Latitudinal patterns of species diversity on South American rocky shores: local processes lead to contrasting trends in regional and local species diversity

CRUZ MOTTA, J. J.; GUTIÉRREZ, J.L.; OTROS 29 AUTORES

JOURNAL OF BIOGEOGRAPHY

WILEY-BLACKWELL PUBLISHING, INC

Lugar: Londres; Año: 2020

0305-0270

Aim: We evaluated whether patterns of species diversity (α, β and γ) of rocky shoreassemblages followed latitudinal gradients (i.e. LDGs) along the South Americancoasts, and tested hypotheses related to potential processes sustaining or disruptingthe expected LDG pattern at various spatial scales.Location: Coasts of South America.Taxon: Macroalgae and sessile/slow-moving macrofauna on intertidal rocky shores.Methods: We evaluated changes in species composition across 143 sites. The degreeof replacement and loss of species at different spatial scales (i.e. coasts, regionsand sites) were estimated to help distinguish among ecological, historical and evolutionaryhypotheses for explaining LDGs. Furthermore, components of diversity andtaxonomic distinctness were measured, and variability in these measures was decomposedusing analysis of covariance. Finally, we examined relationships between diversityand a suite of environmental and anthropogenic variables to identify potentialmechanisms that may be responsible for the reported spatial relationships.Results: Species composition varied with latitude, and this variability was relativelyconsistent on both coasts. At all spatial scales, replacement of species was the dominantphenomenon (>95%), rather than loss in the total number of species (<5%). LDGswere strongly dependent on the diversity component and the spatial scale: generally,positive for regional β-diversity, negative for α-diversity and site β-diversity. Seasurface temperature (SST) was the variable that best explained patterns of diversityalong both coasts (14%?22%), but other regional and local environmental variables associatedwith river discharges, upwelling, confluence of currents, tides and anthropogenicpressures also accounted for an important portion of variation (5%?14% each).Main conclusions: Species diversity of South American rocky shores followed, with interruptions,LDGs. The trend of those LDGs, however, depended on the scale and metricused to describe diversity. It is proposed that patterns of LDGs at various scales are notthe result of a single overarching process but are strongly influenced by local and regionalprocesses. Although the most evident environmental gradient was the decrease in SST towardsthe south, it was demonstrated that regional and local environmental variables werealso important for understanding the increase in regional β-diversity towards the tropics