ABSTRACT
Global climate change is exposing
intertidal organisms to increasing air and sea temperatures and changing
ocean currents, affecting their ability to disperse, survive and
reproduce, and resulting in shifts in their distribution and abundance.
Improved understanding of these shifts requires characterization of
population structure and local adaptation. We estimate the drivers of
population structure in two intertidal gastropod species with
contrasting life histories by assessing neutral and adaptive population
structure and performing redundancy analyses in a seascape genomics
framework. We show putative adaptive divergence between populations of
the broadcast spawning topshell, Steromphala umbilicalis , despite
high rates of neutral gene flow. This adaptive structure was best
explained by geographic structure, separating sites in Wales from all
other British and Irish sites. Larval dispersal, estimated from
biophysical models, was also identified as a minor component explaining
genetic connectivity in this species. For the direct developing
dogwhelk, Nucella lapillus ΒΈ neutral population structure was best
explained by air and sea surface temperatures while putative adaptive
population structure showed a greater influence of wave exposure. These
results support the expected relationship between neutral population
structure and reproductive mode (i.e., greater population structure in
the direct developing N. lapillus compared with a lack of
structure in the broadcast spawning S. umbilicalis ) and highlight
the interactive effects of geographic structure, larval dispersal and
local environment on gene flow and adaptation of intertidal marine
organisms.
Keywords: seascape genomics, molluscs, intertidal,
connectivity, natural selection, adaptation