Sucrose digestion capacity in birds shows convergent coevolution with nectar composition across continents
Todd J. McWhorter,
Jonathan A. Rader,
Jorge E. Schondube,
Susan W. Nicolson,
Berry Pinshow,
Patricia A. Fleming,
Yocelyn T. Gutiérrez-Guerrero,
Carlos Martínez del Rio
Affiliations
Todd J. McWhorter
School of Animal and Veterinary Sciences, University of Adelaide, Roseworthy Campus, SA 5371, Australia; Corresponding author
Jonathan A. Rader
Department of Biology, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599-3280, USA
Jorge E. Schondube
Centro de Investigaciones en Ecosistemas, Universidad Nacional Autónoma de México campus Morelia, Morelia, Michoacán CP 58190, México
Susan W. Nicolson
Department of Zoology and Entomology, University of Pretoria, Pretoria 0002, South Africa
Berry Pinshow
Mitrani Department of Desert Ecology, Swiss Institute for Dryland Environmental and Energy Research, Jacob Blaustein Institutes for Desert Research, Ben-Gurion University of the Negev, 8499000 Midreshet Ben-Gurion, Israel
Patricia A. Fleming
Environmental and Conservation Sciences, Harry Butler Institute, Murdoch University, Murdoch, WA 6150, Australia
Yocelyn T. Gutiérrez-Guerrero
Departamento de Biología Evolutiva, Instituto de Ecología, Universidad Nacional Autonoma de México, Mexico D.F., México
Carlos Martínez del Rio
Department of Zoology and Physiology, University of Wyoming, Laramie, WY 82071-3166, USA
Summary: The major lineages of nectar-feeding birds (hummingbirds, sunbirds, honeyeaters, flowerpiercers, and lorikeets) are considered examples of convergent evolution. We compared sucrose digestion capacity and sucrase enzymatic activity per unit intestinal surface area among 50 avian species from the New World, Africa, and Australia, including 20 nectarivores. With some exceptions, nectarivores had smaller intestinal surfaces, higher sucrose hydrolysis capacity, and greater sucrase activity per unit intestinal area. Convergence analysis showed high values for sucrose hydrolysis and sucrase activity per unit intestinal surface area in specialist nectarivores, matching the high proportion of sucrose in the nectar of the plants they pollinate. Plants pollinated by generalist nectar-feeding birds in the Old and New Worlds secrete nectar in which glucose and fructose are the dominant sugars. Matching intestinal enzyme activity in birds and nectar composition in flowers appears to be an example of convergent coevolution between plants and pollinators on an intercontinental scale.
