Forest cover and fruit crop size differentially influence frugivory of select rainforest tree species in Western Ghats, India (Part II)

Forest fragmentation and habitat loss are major disruptors of plant–frugivore interactions, affecting seed dispersal and altering recruitment patterns of tree species dependent on vertebrate dispersers. In a heterogeneous production landscape (primarily tea and coffee plantations) in the southern Western Ghats, India, we examined effects of surrounding forest cover and fruit crop size on frugivory of four rainforest bird-dispersed tree species (N = 131 trees, ≥ 30 trees per species, observed for 623 h). Frugivore composition differed among the four tree species with the large-seeded Canarium strictum and Myristica dactyloides exclusively dependent on large-bodied avian frugivores, whereas, medium-seeded Persea macrantha and Heynea trijuga were predominantlyvisited by small-bodied and large-bodied avian frugivores, respectively. Using the seed-dispersal-effectiveness framework, we identified effective frugivores and examined their response to forest cover and fruit crop size. Results were idiosyncratic and governed by plant and frugivore traits. Visitations to medium-seeded Persea had a positive relationship with forest cover but the relationship was negative for the large-seeded Myristica. In addition, two of the three effective frugivores for Persea responded to the interactive effect of forest cover and fruit crop size. Frugivore visitations to Hyenea were not related to forest cover or fruit crop and there were too few visitations to Canarium to discern any trends. These results highlight the context-specific response of plant-frugivore interactions to forest cover and fruit crop size influenced by the plant and frugivore traits.

Methods
The gape widths of three individuals per species for 31 bird species found in the Indian subcontinent were measured following DeBeers et al. (2011). De Beer, S. J., Lockwood, G. M., Raijmakers, J. H. F. A., Scott, W. A., Oschadleus, H. D., & Underhill, L. G. (2001) SAFRING: Bird ringing manual.