Lanzaro G C, Touré Y T, Carnahan J, Zheng L, Dolo G, Traoré S, Petrarca V, Vernick K D, Taylor C E
Department of Pathology and Center for Tropical Diseases, University of Texas Medical Branch, Galveston, TX 77555-0609, USA.
Proc Natl Acad Sci U S A. 1998 Nov 24;95(24):14260-5. doi: 10.1073/pnas.95.24.14260.
Chromosomal forms of Anopheles gambiae, given the informal designations Bamako, Mopti, and Savannah, have been recognized by the presence or absence of four paracentric inversions on chromosome 2. Studies of karyotype frequencies at sites where the forms occur in sympatry have led to the suggestion that these forms represent species. We conducted a study of the genetic structure of populations of An. gambiae from two villages in Mali, west Africa. Populations at each site were composed of the Bamako and Mopti forms and the sibling species, Anopheles arabiensis. Karyotypes were determined for each individual mosquito and genotypes at 21 microsatellite loci determined. A number of the microsatellites have been physically mapped to polytene chromosomes, making it possible to select loci based on their position relative to the inversions used to define forms. We found that the chromosomal forms differ at all loci on chromosome 2, but there were few differences for loci on other chromosomes. Geographic variation was small. Gene flow appears to vary among different regions within the genome, being lowest on chromosome 2, probably due to hitchhiking with the inversions. We conclude that the majority of observed genetic divergence between chromosomal forms can be explained by forces that need not involve reproductive isolation, although reproductive isolation is not ruled out. We found low levels of gene flow between the sibling species Anopheles gambiae and Anopheles arabiensis, similar to estimates based on observed frequencies of hybrid karyotypes in natural populations.
冈比亚按蚊的染色体形式，被非正式命名为巴马科型、莫普提型和萨凡纳型，可通过2号染色体上四个臂内倒位的有无来识别。对这些类型在同域分布地点的核型频率研究表明，这些类型代表不同的物种。我们对来自西非马里两个村庄的冈比亚按蚊种群的遗传结构进行了研究。每个地点的种群由巴马科型和莫普提型以及近缘种阿拉伯按蚊组成。确定了每只蚊子的核型，并测定了21个微卫星位点的基因型。许多微卫星已被物理定位到多线染色体上，这使得可以根据它们相对于用于定义类型的倒位的位置来选择位点。我们发现，染色体类型在2号染色体上的所有位点都存在差异，但在其他染色体上的位点差异很少。地理变异很小。基因流似乎在基因组的不同区域有所不同，在2号染色体上最低，这可能是由于与倒位的搭便车效应。我们得出结论，尽管不排除生殖隔离，但观察到的染色体类型之间的大部分遗传差异可以由不需要生殖隔离的力量来解释。我们发现冈比亚按蚊和阿拉伯按蚊这两个近缘种之间的基因流水平较低，这与基于自然种群中杂交核型观察频率的估计结果相似。
