Plant diaspore traits as indicators of mutualistic interactions in woody vegetation patches developing into a grassland-forest mosaic

Abstract

We evaluated the functional relevance of diaspore traits related to disperser attraction (DAT) of woody plants as indicators of plant-disperser mutualisms in the colonization of Araucaria forest patches in southern Brazil. Diaspores of colonizer plant genera were characterized in relation to DAT (diaspore type, size and color). We discriminated the influences of phylogenetic relationships among plant genera, forest patch size and interaction records with frugivorous birds on DAT by using variation partitioning based on Redundancy Analysis (RDA). DAT variation was poorly explained by each factor separately. Nonetheless, variation explanation shared between phylogeny and interactions was considerably high, indicating that the influence of interactions with frugivorous birds on DAT tended to be phylogenetically conserved. Furthermore, the variation related to patch size was high only when shared with phylogeny and interactions. Large, red, orange or brown diaspores, mainly berries and figs were related to more developed patches, while small to medium, violet or black drupes were related to small patches. Patch colonization is likely to result from a balance between plant responses to habitat conditions and plant diaspore traits, which is expected to influence seed deposition patterns depending on habitat use and diaspore handling by dispersers. Although phylogenetic habitat filtering is commonly thought to reflect ecophysiological plant traits, our results suggest that interactions with dispersers could also explain phylogenetic habitat filtering in plants.