Gilbert C, Maree S, Robinson T J
Evolutionary Genomics Group, Department of Botany and Zoology, University of Stellenbosch, Stellenbosch, South Africa.
Cytogenet Genome Res. 2008;121(2):110-9. doi: 10.1159/000125836. Epub 2008 Jun 9.
Golden moles (Chrysochloridae) are small, subterranean mammals endemic to sub-Saharan Africa that together with tenrecs constitute one of six orders in Afrotheria. Here we present a comprehensive karyotypic comparison among six species/subspecies of golden moles based on G-banding and chromosome painting. By expanding the species representation to include a further five species recently published in a companion paper, we were able to map the distribution of telomeric repeats in ten species/subspecies that are representative of six of the nine currently recognized genera. We conclude that: (i) the monophyly of Amblysomus is supported by the amplification of heterochromatin in several pericentric regions and one intrachromosomal rearrangement; (ii) A. hottentotus meesteri groups as sister to a clade that contains A. h. hottentotus, A. h. longiceps, A. h. pondoliae and A. robustus, an association that is underpinned by a shared intrachromosomal rearrangement and the detection of telomeric sequences in the centromeres of all chromosomes of the three A. hottentotus subspecies and A. robustus but, importantly, not in those of A. h. meesteri. These findings indicate an absence of gene flow suggesting that A. h. meesteri should be elevated to specific status. We hypothesize that the lack of gene flow may, in part, reflect hybrid dysgenesis resulting from abnormal meiotic segregation as a consequence of differences in the nature of the centromeric specific satellites; (iii) chromosomes 7 and 13 of Chrysochloris asiatica are fused in both Calcochloris obtusirostris and Eremitalpa granti, but that the position of the centromere in the fused chromosome differs in each species. This suggests that rather than being indicative of common ancestry, the fusion is more likely a convergent character which has arisen independently in each lineage. Furthermore our painting data show two centromeric shifts that are probably autapomorphic for C. obtusirostris. Finally, we conclude that (iv) golden moles are characterized by strong karyotypic conservatism but in marked contrast to the constrained rates of change exhibited by most species, A. robustus is unique in that three autapomorphic fissions define its evolutionary history, and hence the more extensive reshuffling of its genome.
金毛鼹（金毛鼹科）是撒哈拉以南非洲特有的小型地下哺乳动物，与马岛猬一起构成非洲兽总目中六个目之一。在此，我们基于G带和染色体涂染技术，对六种金毛鼹物种/亚种进行了全面的核型比较。通过扩大物种范围，纳入另一篇相关论文中最近发表的另外五个物种，我们得以绘制出十个物种/亚种端粒重复序列的分布图，这些物种/亚种代表了目前九个已确认属中的六个。我们得出以下结论：（i）在几个近心区域异染色质的扩增和一次染色体内重排支持了钝鼹属的单系性；（ii）梅氏金毛鼹与包含霍屯督金毛鼹、长头金毛鼹、蓬多利亚金毛鼹和粗壮金毛鼹的一个分支构成姐妹群，这种关联由一个共享的染色体内重排以及在三个霍屯督金毛鼹亚种和粗壮金毛鼹所有染色体的着丝粒中检测到端粒序列所支撑，但重要的是，在梅氏金毛鼹的染色体着丝粒中未检测到。这些发现表明不存在基因流动，这意味着梅氏金毛鼹应被提升为独立物种。我们推测基因流动的缺乏可能部分反映了由于着丝粒特异性卫星性质差异导致减数分裂分离异常而产生的杂种不育；（iii）亚洲金毛鼹的7号和13号染色体在钝吻金毛鼹和格兰特金毛鼹中均发生了融合，但融合染色体中着丝粒的位置在每个物种中有所不同。这表明这种融合并非共同祖先的指示，而更可能是每个谱系中独立出现的趋同特征。此外，我们的涂染数据显示了两个可能是钝吻金毛鼹独有的着丝粒移位。最后，我们得出结论：（iv）金毛鼹具有很强的核型保守性，但与大多数物种所表现出的有限变化速率形成鲜明对比的是，粗壮金毛鼹独特之处在于三次独有的裂变定义了其进化历史，从而导致其基因组更广泛的重排。
