Résumé
Non-native species experience novel selection pressures in introduced
environments and may interbreed with native
lineages. Species introductions therefore provide opportunities
to investigate repeated patterns of adaptation and introgression across
replicated contact zones. Here, we investigate genetic
parallelism between multiple introduced populations of the invasive marine
mussel, Mytilus galloprovincialis, in the absence (South Africa
and California) and presence of hybridisation with a native congener
(Mytilus planulatus in Batemans Bay and Sydney Harbour,
Australia). Repeatability in post-introduction differentiation
from native-range populations varied between genetically distinct Atlantic
and Mediterranean lineages, with Atlantic-derived introductions displaying
high differentiation (maxFST>0.4) and parallelism at outlier loci.
Identification of long non-coding RNA transcripts
(lncRNA) additionally allowed us to clarify
that parallel responses are largely limited to protein-coding
loci, with lncRNAs likely evolving under evolutionary
constraints. Comparisons of independent hybrid zones
revealed differential introgression most strongly in Batemans
Bay, with an excess of M. galloprovincialis ancestry and
resistance to introgression at loci differentiating parental lineages (M.
planulatus and Atlantic M.
galloprovincialis). Additionally, contigs putatively
introgressed with divergent alleles from a closely related
species, Mytilus edulis, showed stronger introgression
asymmetries compared to genome-wide trends and also diverged in parallel
in both Atlantic-derived introductions. These results suggest that
divergent demographic histories experienced by introduced lineages,
including pre-introduction introgression, influences contemporary
admixture dynamics. Our findings build on previous investigations
reporting contributions of historical introgression to
intrinsic reproductive architectures shared
between marine lineages and illustrate that interspecific
introgression history can shape differentiation between
colonising populations and their hybridisation with
native congeners.