SG: Preference by birds for rare species of fruits and its role in maintaining diversity in plant communities

This project aims to better understand the process of fruit-selection in birds, and in turn, how fruit-selection affects the diversity and composition of plant communities. The vast majority of woody plant species - especially in the most diverse forests - depend on fruit-eating birds to disperse their seeds, but information on the factors governing fruit choice and seed dispersal at a community level is lacking. This project will address this shortcoming through observations and experiments across the Americas. The overarching goal of the research is to test the hypothesis that fruit-eating birds of different sizes and classes increase dispersal rates for plant species that are proportionally rare in the environment. Achieving a better understanding of seed dispersal by birds is critically important to advancing ecology, since plant populations depend on seed dispersal to regenerate, coexist, colonize new areas, shift geographic ranges, and cope with climatic and other environmental changes. Beyond advancing basic science, the knowledge generated by this research will have positive implications for forestry, natural resource management, restoration ecology, and conservation. The activities will result in the training of graduate and undergraduate students, and broaden the education and participation of minorities in the sciences while fostering international collaboration and exchanges between researchers and students from the USA, Peru, and Argentina.

Existing theory and empirical work suggest that equalizing and stabilizing mechanisms involving negative density-dependence (NDD) play key roles in the maintenance of species diversity by conferring advantages to species that are relatively rare in communities. This project will study a little known class of NDD process that, if proven to be of widespread occurrence, can be important for diversity maintenance and the structuring of plant-frugivore mutualistic communities: antiapostatic frugivory and seed dispersal. Antiapostatic frugivory would result in disproportionately high seed dispersal when species' fruits are relatively rare in communities of plants that share frugivorous seed dispersal agents such as birds. To examine the generality of antiapostatic frugivory, this research will conduct field studies in four continental localities representing four distinct plant-frugivore communities. These communities provide fully independent biotic and abiotic elements in which to test occurrence and magnitude of antiapostatic frugivory as they are located across a latitudinal gradient: from eastern North America (Pennsylvania) to southern South America (Patagonia), including two Peruvian forest sites (lowland Amazonian rainforest at Madre de Dios, and an Andean cloud forest at Abra Patricia). In addition to observations of fruit consumption and plant demography, controlled fruit-selection experiments using natural and artificial fruit displays will be conducted.