Diversity of floral visitor communities along urban environmental gradients in Merida, Yucatan, a tropical city in Mexico

Source abstract

Abstract Urbanization transforms landscapes and alters plant and pollinator biodiversity and their interactions. In tropical cities, where species richness is high and interspecific interactions are numerous, how urban development reshapes plant–pollinator communities remains not well understood. We studied diurnal pollinator diversity along urban environmental gradients in Merida, Yucatan, a rapidly growing tropical city. Across 14 urban and peri-urban natural areas, we characterized land cover using satellite images and measured vegetation structure complexity, ground cover complexity, and plant diversity through field surveys. Overall, we recorded 302 pollinator species and morphospecies across nine taxonomic orders, observed on 202 flowering plant species, allowing for a comprehensive community composition assessment. Using generalized linear mixed models, we examined the effects of three land cover gradients (impervious surface, vegetation type, water cover) as well as local habitat features (vegetation structure complexity, ground cover complexity, plant diversity) on pollinator diversity measured with Hill numbers ( q ). Plant diversity had a strong positive impact on pollinator species richness ( q = 0) and moderate but consistently positive effects on Shannon diversity ( q = 1) and Simpson diversity ( q = 2). Sites with tall woody vegetation showed reduced pollinator diversity, while the impervious surface and water cover gradients, along with vegetation and ground cover complexity, had limited explanatory power. These findings highlight that promoting herbaceous floral diversity, rather than dense woody cover, better supports pollinator communities. Overall, our results emphasize the role of vegetation composition and vertical structure in shaping pollinator diversity in tropical cities.