Using niche modelling of indicator species to predict the distribution of xerophitic shrub dune communities in South-Western Portugal

Inland sand dune systems are amongst the most threatened habitat types of Europe. Affected by severe conditions, these habitats present distinct community compositions, which makes them excellent for studying possible interactions among their integrating species and the environment. We focus on understanding the distribution and cooccurrence of the species from dune plant assemblages as a key step for the adequate protection of these habitats. Using data from an extensive survey we identified the shrub species that could be considered indicators of the different xerophytic scrub dune communities in South West Portugal. Then, we modelled the responses of these species to the environmental conditions using Ecological Niche Factor Analysis. We present some preliminary results elucidating whether using species distribution models of indicator species at a regional scale is a valid approach to predict the distribution of the different types of communities inhabiting these endangered habitats.

Can we use niche models of indicator species to predict the distribution of endangered communities?

European-wide conservation policies are based on the identification of priority habitats. However, research on conservation biogeography often relies on the results and projections of species distribution models to assess species' vulnerability to global change. We assess whether the distribution and structure of threatened communities can be predicted by the suitability of the environmental conditions for their indicator species. We present some preliminary results elucidating if using species distribution models of indicator species at a regional scale is a valid approach to predict these endangered communities. Dune plant assemblages, affected by severe conditions, are excellent models for studying possible interactions among their integrating species and the environment. We use data from an extensive survey of xerophytic inland sand dune scrub communities from Portugal, one of the most threatened habitat types of Europe. We identify indicator shrub species of different types of communities, model their geographical response to the environment, and evaluate whether the output of these niche models are able to predict the distribution of each type of community in a different region.

Analysis of size spectra off northwest Africa: a useful indicator in tropical areas?

Changes in the size spectra of demersal fish communities off Cape Verde (1988, 1994), Guinea (1985-1995), and Mauritania (1987-2001) were studied. Intercepts and slopes showed opposite trends for Guinea and Mauritania, but were relatively stable in spite of a strong increase in landings per unit area. For Cape Verde, there were marked changes in size structure, seemingly inconsistent with the more moderate fishing pressure there. Changes in size structure do not seem to be suitable indicators of the effects of fishing in areas characterized by faster growth rates, small sizes, high species diversity, and complex interrelationships, such as the tropics. (c) 2005 International Council for the Exploration of the Sea. Published by Elsevier Ltd. All rights reserved.