Biogeographical boundaries, functional group structure and diversity of Rocky Shore communities along the Argentinean coast

PLoS One. 2012;7(11):e49725. doi: 10.1371/journal.pone.0049725. Epub 2012 Nov 16.

Abstract

We investigate the extent to which functional structure and spatial variability of intertidal communities coincide with major biogeographical boundaries, areas where extensive compositional changes in the biota are observed over a limited geographic extension. We then investigate whether spatial variation in the biomass of functional groups, over geographic (10's km) and local (10's m) scales, could be associated to species diversity within and among these groups. Functional community structure expressed as abundance (density, cover and biomass) and composition of major functional groups was quantified through field surveys at 20 rocky intertidal shores spanning six degrees of latitude along the southwest Atlantic coast of Argentina and extending across the boundaries between the Argentinean and Magellanic Provinces. Patterns of abundance of individual functional groups were not uniformly matched with biogeographical regions. Only ephemeral algae showed an abrupt geographical discontinuity coincident with changes in biogeographic boundaries, and this was limited to the mid intertidal zone. We identified 3-4 main 'groups' of sites in terms of the total and relative abundance of the major functional groups, but these did not coincide with biogeographical boundaries, nor did they follow latitudinal arrangement. Thus, processes that determine the functional structure of these intertidal communities are insensitive to biogeographical boundaries. Over both geographical and local spatial scales, and for most functional groups and tidal levels, increases in species richness within the functional group was significantly associated to increased total biomass and reduced spatial variability of the group. These results suggest that species belonging to the same functional group are sufficiently uncorrelated over space (i.e. metres and site-to-site ) to stabilize patterns of biomass variability and, in this manner, provide a buffer, or "insurance", against spatial variability in environmental conditions.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Argentina
  • Atlantic Ocean
  • Biodiversity*
  • Biomass*
  • Ecosystem*
  • Environment
  • Geography*
  • Population Density

Grants and funding

E.A.W. appreciates support from a Rhodes University Postdoctoral Fellowship. Funding for this project was provided by the South African Research Chairs Initiative of the Department of Science and Technology and National Research Foundation to C.M., grants from the Andrew Mellon Foundation to C.M. and S.A.N., a Consejo Nacional de Investigaciones Científicas y Técnicas (Conicet) grant to G.P., and by Fondo de Financiamiento de Centros de Excelencia en Investigación - Fondo Nacional de Desarrollo Científico y Tecnólogico (Fondap-Fondecyt) 15001-001 to the Center for Advanced Studies in Ecology and Biodiversity to S.A.N. P.P. was supported by a Comisión Nacional de Investigación Científica y Tecnológica doctoral scholarship. The continuous support from the Andrew Mellon Foundation to conduct large-scale studies is deeply acknowledged. We acknowledge additional support by FONDECYT 1100920 to E.A.W., FONDECYT 1070335 to S.A.N., and the Center of Marine Conservation Nucleo Milenio Initiative P10-033F. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.