Data from: Examination of hemiplasy, homoplasy and phylogenetic discordance in chromosomal evolution of the Bovidae

Robertsonian chromosomal fusions predominate in shaping the genomes of many species of Bovidae. These and other cytogenetic data (from 52 taxa representing 51 species and 9 tribes of Bovidae) were (i) examined for usefulness in defining phylogenetic relationships and (ii) subsequently mapped to a consensus tree based on mitochondrial and nuclear DNA gene sequences with divergence dates of the corresponding species calculated from cytochrome b sequences. This permitted persistence time estimates for the various rearrangements. The chromosomal data resulted in an unsupported higher-level topology, but with recognition of the monophyly of some genera and tribes within Bovidae. The distribution and temporal spread of character states on the species tree is suggestive of a restricted role for hemiplasy (the retention of an ancestral chromosomal polymorphism through multiple speciation events) and for introgression (resulting from secondary contact among taxa), processes that can potentially lead to phylogenetic discordance. We conclude that the most probable interpretation for these data is that genuine karyotypic homoplasy predominates, but that hemiplasy (and/or introgression) is a realistic hypothesis for the observed patterns of several shared characters in Bovidae.

罗伯逊染色体融合（Robertsonian chromosomal fusions）在塑造众多牛科（Bovidae）物种的基因组过程中占据主导地位。本研究整合了来自牛科9族、51种共52个类群的此类数据及其他细胞遗传学数据，(i) 评估其在界定系统发育关系方面的应用价值，(ii) 随后将这些数据映射至基于线粒体与核DNA基因序列构建的共识系统树，并通过细胞色素b（cytochrome b）序列计算对应物种的分化时间，由此可估算各类染色体重排的存续时长。染色体数据虽构建出未得到支持的高级支系拓扑结构，但明确了牛科内部分属及族的单系性。对物种树中各性状状态的分布与时序分布的分析表明，半同塑（hemiplasy，即祖先染色体多态性经多次物种形成事件得以保留）与基因渐渗（introgression，由类群间二次接触引发）的作用相对有限，而这两类过程均可能引发系统发育冲突。本研究最终认为，针对该数据最合理的解读是真正的核型同塑（karyotypic homoplasy）占据主导地位，但半同塑（和/或基因渐渗）可合理解释牛科中多个共有性状的观测分布模式。