| Popis: |
The major lineages of nectar feeding birds (hummingbirds, sunbirds, honeyeaters, flower-piercers, and lorikeets) are considered examples of convergent evolution. Hummingbirds and flower-piercers are found only in the New World, whereas sunbirds, honeyeaters, and lorikeets are found in the Old World. We compared sucrose digestion capacity and sucrase enzymatic activity per intestinal surface area among 50 avian species from the New World, Africa, and Australia including species within the specialized nectar-feeding lineages. With some exceptions, specialized nectarivores had smaller intestinal surfaces, greater sucrose hydrolysis capacity, and greater sucrase activity per intestinal area. Convergence analysis showed high values for sucrose hydrolysis and sucrase activity per intestinal surface area in specialist nectarivores, matching the high proportion of sucrose in the nectar of the plants they pollinate. Plants pollinated by non-specialized nectar-feeding birds in the Old and New Worlds secrete nectar with primarily glucose and fructose. Convergence between intestinal enzyme activity in birds and nectar composition in flowers appears to be an example of convergent coevolution between plants and pollinators at an intercontinental scale. |
