Plant dispersal systems in Neotropical forests: availability of dispersal agents or availability of resources for constructing zoochorous fruits?

Abstract

AbstractAimWe used abiotic and biotic factors as predictors of the proportions of different dispersal systems in Neotropical forests, to test whether the geographical patterns in dispersal systems are mostly related to the availability of resources for constructing zoochorous fruits or to the availability of dispersal agents.Location101 one‐hectare vegetation plots established in eight Holdridge life‐zones in Colombian Neotropical forests.MethodsWe assigned dispersal systems to 2262 species and 1210 morphospecies, using the relative frequency and relative abundance of endozoochory, synzoochory, anemochory and hydrochory per plot as response variables. We assessed the relationships between dispersal systems and ecological factors (elevation, climatic and edaphic variables, raw and weighted richness of potential frugivores, biomass of primates, wind speed, flooding regime and fragmentation), controlling for spatial autocorrelation and phylogenetic constraints.ResultsEndozoochory was highly represented in all plots. High levels of rainfall and low precipitation seasonality were associated with high proportions of zoochory (endozoochory and synzoochory) and low proportions of anemochory. The biomass of primates was positively associated with the relative abundance of endozoochory, and the weighted richness of frugivores was positively associated with the relative frequency of endozoochory. Contrary to the resource‐availability hypothesis, synzoochory (the most expensive dispersal system in terms of plant investment in fruit mass) was most common in soils with low carbon densities. Finally, the proportions of anemochory and hydrochory were highest in windy areas and flooded forests, respectively.Main conclusionsAlthough there is a relationship between rainfall, zoochory and anemochory, the absence of any positive relationships between zoochory, temperature, soil total nitrogen density and soil carbon density shows that the proportions of dispersal systems in Colombian Neotropical forests are mostly related to the availability of dispersal agents.