DOI: 10.5061/dryad.540cc05
title: Data from: Twin introductions by independent invader mussel lineages are both associated with recent admixture with a native congener in Australia

description: 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 diversity and invasive species
 spread. Here, we investigate the contributions of recent divergence
 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 southeastern
 Australia originate from genetically divergent 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 sampled in Tasmania are representative of the
 endemic Australian taxon (M. planulatus), but share strong genetic
 affinities to M. galloprovincialis. Demographic inferences indicate
 late-Pleistocene divergence 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 sampling of closely related lineages in both
 sympatric (e.g., Australian populations) and allopatric (e.g.,
 northern-hemisphere Mytilus taxa) ranges are necessary to accurately (i)
 interpret patterns of intraspecific differentiation and to (ii)
 distinguish contemporary invasive introgression from signatures left by
 recent divergence histories in high dispersal marine species. More
 broadly, our study fills a significant gap in systematic knowledge of
 native Australian biodiversity and sheds light on the intrinsic challenges
 for invasive species research when native and introduced species
 boundaries are not well-defined.
description: ReferenceTranscriptome_Files1) Mytilus galloprovincialis de novo transcriptome assembly, containing 159,985 nuclear sequences. This file was used as a reference assembly for variant discovery and as input for all downstream genomic analyses. 2) Reference assembly of 12 protein-coding female mitochondrial genes used for SplitsTree analyses.FilteredVCF_Files_PopGenomicAnalysesFiltered VCF files used as input for principal component analyses and population genomic analyses performed in Admixture, TreeMix, SplitsTree and TWISST. Sample IDs and population information is contained in the file pop.file.mytilusReads2snps_VCF_FilesVCF files generated by Reads2snps program. These files were filtered and used as empirical input for approximate Bayesian computations (ABC). Filtering of empirical data and ABC inferences were conducted using custom R scripts available at https://github.com/dinmatias