Coastal biophysical processes and the biogeography of rocky intertidal species along the south-eastern Pacific

Aim: We assess the spatial distribution of a suite of coastal biophysical characteristics and how their variability is related to the distribution and geographic range of a diverse assemblage of coastal benthic species with different larval dispersal strategies. Location: South-eastern Pacific (SEP) coast between 18°20′S and 42°35′S. Methods: Biophysical variability was assessed using chlorophyll-a concentration, sea surface temperature and the signal of turbid river plumes derived from MODIS onboard the Aqua satellite. We established the dominant spatial components using wavelet and coherence analysis, and evaluated the biogeographic structure of 51 rocky intertidal species sampled over ~2,600 km along the SEP using multivariate classification and regression trees. Results: Biogeographic breaks detected here were consistent with recent biogeographic classification schemes. Distribution breakpoints for species with lecithotrophic larvae clustered around 30°S. We observed a previously unreported break in the distribution of species with planktotrophic larval dispersal strategies around 35°S. These breaks are related to coherence in the spatial structure of sea surface temperature, chlorophyll-a and river outflow over different temporal scales. Regions with similar biophysical characteristics, and the breaks the separate them, are in striking agreement with the biogeographic patterns revealed by the multivariate classification trees. Main conclusions: Our results reconcile patterns of biogeographic structure reported for other groups of species along the SEP coast. We suggest that river outflow, a poorly studied coastal environmental forcing, may play an important role in determining the geographic distribution of rocky shore species, probably through its effects on larval dispersal patterns.