Molecular evidence of incipient speciation within Anopheles gambiae s.s. in West Africa.
We karyotyped and identified by polymerase chain reaction restriction fragment length polymorphism (PCR-RFLP) analysis Anopheles gambiae s.s. samples collected in several African countries. The data show the existence of two non-panmictic molecular forms, named S and M, whose distribution extended from forest to savannahs. Mosquitoes of the S and M forms are homosequential standard for chromosome-2 inversions in forest areas. In dry savannahs, S is characterized mainly by inversion polymorphisms typical of Savanna and Bamako chromosomal forms, while M shows chromosome-2 arrangements typical of Mopti and/or Savanna and/or Bissau, depending on its geographical origin. Chromosome-2 inversions therefore seem to be involved in ecotypic adaptation rather than in mate-recognition systems. Strong support for the reproductive isolation of S and M in Ivory Coast comes from the observation that the kdr allele is found at high frequencies in S specimens and not at all in chromosomal identical M specimens. However, the kdr allele does not segregate with molecular forms in Benin.
della Torre
A
A
Istituto di Parassitologia, Fondazione Pasteur - Cenci Bolognetti, Università di Roma La Sapienza, Piazzale Aldo Moro 5, 00185, Rome, Italy. ale.dellatorre@uniroma1.it
Fanello
C
C
Akogbeto
M
M
Dossou-yovo
J
J
Favia
G
G
Petrarca
V
V
Coluzzi
M
M
D000354:Africa, Western; D000483:Alleles; D000818:Animals; D000852:Anopheles / Q000145:classification / Q000235:genetics*; D017344:Genes, Insect