Adaptation at a snail’s pace: Successful invasion without rapid
adaptation in new thermal environments by Atlantic oyster drills
(Urosalpinx cinerea)
Abstract
Invasive species with native ranges spanning strong environmental
gradients that establish in new habitats are particularly well-suited
for examining the roles of selection and population history in rapid
environmental adaptation, providing insight into potential evolutionary
responses to climate change. The Atlantic oyster drill (Urosalpinx
cinerea) is a marine snail with a native range spanning the strongest
marine thermal gradient in the world that has established invasive
populations on the U.S. Pacific coast. Here, we leverage this system
using genome-wide SNPs and environmental data to examine invasion
history and identify genotype-environment associations indicative of
local adaptation across its native range, and then assess evidence for
predicted allelic frequency shifts signaling rapid adaptation in
invasive populations. We demonstrate strong genetic structuring among
native regions aligned with life history expectations and identify
southern New England as the source of invasive populations. We also
identify putatively thermally adaptive loci across the native range, for
which two invasive populations show significant divergence from source
populations. However, we find no evidence of directional shifts in
allele frequencies as would be predicted by environmental selection,
suggesting that divergence is likely due to genetic drift rather than
rapid adaptation. Alternatively, the success of new populations in
environments differing from their origin may be due to relaxed selection
pressures associated with more benign conditions, and/or standing
capacity for phenotypic plasticity. This demonstrates the utility of
invasive species for understanding evolutionary responses to changing
environments, and the importance of considering population history and
environmental selection pressures when evaluating adaptative capacity.