Estrutura das redes frugívoros-plantas e atributos funcionais de espécies vegetais consumidas por vertebrados em áreas urbanas

Abstract

Frugivory refers to the consumption of fruit by animals that can serve as seed dispersers, transporting diaspores away from the parent plant, thus characterizing a mutualistic interaction. Landscape changes caused by urbanization affect biodiversity, leading some species to disappear while others may become more common, with consequences for the ecological interactions they participate in. The network approach is often applied to understand the structure and functioning of community-scale interactions, as well as to understand the role played by the different species that make them up. In this study I assessed how studies on frugivory in urban areas are distributed globally, how frugivore-plant interaction networks are structured, and whether the functional diversity of plants and birds affects the structure of these networks. I also assessed whether the characteristics of the fruit consumed by birds differ among cities in tropical, subtropical and temperate environments. To address these questions, I conducted a literature review of studies on frugivory in urbanized environments. I found 88 studies, but only 12 of them addressed the scale of communities, and most of these were conducted in Brazil. The arboreal habit was the most frequent (56.6%) in the species consumed by frugivores, and predominated in the tropical and subtropical zones, while the temperate zone showed a higher frequency of herbs (13.1%). Treelets were also more common in the tropics. In terms of origin, native species (58.4%) were less frequent in the temperate zone, while exotic species (33.8%) were more common. Drupes (33.1%) and berries (27.1%) were more frequent in the tropics and subtropics, while achenes (14.1%) predominated in the temperate zone. Fruit length and width also varied across zones, with smaller fruits being more common in subtropical and temperate regions, whereas larger fruits predominated in the tropical zone. However, their color did not differ significantly between zones. Among the ten interaction networks analyzed, only one had a modular structure, and six networks had a nested structure. The Functional Richness of plants and frugivores was in general low, while Functional Uniformity and Functional Divergence showed higher values, mainly for plants. Among the most central plant species in the networks (highest values of betweenness centrality and closeness centrality) are the plants Ligustrum sinense, Castila tunu, Inga laurina, Syzygium cumini and the birds Ramphocelus carbo and Thraupis sayaca. Although most studies focus on tropical zones, there are still significant gaps in urban areas of ecosystems such as the Amazon and the Caatinga. Regions such as the Afro-tropics and Indo-Malaysia also lack research on frugivory in urban environments. Variations in plant attributes between climatic zones reflect adaptations to local environmental conditions and shape functional diversity. The nested structure observed in most networks indicates ecological simplification, favoring generalist species in urban environments. Although exotic species are important in some urban environments because they are the main resource and attract frugivores, an excess of exotic plants can interfere with the dispersal of native species. Functional diversity did not significantly influence network structure, which may be related to differences in the degree of urbanizations and seasonality of the evaluated cities, as well as variation in sampling effort among studies. Results of this work reinforces the importance of expanding studies on frugivory to undersampled areas and indicate the homogenization of ecological interactions in urban contexts.