The effect of habitat fragmentation on frugivores and seed dispersers in fossil forests of the Western Ghats, India

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E S Nimisha and V B Sreekumar, Forest Botany, Kerala Forest Research Institute, Thrissur, India

Background/Question/Methods
Forest fragmentation is a major threat to Tropical Montane Cloud Forests in the Anthropocene. It is a complex ecosystem that represents some of the most threatened ecosystems globally. Seed dispersal is an essential process as it influences ecosystem dynamics and biodiversity. Yet, the impact of frugivores and dispersers on the regeneration of a highly fragmented ecosystem with low regeneration capacity is poorly investigated. Understanding the consequence of habitat fragmentation to seed dispersal network will support policymaking and implementing conservation strategies for retaining a well-balanced ecosystem. Here, we examined how fragment size and disturbance of a Tropical Mountain Cloud Forest affects the frugivore community assemblage and seed dispersal, for two consecutive years. 92 fleshy fruiting tree species from 20 forest patches at different altitudes (1700m- 2300m) were scanned for the frugivores and seed dispersers. Observations were carried out for 15-minute intervals, during which fruit handling, feeding and dispersal by the frugivores were noted. We calculated the species richness of fruiting trees, frugivores and dispersers. Frugivore functional trait diversity (FD; functional richness, evenness, dispersion) for each forest patch of different size and varying degrees of fragmentation were also calculated. Defecated fruits and seed from different points were collected for the identification of frugivore, seed dispersers and germination analysis.
Results/Conclusions
Increasing forest-patch size had a positive effect, and increasing patch isolation had a negative effect on the frugivore and seed disperser diversity. The germination rate of dispersed seeds were higher at high fragment size compared to isolated and open fragments. Larger fragments with high vegetation diversity support more avian frugivores and provide microsites for seedling establishment. We also identified that large birds and rodents were the major channels linking these isolated forest patches. Forest fragmentation can thus adversely affect Tropical Montane Cloud Forest, where wind and frost are very frequent events. This is worsened by the very low regeneration potential of trees and, the absence of different dispersal mechanisms. Thus, this ecosystem relies on birds and animals for dispersal. Given the inevitable role of seed dispersal networks at forest patches, there is an urgent need to focus more on conservation actions towards seed-dispersal networks, for the restoration of fragmented habitats under threat.