Effect of green spaces and floral composition on the community of flower visitors in a piedmont city in Argentina

In cities, human activities transform the native composition of plant communities into a mixture of native and exotic species. This new plant community shapes the composition of floral visitor communities persisting in urban environments. Recognizing the value of the diversity of urban pollinator communities can help quantify the conservation significance of cities. The aims of this work are: 1) to understand the effect of urbanization on flower visitors by comparing pollinator communities in natural and urban landscapes; 2) to quantify the influence of floral resources on floral visitors, and 3) to assess the impact of green spaces in urban environments on the composition of the flower-visitor community. We explored plant communities and floral visitors in five urban green spaces in a low urbanized city in Tucumán, Argentina, and in five natural protected areas located adjacent to the city. We found a greater diversity of flowering plants in the urban environment; mainly represented by exotic plant species and a lower diversity of the pollinator community than in the natural landscape. Pollinator diversity also showed a positive association with plant richness, while it was negatively affected by the proportion of exotic plants and the increase in flower density. Within city, distance to green spaces negatively affects the diversity of pollinators. Our results show that floral visitor communities in urban environments are less diverse than those in natural sites. Therefore, the composition of the plant community in the city, mainly exotic seems to affect communities of urban floral visitors. Our findings suggest that cities without intensive urbanization, and that still share many species with the closest natural space, may focus on urban planning that considers development alternatives that contribute to the conservation of pollinators.