Context-Dependent Physiological Responses in Scurria Limpets Are Not Associated With Latitudinal Gradients or...

Biogeographic breaks represent crucial ecological junctures where species encounter novel environments that challenge their physiological limits and influence evolutionary trajectories. Two biogeographic breaks delineate distinct environmental regimes along the Chilean coastline on the Southeastern Pacific. In particular, the equatorward break, situated around 30° S-32° S, marks a transition from semi-permanent upwelling to seasonal and intermittent upwelling poleward. The environmental break maintains a heterogeneous landscape for all coastal species along the region. Marine invertebrates, particularly intertidal ectothermic species such as limpets of the Scurria genus, exhibit diverse physiological responses to variation in the thermal environment. We characterized the physiological performance of five Scurria limpet species by measuring metabolic rate (oxygen consumption) and heart rate, together with buoyant weight as a proxy of shell calcification, under a standardized acclimation design under controlled laboratory conditions in individuals sourced from four locations spanning 17° of latitude, including the 30° S-32° S biogeographic break. We tested if the observed geographic variation in phenotypic traits was associated with differences in sea surface temperature, geographic location, and population genetic structure. Our findings indicate that the observed variation in metabolic traits among localities does not follow a latitudinal trend or mirror the biogeographic origin of the populations. We found no evidence supporting the role of latitudinal metabolic compensation or local adaptation in metabolism in explaining the distribution of limpets. However, significant differences in these traits among locations were observed, varying among species between sites but showing little to no correlation with the documented genetic structure.