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 explosion has prompted understandable concern that there has been substantial oversplitting in the mouse lemur clade. Here, we take an integrative approach to investigate species diversity in two pairs of sister lineages that occur 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 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 them. 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 and calibrated with pedigree-based mutation rates and are considerably more recent than previously published fossil-calibrated concatenated likelihood estimates, however. 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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隐性灵长类动物的物种形态的隐匿模式：小地方性小鼠狐猴和多物种合并

鼠狐猴（Microcebus）是分布在马达加斯加的形态隐秘的灵长类动物的辐射，在过去的二十年中，这种物种的数量激增。这种分类爆炸引起了人们的理解，那就是鼠标狐猴进化枝中存在大量的过度分裂。在这里，我们采用一种综合方法来研究马达加斯加东北部某个地区发生的两对姊妹谱系中物种多样性，这些物种具有较高的微地方病流行水平，并预测有栖息地丧失。我们使用三种物种的多物种合并（MSC）物种定界方法和以前鉴定为具有不同mtDNA的未描述谱系分析了RADseq数据。有效种群数量，基因流水平，按距离隔离的模式，并在其中找到了物种划界的结果。尽管所有测试均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.meiermeieri和M.lehilahytsara的物种水平区分；当使用家谱不一致指数（gdi）时，这一结果尤其令人震惊。尽管估计发散时间小于1 Ma，但非姐妹血统在本研究采样的两个地点同时发生。这表明在焦点谱系以及一般在小鼠狐猴进化枝中生殖隔离迅速发展。此处报告的发散时间估计是基于MSC并使用基于谱系的突变率进行校准的，但是比以前公布的化石校准的串联可能性估计值要晚得多。我们讨论了这种差异的可能解释，并指出在这种情况下偏向MSC估计存在理论上的合理性。