent differences in pollution among species and demonstrated no correlation between pollution and population trends, suggesting pollution is likely not a major driver for population declines of EAAF shorebirds. However, ongoing and locally heavy environmental degradation and exposure to other contaminants not investigated here, such as POPs, warrants continued consideration when managing EAAF shorebird populations.

Genetic, phenotypic and ecological differentiation suggests incipient speciation in two Charadrius plovers along the Chinese coast.

BACKGROUND: Speciation with gene flow is an alternative to the nascence of new taxa in strict allopatric separation. Indeed, many taxa have parapatric distributions at present. It is often unclear if these are secondary contacts, e.g. caused by past glaciation cycles or the manifestation of speciation with gene flow, which hampers our understanding of how different forces drive diversification. Here we studied genetic, phenotypic and ecological aspects of divergence in a pair of incipient shorebird species, the Kentish (Charadrius alexandrinus) and the White-faced Plovers (C. dealbatus), shorebirds with parapatric breeding ranges along the Chinese coast. We assessed divergence based on molecular markers with different modes of inheritance and quantified phenotypic and ecological divergence in aspects of morphometric, dietary and climatic niches. RESULTS: Our integrative analyses revealed small to moderate levels of genetic and phenotypic distinctiveness with symmetric gene flow across the contact area at the Chinese coast. The two species diverged approximately half a million years ago in dynamic isolation with secondary contact occurring due to cycling sea level changes between the Eastern and Southern China Sea in the mid-late Pleistocene. We found evidence of character displacement and ecological niche differentiation between the two species, invoking the role of selection in facilitating divergence despite gene flow. CONCLUSION: These findings imply that ecology can indeed counter gene flow through divergent selection and thus contributes to incipient speciation in these plovers. Furthermore, our study highlights the importance of using integrative datasets to reveal the evolutionary history and assist the inference of mechanisms of speciation.

Planar Perovskite Solar Cells Using Perovskite CsPbI3 Quantum Dots as Efficient Hole Transporting Layers.

Perovskite CsPbI3 quantum dots (QDs) were synthesized as a hole-transporting layer (HTL) of a planar perovskite solar cell (PSC). By using the Octam solution during the ligand engineering, CsPbI3 QDs exhibits a denser grain and a larger grain size due to the short-chain ligands of Octam. In addition, CsPbI3 QDs with the Octam solution showed a smooth and uniform surface on MAPbI3 film, indicating the QDs improved the microstructure of the MAPbI3 perovskite film. As a result, the PSC with CsPbI3 QDs as an HTL has the optimal open-circuit voltage as 1.09 V, the short-circuit current as 20.5 mA/cm2, and the fill factor (FF) as 75.7%, and the power conversion efficiency (PCE) as 17.0%. Hence, it is inferred that introducing QDs as a HTL via the ligand engineering can effectively improve the device performance of the PSC.