Most woody tropical plants require animals - usually a fruit-eating vertebrate like a bird - to disperse their seeds. Ecologists are convinced that animal-mediated dispersal is indeed a very important process that contributes to the maintenance, diversity, and resilience of communities such as tropical forests. However, we don't know exactly how it works to maintain diversity despite the mere agency of dispersal, especially in light of so many other biotic and abiotic forces acting upon communities. Here I present evidence advancing the notion that a very simple behavioral mechanism - diet mixing - is a fundamental diversity-maintenance mutualistic mechanism that generate and propagate patterns and community structure in tropical forests. For this I will present evidence from field studies, field experiments, and models.
Results/Conclusions
Data from field studies show that diet mixing over short time scales (i.e. a few minutes) is commonplace. Diet-mixing results in co-dispersal of plants with disparate abundance ranks in the community (i.e., rare and common). Co-dispersal of rare and common species creates antiapostatic or "rare-biased" dispersal: the common species is under-represented in the seed rain, while the rare species is over-represented. Data from field experiments examining the role of frugivores the assembly of successional forests show that rare-biased dispersal increases the diversity and the composition of successional forests relative to null expectations under random dispersal. Theoretical models confirm that rare-biased dispersal can only arise as a behavioral mechanism of foraging animals. Understanding frugivore-effects on community assembly and forest regeneration is necessary to better cope with deforestation-regeneration dynamics that are characteristic of the Anthropocene.