Shifts in southern endpoints of distribution in rocky intertidal species along the south-eastern Pacific coast

Aim Despite the pervasive and well-documented effects of global warming on species' ranges in terrestrial taxa and systems, the effect of sea surface warming has been poorly studied in marine systems. Here we analyse changes in the southern endpoints of distribution of rocky intertidal species (gastropods and chitons) along the Chilean coast, and trends in sea surface temperature (SST), using data collected during the last half-century. Location South-eastern Pacific coast, between 18degrees20' S and 42degrees35' S. Methods Past southern endpoints of distribution were obtained for 10 intertidal species from museum collections and literature reviews. Current endpoints are based on field sampling conducted between 1998 and 2000. Changes in the position of southern endpoints were analysed individually for each species, as well as for the entire assemblage of species included in the analysis. SST records encompassing 51-57 years were obtained from five coastal stations located between 18degrees and 36degrees S. Results and main conclusions Most species (eight of 10) did not show expansion of their southern endpoint. The proportion of species expanding, contracting or maintaining their southern limit did not differ from chance expectation. On average, species showed small (1degrees latitude), non-significant contractions, with low rates of decadal change (0.18degrees latitude per 10 years). This pattern can be explained by changes in SST, which showed a weak warming trend (and at some sites even cooling) along the Chilean coast during the last 57 years. Our results show that different regional warming trends occur, and suggest that generalizations about poleward shifts in species ranges cannot be made. However, our results support the hypothesis that temperature is a major determinant of species range dynamics.