Diversity and Spatial Distribution of Predacious Dolichopodidae (Insecta: Diptera) on Organic Vegetable Fields and Adjacent Habitats in Brazil

Abstract

Adults of the fly family Dolichopodidae (Diptera) are general predators on small soft-bodied invertebrates, and often are abundant in agroecosystems. However, information about their diversity and spatial distribution in agricultural landscapes are scarce. Using structured sampling, we identified the species of Dolichopodidae associated with organic vegetable crops, fallow, agroforestry, and native vegetation in the Federal District of Brazil, and evaluate their richness and abundance. We collected 70 species Dolichopodidae distributed in 17 genera and 9 subfamilies. Of these, some 80% of the specimens belong to the following 5 taxa: Chrysotus spectabilis (Loew), Thrypticus violaceous Van Duzee, Condylostylus depressus (Aldrich), Condylostylus “caudatus group” females, and Condylostylus erectus Becker (all Diptera: Dolichopodidae). Habitats with vegetable crops harbored a higher abundance and number of species (diversity α), with a gradual reduction towards more forested environments of native vegetation. This is an inverse gradient with the general patterns of community studies with other taxa. We also verified the importance of less disturbed habitats over time in the agricultural landscape, such as agroforestry and native vegetation, as complementary habitats for the maintenance and conservation of dolichopodid species in particular, a scenario to be tested for other insect groups. Resumo Os adultos da familia das moscas Dolichopodidae (Diptera) sao predadores generalistas de pequenos invertebrados de corpo mole, sendo geralmente abundantes em agroecossistemas. No entanto, informacoes sobre sua diversidade e distribuicao espacial em paisagens agricolas sao escassas. A partir de amostragens locais, identificamos as especies de Dolichopodidae associadas a hortalicas orgânicas, pousio, agrossilvicultura e vegetacao nativa no Distrito Federal, Brasil, e avaliamos sua riqueza e abundância. Foram coletadas 70 especies de Dolichopodidae distribuidas em 17 generos e 9 subfamilias. Destes, cerca de 80% dos especimes pertencem aos seguintes 5 taxons: Chrysotus spectabilis (Loew), Thrypticus violaceous Van Duzee, Condylostylus depressus (Aldrich), Condylostylus “grupo caudatus” e Condylostylus erectus Becker (todos dipteros: Dolichopodidae). Habitats com hortalicas abrigavam a maior abundância e numero de especies (diversidade α), com uma reducao gradual em direcao a ambientes mais florestados de vegetacao nativa. Este e um gradiente inverso com os padroes gerais de estudos comunitarios com outros taxons. Tambem verificamos a importância de habitats menos perturbados ao longo do tempo na paisagem agricola, como agrofloresta e vegetacao nativa, como habitats complementares para a manutencao e conservacao de especies de diclopodideos em particular. Este e um cenario a ser testado para outros grupos de insetos. Key Words: biological control; Neotropical region; Cerrado; habitat management; species richness; organic agro-ecosystems View this article in BioOne