TY - JOUR
T1 - Chromosome Inversions, Genomic Differentiation and Speciation in the African Malaria Mosquito Anopheles gambiae
AU - Lee, Yoosook
AU - Collier, Travis C.
AU - Sanford, Michelle R.
AU - Marsden, Clare D.
AU - Fofana, Abdrahamane
AU - Cornel, Anthony J.
AU - Lanzaro, Gregory C
PY - 2013/3/20
Y1 - 2013/3/20
N2 - The African malaria vector, Anopheles gambiae, is characterized by multiple polymorphic chromosomal inversions and has become widely studied as a system for exploring models of speciation. Near complete reproductive isolation between different inversion types, known as chromosomal forms, has led to the suggestion that A. gambiae is in early stages of speciation, with divergence evolving in the face of considerable gene flow. We compared the standard chromosomal arrangement (Savanna form) with genomes homozygous for j, b, c, and u inversions (Bamako form) in order to identify regions of genomic divergence with respect to inversion polymorphism. We found levels of divergence between the two sub-taxa within some of these inversions (2Rj and 2Rb), but at a level lower than expected and confined near the inversion breakpoints, consistent with a gene flux model. Unexpectedly, we found that the majority of diverged regions were located on the X chromosome, which contained half of all significantly diverged regions, with much of this divergence located within exons. This is surprising given that the Bamako and Savanna chromosomal forms are both within the S molecular form that is defined by a locus near centromere of X chromosome. Two X-linked genes (a heat shock protein and P450 encoding genes) involved in reproductive isolation between the M and S molecular forms of A. gambiae were also significantly diverged between the two chromosomal forms. These results suggest that genes mediating reproductive isolation are likely located on the X chromosome, as is thought to be the case for the M and S molecular forms. We conclude that genes located on the sex chromosome may be the major force driving speciation between these chromosomal forms of A. gambiae.
AB - The African malaria vector, Anopheles gambiae, is characterized by multiple polymorphic chromosomal inversions and has become widely studied as a system for exploring models of speciation. Near complete reproductive isolation between different inversion types, known as chromosomal forms, has led to the suggestion that A. gambiae is in early stages of speciation, with divergence evolving in the face of considerable gene flow. We compared the standard chromosomal arrangement (Savanna form) with genomes homozygous for j, b, c, and u inversions (Bamako form) in order to identify regions of genomic divergence with respect to inversion polymorphism. We found levels of divergence between the two sub-taxa within some of these inversions (2Rj and 2Rb), but at a level lower than expected and confined near the inversion breakpoints, consistent with a gene flux model. Unexpectedly, we found that the majority of diverged regions were located on the X chromosome, which contained half of all significantly diverged regions, with much of this divergence located within exons. This is surprising given that the Bamako and Savanna chromosomal forms are both within the S molecular form that is defined by a locus near centromere of X chromosome. Two X-linked genes (a heat shock protein and P450 encoding genes) involved in reproductive isolation between the M and S molecular forms of A. gambiae were also significantly diverged between the two chromosomal forms. These results suggest that genes mediating reproductive isolation are likely located on the X chromosome, as is thought to be the case for the M and S molecular forms. We conclude that genes located on the sex chromosome may be the major force driving speciation between these chromosomal forms of A. gambiae.
UR - http://www.scopus.com/inward/record.url?scp=84875190674&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=84875190674&partnerID=8YFLogxK
U2 - 10.1371/journal.pone.0057887
DO - 10.1371/journal.pone.0057887
M3 - Article
C2 - 23526957
AN - SCOPUS:84875190674
VL - 8
JO - PLoS One
JF - PLoS One
SN - 1932-6203
IS - 3
M1 - e57887
ER -