Publication
Twin introductions by independent invader mussel lineages are both associated with recent admixture with a native congener in Australia
Publisher:
Wiley
Date:
18-09-2020
DOI:
10.1111/EVA.12857
Abstract: Introduced species can impose profound impacts on the evolution of receiving communities with which they interact. If native and introduced taxa remain reproductively semi‐isolated, human‐mediated secondary contact may promote genetic exchange across newly created hybrid zones, potentially impacting native genetic ersity and invasive species spread. Here, we investigate the contributions of recent ergence histories and ongoing (post‐introduction) gene flow between the invasive marine mussel, Mytilus galloprovincialis, and a morphologically indistinguishable and taxonomically contentious native Australian taxon, Mytilus planulatus . Using transcriptome‐wide markers, we demonstrate that two contemporary M. galloprovincialis introductions into south‐eastern Australia originate from genetically ergent lineages from its native range in the Mediterranean Sea and Atlantic Europe, where both introductions have led to repeated instances of admixture between introduced and endemic populations. Through increased genome‐wide resolution of species relationships, combined with demographic modelling, we validate that mussels s led in Tasmania are representative of the endemic Australian taxon ( M. planulatus ), but share strong genetic affinities to M. galloprovincialis . Demographic inferences indicate late‐Pleistocene ergence times and historical gene flow between the Tasmanian endemic lineage and northern M. galloprovincialis , suggesting that native and introduced taxa have experienced a period of historical isolation of at least 100,000 years. Our results demonstrate that many genomic loci and sufficient s ling of closely related lineages in both sympatric (e.g. Australian populations) and allopatric (e.g. northern hemisphere Mytilus taxa) ranges are necessary to accurately (a) interpret patterns of intraspecific differentiation and to (b) distinguish contemporary invasive introgression from signatures left by recent ergence histories in high dispersal marine species. More broadly, our study fills a significant gap in systematic knowledge of native Australian bio ersity and sheds light on the intrinsic challenges for invasive species research when native and introduced species boundaries are not well defined.