Community context, resource dynamics, and body size differences shape multidimensional niche overlap among avian frugivores in South Asian tropics

<title>Abstract</title> <p> Understanding how niche overlap is structured across multiple dimensions is central to explaining species coexistence. Most studies examining niche overlap focus on a single axis, and our understanding of ecological conditions that promote niche overlap is limited. Here, we examined multidimensional niche overlap among avian frugivores along dietary, vertical space-use, and temporal axes in tropical evergreen forests of Anamalai and Namdapha Tiger Reserves in the Western Ghats and eastern Himalaya, respectively. These sites differed in frugivore species richness but were otherwise environmentally similar. Using &gt; 1100 hours of focal observations, we quantified pairwise frugivore niche overlap and tested how they varied with frugivore species richness, fruit abundance, tree identity, and body-size differences between species. Observed pairwise overlaps were lower than expected by chance across all niche dimensions, and were 1.6–2.2 times lower in Namdapha, the more species-rich site, indicating stronger niche differentiation in the more diverse assemblage. Overlap increased on trees with larger fruit crops and was particularly higher on <italic>Ficus</italic> . Overlap declined with increasing body-size differences between interacting frugivores. Our findings suggest that multidimensional niche overlap in tropical frugivore assemblages is structured by competition, local resource context, and species traits, thereby providing useful insights into the mechanisms promoting coexistence in diverse tropical communities. </p>