A plaza too far: High contrast in butterfly biodiversity patterns between plazas and an urban reserve in Brazil

The extent of biodiversity in the urban setting is related to the degree of land transformation and the relative quantity of green spaces in the city. Large tracts of green spaces may harbor species and serve as sources of colonists to other urban spaces, but the degree to which this occurs is not well known, particularly in cities in the tropics. Here we evaluate if a large urban green space (Dunas State Park) affects the diversity of fruit-feeding butterflies in city plazas. We sampled 18 plazas, varying in size (1000 to >3000 m2) and distance to the Park's edge (up to 3000 m). In each plaza, we measured number of trees, plant cover in it and in surrounding buffers of up to 200 m. Butterflies were captured using standardized traps. We found that butterfly communities were significantly different between Park and plazas, and that individuals plazas represented a poor sample of the total butterfly diversity. Distance to the park did not influence butterfly communities in the plazas, nor did any of the local plaza characteristics. Plazas harbored mostly generalist species and experienced more fluctuations in butterfly abundance than the Park. The Park is the only significant repository of fruit-feeding butterfly biodiversity in our system. We conclude that the urban setting is a strong filter for species settlement, a worrisome conclusion for tropical cities. We offer advice on how city planners may improve this trend.