Department of Karyosystematics, Zoological Institute of Russian Academy of Sciences, Universitetskaya nab. 1, 199034, St. Petersburg, Russia.
Department of Ecology & Evolutionary Biology, University of California Santa Cruz, 95064, Santa Cruz, CA, USA.
Sci Rep. 2017 Aug 15;7(1):8199. doi: 10.1038/s41598-017-08525-6.
Despite predictions of the classic, hybrid-sterility model of chromosomal speciation, some organisms demonstrate high rate of karyotype evolution. This rate is especially impressive in Agrodiaetus butterflies that rapidly evolved the greatest chromosome number diversity known in animal kingdom within a single subgenus. Here we analyzed karyotype evolution in Agrodiaetus using phylogenetic comparative methods. We found that chromosome numbers possess a strong phylogenetic signal. This disproves the chromosome megaevolution model that proposes multiple chromosome rearrangements to accumulate independently in each of closely related species. We found that Brownian motion gives a more adequate description of observed trait changes than Ornstein-Uhlenbeck model. This indicates that chromosome numbers evolve via random walk along branches of the phylogeny. We discovered a correlation between karyotype changes and phylogeny branch lengths. This gradual pattern is inconsistent with the hybrid-sterility model which, due to association of major chromosome changes with cladogenetic events, predicts a high degree of punctualism in karyotype evolution. Thus, low underdominace of chromosomal rearrangements and/or prevalence of the recombination-suppression model over the hybrid-sterility model of chromosome speciation are the most common engines of the runaway chromosome number change observed.
尽管存在经典的染色体物种形成杂种不育模型的预测，但有些生物表现出很高的染色体组进化率。在 Agrodiaetus 蝴蝶中，这种速率尤为显著，它们在一个亚属内迅速进化出了动物界已知的最大染色体数目多样性。在这里，我们使用系统发育比较方法分析了 Agrodiaetus 的染色体组进化。我们发现染色体数目具有很强的系统发育信号。这否定了染色体巨型进化模型，该模型提出多个染色体重排可以在密切相关的物种中独立积累。我们发现布朗运动比奥恩斯坦-乌伦贝克模型更能充分描述观察到的特征变化。这表明染色体数目是通过沿着系统发育分支的随机游走进化的。我们发现了染色体组变化与系统发育分支长度之间的相关性。这种渐进模式与杂种不育模型不一致，因为主要染色体变化与分支事件相关，这预测了染色体组进化中的高度点状。因此，染色体重排的低劣势和/或重组抑制模型相对于染色体物种形成的杂种不育模型的普遍存在，是观察到的失控染色体数变化的最常见原因。
