Contrasting effects of frugivore assemblages and phylogeny on global variation in fruit length and width

Aim: The evolution of fruit size is poorly understood, though long-standing hypotheses, the dispersal syndrome hypothesis and correlated evolution hypothesis, have highlighted the influence of frugivores and phylogeny on fruit size variation.Location: Interaction networks were extracted from studies carried out in Asia, Europe, Africa, Hawaii, Australia, New Zealand and the Neotropics.Time Period: Up to 50 years between 1970 and 2022.Major Taxa Studied: Frugivores (birds and mammals) and fleshy-fruited plants.Methods: We compiled a global data set on fruit size (i.e. width and length) and plant traits (i.e. leaf area and plant height) for 349 fleshy-fruited plants, and the body mass of frugivores from 326 interaction networks. We constructed a plant phylogeny from a mega-tree containing 74,533 vascular plant species and we calculated Pagel's lambda to assess the phylogenetic signal in plant traits and fruit size. Phylogenetic generalized linear mixed model (PGLMM) was used to reveal relationships between fruit size and plant traits as well as the body mass of interacting frugivores. We used phylogenetic partial R2s regression model to tease apart the effects of body mass of frugivores, leaf area, plant height and plant phylogeny on the evolution of fruit size.Results: We show that the global variation in fruit width is better explained by frugivorous assemblages than by phylogeny and plant functional traits (leaf area and plant height). Despite the significant evolutionary correlation between fruit length and width, fruit length appears to be more phylogenetically constrained and less sensitive to frugivore-driven selection than fruit width.Main Conclusion: In light of the two original hypotheses, our study demonstrates a global phylogenetic constraint on fruit length and frugivore-driven selection on fruit width, provides a novel mechanistic explanation for the evolution of fruit size across fleshy-fruited plant species. Our findings contribute to a deeper understanding of the complex interplay between frugivory, phylogeny and plant traits in the evolution of fruit size, offering valuable insights into the broader context of published findings and hypotheses in this field.