Abstract
BackgroundChromosomal inversions have been considered to be potentially important barriers to gene flow in many groups of animals through their effect on recombination suppression in heterokaryotypic individuals. Inversions can also enhance local adaptation in different groups of organisms and may often represent species-specific differences among closely related taxa. We conducted a study to characterize the 2La inversion karyotypes of An. gambiae sensu stricto mosquitoes sampled from the Kilombero Valley (Tanzania) using a newly designed PCR assay.ResultsWe frequently encountered a (687 bp) fragment which was only present in the Kilombero Valley populations. Laboratory crossing between An. gambiae s.s. from Njage (Tanzania) and Kisumu (Western Kenya) populations resulted in F1 offspring carrying the observed fragment. Karyotype analysis did not indicate differences in 2La region chromosome morphology between individuals carrying the PCR fragments, the 207 bp fragment, or the 687 bp fragement.ConclusionThe observed insertion/deletion polymorphism within the region amplified by the 2La PCR diagnostic test may confound the interpretation of this assay and should be well considered in order to maintain an acceptable level of reliability in studies using this assay to describe the distribution and frequency of the 2La inversion among natural populations of An. gambiae s.s.
Highlights
Chromosomal inversions have been considered to be potentially important barriers to gene flow in many groups of animals through their effect on recombination suppression in heterokaryotypic individuals
All An. gambiae s.s. belonged to the S molecular form
Both An. gambiae s.s. and An. arabiensis were found in all villages except Ukindu
Summary
Chromosomal inversions have been considered to be potentially important barriers to gene flow in many groups of animals through their effect on recombination suppression in heterokaryotypic individuals. The Anopheles gambiae complex consists of seven closely related species, including two of the most important vectors of malaria in Africa, An. gambiae s. Various 2La chromosome inversions play a role in the subdivision of An. gambiae s.s. populations from West and Central Africa [1,2,4,5] and the seven recognised species (page number not for citation purposes). Such behavioural heterogeneity may have serious epidemiological impact and may influence the outcome of malaria vector control programmes. The indoor residual spraying (IRS) strategy will not uniformly impact the An. gambiae s.s. population [9] as this approach will miss the subpopulation that rests outdoors
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