Post-Dispersal Seed Predation Rates in a Puerto Rican Pasture

Abstract

The dispersal and survival of seeds are two of the main factors limiting forest regeneration in tropical pastures of anthropogenic origin. Here we report on the quantity, diversity, and predation rates of seeds dispersed by birds in a pasture in northern Puerto Rico. From May through August of 2009, we sampled the bird-generated seed rain under isolated trees and shrubs in the pasture using seed traps. The pasture was adjacent to a fragment of secondary forest that served as the source of seeds. The seed traps collected 3,844 seeds (including pieces) belonging to 28 plant species, with five species accounting for 78.6 percent of the sample. Predation of seeds —calculated as the ratio of seed fragments to intact seeds- was detected in eleven plant species, with some species suffering significantly higher predation rates than others. For example, seeds of Cissampelos pereira and Casearia Sylvestris experienced low predation (<0.3), while the majority of seeds from Cordia polycephala and Erythroxylon brevipes where predated (>0.6). Predation rates where in an inverse relationship with the density of seed deposition and with seed size across species. The physical evidence on the seed traps (i.e., seed coat fragments, fecal samples) points to rodents as the main agents of seed predation. We conclude that post-dispersal seed predation by rodents can serve as an important ecological filter that could shape the early community dynamics of forest recovery in abandoned Puerto Rican pastures.