Specific interactions between bats and streblid flies in an urban Atlantic forest fragment.

Specificity patterns of host parasite interactions is a key component in disease ecology, varying considerably among groups. Hematophagous flies of families Streblidae and Nycteribiidae are obligate ectoparasites of bats exhibiting high host specificity from millions of years of coevolution. Despite Brazilian megadiversity of bats and parasitic flies, knowledge about these interactions in fragmented urban environments remains limited, crucial for understanding urbanization effects. This study characterized diversity and network structure between bats and ectoparasitic flies (Diptera: Streblidae) in an urban Atlantic Forest fragment in São Paulo city. Over twelve months (from October 2015 to September 2016), 68 phyllostomid bats from three species were captured: Artibeus lituratus (n=28), A. fimbriatus (n=14), and Sturnira lilium (n=26). All individuals were parasitized (prevalence=100%), harbouring 212 flies from five Streblidae species: Paratrichobius longicrus (n=97), Megistopoda aranea (n=45), M. proxima (n=35), Aspidoptera falcata (n=34), and A. phyllostomatis (n=1). Prevalence and abundance of fly species differed significantly among hosts, with P. longicrus mainly associated with A. lituratus, M. aranea with A. fimbriatus, and M. proxima and A. falcata with S. lilium. The interaction network showed moderate specialization (H₂'=0.742) and modularity (Q=0.544), with values lower than preserved Neotropical forests. Fly species such as P. longicrus may act as bridge vector among bat species. Our results contribute to understanding host-parasite interactions in Neotropical urban environments and emphasize ecological importance in managing urban green areas harboring functional parasite communities.