Centre for Ecological Genomics and Wildlife Conservation, Department of Zoology, University of Johannesburg, Auckland Park 2000, South Africa.
Mammal Research Institute, Department of Zoology and Entomology, University of Pretoria, Pretoria 0002, South Africa.
Mol Phylogenet Evol. 2019 Jan;130:181-197. doi: 10.1016/j.ympev.2018.10.017. Epub 2018 Oct 17.
The family Bathyergidae (comprising six genera) is a group of subterranean rodents endemic to sub-Saharan Africa. Our understanding of the evolution and species richness of the South African bathyergid genera Georychus, Bathyergus and Cryptomys is limited, with the majority of species listed as Least Concern by the IUCN Red List of Threatened Species. Genetic data suggest that several cryptic species may be present in these genera. To explore genetic and ecological distinctiveness, and evaluate taxonomic richness across the ranges of Georychus, Bathyergus and to a lesser degree, Cryptomys, as well as evaluate possible scenarios which have historically influenced evolutionary patterns, we employed four protein coding markers (one mitochondrial and three nuclear) along with distribution wide sampling schemes and large sample sizes. In addition, possible ecological differences among the different intra-generic clades were explored. Genera appear to have originated in the north-eastern interior of South Africa, following novel habitats created through the Post-African I erosion cycle and dramatic changes in climate and phytogeography. In each genus, multiple geographically discrete genetic lineages (clades) are supported by both the mitochondrial and nuclear data. These lineages bear signature of the fragmentation of wider historical distributions through major environmental changes since the middle Miocene (major uplift events, Post-African II erosion cycle, drainage evolution of major river systems, sea-level fluctuations as well as climatic changes and vegetation shifts), thereby leading to long-term isolation. Along with protracted periods of separation, it appears that ecological differences further delimit the lineages in relation to geology, phytogeographic preference, elevation, rainfall and temperature. As such, two lineages in Georychus (Clades 1 and 2) and one lineages in Cryptomys (Clade I) occur at higher elevations above the Great Escarpment (in older deposits harbouring grassland vegetation, with higher rainfall and lower daily temperatures), with the remaining lineages within these genera (Clades 3, 4 and 5 in Georychus and Clades III and IV in Cryptomys) occupying a low-land distribution with contrasting climatic and geological characteristics. Although significant differences in ecological variables were also observed between Bathyergus clades, these were not consistent, given their largely low-land distributions. Our results corroborate and expand previous suggestions that several cryptic species are present within the South African Bathyergidae.
穴兔科（包括六个属）是一组特产于撒哈拉以南非洲的地下啮齿动物。我们对南非穴兔属（Georychus）、滨兔属（Bathyergus）和毛丝鼠属（Cryptomys）的进化和物种丰富度的了解有限，大多数物种在 IUCN 红色名录中被列为“无危”。遗传数据表明，这些属中可能存在几个隐种。为了探索遗传和生态上的独特性，并评估 Georychus、Bathyergus 和在较小程度上 Cryptomys 的分类丰富度，同时评估历史上可能影响进化模式的各种情况，我们使用了四个蛋白质编码标记（一个线粒体标记和三个核标记），以及广泛的分布采样方案和大样本量。此外，还探讨了不同种内分支之间可能存在的生态差异。这些属似乎起源于南非东北部内陆，是在非洲后侵蚀循环和气候与植物地理剧烈变化所创造的新栖息地之后出现的。在每个属中，线粒体和核数据都支持多个地理上离散的遗传谱系（分支）。这些谱系具有通过从中新世中期以来的重大环境变化（主要隆起事件、非洲后 II 侵蚀循环、主要河流系统的排水演化、海平面波动以及气候变化和植被变化）导致更广泛历史分布碎片化的特征，从而导致长期隔离。除了长期的分离之外，看来生态差异进一步限制了与地质、植物地理偏好、海拔、降雨量和温度有关的谱系。因此，Georychus 中的两个谱系（分支 1 和 2）和 Cryptomys 中的一个谱系（分支 I）出现在大悬崖以上的较高海拔（在较老的沉积物中，含有草原植被，降雨量较高，日温差较低），而这些属中的其余谱系（Georychus 中的分支 3、4 和 5 和 Cryptomys 中的分支 III 和 IV）则分布在低地，具有截然不同的气候和地质特征。尽管在滨兔属的各分支之间也观察到生态变量的显著差异，但鉴于它们主要分布在低地，这些差异并不一致。我们的研究结果证实并扩展了先前的建议，即南非穴兔科中存在几个隐种。
