San Diego Zoo Institute for Conservation Research, San Diego Zoo Global, 15600 San Pasqual Valley Road, Escondido, CA 92027.
J Hered. 2014 May-Jun;105(3):324-33. doi: 10.1093/jhered/esu004. Epub 2014 Feb 10.
Robertsonian (Rb) translocations, in particular centric fusions, are thought to play a primary role in evolution and speciation of the Bovidae family. However, Rb fusions are often polymorphic within species, being suggested as phylogenetically uninformative characters. This work studies chromosome variation in 72 captive individuals of 6 species of Alcelaphini (Antilopinae): The hartebeest (genus Alcelaphus), hirola (Beatragus), black and blue wildebeests (Connochaetes), and the topi and bontebok (Damaliscus). We infer the phylogenic relationships among Alcelaphini species and determine patterns of chromosomal evolution using G-banded karyotypes and complete mitochondrial genome sequences. The molecular phylogeny showed an early divergence of Connochaetes, followed by the split of Alcelaphus plus Beatragus + Damaliscus as sister taxa. Mitochondrial and chromosomal phylogenies only differed in the position of the critically endangered Beatragus, likely due to homoplasic chromosome characters. Patterns of chromosome evolution, reconstructed using a probabilistic approach, suggest that chromosome changes leading to speciation in Alcelaphini do not exclusively involve consecutive reduction of diploid number through centric fusion but also the losses and reversions of Rb translocations in Beatragus and Damaliscus lineages. Our results provide evidence that complex scenarios of chromosomal rearrangements can be detected in relatively recent-diverged bovids, as in this group of antelopes.
罗伯逊易位（Rb），特别是着丝粒融合，被认为在牛科家族的进化和物种形成中起主要作用。然而，Rb 融合在物种内通常是多态的，被认为是系统发育上无信息的特征。这项工作研究了 6 种 Alcelaphini（Antilopinae）中的 72 只圈养个体的染色体变异：黑斑羚（属 Alcelaphus）、黑角马（Beatragus）、黑和蓝角马（Connochaetes），以及转角牛羚和马羚（Damaliscus）。我们推断了 Alcelaphini 物种之间的系统发育关系，并使用 G 带核型和完整的线粒体基因组序列确定了染色体进化模式。分子系统发育表明 Connochaetes 早期分化，随后是 Alcelaphus 加 Beatragus + Damaliscus 作为姐妹分类群的分裂。线粒体和染色体系统发育仅在濒危的 Beatragus 的位置上有所不同，这可能是由于染色体特征的同型性。使用概率方法重建的染色体进化模式表明，导致 Alcelaphini 物种形成的染色体变化不仅涉及通过着丝粒融合连续减少二倍体数量，还涉及 Beatragus 和 Damaliscus 谱系中 Rb 易位的丢失和回复。我们的结果提供了证据，表明在相对近期分化的牛科动物中，可以检测到复杂的染色体重排场景，就像在这群羚羊中一样。
