Focal plant and neighbourhood fruit crop size effects on fruit removal by frugivores in a semi-arid landscape invaded by Lantana camara L.
Mutualistic associations between frugivorous vertebrates and fleshy-fruited plants result in seed dispersal, a vital ecological process affecting plant populations and communities. Invasive fleshy-fruited plants can easily integrate into existing mutualistic networks if generalist frugivorous species start consuming invasive fruit. Additionally, the presence of a copiously fruiting invasive plant in the neighbourhood of fruiting native plants could affect the fruit removal from such plants by either reducing (competitive interaction), increasing (facilitative interaction) or not affecting (no interaction) visits by frugivorous vertebrates. In this study, we explore the effects of the presence of a fruiting invasive shrub Lantana camara L. in the neighbourhood of fruiting native species Erythroxylum monogynum Roxb. and Flueggea leucopyrus Willd. on the visit and fruit removal rate by avian frugivores in a semi-arid bird preserve in southern India. We conducted plant watches within fruiting patches of 30 m radius and observed the identity, numbers and fruit-handling behaviour by avian frugivores on focal native plants. We found that, on average, for the same fruit crop size, E. monogynum received more visits and more fruit removal than F. leucopyrus irrespective of the presence of fruiting neighbours. Focal tree fruit crop size was a better predictor of frugivore behaviour than the fruit crop size of neighbouring plants (both native and invasive) and was positively associated with frugivore visit rate and fruit removal from focal plants. We infer that there is little evidence for facilitation or competition by invasive neighbours for the dispersal services of vertebrate mutualists at the spatial and temporal scale examined in this study. Longer-term, larger-scale data are required to assess the changing impacts of invasive plants on native plant-frugivore interactions.