Productivity (trophic energy) is one of the most important factors promoting variation in species richness. A variety of species-energy relationships have been reported, including monotonically positive, monotonically negative, or unimodal (i.e. hump-shaped). The exact form of the relationship seems to depend, among other things, on the spatial scale involved. However, the mechanisms behind these patterns are still largely unresolved, although many hypotheses have been suggested. Here we report a case of local-scale positive species-energy relationship. Using 14 local fish assemblages in tropical forested headwater streams (Bolivia), and after controlling for major local abiotic factors usually acting on assemblage richness and structure, we show that rising energy availability through leaf litter decomposition rates allows trophically specialized species to maintain viable populations and thereby to increase assemblage species richness. By deriving predictions from three popular mechanistic explanations, i.e. the 'increased population size', the 'consumer pressure', and the 'specialization' hypotheses, our data provide only equivocal support for the latter. To cite this article: P.A. Tedesco et al., C. R. Biologies 330 (2007).
Nota bibliográficaFunding Information:
This work was supported by the ‘Institut de recherche pour le développement’ (IRD) and by the long-term research plans of the Masaryk University (Czech Ministry of Education, MSM 0021622416). The original idea of doing this work emerged after stimulating discussions at the Energy and Geographic Variation in Species Richness working group supported by the National Center for Ecological Analysis and Synthesis (NCEAS), a Center funded by the NSF (Grant No. DEB-0072909) and the University of California at Santa Barbara. We are grateful to David Currie, Bradford Hawkins, Olivier Dangles, Éric Chauvet, Thierry Boulinier, and Kirk Winemiller for discussion and/or comments on previous versions of the manuscript.