The Triannulatus Complex of
Anopheles (
Nyssorhynchus)
consists of at least three sibling species, namely
Anopheles triannulatus
s.s.,
Anopheles halophylus
and a third undescribed member herein referred to as
An. triannulatus "C". Sympatric anophelines belonging to species complexes, even though closely related, may exploit different environments such as larval habitats. In this paper we hypothesize that rainfall and seasonal flooding would distinctly influence the availability of larval habitats and consequently the seasonal population dynamics of sympatric members of the Triannulatus Complex. A reflection of this is distinct seasonal biting frequencies exhibited by three members of the Triannulatus Complex at a site in Central Brazil. Population dynamics seem to be influenced by the water level in the local rivers, although biting frequency of all three species was negatively influenced by rainfall.
An. triannulatus s.s. was more abundant following the end of the rainy season, but notably 30 to 60 days after flooding. On the other hand, An. halophylus and
An. triannulatus C peaked during the middle of the dry season, when water impoundments have no inflow, are somewhat reduced in size and the water becomes brackish. Differences in population dynamics were greater between
An. triannulatus s.s. and
An. halophylus and
An. triannulatus C than between
An. halophylus and
An. triannulatus C. This might reflect differences in larval habitat exploitation and therefore spatial segregation among these members of the complex.
