Xenarthra (sloths, anteaters, and armadillos) are the quintessential South American mammals. Among the xenarthrans, sloths constitute the most diverse paleontologically with almost 100 fossil genera recorded. However, this abundant sloth fauna in the Americas became extinct around 10,000 years ago. Only six species belonging to two genera, Bradypus (four three-toed sloth species) and Choloepus (two two-toed sloth species) are alive today in Central and South America. Bradypus variegatus is the sloth species with the widest geographical distribution in the Neotropics. Some regional population genetics have been reported, especially in Brazil, but with limited sample sizes. Herein, we sequenced 77 samples of Bradypys variegatus (Panama, Colombia, Venezuela, Peru, Bolivia, and Brazil; 65 new samples and 12 from GenBank), plus one B. tridactylus, one B. pygmaeus, and five B. torquatus (one new and four from GenBank) at the mitochondrial (mt) control region. Additionally, 25 of these samples, representing the four species, were sequenced for the entire mitochondrial genome. Our results indicate that there are at least six main genetically different haplogroups of B. variegatus. They are the trans-Andean, western Amazon (with some other internal groups), Tapajos River, Tocantins River, Negro River, and the Brazilian eastern Atlantic forest (with two recognizable sub-groups in northern and southern areas) ones, with the ancestor of the trans-Andean haplogroup the first to diverge. A very strong genetic heterogeneity and a striking spatial pattern were detected among these different geographical areas, with the trans-Andean, western Amazon, and Tocantins populations showing the highest levels of genetic diversity, meanwhile the Tapajos and the Brazilian eastern populations yielding lower levels of genetic diversity. The following conclusions were as follows: 1) B. torquatus should be considered as a different genus (Scaeopus) because of its extreme genetic differences from other Bradypus taxa as was previously claimed by other authors; 2) B. pygmaeus is not a recent species adapted to Holocene island environments from the Central America B. variegatus group; and 3) if we adopt a strict version of the Phylogenetic Species Concept (PSC), the highly significant monophyletic clade of the trans-Andean B. variegatus population should be defined as a valid and differentiated species of three-toed sloth. However, we are reluctant to define this population as a new species until new data shows possible strong karyotype differences and/or pre- or post-zygote reproductive barriers (Biological Species Concept, BSC) between the trans and the cis-Andean populations of the three-toed brown-throated sloth.

中文翻译：

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Bradypus (三趾树懒, Pilosa: Bradypodidae, Mammalia) 的分子系统发育学和 Bradypus variegatus (Brown-Throated 三趾树懒) 与线粒体基因序列的系统地理学

Xenarthra（树懒、食蚁兽和犰狳）是典型的南美哺乳动物。在 xenarthrans 中，树懒构成了最多样化的古生物学，记录了近 100 个化石属。然而，美洲这种丰富的树懒动物群在大约 10,000 年前就灭绝了。今天，在中美洲和南美洲，只有属于两个属的六个物种，即 Bradypus（四种三趾树懒物种）和 Choloepus（两种两趾树懒物种）。Bradypus variegatus 是新热带地区地理分布最广的树懒物种。已经报道了一些区域人口遗传学，特别是在巴西，但样本量有限。在此，我们对 77 个 Bradypys variegatus 样本（巴拿马、哥伦比亚、委内瑞拉、秘鲁、玻利维亚和巴西；65 个新样本和 12 个来自 GenBank 的样本）以及 1 个 B. tridactylus 进行了测序，一个 B. pygmaeus 和五个 B. torquatus（一个新的，四个来自 GenBank）在线粒体 (mt) 控制区域。此外，代表四个物种的 25 个样本对整个线粒体基因组进行了测序。我们的结果表明 B. variegatus 至少有六个主要的遗传不同的单倍群。它们是跨安第斯山脉、亚马逊西部（有一些其他内部群）、塔帕霍斯河、托坎廷斯河、内格罗河和巴西东部大西洋森林（在北部和南部地区有两个可识别的亚群），它们的祖先是跨安第斯单倍群的第一个发散。在这些不同的地理区域中发现了非常强的遗传异质性和显着的空间模式，包括跨安第斯山脉、亚马逊西部、和托坎廷斯种群的遗传多样性水平最高，而塔帕霍斯种群和巴西东部种群的遗传多样性水平较低。以下结论如下： 1) B. torquatus 应被视为一个不同的属 (Scaeopus)，因为它与其他作者先前声称的其他 Bradypus 分类群存在极端的遗传差异；2) B. pygmaeus 不是来自中美洲 B. variegatus 群的适应全新世岛屿环境的新近物种；3) 如果我们采用严格的系统发育物种概念 (PSC)，跨安第斯 B. variegatus 种群的高度显着的单系进化枝应被定义为三趾树懒的有效和分化物种。然而，