The functional ecology of an adaptive radiation: stable isotopes, niches, phylogenies and kidneys

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Despite their status as the most diverse lineage of birds and their occupation of nearly every terrestrial habitat on the planet, songbirds (passerines, or perching birds) have rarely adapted to become marine specialists. The paucity of marine species among passerines is probably due to the absence of functional salt glands and to the relative inability of bird kidneys to produce highly concentrated urine, which prevents them from coping with the salt loads that accompany marine resources. This project will track the evolutionary pathways that led to a marine niche in an evolutionary radiation of a group of South American songbirds in which two species have independently become marine specialists. The group also includes freshwater specialists and species that occupy both freshwater and marine habitats. We will also investigate the physiological mechanisms that facilitated the transition from a freshwater to a marine environment. Achieving these objectives demands three complementary approaches: 1) using molecular techniques to elucidate the evolutionary relationship among the species in the group; 2) using stable isotopes to quantify the relative reliance of each of these species on marine resources, and 3) using physiological and morphological measurements to assess the traits that allow marine species to cope with the salt loads that accompany the use of marine resources. This project is fundamentally interdisciplinary and hence its participants include a physiologist, a phylogenetic systematist, and a statistician. The project is also an international collaboration that includes scientists from Chile and Brazil. Expeditionary physiology aims to explore the planet's functional biodiversity, and this project is an ideal instrument for communicating biology and inspiring young scholars. This project is a collaboration with elementary and middle school teachers across Wyoming to develop classroom exercises and interactive, web-based, virtual expeditions in order to make the research accessible to their students.