Genomic Islands of Speciation in Anopheles gambiae

By Thomas L. Turner, Matthew W. Hahn, Sergey V. Nuzhdin. PLoS Biology, 2005

756 citations recorded by the source corpus.

The African malaria mosquito, Anopheles gambiae sensu stricto (A. gambiae), provides a unique opportunity to study the evolution of reproductive isolation because it is divided into two sympatric, partially isolated subtaxa known as M form and S form. With the annotated genome of this species now available, high-throughput techniques can be applied to locate and characterize the genomic regions contributing to reproductive isolation. In order to quantify patterns of differentiation within A. gambiae, we hybridized population samples of genomic DNA from each form to Affymetrix GeneChip microarrays. We found that three regions, together encompassing less than 2.8 Mb, are the only locations where the M and S forms are significantly differentiated. Two of these regions are adjacent to centromeres, on Chromosomes 2L and X, and contain 50 and 12 predicted genes, respectively. Sequenced loci in these regions contain fixed differences between forms and no shared polymorphisms, while no fixed differences were found at nearby control loci. The third region, on Chromosome 2R, contains only five predicted genes; fixed differences in this region were also verified by direct sequencing. These “speciation islands” remain differentiated despite considerable gene flow, and are therefore expected to contain the genes responsible for reproductive isolation. Much effort has recently been applied to locating the genes and genetic changes responsible for reproductive isolation between species. Though much can be inferred about speciation by studying taxa that have diverged for millions of years, studying differentiation between taxa that are in the early stages of isolation will lead to a clearer view of the number and size of regions involved in the genetics of speciation. Despite appreciable levels of gene flow between the M and S forms of A. gambiae, we were able to isolate three small regions of differentiation where genes responsible for ecological and behavioral isolation are likely to be located. We expect reproductive isolation to be due to changes at a small number of loci, as these regions together contain only 67 predicted genes. Concentrating future mapping experiments on these regions should reveal the genes responsible for reproductive isolation between forms.

Subfields: Cellular and Molecular Neuroscience, Molecular Biology, Public Health, Environmental and Occupational Health

View Paper: https://www.semanticscholar.org/paper/987693b475bd5bcc3143bb500d7028ab240d4a5e

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Citations in the corpus

Reanalysis suggests that genomic islands of speciation are due to reduced diversity, not reduced gene flow (2014, methodology): “Surprisingly, absolute measures have either not been considered by most researchers (but see Noor & Bennett 2009; Nach-man & Payseur 2012), or relative measures were mistak-enly thought to be absolute (a mistake one of us has made; Turner et al. 2005).”
Divergent selection and heterogeneous genomic divergence (2009, background): “Turner et al. (2005) found that differentiation between forms of Anopheles gambiae mosquitoes involved 1.2% of the genome and was clustered into three genomic regions comprising less than 2 Mb. Clustering was somewhat weaker between house mouse (Mus musculus) subspecies, where differentiated…”
Divergence with Gene Flow: Models and Data (2010, background): “…not can help to identify genomic locations that are contributing more than the average to divergence, as well as to reveal aspects of the genetic architecture that seem to be important for speciation (Geraldes et al. 2006, Machado et al. 2002, Rieseberg et al. 1999, Turner et al. 2005, Wu 2001).”
Genome-wide evidence for speciation with gene flow in Heliconius butterflies (2013, background): “Some loci are likely to be shared between incipient species, while selection maintains divergence at others (Turner et al. 2005; Nosil et al. 2009).”