Species identity influences secondary removal of seeds of Neotropical pioneer tree species

Abstract

Primary dispersal agents move seeds from the maternal plant to the soil surface where they are often moved again by secondary dispersal agents. However, the extent to which different species in the same location experience secondary dispersal is often unknown despite the importance of this mechanism for determining recruitment opportunities and consequently community structure. Here we examine the secondary removal rates of 12 Neotropical pioneer species placed either on or 2 cm below the soil surface at five locations in lowland tropical forest on Barro Colorado Island, Panama. We investigated whether species identity, primary dispersal mode (animal or wind), dormancy type, seed mass, and capacity to persist in the seed bank were correlated with removal rate. We also investigated whether season (dry or wet) influences removal from the soil surface. In general, both superficial and buried seeds were highly mobile. We found an effect of primary dispersal mode and dormancy type on removal rates both on (12 species) and beneath the soil surface (six species). However, this pattern was largely driven by species identity. Season had no influence on seed removal rates from the soil surface. The dispersal of small-seeded pioneer species is highly species dependent, indicating that generalizations made using broader categories, such as primary dispersal mode or dormancy type, do not accurately describe the observed patterns hindering our understanding of community assembly within even a single functional group of plants.