Mouse lemurs (Microcebus) are a radiation of morphologically cryptic primates distributed throughout Madagascar for which the number of recognized species has exploded in the past two decades. This taxonomic revision has prompted understandable concern that there has been substantial oversplitting in the mouse lemur clade. Here, we investigate mouse lemur diversity in a region in northeastern Madagascar with high levels of microendemism and predicted habitat loss. We analyzed RADseq data with multispecies coalescent (MSC) species delimitation methods for two pairs of sister lineages that include three named species and an undescribed lineage previously identified to have divergent mtDNA. Marked differences in effective population sizes, levels of gene flow, patterns of isolation-by-distance, and species delimitation results were found among the two pairs of lineages. Whereas all tests support the recognition of the presently undescribed lineage as a separate species, the species-level distinction of two previously described species, M. mittermeieri and M. lehilahytsara is not supported - a result that is particularly striking when using the genealogical discordance index (gdi). Non-sister lineages occur sympatrically in two of the localities sampled for this study, despite an estimated divergence time of less than 1 Ma. This suggests rapid evolution of reproductive isolation in the focal lineages, and in the mouse lemur clade generally. The divergence time estimates reported here are based on the MSC calibrated with pedigree-based mutation rates and are considerably more recent than previously published fossil-calibrated relaxed-clock estimates. We discuss the possible explanations for this discrepancy, noting that there are theoretical justifications for preferring the MSC estimates in this case.

中文翻译：

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隐秘灵长类动物物种形成的隐秘模式：微地方性鼠狐猴和多物种聚结

鼠狐猴 (Microcebus) 是分布在马达加斯加各地的形态神秘的灵长类动物的一种辐射，在过去的二十年中，已识别的物种数量激增。这种分类修订引起了可以理解的担忧，即小鼠狐猴进化枝中存在大量过度分裂。在这里，我们调查了马达加斯加东北部一个地区的小鼠狐猴多样性，该地区具有高水平的微特有性和预测的栖息地丧失。我们使用多物种聚结 (MSC) 物种界定方法分析了 RADseq 数据，用于两对姐妹谱系，其中包括三个命名物种和一个先前确定具有不同 mtDNA 的未描述谱系。有效种群规模、基因流动水平、距离隔离模式的显着差异，并在两对谱系中发现了物种界定结果。尽管所有测试都支持将目前未描述的谱系识别为一个单独的物种，但不支持两个先前描述的物种 M. mittermeieri 和 M. lehilahytsara 的物种水平区别 - 当使用系谱不一致指数时，这一结果特别引人注目(gdi)。尽管估计的分歧时间小于 1 Ma，但非姐妹谱系在本研究采样的两个地方同域发生。这表明焦点谱系和小鼠狐猴进化枝中生殖隔离的快速进化。这里报告的发散时间估计是基于用基于谱系的突变率校准的 MSC，并且比以前发表的化石校准的松弛时钟估计要新得多。我们讨论了对这种差异的可能解释，并指出在这种情况下首选 MSC 估计有理论上的理由。