Oceanographic currents, geographic patterns and local environment
contribute to neutral and adaptive genetic structure in two intertidal
marine gastropods with contrasting life-histories
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¸ 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.