Green area size rather than urbanization ecological index modulates the specialization of flower-visitor networks of Leguminosae trees in a tropical metropolis in Brazil

Abstract

Urbanization and the size of green areas can alter numerous environmental and biological factors, including the ecological interactions between plants and animals in urban areas. Urban green areas contribute positively to the maintenance of biodiversity, provide resources for pollinators, and bring numerous benefits to the population in terms of ecosystem services. This study aimed to evaluate the effect of urbanization and the size of green areas on the interaction networks between Leguminosae trees pollinated by bees and their floral visitors. The study was carried out in eight urban green spaces in Recife, a Brazilian metropolis, in northeastern Brazil, with 10 species of native and exotic Leguminosae trees. In general, (1) Trigona spinipes and Xylocopa frontalis showed greater interaction with the Leguminosae; (2) increases in urbanization reduces the number of flower/inflorescence, the number of total visits and the generality, despite increasing interaction evenness between the Leguminosae pollinated by bees and their floral visitors; (3) increases in the size of urban green areas favours the interaction evenness of networks, the selectivity of occasional pollinators and harbour more specialized plant species; (4) simultaneously, reductions in urbanization and increases in urban green area size are associated with increased specialization of Leguminosae species. Our study highlights that urban green areas in tropical cities have enormous potential to sustain plant communities and floral visitors/pollinators, especially native bees. To manage urban biodiversity in the long term, cooperation between policymakers, conservation organizations, scientists and the population is essential to understand how species interact in complex and diverse urban landscapes and their importance for human well-being.

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