Data from: Inter-island divergence within Drosophila mauritiana, a species of the D. simulans complex: past history and/or speciation in progress?

Speciation with gene flow may be more common than generally thought making detailed understanding of the extent and pattern of genetic divergence between geographically isolated populations useful. Species of the Drosophila simulans complex provide a good model for speciation and evolutionary studies; understanding their population genetic structure will increase our understanding of the context in which speciation has occurred. Here we describe the genetic diversity and the genetic differentiation, at mitochondrial and nuclear loci, of two distant populations of D. mauritiana (Mauritius and Rodrigues Islands). We surveyed the two populations for their mitochondrial types, eight nuclear genes and 18 microsatellite loci. A new mitochondrial type is fixed in the Rodrigues population of D. mauritiana. The two populations are highly differentiated, their divergence appears relatively ancient (100,000 years) compared to the origin of the species, around 0.25 MYA, and they exhibit very limited gene flow. However, they have similar levels of divergence from their sibling, D. simulans. Both nuclear genes and microsatellites revealed contrasting demographic histories between the two populations; expansion for the Mauritius population and stable population size for the Rodrigues Island population. The pronounced geographic structure discovered within D. mauritiana in addition to the low amount of genetic exchange between those two island populations is significant for understanding how the genetic structuring of the species contributes to its evolutionary history, and clearly merits further attention in the broad context of speciation.

存在基因流的物种形成过程可能比学界普遍认知的更为常见，因此深入解析地理隔离种群间遗传分化的程度与模式具有重要学术价值。拟暗果蝇复合体（Drosophila simulans complex）是物种形成与进化生物学研究的优质模型类群；明晰其种群遗传结构，将有助于我们进一步理解物种形成发生的具体演化背景。本研究针对毛里求斯果蝇（D. mauritiana）的两个远缘种群（分别采自毛里求斯岛与罗德里格斯岛），对其线粒体与核基因位点的遗传多样性及遗传分化特征进行了系统描述。我们对这两个种群的线粒体单倍型、8个核基因以及18个微卫星（microsatellite）位点进行了分型检测与分析。研究发现，毛里求斯果蝇的罗德里格斯种群中固定了一种全新的线粒体单倍型。两个种群间分化程度极高，相较于该物种约25万年前的起源时间，二者的分化事件相对古老（距今约10万年），且基因交流极为有限。不过，它们与姊妹种拟暗果蝇（D. simulans）的遗传分化水平相近。核基因与微卫星位点的分析结果均显示，两个种群的种群历史动态存在显著差异：毛里求斯种群经历了种群扩张过程，而罗德里格斯岛种群的种群规模长期保持稳定。本次研究在毛里求斯果蝇内部发现了显著的地理种群结构，加之这两个岛屿种群间极低的遗传交换率，这一发现对于理解该物种的遗传结构如何塑造其进化历史具有重要意义，同时也明确了其在物种形成研究的宏观框架中值得进一步关注与深入探索。