Cytotaxonomy and ecology of four species in the Simulium perflavum Group (Diptera: Simuliidae) and associated black flies in Central Amazonia, Brasil

Abstract

I evaluated the cytotaxonomic and ecological relationships among four species in the Simulium perflavum Group (S. maroniense, S. perflavum, S. rorotaense and S. "X") in Brasilian Amazonia, and their ecological relationships with other black fly species in the Central Amazon. In addition, black fly species richness in the Central Amazon was evaluated in relation to environmental parameters. Five species were added to the seven known black flies of this region; two of them were described as new (S. "X" and S. "C"). Novel morphological characters of species in the S. perflavum group are provide and the species S. maroniense is revalidated. Similarities in the banding sequences of larval polytene chromosome, relative to other black flies, suggest that this group is monophyletic. I suggest the presence oof four cytotypes, probably sibling species in S. maroniense, each related to specific geographic locations, landscape types and temperatures. Habitat characteristics of the four nominal species overlapped, but S. perflavum occupied smaller in open areas, with sandy bottoms and high pH, whereas S. maroniense, S. rorotaense and S. "X" were found mostly in medium to large, rocky streams and lower pH.Larvae were found in streams flowing through savanna and through disturbed areas. Characteristics of the stream channel (size, streambed type), pH, presence of impoundments and agriculture are important predictors of larval occurrence for this species. Twelve species were found in Central Amazonia: S. goeldii Cerqueira and Nunes de Mello, S. "6-B1"(dellome Filho) , S. quadrifidum Lutz, S. cauchene Floch and Abonnenc, S.rorotaense Floch and Abonnenc, S. maroniense Floch and Abonnenc, S. perflavum Roubada, S. iracouboense Floch and Abonnenc. S. argentiscutum Shelley and Luna Dias, S. "A", S. "C" and S. "X". Cluster analysis of black fly species co-occurrences in Central Amazonia indicated three groups of species, each probably reflecting physical characteristics of the habitat (riparian vegetation, landscape type and presence of impoundments). Species richness also was associated with physica characteristics of the environment; high species richness was associated with low temperature, bedrock streams and absence of impoundments, whereas low species richness was associated with presence of impoundments and agricultural areas. Black fly species in Brazilian Amazonia appear to respond to physical factors in the same way that temperature zone species respond, suggesting that factors controlling black fly distributions might be universal in nature.