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 ...