Reference transcriptomes for three species of sacoglossan sea slug

Understanding how species may respond to climate change is of paramount
importance. Species that occupy highly heterogenous environments such as
intertidal zone estuarine habitats, provide an ideal test case for
examining phenotypic and genomic adaptations to different environmental
conditions, which may influence their response to rapidly shifting
climatic conditions. The California coast is projected to experience
changes in both temperature and salinity, which currently vary seasonally
and latitudinally. Using comparative transcriptomics, I documented
patterns of positive selection between the northern dwelling
planktotrophic sacoglossan sea slug Alderia modesta which is remarkably
tolerant of low temperatures and low salinities and its southern congener
Alderia willowi which exhibits a striking flexibility for larval type in
response to seasonally shifting changes in temperature and salinity. Out
of over four thousand one-to-one orthologous genes, I found a signal of
positive selection between Alderia willowi and A. modesta for genes
involved in cell membrane and cell transport, particularly ion homeostasis
(Aquaporin), cell-cell signal transduction, and phosphorylation (NADH
dehydrogenase) Positive selection for ion homeostasis in A. modesta has
implications for its ability to tolerate the lower salinity of its
northern range and in A. willowi substitutions in NADH may assist in high
temperature tolerance of its southern California habitats. Identifying
these candidate genes enables future studies of their functionalization as
we seek to understand the relationship between phenotype and genotype in
species whose phenotypes are influenced by environmental conditions.