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Invasive species are predicted to adjust their morphological, physiological and life-history traits to adapt to their non-native environments. Although a loss of genetic variation during invasion may restrict local adaptation, introduced species often thrive in novel environments. Despite being founded by just a few individuals, Bombus terrestris (Hymenoptera: Apidae) has in less than 30 years successfully spread across the island of Tasmania (Australia), becoming abundant and competitive with native pollinators. We use RADseq to investigate what neutral and adaptive genetic processes associated with environmental and morphological variation allow B. terrestris to thrive as an invasive species in Tasmania. Given the widespread abundance of B. terrestris, we expected little genetic structure across Tasmania and weak signatures of environmental and morphological selection. We found high gene flow with low genetic diversity, although with significant isolation-by-distance and spatial variation in effective migration rates. Restricted migration was evident across the mid-central region of Tasmania, corresponding to higher elevations, pastural land, low wind speeds and low precipitation seasonality. Tajima's D indicated a recent population expansion extending from the south to the north of the island. Selection signatures were found for loci in relation to precipitation, wind speed and wing loading. Candidate loci were annotated to genes with functions related to cuticle water retention and insect flight muscle stability. Understanding how a genetically impoverished invasive bumblebee has rapidly adapted to a novel island environment provides further understanding about the evolutionary processes that determine successful insect invasions, and the potential for invasive hymenopteran pollinators to spread globally., (© 2023 The Authors. Molecular Ecology published by John Wiley & Sons Ltd.)

Identifying isolated populations is a key step towards enacting effective conservation management. European lobsters (Homarus gammarus) from Oosterschelde in the Netherlands are subject to fishery pressure and have previously been reported as genetically differentiated. They are also putatively of transplanted origin and have subsequently endured recent bottlenecking and environmental change. We assessed Oosterschelde lobsters to evaluate their demographic independence and appraise potential founder effects and evolutionary responses to isolation. Using restriction-site associated DNA sequencing, we genotyped 6185 single nucleotide polymorphisms across 188 individuals from 27 sites across the Atlantic range of H. gammarus to investigate population genetic diversity, structure, and potential adaptation. Our results show that Oosterschelde lobsters are genetically divergent from other stocks. We evidence extensive differentiation via both neutral and outlier loci, indicative of strong biophysical and demographic isolation, and detect signatures of reduced genetic diversity that may reflect weak founder effects or subsequent population contractions. Among outlier loci, we identify candidates for range-wide local adaptation via variants in genes of important biological functionality and link a private allele of Oosterschelde to a locus potentially conveying adaptive tolerance to environmental hypoxia. Given our findings, we advise proactive monitoring of Oosterschelde lobsters to explore whether existing management measures effectively conserve this discrete, self-recruiting population. [ABSTRACT FROM AUTHOR]

Aim: The Mediterranean Basin is a global biodiversity hotspot and has one of the longest histories of human–biota interactions. Islands host a large fraction of Mediterranean diversity and endemism, but the relative importance of natural versus human‐mediated colonisation processes in shaping the distribution and genetic structure of Mediterranean island fauna remains poorly understood. Here, we combine population genomics, demographic models and palaeoshoreline reconstructions to establish the island‐colonisation dynamics of wall lizards in Mediterranean archipelagos. Location: Four Mediterranean archipelagos in Italy and Croatia. Taxon: The wall lizard Podarcis siculus. Methods: We used ddRAD sequencing to genotype 140 lizards from 23 island and mainland populations. Analyses of admixture and site frequency spectra were used to reconstruct population structure, demographic history and variation of gene flow through time. Genomic results were integrated with palaeogeographical reconstructions and were compared to archaeological evidence of human presence on these islands. Results: Although many island populations of this species are assumed to be non‐native, we find that many islands were colonised long before any known human settlements (230,000–12,000 years ago). This natural colonisation most likely occurred through land bridges during glacial marine regression or by over‐sea rafting. On the other hand, islands distant from the continent were often colonised recently, and some of the estimated island colonisation times match historical records of human arrival. We also determine that long‐established island populations generally show lower genetic diversity compared to proximate mainland populations, contrary to recently colonised islands that must have experienced higher rates of post‐colonisation gene flow. Main Conclusion: Our integrated approach provides us with the power to accurately quantify the origin, timing and mode of island colonisation. This framework helps to clarify the biogeographical and evolutionary history of island populations, with important implications for conservation and management of island biodiversity. [ABSTRACT FROM AUTHOR]