Hybrid sterility in crosses between two Brazilian sibling species of the Anopheles albitarsis complex

Abstract

BackgroundComplexes of cryptic species are common in several taxa and this is also the case in the Anopheles genus, a group including all known human malaria vectors. The Anopheles albitarsis complex comprises at least nine cryptic species, some of which are implicated as vectors of human malaria. Several different types of data have been generated for this species complex such as cytogenetics, alloenzymes, morphological and feeding behavioral, hybridization experiments, RAPD-PCR and RFLP and mitochondrial and nuclear markers. Studies focused on its postzygotic isolation are still somewhat rare in the literature despite their importance to understand the speciation process and the level of gene flow potentially occurring among the different sibling species.MethodsHybridization experiments between Anopheles albitarsis s.s. and Anopheles marajoara, as well as backcrosses between hybrids and Anopheles albitarsis s.s., were performed using the induced mating technique. Results were compared to intraspecific crosses. Larva-to-adult viability and sex ratio were also assessed.ResultsMale hybrids show very low insemination rates and nearly complete sterility, apparently due to abnormalities in their reproductive organs. Evidence of partial sterility among the hybrid females was also observed.ConclusionsOur data indicated that Anopheles albitarsis s.s. and Anopheles marajoara show a high level of postzygotic isolation with a strong hybrid male sterility. This result is consistent with the Haldane’s rule which states that in interspecific crosses the heterogametic sex is the first to be affected. However, the fact that the females are not completely sterile raises the possibility of introgression between these two siblings species.

Unveiling mosquito cryptic species and their reproductive isolation

“…gambiae and An. coluzzii have a geographical range spanning sub-Saharan Africa and encompassing a variety of ecological settings (Fossog et al, 2015). Within pericentromeric regions of chromosomes X, 3 and arm 2R, mosquitoes segregated into two highly distinct clades, largely corresponding to the two species as determined by conventional molecular diagnostics, consistent with previous studies finding that genome regions of reduced recombination are associated with stronger differentiation between closely related species (Cruickshank and Hahn 2014).…”

“…This result is consistent with the Haldane's rule, which states that in interspecific crosses, the heterogametic sex is the first to be affected. However, the fact that the females are not completely sterile raises the possibility of introgression between these two sibling species (Fontoura et al ., 2014).…”

Insecticide Resistance in Anopheles Albitarsis S.S. From a Rice Production Field, With the First Record of Kdr Mutation in This Species 

“…In the laboratory, we morphologically classi ed the insects as An. albitarsis, following the Anopheles key of Consoli e Lourenço-de Oliveira (1994) and were induced to lay eggs to obtain the F1 generation, as previously described [38]. Insectary conditions and mosquito rearing.…”

“…We randomly selected the DNA of 11 ALBI-eld and 10 ALBI-lab individual females for this analysis. We deployed the primers LCO1490 (5'-GGTCAACAAATCATAAAGATATTGG-3') and HCO2198 (5'-TAAACTTCAGGGTGACCAAAAAATCA-3') [46] in a PCR ampli cation reaction as described elsewhere [47]. The puri ed amplicons were submitted to the Sanger sequencing method with the kit Big Dye 3.1 (Applied Biosystems) and followed to the DNA sequencing facility "Plataforma de Sequenciamento PDTIS/ Fiocruz".…”