Twenty-three years of convergence in community responses along a large geographic gradient

Abstract: Understanding how multispecies assemblages jointly respond to environmental fluctuations is one of the main challenges for modern ecology. Using Hierarchical Modelling of Species Communities (HMSC), we aimed to disentangle spatial and temporal changes over the past two decades in the composition of intertidal zone communities spread across nine-degrees of latitude along the Humboldt upwelling ecosystem. We found that taxonomic classification and species traits were weakly associated with species responses to seawater temperature variability patterns. However, there has been a consistent increase in the occurrence of macroalgal and invertebrate species across the region. No species decreased their occurrence over time. The occurrence of different macroalgal species was more sensitive to mean sea-surface-temperature than invertebrates, and their responses shifted from positive in the north to negative in the southern sites. Our findings suggest a lack of community-wide changes, which may be modulated by the regional cooling driven by the intensification of coastal upwelling.