Deciphering seed dispersal decisions: Size, not tannin content, drives seed fate and survival in a tropical forest

摘要

Scatter‐hoarding animals can dramatically affect plant survival by depositing seeds in favorable microhabitats away from parent plants (seed dispersal) and by consuming seeds (seed predation). By understanding how scatter hoarders make seed dispersal decisions, we can infer how different plant chemical defenses or seed set strategies may influence seed survival and, ultimately, plant recruitment. We used a wild population of Central American agoutis,Dasyprocta punctata , to experimentally test how seed chemistry and size influence seed fates in a tropical premontane wet forest in Costa Rica. We hypothesized that seeds perceived by agoutis to be very valuable (large, non‐toxic seeds) would be taken far from sources and preferentially cached over less valuable (small, toxic) seeds. Using artificial seeds created from baked polymer clay and peanuts, we manipulated seed chemistry (0%, 2%, 15% tannic acid) and size (4, 14, 24?g) in fully factorial paired‐choice field experiments. We tracked the fates of individually numbered thread‐marked seeds in space and time. There was no difference in the handling, regardless of size, of non‐toxic and toxic seeds by agoutis. Large (24?g) seeds were moved farthest and preferentially hoarded by agoutis, whereas small (4?g) seeds were mostly eaten in?situ. By experimentally manipulating seed chemistry and size with a high degree of replication using artificial seeds in the field, we have determined how these plant functional traits affect agouti seed dispersal decisions, with implications for plant propagation and the evolution of seed size.