Avian frugivory and seed dispersal of a large fruited tree in an Indian moist deciduous forest

•We examined role of avian frugivores on survival of a large fruited tree along a forest degradation gradient.•Seed dispersal kernel showed average longer dispersal distance in dense forest compared to degraded areas.•Canopy foliage abundance along with avian frugivore behavior determined seed distribution.•Findings indicate need for conservation of large avian frugivores for regeneration of focal species in degraded areas.

Seed dispersal systems in degraded areas can be compromised following the decline of large-bodied frugivore populations responsible for their dispersal. In this context we examined the seed dispersal ecology of a large fruited deciduous tree (Dillenia pentagyna) along a forest degradation gradient in India. We examined the effect of structural components of vegetation and frugivore foraging behavior on D. pentagyna seed dispersal. Depauperate mammalian community and declined large avian frugivores e.g. hornbills in our study site make this system a specialized one and currently dependent on only two large bodied avian frugivores. Seed dispersal followed an overall leptokurtic pattern and the seed dispersal kernels were best explained by an inverse power function. Seed dispersal kernels in dense forest indicated longer dispersal distances than moderately dense forest and degraded forest. In degraded areas, no dispersal away from the crown was recorded for D. pentagyna and it occurred at low density. Canopy foliage abundance of the surrounding vegetation of the focal trees was best explained by quantity of seed dispersal by large avian frugivores. The number of avian frugivore species those are effective disperser of D. pentagyna decreased along the degradation gradient. Avian frugivore behavior in terms of visitation and seed swallowed is a determining factor that controls quantity of seed dispersal. Our study underscores deleterious impact of forest degradation on avian disperser community which in turn would affect regeneration capacity of degraded forest.