Pollen, seed and gene dispersal of a tropical herb across a fragmented landscape.

Speaker: Marina Cortes (Columbia University ,New York)

Abstract

Gene flow is one of the most critical processes determining the genetic structure of plant populations, with seed dispersal primarily affecting spatial structure and pollination having important consequences for the maintenance of genetic diversity. Natural landscapes have been suffering from constant anthropogenic modifications that ultimately affect pollination and seed dispersal processes. However, little is known about how gene dispersal via pollen and seed movement varies across modified tropical landscapes. Here we aimed to investigate the contribution of pollen and seed dispersal to gene flow of the Amazonian plant Heliconia acuminata (Heliconiaceae), a common understory species pollinated and seed-dispersed by birds. The study was conducted in two continuous forest sites and three 1-ha fragments in the Biological Dynamics of Forest Fragments Project, Manaus, Brazil. Data consisted of flowering plants and established seedlings (from 1999 to 2009) genotyped at 10 microsatellite markers. We used a Bayesian approach to jointly estimate parentage and characterize pollen and seed dispersal kernels by making use of genetic data, spatial location and plant reproductive phenology. Contrary to the expectation that forest fragmentation disrupts gene flow, we found that populations in forest fragments presented higher averages of pollination and seed dispersal distances. Also, seed and pollen movement were more distance restricted in the continuous forest with higher density of flowering plants. Pollinators and seed dispersers are likely to be using fragments and moving across the landscape bringing pollen and seeds from outside the fragments. Giving continuous and elevated local spatial availability of flowers and fruits, birds may concentrate foraging within smaller areas generating a more distance-limited dispersal in continuous forest sites. In conclusion, gene flow is enhanced in forest fragments indicating that behavior of pollinators and seed dispersers change across a heterogeneous landscape due to configuration of habitats and spatial and temporal availability of food resources.