Conserving the Diversity of Ecological Interactions: The Role of Two Threatened Macaw Species as Legitimate Dispersers of “Megafaunal” Fruits

Abstract

The extinction of ecological functions is increasingly considered a major component of biodiversity loss, given its pervasive effects on ecosystems, and it may precede the disappearance of the species engaged. Dispersal of many large-fruited (>4 cm diameter) plants is thought to have been handicapped after the extinction of megafauna in the Late Pleistocene and the recent defaunation of large mammals. We recorded the seed dispersal behavior of two macaws (Anodorhynchus hyacinthinus and Anodorhynchus leari) in three Neotropical biomes, totaling >1700 dispersal events from 18 plant species, 98% corresponding to six large-fruited palm species. Dispersal rates varied among palm species (5%−100%). Fruits were moved to perches at varying distances (means: 17−450 m, maximum 1620 m). Macaws also moved nuts after regurgitation by livestock, in an unusual case of tertiary dispersal, to distant perches. A high proportion (11%−75%) of dispersed nuts was found undamaged under perches, and palm recruitment was confirmed under 6%−73% of the perches. Our results showed that these macaws were legitimate, long-distance dispersers, and challenge the prevailing view that dispersal of large-fruited plants was compromised after megafauna extinction. The large range contraction of these threatened macaws, however, meant that these mutualistic interactions are functionally extinct over large areas at a continental scale.

Keywords

• caatinga
• cerrado
• ecosystem services
• hyacinth macaw
• lear’s macaw
• megafauna
• palms
• pantanal
• plant-animal mutualisms
• seed dispersal