Antonio-Nkondjio Christophe, Simard Frédéric, Cohuet Anna, Fontenille Didier
Laboratoire IRD de Recherche sur le Paludisme, Organisation de Coordination pour la Lutte contre les Endémies en Afrique Centrale, BP 288, Yaoundé, Cameroon.
Infect Genet Evol. 2002 Oct;2(1):69-72. doi: 10.1016/s1567-1348(02)00084-9.
Anopheles moucheti is a major human malaria vector in the vicinity of slow moving rivers in the tropical forests of Central Africa. Morphological variations in natural populations of A. moucheti led to the designation of three morphological forms named A. moucheti moucheti, A. moucheti nigeriensis and A. moucheti bervoetsi. Using allozyme markers, we investigated to which extent morphological and/or geographical populations of A. moucheti were genetically differentiated. Mosquitoes were collected from four villages 20-200 km distant apart in south Cameroon, where specimens from each morphological form were found in sympatry. All populations appeared highly homogenous across both morphological type and geographic location. Significant genetic differentiation was only observed between two locations 150 km apart (F(st)=0.029; P=0.006), while no pairwise F(st) estimate between morphological forms reached statistical significance. Further evidence against any taxonomic value of this morphological classification was provided by direct observation of morphological variation within the progeny of field-collected females from all three types. Single female offspring always belonged to at least two morphologically recognised types and most often, a mixture of all three forms was observed. Our results therefore demonstrate that morphological variability within A. moucheti natural populations is not indicative of speciation. With this respect, restricted migration of individuals across river systems may be a more important factor in shaping population genetic structure of A. moucheti.
穆氏按蚊是中非热带森林中水流平缓的河流附近主要的人类疟疾传播媒介。穆氏按蚊自然种群的形态变异导致了三种形态类型的命名，即穆氏按蚊指名亚种、穆氏按蚊尼日利亚亚种和穆氏按蚊贝氏亚种。我们利用等位酶标记研究了穆氏按蚊的形态和/或地理种群在遗传上的分化程度。在喀麦隆南部相距20 - 200公里的四个村庄采集了蚊子，在这些村庄中发现了每种形态类型的标本同域分布。所有种群在形态类型和地理位置上都表现出高度的同质性。仅在相距150公里的两个地点之间观察到显著的遗传分化（Fst = 0.029；P = 0.006），而形态类型之间的成对Fst估计值均未达到统计学显著水平。对所有三种类型的野外采集雌性后代的形态变异进行直接观察，进一步证明了这种形态分类没有任何分类学价值。单个雌性后代总是至少属于两种形态上可识别的类型，而且最常见的是观察到三种类型的混合。因此，我们的结果表明，穆氏按蚊自然种群内的形态变异性并不表明物种形成。在这方面，个体在河流系统间的有限迁移可能是塑造穆氏按蚊种群遗传结构的一个更重要因素。
