Floral visitors in urban gardens and natural areas: Diversity and interaction networks in a neotropical urban landscape

Abstract

Because cities concentrate 50% of the world’s population, and are experiencing a re-emergence of urban agriculture, we investigated the influences of urban agriculture and surrounding natural areas on floral visitors (bees, wasps, butterflies and flies) and plant species in San Cristóbal de Las Casas, Mexico.Throughout the frost, dry and rainy seasons of 2015, we sampled floral visitors in nine urban gardens and nine natural areas. We found 210 floral visitor species: 78% pollinators, 18% predators, and 4% florivores. Rarefaction curves showed that natural areas harbor significantly more floral visitor species (148) than home gardens (132). However, the differences in species composition between habitats and seasons highlight the need to view natural areas and home gardens as complementary habitats with which floral visitors interact in varying ways, during successive seasons, to meet different needs. Furthermore, mean species richness of floral visitors was influenced mainly by seasonality, and increased as seasons progressed from the dry, frost season to the rainy season. Nonetheless, some taxa were influenced by both season and habitat type. Floral visitor abundance was influenced by both habitat type and season, with home gardens showing higher abundance across seasons. Moreover, interaction networks for each season were more asymmetric in natural areas than in home gardens. Urban cover in the surrounding landscape influenced in a quadratic way the species number of floral visitors, but not their abundance. Thus, our results are evidence that natural areas surrounding cities and urban agriculture contribute to floral visitor communities and their networks.