喀麦隆和尼日利亚野生黑猩猩的群体遗传学表明，选择在黑猩猩亚种的进化中发挥了积极作用。
The population genetics of wild chimpanzees in Cameroon and Nigeria suggests a positive role for selection in the evolution of chimpanzee subspecies.
机构信息
Department of Biology, Drexel University, Philadelphia 19104, Pennsylvania, USA.
出版信息
BMC Evol Biol. 2015 Jan 21;15:3. doi: 10.1186/s12862-014-0276-y.
BACKGROUND
Chimpanzees (Pan troglodytes) can be divided into four subspecies. Substantial phylogenetic evidence suggests that these subspecies can be grouped into two distinct lineages: a western African group that includes P. t. verus and P. t. ellioti and a central/eastern African group that includes P. t. troglodytes and P. t. schweinfurthii. The geographic division of these two lineages occurs in Cameroon, where the rages of P. t. ellioti and P. t. troglodytes appear to converge at the Sanaga River. Remarkably, few population genetic studies have included wild chimpanzees from this region.
RESULTS
We analyzed microsatellite genotypes of 187 wild, unrelated chimpanzees, and mitochondrial control region sequencing data from 604 chimpanzees. We found that chimpanzees in Cameroon and eastern Nigeria comprise at least two, and likely three populations. Both the mtDNA and microsatellite data suggest that there is a primary separation of P. t. troglodytes in southern Cameroon from P. t. ellioti north and west of the Sanaga River. These two populations split ~200-250 thousand years ago (kya), but have exchanged one migrant per generation since separating. In addition, P. t. ellioti consists of two populations that split from one another ~4 kya. One population is located in the rainforests of western Cameroon and eastern Nigeria, whereas the second population appears to be confined to a savannah-woodland mosaic in central Cameroon.
CONCLUSIONS
Our findings suggest that there are as many as three genetically distinct populations of chimpanzees in Cameroon and eastern Nigeria. P. t. troglodytes in southern Cameroon comprises one population that is separated from two populations of P. t. ellioti in western and central Cameroon, respectively. P. t. ellioti and P. t. troglodytes appear to be characterized by a pattern of isolation-with-migration, and thus, we propose that neutral processes alone can not explain the differentiation of P. t. ellioti and P. t. troglodytes.
背景
黑猩猩（Pan troglodytes）可分为四个亚种。大量系统发育证据表明，这些亚种可分为两个截然不同的谱系：一个是西部非洲群体，包括 P. t. verus 和 P. t. ellioti；另一个是中部/东部非洲群体，包括 P. t. troglodytes 和 P. t. schweinfurthii。这两个谱系的地理划分发生在喀麦隆，P. t. ellioti 和 P. t. troglodytes 的范围似乎在萨纳加河交汇。值得注意的是，很少有种群遗传研究包括来自该地区的野生黑猩猩。
结果
我们分析了 187 只野生、无关黑猩猩的微卫星基因型和 604 只黑猩猩的线粒体控制区测序数据。我们发现喀麦隆和尼日利亚东部的黑猩猩至少由两个，可能是三个种群组成。线粒体 DNA 和微卫星数据均表明，在喀麦隆南部，P. t. troglodytes 与 Sanaga 河以北和以西的 P. t. ellioti 存在主要分离。这两个种群在 20 万至 25 万年前（kya）分裂，但自分离以来，每代都有一个移民交换。此外，P. t. ellioti 由两个种群组成，它们在 4 kya 前彼此分离。一个种群位于喀麦隆西部和尼日利亚东部的雨林中，而第二个种群似乎局限于喀麦隆中部的热带稀树草原镶嵌区。
结论
我们的研究结果表明，喀麦隆和尼日利亚东部可能存在多达三个遗传上截然不同的黑猩猩种群。喀麦隆南部的 P. t. troglodytes 由一个种群组成，该种群与喀麦隆西部和中部的两个 P. t. ellioti 种群分别分离。P. t. ellioti 和 P. t. troglodytes 似乎具有隔离伴迁移的特征，因此，我们认为中性过程本身不能解释 P. t. ellioti 和 P. t. troglodytes 的分化。
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