Seed dispersal by macaws shapes the landscape of an Amazonian ecosystem

Abstract

Seed dispersal is one of the most studied plant–animal mutualisms. It has been proposed that the dispersal of many large-seeded plants from Neotropical forests was primarily conducted by extinct megafauna, and currently by livestock. Parrots can transport large fruits using their beaks, but have been overlooked as seed dispersers. We demonstrate that three macaws (Ara ararauna, A. glaucogularis and A. severus) are the main dispersers of the large-seeded motacú palm Attalea princeps, which is the biomass-dominant tree in the Bolivian Amazonian savannas. Macaws dispersed fruits at high rates (75–100% of fruits) to distant (up to 1200 m) perching trees, where they consumed the pulp and discarded entire seeds, contributing to forest regeneration and connectivity between distant forests islands. The spatial distribution of immature palms was positively associated to the proximity to macaws’ perching trees and negatively to the proximity to cattle paths. The disperser role of livestock, presumably a substitute for extinct megafauna, had little effect due to soil compaction, trampling and herbivory. Our results underscore the importance of macaws as legitimate, primary dispersers of large-seeded plants at long distances and, specifically, their key role in shaping the landscape structure and functioning of this Amazonian biome.

Overlooked Parrot Seed Dispersal in Australia and South America: Insights on the Evolution of Dispersal Syndromes and Seed Size in Araucaria Trees

“…Moreover, cockatoos also dropped intact and partially-eaten seeds when extracting them from the cones, making them available under parent trees to other bird species as well as cockatoos (this study) and small mammals (Smith et al, 2005(Smith et al, , 2007 that can act as secondary seed dispersers. Overall, our results add to recent findings showing that parrots are not merely seed predators but can be involved in plant-parrot mutualismantagonism continuums (Montesinos-Navarro et al, 2017) where they can play a key role as seed dispersers (Boehning-Gaese et al, 1999;Blanco et al, 2015Blanco et al, , 2016Blanco et al, , 2018Tella et al, 2015Tella et al, , 2016aBaños-Villalba et al, 2017).…”

Associated evolution of fruit size, fruit colour and spines in Neotropical palms

“…When we performed the same analyses without this clade, the estimated difference in evolutionary optima of fruit size between lineages with and without spines was much more pronounced. Attalea fruits are dull‐coloured and fibrous, and seeds have a thick and hard protective coat (Silvius, 2005) related to dispersal by scatter‐hoarding rodents and parrots rather than large mammals (Baños‐Villalba et al, 2017; Dracxler & Forget, 2017). Thus, trait evolution in Attalea may have been strongly influenced by interactions with rodents and parrots and less influenced by interactions with other groups such as large‐bodied frugivorous, which would explain no association between spinescence and large fruits.…”

“…One particular genus of spineless palms with very large seeds, Attalea , significantly raises the mean size of fruits in palms without spines. Attalea fruits are highly fibrous and known to be dispersed mainly by scatter‐hoarding rodents and parrots (Baños‐Villalba et al, 2017; Dracxler & Forget, 2017), therefore being often associated with a third particular seed‐dispersal syndrome. To understand how this genus affects the obtained results, we performed a sensitivity analysis by removing Attalea from the phylogeny and rerunning the analyses (see Supplementary Material).…”

Synzoochory: the ecological and evolutionary relevance of a dual interaction

“…In addition, synzoochory has been related to dyszoochory ( dys ‐ meaning ‘ill’ or ‘bad’), the dispersal of seeds by granivores that accidentally lose them during transport, and stomatochory ( stomato ‐ meaning ‘mouth’), the transport of seeds in the bill or mouth (van der Pijl, ; Iluz, ). These two dispersal modes have been observed in ants (Wolff & Debussche, ; Rico‐Gray & Oliveira, ), granivorous birds like pigeons and parrots (Böhning‐Gaese, Gaese & Rabemanantsoa, ; Blanco et al ., ; Tella et al ., ; Baños‐Villalba et al ., ) and some granivorous mammals, such as bats and primates, which drop seeds while feeding (Kevan & Gaskell, ; Barnett et al ., ). Although they share some common characteristics, synzoochory is unique because it is a dispersal mode provided by animals that intentionally move and cache seeds, albeit unintentionally losing some of them.…”