1 Citation
Assisted colonisation, the introduction of species beyond their historical
range, is increasingly necessary for conserving species. However,
empirical evidence of the long-term genetic outcomes of assisted
colonisation is grossly lacking. A risk associated with moving species
beyond their native range is the possibility of interspecific
hybridisation with a closely related species, potentially resulting
in outbreeding depression or the genetic swamping of a parental species.
Here, we use a combination of genome-wide Single Nucleotide
Polymorphism (SNP) markers and mitochondrial DNA sequencing to determine
the long-term genetic consequences of introducing the intertidal
periwinkle Bembicium vittatum (a direct developer) beyond its native range
and into the native range of its congener Bembicium auratum (a species
with planktotrophic larval dispersal). We found novel evidence of natural,
multigenerational hybridisation between marine invertebrates with
different modes of development. Intriguingly, introgression was highly
asymmetrical initially, but became more evenly bidirectional as the
population became more admixed. There was a significant decline in the
frequency of alleles from the introduced B. vittatum over time, providing
evidence of genetic swamping. The present study also provides potential
evidence of outbreeding depression, in the form of cytonuclear
incompatibilities, leading to the observed pattern of
asymmetrical introgression. This study reveals the potential for
unexpected mixing between species when reproductive barriers are not well
understood, resulting in failure of pure B. vittatum to persist at the
translocation site, a major concern associated with assisted colonisation.
Without long-term genetic monitoring interspecific hybridisation
between B. vittatum and B. auratum would have gone undetected,
highlighting the importance of long-term monitoring to detect
unintentional negative consequences of conservation translocations.
Successful assisted colonisation requires an understanding of the
potential for interspecific hybridisation between the threatened species
and closely related native species, to reduce the risk of adverse
outcomes.