Abstract
Defaunation of large-bodied animals threatens essential ecosystem functions, such as seed dispersal. However, the consequences of this human-induced downsizing of animal communities for plant-frugivore trait matching-the alignment between frugivory-related plant traits (e.g., fruit size) and frugivore traits (e.g., body mass)-remain unquantified at macroecological scales. Here, we examine how human disturbance and environmental conditions influence trait matching in tropical plant-frugivore networks. We compiled fruit size data for 1927 plant species from primary sources, along with body mass and dietary information for 1120 frugivorous animal species (birds, mammals and reptiles), and integrated these with 12,708 plant-frugivore interactions recorded across 102 networks. Using fourth-corner analyses and structural equation models (SEMs), we quantified how human disturbance and environmental conditions directly and indirectly affected trait matching strength (fruit-size-to-body-mass correlation) across networks. SEMs revealed that human disturbance weakened trait matching by reducing the range of frugivore body masses within networks, whereas wet and productive environments promoted a higher proportion of fruit in frugivore diets, leading to stronger trait matching. Our results demonstrate that human disturbance weakens plant-frugivore trait matching through the downsizing of animal communities, thereby providing a quantitative assessment of the decoupling of coevolved relationships between fruiting plants and their animal seed dispersers.