Evidence for a discrete evolutionary lineage within Equatorial Guinea suggests that the tsetse fly Glossina palpalis palpalis exists as a species complex

Tsetse flies of the palpalis group are major vectors of Human African Trypanosomiasis in Africa. Accurate knowledge of species identity is essential for vector control. Here we combine ribosomal internal transcribed spacer 1 (ITS1), mitochondrial Cytochrome Oxidase 1 (COI) and microsatellites to determine the population structure and phylogenetic relations of G. p. palpalis in Equatorial Guinea. COI sequence data suggest that G. p. palpalis in Equatorial Guinea are a distinct subspecies from previously described G. p. palpalis in West Africa and Democratic Republic of Congo. G. p. palpalis in Equatorial Guinea and DRC share a common ancestor which diverged from West African G. p. palpalis around 1.9 million years ago. Previous ITS1 length polymorphism data suggested the possible presence of hybrids in Equatorial Guinea. However, ITS1 showed incomplete lineage sorting compared to clearly defined COI groups, and data from twelve unlinked microsatellites provided no evidence of hybridization. Microsatellite data indicated moderate but significant differentiation between the populations analysed (Rio Campo, Mbini and Kogo). Moreover, unlike previous studies of G. p. palpalis, there was no evidence for heterozygote deficiency, presence of migrants, or cryptic population structure. Variance effective population size at Rio Campo was estimated at 501 to 731 assuming 8 generations/year. This study of the population genetics of G. p. palpalis in central Africa provides the first estimate of genetic differentiation between geographically separated G. p. palpalis populations.

采采蝇（Tsetse flies）须舌蝇组（palpalis group）是非洲人类非洲锥虫病（Human African Trypanosomiasis）的主要传播媒介。精准掌握物种鉴定信息对媒介防控工作至关重要。本研究联合核糖体内部转录间隔区1（ribosomal internal transcribed spacer 1，ITS1）、线粒体细胞色素氧化酶1（mitochondrial Cytochrome Oxidase 1，COI）与微卫星标记，解析赤道几内亚境内须舌蝇指名亚种（G. p. palpalis）的种群结构与系统发育关系。COI序列数据表明，赤道几内亚境内的须舌蝇指名亚种与此前已报道的西非及刚果民主共和国境内的该亚种属于不同亚种。赤道几内亚与刚果民主共和国的须舌蝇指名亚种拥有共同祖先，该祖先约于190万年前与西非的须舌蝇指名亚种发生分化。此前的ITS1长度多态性研究曾提示，赤道几内亚境内可能存在杂交个体。然而相较于聚类清晰的COI类群，ITS1存在不完全谱系分选现象；且来自12个非连锁微卫星位点的数据未提供任何杂交事件的相关证据。微卫星数据分析显示，本次研究涉及的里奥坎波、姆比尼与科戈三个种群之间存在中等程度但显著的遗传分化。此外，与此前针对须舌蝇指名亚种的研究不同，本研究未检测到杂合子缺失、迁移个体存在或隐秘种群结构的相关信号。假设每年存在8个世代，里奥坎波种群的方差有效种群大小估计为501至731。这项针对中非地区须舌蝇指名亚种的种群遗传学研究，首次量化了地理隔离的须舌蝇指名亚种种群间的遗传分化水平。