Rodent seed predation: effects on seed survival, recruitment, abundance, and dispersion of bird-dispersed tropical trees.
Tropical tree species vary widely in their pattern of spatial dispersion. We focus on how seed predation may modify seed deposition patterns and affect the abundance and dispersion of adult trees in a tropical forest in India. Using plots across a range of seed densities, we examined whether seed predation levels by terrestrial rodents varied across six large-seeded, bird-dispersed tree species. Since inter-specific variation in density-dependent seed mortality may have downstream effects on recruitment and adult tree stages, we determined recruitment patterns close to and away from parent trees, along with adult tree abundance and dispersion patterns. Four species (Canarium                         resiniferum, Dysoxylum                         binectariferum, Horsfieldia                         kingii, and Prunus                         ceylanica) showed high predation levels (78.5-98.7%) and increased mortality with increasing seed density, while two species, Chisocheton                         cumingianus and Polyalthia                         simiarum, showed significantly lower seed predation levels and weak density-dependent mortality. The latter two species also had the highest recruitment near parent trees, with most abundant and aggregated adults. The four species that had high seed mortality had low recruitment under parent trees, were rare, and had more spaced adult tree dispersion. Biotic dispersal may be vital for species that suffer density-dependent mortality factors under parent trees. In tropical forests where large vertebrate seed dispersers but not seed predators are hunted, differences in seed vulnerability to rodent seed predation and density-dependent mortality can affect forest structure and composition.
Post-graduate Program in Wildlife Biology and Conservation, National Centre for Biological Sciences, GKVK Campus, Bellary Road, Bangalore 560 065, India. nandinivelho@gmail.com
Nandini
N
Velho
Kavita
K
Isvaran
Aparajita
A
Datta
D000818:Animals; D017753:Ecosystem; D005247:Feeding Behavior / Q000502:physiology*; D007194:India; D011156:Population Density; D027861:Prunus / Q000502:physiology; D012377:Rodentia / Q000502:physiology*; D012639:Seeds; D014197:Trees; D014329:Tropical Climate