Nectar characteristics of hummingbird-visited ornithophilous and non-ornithophilous flowers from Cerrado, Brazil

Abstract

Hummingbirds in the Cerrado, the seasonal savannas in Central Brazil, visit both ornithophilous and non-ornithophilous flowers to collect nectar, which is the main source of energy and nutrients to these pollinators. The aim of the present study was to assess the volume, concentration, energy content and sugar composition of nectar collected from 34 hummingbird-visited flower species. We expect that nectar traits of non-ornithophilous species visited by hummingbirds are similar to those of ornithophilous species. Nectar samples were collected from different plant formations in the Cerrado region at Panga Ecological Station, Uberlândia City, Minas Gerais State, Brazil. Samples were obtained from 19 ornithophilous, 10 entomophilous and five chiropterophilous species. Nectar traits, such as volume, sugar concentration and energy content, did not significantly differ between ornithophilous and non-ornithophilous flowers. However, about 80% of the sampled species had sucrose-rich nectar, whereas other species, mainly chiropterophilous, had hexose-rich nectar. Overall, ornithophilous and chiropterophilous flower nectars shared similar energy content. On the other hand, the sugar-chemical composition of nectar from ornithophilous flowers was more similar to that of sucrose-rich entomophilous flowers. There is broad consensus that the nectar in flowers of hummingbird-pollinated species is rich in sucrose. However, hummingbirds visit several savanna plant species unrelated to the ornithophilous pollination syndrome. This trend indicates that hummingbirds show plasticity in selecting plant nectar sources when feeding, mainly in resource-fluctuating environments such as the Cerrado.