The balance of propagule supply and environmental filtering on the structure of an intertidal rocky shore metacommunity
Environment-driven variations in the supply of individuals to local assemblages can determine patterns of community structure. Alternatively, post-settlement processes can erase any signal of recruitment, a result shown in benthic rocky shores, but typically using small sets of competing species. In a community-wide context, instead, we tested the relationships between larval recruitment and environmental filtering with adult community structure of the intertidal rocky shore metacommunity in northern-central Chile, where coastal upwelling around a major topographic feature (30.25ºS; Punta Lengua de Vaca, PLV) maintains a persistent spatial structure in sea surface temperature (SST) variability. To test these relationships, we conducted a monitoring study between 2009 and 2013 at twelve sites along ~400 km of shore. SST, recruitment rates, and species abundances were analysed with Canonical Analyses of Principal coordinates and Generalised Additive Models.
Sites located around PLV presented colder SST, lower recruitment rates, reduced invertebrate abundances, and higher algal abundance than sites located north of PLV, in accordance with expectations from upwelling-transport models. In addition, two sites located further north from PLV, but sharing environmental conditions with those located near and south of PLV, showed similar multivariate patterns of larval recruitment and adult abundances. The multivariate structures of SST and larval recruitment rates were significantly and jointly related with adult community structure across all sites. We suggest that the balance between dominant patterns of spatiotemporal variability in physical conditions—chiefly the seasonal cycle and synoptic-scale (days to weeks) patterns—sets local constraints for larval recruitment rates and the local abundance of dominant species, thus modulating the structure of functionally distinct assemblages in this metacommunity.