Widespread Divergence Between Incipient Anopheles gambiae Species Revealed by Whole Genome Sequences

Abstract

The Afrotropical mosquito Anopheles gambiae sensu stricto (A. gambiae), a major vector of malaria, is currently undergoing speciation into the M and S molecular forms. These forms have diverged in larval ecology and reproductive behavior through unknown genetic mechanisms, despite considerable levels of hybridization. Previous genome-wide scans using gene-based microarrays uncovered divergence between M and S that was largely confined to gene-poor pericentromeric regions, prompting a speciation-with-ongoing-gene-flow model that implicated only ~3% of the genome near centromeres in the speciation process. Here, based on the complete M and S genome sequences, we report widespread and heterogeneous genomic divergence inconsistent with appreciable levels of inter-form gene flow, suggesting a more advanced speciation process and greater challenges to identify genes critical to initiating that process.

Genomic islands of divergence are not affected by geography of speciation in sunflowers

“…Our results, along with a growing number of genomic studies of speciation, support the view that even for species still exchanging genes, divergence is typically maintained in numerous independent genomic regions [28][29][30][31] , rather than in a few large islands of divergence. While there are reports of simpler genetic architectures of divergence, at least in some instances (especially early studies), scan resolution appears to have been too low to detect smaller islands of divergence (for example, Hahn et al 32 ).…”

Population genetics of malaria resistance in humans

“…Support for this hypothesis comes from some molecular analysis of P. falciparum strains that suggests that the African malaria population expanded around 10 000 years ago and spread to other areas (Joy et al, 2003). In addition, chromosomal data from the mosquito vector Anopheles gambiae support contemporaneous speciation (Coluzzi et al, 2002 see also;Lawniczak et al, 2010 andNeafsey et al, 2010). Recent analysis suggests that P. falciparum in humans is the result of cross-species transmission from gorillas (Liu et al, 2010).…”

Genomic divergence during speciation: causes and consequences

“…Likewise, as discussed in the article by Hahn et al [29], initial work on molecular forms of Anopheles mosquitoes detected multiple, yet few (i.e. three), regions of differentiation [42], but subsequent finer scale sequencing detected numerous other regions of differentiation [54].…”

“…These results are qualitatively consistent with some past work, such as the study by Strasburg et al [64] examining divergence between hybridizing sunflower species, who reported that genetic divergence is not accentuated within inversions, except perhaps near chromosomal breakpoints, where recombination is particularly reduced. Moreover, widespread adaptive divergence in collinear regions is being increasingly documented [18,26,49,54,64]. Indeed, theoretical work by Feder & Nosil [65] showed that there is no reason for the vast majority of loci contributing to reproductive isolation to reside in inversions; they should also be commonly found in collinear regions.…”