Population cytogenetic and molecular evidence for existence of a new species in Anopheles fluviatilis complex...

Anopheles fluviatilis James, an important malaria vector in the Oriental region has been established as a complex of at least three cryptic species which vary in their biological characteristics and malaria transmission potential. The sibling species S, T and U of Fluviatilis Complex can be identified by examination of species-specific fixed inversions in the polytene chromosomes and can also be differentiated by an allele-specific PCR assay based on differences in the D3 region of 28S ribosomal DNA (rDNA) of these species. Here we report a new An. fluviatilis population from villages under Laksar Community Health Centre, District Haridwar (Uttarakhand state), India which differs from the three sibling species of Fluviatilis Complex by two fixed paracentric inversions, s(1) and S in polytene chromosome arms 2 and 3 respectively. Longitudinal study carried out in study villages showed that the new cytotype was sympatric with species T and U in all the collections and no inversion heterozygotes were observed between them. Thus presence of two fixed paracentric inversions in polytene chromosomes with total absence of inversion heterozygotes demonstrates reproductive isolation which unequivocally establishes this cytological variant as a new species, provisionally designated as species V in the Fluviatilis Complex. Analysis of DNA sequences of D3 domain of 28S rDNA and ITS 2 region has also shown that species V is distinctly different from species S, T and U. With the discovery of new species in the Fluviatilis Complex, in-depth studies are required to know its distribution pattern and biological characteristics and to ascertain its role in malaria transmission.