Rodent seed predation: effects on seed survival, recruitment, abundance, and dispersion of bird-dispersed tropical trees

Abstract

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.

Plant Species Composition and Their Conspecific Association in Natural Tropical Rainforest, South Papua

“…That is probably because of that the presence of animals such as birds, bats, and rodents feeding the fruits. Other study showed that the presence of rodents in tropical forest will contribute in recruitments of plants and its distribution (Velho, Isvaran, & Datta, 2012). Then, the animals play a crucial role in seed dispersals of those species (Chapman & Chapman, 1995).…”

Phenology, Seed Dispersal and Regeneration Patterns of Horsfieldia Kingii, a Rare Wild Nutmeg

“…However, seeds that fall beneath nest trees are also vulnerable to predation by rodents. Recent studies have established the high levels of predation by rodents on Horsfieldia seeds [50,51].…”

“…Further studies of inter-annual variation in seed production are needed to determine whether the species is a mast fruiting species [21]. Seed predation is an important factor affecting seed survival [50,51], but further studies are required to understand the role of abiotic factors in determining the recruitment and adult tree distribution of this species.…”

“…Although we did not measure pollination rates, the poor fruit set may be partly due to pollination failure [18]. Estimates of tree density of Horsfieldia in the study area range from 0.54 trees/ha [50] to 1.14 trees/ha [49], and it has a scattered distribution, with mean nearest neighbor distance between adult trees estimated to be 131 m [50]. The distances between male and female trees are likely to be even greater, potentially affecting pollination rates [34].…”

Tree Association with Pometia and its Structure in Logging Concession of South Papua Forest

“…Biotic factors can also influence dynamics of the stand where flora and fauna have functioned as either facilitation or competition (Velho et al 2012). In the tropical rainforest, many trees grow in the same area resulting in competition to get a place.…”