Local temperature adaptation among populations of Tigriopus californicus along the North American West Coast

Many current models predicting the effects of climate change assume species are homogenous across geographic distribution and life stage. However local adaptations may result in variable impacts of climate change across isolated populations. Furthermore, individuals of different life stages may exhibit different tolerances to variations in climatic conditions. We use the widely distributed tide pool copepod Tigriopus californicus as a model organism to test differences in thermal tolerance across populations and life stage of broadly distributed species. We tested the thermal tolerance of seven populations (spanning 15° in latitude) from the northern extent of the species range. We found that thermal tolerance differed among populations and life stage. However the degree of differentiation between populations was less pronounced in these northern populations than previously observed in southern populations. This is likely due to significantly less interpopulation mtDNA differentiation in the northern extent of the range than in the southern