Diversity of Dispersal Systems in Igapó Forests: An Analysis of Local Tree Diversity, Species Turnover, and Dispersal Systems

Abstract

The extended flooding period in igapo imposes certain constraints that species need to overcome in order to successfully survive. Among the wide array of strategies that species need to adjust when living in flooded systems, seed dispersal is a major factor to guarantee successful colonization. Seed dispersal is one of the most important mechanisms shaping the structure and composition of tree communities, and the seed dispersal strategies are expected to change from flooded and non-flooded systems. However, our knowledge on the diversity in seed dispersal strategies and how it varies across landscapes is still limited. Here, we examined patterns of floristic composition and seed dispersal strategies for igapo forests in Colombia and compared it to forests in varzea and terra firme. We hypothesized that despite the low species diversity, flooding forests will exhibit higher diversity in dispersal systems compared to terra firme forests, since seed dispersal by water and by fish is also possible in these forests along with zoochory. As expected, we found that flooded forests exhibit low species diversity but high levels of dispersal diversity, while terra firme forests exhibited the highest levels of species diversity and a strong dominance of endozoochory. These results suggest that the mosaic of landscape units in the lowland tropical region exhibit important differences in species composition and in dispersal system diversity, being endozoochory the best strategy in mature forests, such as terra firme. Diversity of dispersal systems is still poorly known for species rich-ecosystems such as tropical forests. We show that striking differences in species dispersal strategies can be found across flooded and non-flooded forests in the Amazon Basin. Further insights into the mechanisms maintaining diversity in these systems are needed to integrate information on seed dispersal strategies.