Temporal variation in extrafloral nectar secretion in different ontogenic stages of the fruits of Alibertia verrucosa S. Moore (Rubiaceae) in a Neotropical savanna

Abstract

In this study, we evaluate the temporal variation in extrafloral nectaries (EFNs) secretion in different ontogenic stages of Alibertia verrucosa (Rubiaceae) fruits in a Neotropical savanna. We observe greater nectar secretion rate in fruits of intermediate size compared with young or ripe fruit, indicating that they are possibly more protected by ants. In addition, the nectar secretion was higher at night, a pattern that could be associated with an increase of herbivore pressure and water stress during the daylight hours. In fact, due to the high temperature and low humidity during the day in savannas, most herbivores display strong nocturnal activity, and plants can avoid nectar secretion in this period. Our results indicate that A. verrucosa can change the ants' attraction according to EFN secretion during the ontogenic stages of the fruits, probably secreting more nectar when the biotic defense are more necessary for the protection of the fruits and the plant as a whole.