Conn Jan E, Vineis Joseph H, Bollback Jonathan P, Onyabe David Y, Wilkerson Richard C, Póvoa Marinete M
Department of Biology, University of Vermont, Burlington, Vermont, USA.
Am J Trop Med Hyg. 2006 May;74(5):798-806.
Anopheles darlingi is the primary malaria vector in Latin America, and is especially important in Amazonian Brazil. Historically, control efforts have been focused on indoor house spraying using a variety of insecticides, but since the mid-1990s there has been a shift to patient treatment and focal insecticide fogging. Anopheles darlingi was believed to have been significantly reduced in a gold-mining community, Peixoto de Azevedo (in Mato Grosso State), in the early 1990s by insecticide use during a severe malaria epidemic. In contrast, although An. darlingi was eradicated from some districts of the city of Belem (the capital of Para State) in 1968 to reduce malaria, populations around the water protection area in the eastern district were treated only briefly. To investigate the population structure of An. darlingi including evidence for a population bottleneck in Peixoto, we analyzed eight microsatellite loci of 256 individuals from seven locations in Brazil: three in Amapa State, three in Para State, and one in Mato Grosso State. Allelic diversity and mean expected heterozygosity were high for all populations (mean number alleles/locus and H(E) were 13.5 and 0.834, respectively) and did not differ significantly between locations. Significant heterozygote deficits were associated with linkage disequilibrium, most likely due to either the Wahlund effect or selection. We found no evidence for a population bottleneck in Peixoto, possibly because the reduction was not extreme enough to be detected. Overall estimates of long-term N(e) varied from 92.4 individuals under the linkage disequilibrium model to infinity under the heterozygote excess model. Fixation indices and analysis of molecular variance demonstrated significant differentiation between locations north and south of the Amazon River, suggesting a degree of genetic isolation between them, attributed to isolation by distance.
达林按蚊是拉丁美洲主要的疟疾传播媒介，在巴西亚马逊地区尤为重要。历史上，防控措施主要集中在使用各种杀虫剂进行室内房屋喷洒，但自20世纪90年代中期以来，已转向患者治疗和局部杀虫剂喷雾。据信，在20世纪90年代初，马托格罗索州的佩肖托·德阿泽维多金矿社区，由于在严重疟疾流行期间使用杀虫剂，达林按蚊数量大幅减少。相比之下，尽管1968年为减少疟疾从帕拉州首府贝伦市的一些地区根除了达林按蚊，但东部地区水源保护区周围的种群仅得到了短暂处理。为了研究达林按蚊的种群结构，包括佩肖托是否存在种群瓶颈的证据，我们分析了来自巴西七个地点的256个个体的八个微卫星位点：阿马帕州的三个地点、帕拉州的三个地点和马托格罗索州的一个地点。所有种群的等位基因多样性和平均期望杂合度都很高（平均每个位点的等位基因数和H(E)分别为13.5和0.834），不同地点之间没有显著差异。显著的杂合子缺失与连锁不平衡有关，最有可能是由于瓦伦德效应或选择。我们没有发现佩肖托存在种群瓶颈的证据，可能是因为减少程度不够极端，无法检测到。长期有效种群大小的总体估计值从连锁不平衡模型下的92.4个个体到杂合子过剩模型下的无穷大不等。固定指数和分子方差分析表明，亚马逊河以北和以南的地点之间存在显著差异，表明它们之间存在一定程度的遗传隔离，这归因于距离隔离。
