The fruit dispersion of Adenostemma brasilianum (Asteraceae) by birds: an experimental approach

The pantropical genus Adenostemma (Asteraceae) includes mostly herbs which occur in wet forests and stream edges. They produce a large number of small fruits or cypselae, covered by glandular hairs and bearing a particular glandular pappus. These morphological characteristics of the fruits have been associated, but never tested, with dispersion by adhesion to birds' feathers. We developed for the first time an experimental study to demonstrate the ability of the fruits of Adenostemma brasilianum (Pers.) Cass. to adhere to birds' feathers. We performed three different experiments to test both the adherence and retention time of the fruits, with: 1) individual feathers, 2) taxidermied birds mounted in a life-like position, and 3) live captive birds. The fruits were effective in attaching to feather barbs under the three experiments and were able to remain attached for a period of time, supporting previous hypotheses that epiornithochory could be directly involved in the process of fruit dispersion. Our results are especially relevant in the understanding of biogeographic patterns in Adenostemma, given the importance of birds as fruit dispersion agents.