The inverse biodiversity gradient of rocky shore assemblages along the Argentinean coast.

PALOMO, G; BIGATTI G.; M. BAGUR, J. L. GUTIERREZ & J.J. CRUZ-MOTTA.

Congreso; World Conference on Marine Biodiversity; 2011

Identifying latitudinal patterns in species richness can be useful to predict biodiversity changes due to climate change. As part of the activities of NaGISA (Census of Marine Life) and the South American Research Group on Coastal Ecosystems, we sampled the biodiversity of Argentinean rocky intertidal shores along 4700 km of coast. A hierarchical nested design was used to sample seven locations separated by hundreds of kilometers. Two sites separated 1 to 5 km were selected within each location. At each site, the abundance of animals and algae was determined in 10 quadrats (0.25 m2) demarcated at each of three shore levels (high, mid and low). Contrary to the general postulate that the number of species decreases from tropics to poles, our data shows a positive, significant linear relationship between species richness and latitude. Biodiversity was impressively low, with only 104 species detected along the entire region. Species richness increased from 17 species in the northernmost sites (37º S) to 42 species in the southernmost ones (54º S). Understanding the role of climate in determining this inverse biodiversity gradient will help elucidate whether rising temperatures could lead to changes in species distributional ranges and overall biodiversity losses toward the higher latitudes.