Necromys is a genus of sigmodontine rodent that inhabits grasslands and scrublands in South America. Eight extant species are recognized in the genus; one of these is Necromys lactens, which inhabits high-elevation grasslands in the Yungas from south-central Bolivia to northwestern Argentina. Morphological variation in N. lactens has been recognized by the description of three nominal forms. Geographically structured genetic diversity also has been observed, but a thorough revision of these nominal forms within an integrative framework has yet to be performed. We conducted a phylogeographic assessment based on an 801 base-pair fragment of the cytochrome-b gene that guided morphometric analyses (univariate and multivariate comparisons) of patterns of geographic variation in the species, and the distinction of its nominal forms. Haplotypes of N. lactens form a well-supported and geographically structured clade. Within it, there are two main clades; haplotypes from the northern range form a well-supported clade, sister and allopatric to a weakly supported southern clade, which includes variants collected at or near the type localities of three nominal forms. In turn, both main clades are composed by two allopatric subclades. Morphometric analyses indicated no differences in shape of the skull among the three nominal forms or between the recovered clades and subclades. Taking together all the available evidence, we consider N. lactens to be a monotypic species.

中文翻译：

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分子和形态计量学证据显示，分配给 Necromys lactens（啮齿目、仓鼠科）的名义形式的分类地位

Necromys 是一种啮齿动物属，栖息于南美洲的草原和灌木丛中。该属有八个现存的物种。其中之一是 Necromys lactens，它栖息在从玻利维亚中南部到阿根廷西北部的永加斯的高海拔草原。N.lactens 的形态变异已通过三种名义形式的描述得到认可。还观察到了地理结构的遗传多样性，但尚未在综合框架内对这些名义形式进行彻底修订。我们基于细胞色素 b 基因的 801 碱基对片段进行了系统地理学评估，该片段指导物种地理变异模式的形态计量分析（单变量和多变量比较），以及其名义形式的区别。N 的单倍型。乳链形成一个得到良好支持和地理结构的进化枝。在其中，有两个主要的进化枝；来自北部范围的单倍型形成了一个支持良好的进化枝、姐妹和异源进化枝到一个弱支持的南部进化枝，其中包括在三种名义形式的类型位置或附近收集的变体。反过来，两个主要进化枝由两个异域子进化枝组成。形态测量分析表明，三种名义形式之间或回收的进化枝和子进化枝之间的头骨形状没有差异。综合所有可用证据，我们认为 N.lactens 是一种单型物种。其中包括在三种名义形式的类型位置处或附近收集的变体。反过来，两个主要进化枝由两个异域子进化枝组成。形态测量分析表明，三种名义形式之间或回收的进化枝和子进化枝之间的头骨形状没有差异。综合所有可用证据，我们认为 N.lactens 是一种单型物种。其中包括在三种名义形式的类型位置处或附近收集的变体。反过来，两个主要进化枝由两个异域子进化枝组成。形态测量分析表明，三种名义形式之间或回收的进化枝和子进化枝之间的头骨形状没有差异。综合所有可用证据，我们认为 N.lactens 是一种单型物种。