Sugar and protein digestion in flowerpiercers and hummingbirds: a comparative test of adaptive convergence |
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Authors: | Email author" target="_blank">J?E?SchondubeEmail author C?Martinez del Rio |
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Institution: | (1) Department of Ecology and Evolutionary Biology, University of Arizona, Tucson, AZ 85721-0088, USA;(2) Centro de Investigaciones en Ecosistemas, UNAM, Apartado Postal 27-3 (Xangari), 58089 Morelia, Michoacán, Mexico;(3) Department of Zoology and Physiology, University of Wyoming, Laramie, WY 82071-3166, USA |
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Abstract: | Flowerpiercers are the most specialized nectar-feeding passerines in the Neotropics. They are nectar robbers that feed on the sucrose-rich diet of hummingbirds. To test the hypothesis that flowerpiercers have converged with hummingbirds in digestive traits, we compared the activity of intestinal enzymes and the gut nominal area of cinnamon-bellied flowerpiercers (Diglossa baritula) with those of eleven hummingbird species. We measured sucrase, maltase, and aminopeptidase-N activities. To provide a comparative context, we also compared flowerpiercers and hummingbirds with 29 species of passerines. We analyzed enzyme activity using both standard allometric analyses and phylogenetically independent contrasts. Both approaches revealed the same patterns. With the exception of sucrase activity, hummingbirds digestive traits were indistinguishable from those of passerines. Sucrase activity was ten times higher in hummingbirds than in passerines. Hummingbirds and passerines also differed in the relationship between intestinal maltase and sucrase activities. Maltase activity was two times higher per unit of sucrase activity in passerines than in hummingbirds. The sucrase activity of D. baritula was much lower than that of hummingbirds, and not unlike that expected for a passerine of its body mass. With the exception of aminopeptidase-N activity, the digestive traits of D. baritula were not different from those of other passerines.Abbreviations Km Michaelis-Menten constant - PDAP phenotypic diversity analysis program - PIC phylogenetic independent contrast - Vmax maximal reaction velocityCommunicated by G. Heldmaier |
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Keywords: | Comparative method Diglossa baritula Hummingbirds Sucrase activity Sugar and protein digestion |
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