Little things in the cities: green spaces management shapes species centrality in ant-diaspore network in a vast Tropical City

Species interactions play a critical role in ecosystem functioning, where mutualistic relationships shape ecological dynamics. We assessed structural changes in the myrmecochoric network due to urbanization by exploring ant-diaspore interactions across urban green spaces with varying management practices and vegetation heterogeneity. Thus, we tested whether species importance and dispersal effectiveness is jeopardized by urbanization impact. We hypothesized that urbanization intensification, characterized here as habitat simplification through frequent and intense local management, would disproportionately affect large-bodied ants (> 10 mm), thereby reducing seed dispersal efficiency. We studied 14 green spaces in a Brazilian metropolis, recording ant behavior towards artificial diaspores to assess seed dispersal effectiveness. We calculated ant centrality for each green space and type of behavior upon the diaspores. We also computed diaspore removal efficiency (DRE) across the management and urbanization gradient. We found the core of central ant species changed between preserved and managed green spaces and according to the behavior towards diaspores. The management intensity also differed in terms of dispersal efficiency. We classified ants into six functional groups, where epigaeic generalist predators stood out, removing diaspores for longer distances, especially in the most preserved areas. The change in the composition of central species among urban green spaces underlines the importance of urban heterogeneity acting as a filter that selects species with different niche specificities and efficiency in their functional roles. Altogether, our results suggest that the functional structure of ant assemblages significantly influences the spatial dynamics of diaspore removal in the city, underscoring how the quality of biotic interactions, particularly those performed by epigaeic generalist predators, contributes to long-distance diaspore dispersal, even within a highly modified urban matrix. With 70% of humanity projected to inhabit urban areas by 2050, our results underscore the urgency of designing green infrastructures that support ecological functionality. This need is particularly important in tropical cities, which simultaneously harbor the highest biodiversity and threatened ecosystems on Earth.