Early Consequences of Seed Dispersal for a Neotropical Tree (Virola surinamensis)

Abstract

We examined the effects of distance from a fruiting conspecific, light environment, and initial seed size on survivorship using Virola surinamensis seeds and seedlings placed in concentric rings around fruiting Virola trees. Insects and mammals killed 99.2% of seeds and seedlings between fruit drop and exhaustion of parental endosperm at 12 wk after germination. During this time, survival was not influenced by either seed size or light environment, but up to a 44—fold advantage accrued to seeds dropped 45 m from a fruiting tree as compared with those underneath Virola crowns. Seeds that germinated under and near fruiting Virola trees suffered disproportionate attack from a curculionid weevil (Conotrachelus sp. nov.). Both large initial seed size and favorable light environments (assessed by canopy photographs) enhanced seedling vigor at 18 wk of age. Among those seedlings that escaped predation beyond the exhaustion of parental seed stores, a difference of as little as 1% in the amount of canopy open overhead distinguished seedlings with three leaves (3.5% open) from those with two leaves (2.3% open). Our results demonstrate clear advantages to local seed dispersal for a tree the rainforest canopy. They further suggest that dispersal of seeds >20m by large birds, such as guans (Penelope purpurascens) and toucans (Ramphastos sulfuratus and R. swainsonii), is more favorable for seedling survival than that of the smaller trogons (Trogon massena) and motmots (Baryphthengus martii), which regurgitate seeds under or near the tree crown.