Research paperDeforestation drives functional diversity and fruit quality changes in a tropical tree assemblage

- The pervasive effects of forest loss on functional richness and functional evenness.
- Forest cover was correlated with the contents of protein and lipids in fruits.
- Forest cover affect the capacity of the forests for provisioning fruit resources.
- The maintenance of forested landscapes will guarantee the quality of resources.

Functional traits associated with plant-animal interactions are essential for forest functionality, given that a higher diversity of fruit traits is likely to maintain a more diverse assemblage of frugivores and consequently promote the seed dispersal function. Yet, shade-intolerant species tend to persist in human-modified landscapes in the long term, which in turn is expect to reduce fruit trait diversity. Here we evaluate how forest cover at the landscape-scale influences the functional diversity of fruit traits, considering the zoochoric tree community and two regeneration strategies separately (shade-tolerant and shade-intolerant species). We sampled 20 forest remnants in the Brazilian Atlantic Forest, located in landscapes with forest cover ranging from 2 to 93%. In each remnant, we established five plots of 25 × 4 m and marked all trees ≥5 cm diameter at breast height (DBH). We compared morphological and chemical attributes of fleshy fruits directly related to the attraction of frugivores, and evaluated the similarity of the zoochoric tree assemblage composition along the forest cover gradient, taking into account the two regeneration strategies. We calculated four functional indices (richness, evenness, divergence, and community-level weighted means of trait values) and used either linear models or spatial mixed linear models to evaluate the effects of forest cover on functional diversity. Our main results revealed that forest cover loss has negatively affected fruit functional diversity for the overall zoochoric community. Forest cover loss also affected functional richness and functional eveness for total and shade-tolerant species, and was positively correlated with the content of protein and lipid in fruits of shade-intolerant species. Additionally, sites exhibiting a lower amount of forest cover showed greater compositional similarity among shade-intolerant species but reduced similarity among shade-tolerant species. We conclude that patterns of species reassembly triggered by landscape-scale deforestation decreases the capacity of the remaining forest for provisioning food resources for frugivore assemblages. The maintenance of shade-tolerant species is pivotal in deforested areas, since their fruit quality is not offset by shade-intolerant species. This is particularly important, mainly because shade-intolerant species are those still persisting in disturbed forests; however, their presence will not provide the same food quality supplied by those species lost.