Data from: Phenotypic and transcriptomic responses to salinity stress across genetically and geographically divergent Tigriopus californicus populations

Species inhabiting the North American west coast intertidal must tolerate
an extremely variable environment, with large fluctuations in both
temperature and salinity. Uncovering the mechanisms for this tolerance is
key to understanding species’ persistence. We tested for differences in
salinity tolerance between populations of Tigriopus californicus copepods
from locations in northern (Bodega Reserve) and southern (San Diego)
California known to differ in temperature, precipitation, and humidity. We
also tested for differences between populations in their transcriptomic
responses to salinity. Although these two populations have ~20% mtDNA
sequence divergence and differ strongly in other phenotypic traits, we
observed similarities in their phenotypic and transcriptomic responses to
low and high salinity stress. Salinity significantly affected respiration
rate (increased under low salinity and reduced under high salinity) but we
found no significant effect of population on respiration or a population
by salinity interaction. Under high salinity, there was no population
difference in knockdown response but northern copepods had a smaller
knockdown under low salinity stress, corroborating previous results for T.
californicus. Northern and southern populations had a similar
transcriptomic response to salinity based on a principle components
analysis, although differential gene expression under high salinity stress
was three times lower in the northern population compared to the southern
population. Transcripts differentially regulated under salinity stress
were enriched for ‘amino acid transport' and ‘ion transport’
annotation categories, supporting previous work demonstrating that the
accumulation of free amino acids is important for osmotic regulation in T.
californicus.