Meeting Abstract

38.2  Jan. 5  Neutrons, Niches, and Adaptive Radiation in Cinclodes Ovenbirds MARTINEZ DEL RIO, C.*; SABAT, P.; Univ. of Wyoming; Univ. de Chile cmdelrio@uwyo.edu

Passerines are astoundingly speciose and ecologically diverse. However, remarkably few songbird species have evolved a marine habit. The genus Cinclodes (Furnariidae) is an exception. In addition to species that inhabit terrestrial/freshwater streams and species that shift between freshwater and marine habitats, it includes two strictly marine species. We present evidence that supports the idea that Cinclodes satisfies the criteria for an ecological radiation: 1) The clade is monophyletic, 2) it experienced recent speciation accompanied by phenotypic diversification, and 3) the osmoregulatory traits of five Cinclodes species satisfies the criterion of adaptive phenotype-environment correlation. The carbon isotopic composition of the birds� tissues diagnosed the degree of reliance on marine food sources and was positively correlated with renal traits responsible for urine concentration. We contend that radiation in Cinclodes was mediated by the rapid evolution of osmoregulatory traits. The capacity to withstand salty diets of C. nigrofumosus, one of the coastal species, exceeded that of most songbirds. Carbon and nitrogen stable isotope measurements of bird�s tissues differentiated the seasonal dependence of Cinclodes species on intertidal, terrestrial, and freshwater food webs, and allowed assessing the contribution of intra- and inter-individual variation to each species� niche width. Stable isotopes measurements were useful as covariates in comparative analyses, and as tools to quantify ecological niches.