Meeting Abstract
Brown’s Resource Breadth Hypothesis posits that species that can exploit a broader range of consumable resources have broader geographic ranges. We tested the isotopic version of Brown’s hypothesis in ovenbirds of the genus Cinclodes (family Furnariidae). Briefly, we used isotopic niches as surrogates for ecological ones. We predicted a positive evolutionary correlation between the width of the niches defined by the isotopic values of hydrogen and oxygen and those defined by the isotopic values of nitrogen and oxygen. The former describe the altitudinal and latitudinal range of a species, whereas the latter estimate the breadth of habitats and resources used. In support of Brown’s hypothesis, we found that the width of carbon/nitrogen niches was positively correlated with that of oxygen/hydrogen. This result was independent of whether we accounted for phylogenetic relationships or not, and hence, appears to be a robust result. In Cinclodes the range of altitudinal and latitudinal ranges seems to be positively correlated with the breadth of habitats and resources used by species. We also estimated the phylogentic signal of both isotopic width and isotopic position. We found that Cinclodes niches are more evolutionary divergent than predicted by a Brownian model of evolution. This result suggests that the isotopic niches of Cinclodes are not phylogenetically conserved. To our knowledge these results are the first attempt using isotopic niches to test hypotheses about how ecological niches evolve.
