Seedling recruitment distribution of Dipteryx oleifera correlates with bat roosting palms and seed sources

Background/Question/Methods We investigated the relative contribution of seed dispersal on seedling recruitment in tropical rainforests. The research focuses on understanding the effect of bat seed dispersal and terrestrial mammalian seed dispersal on seedling spatial distribution. We investigated whether seedling recruitment of Dipteryx oleifera occurs away from conspecific adult trees and correlates with palm species distribution as a result of bat and terrestrial mammal seed dispersal. Mapping of seeds and seedlings from 2002 to 2007 within a 6.5 ha permanent plot in southestern Nicaragua from 2002 to 2007. The sample size is large for studies of seedling fate in tropical rain forest. The fate of about 5,000 seeds and 10,000 seedlings was followed during the research period. Terrestrial and flying mammals trapping assessments were conducted during the research. Results/Conclusions Our field results showed that bats select palm species located away from adult D. oleifera to roost; and seeds are deposited below these roosting sites. We used artificial seed piles to investigate density and distance effects on seed fate in D. oleifera. Our findings suggest a statistically significant effect on seed predation with respect to adult trees but only in artificial seed piles with high densities; the effect on germination rates was not quite significant. Seedling recruitment as a function of the distance to the natural seed piles suggests that secondary seed dispersal by terrestrial mammals could enhance seedling survival. We mapped the location of all potential roosting palm species that were most frequently used as bat feeding roosts (Astrocaryum alatum, Welfia regia and Cryosophila warscewiczii) and correlated their location with the distribution of seedling survival within the permanent plot. The results of a cross-correlation (Ripley's functions and Getis's Maps) are statistically significant and show a positive correlations between seedling survival and the distribution of A. alatum away from large adult trees of D. oleifera. The observed seedling recruitment is consistent with the pattern expected by the Janzen-Connell hypothesis and is enhanced by bat and terrestrial mammal seed dispersal.