Department of Zoology, Comenius University in Bratislava, Bratislava, 84215, Slovak Republic.
Department of Biological Sciences, University of Ulsan, Ulsan, 44610, Korea.
Sci Rep. 2017 Aug 30;7(1):9918. doi: 10.1038/s41598-017-09472-y.
Ciliates are a suitable microbial model to investigate trait-dependent diversification because of their comparatively complex morphology and high diversity. We examined the impact of seven intrinsic traits on speciation, extinction, and net-diversification of rhynchostomatians, a group of comparatively large, predatory ciliates with proboscis carrying a dorsal brush (sensoric structure) and toxicysts (organelles used to kill the prey). Bayesian estimates under the binary-state speciation and extinction model indicate that two types of extrusomes and two-rowed dorsal brush raise diversification through decreasing extinction. On the other hand, the higher number of contractile vacuoles and their dorsal location likely increase diversification via elevating speciation rate. Particular nuclear characteristics, however, do not significantly differ in their diversification rates and hence lineages with various macronuclear patterns and number of micronuclei have similar probabilities to generate new species. Likelihood-based quantitative state diversification analyses suggest that rhynchostomatians conform to Cope's rule in that their diversity linearly grows with increasing body length and relative length of the proboscis. Comparison with other litostomatean ciliates indicates that rhynchostomatians are not among the cladogenically most successful lineages and their survival over several hundred million years could be associated with their comparatively large and complex bodies that reduce the risk of extinction.
纤毛虫是研究特征依赖性多样化的合适微生物模型，因为它们具有相对复杂的形态和高度多样性。我们研究了七个内在特征对有吻毛目纤毛虫（一群相对较大的、捕食性的纤毛虫，具有携带背毛刷（感觉结构）和毒囊（用于杀死猎物的细胞器）的吻毛）的物种形成、灭绝和净多样化的影响。二态物种形成和灭绝模型的贝叶斯估计表明，两种类型的挤出体和两排背毛刷通过降低灭绝来提高多样化。另一方面，更多的收缩泡及其背部位置可能通过提高物种形成率来增加多样化。然而，特定的核特征在其多样化率方面没有显著差异，因此具有不同大核模式和微核数量的谱系产生新物种的可能性相似。基于似然的定量状态多样化分析表明，有吻毛目纤毛虫符合科普规则，即它们的多样性随体长和吻毛相对长度的增加呈线性增长。与其他有毛目纤毛虫的比较表明，有吻毛目纤毛虫并不是分类上最成功的谱系之一，它们在数亿年的时间里得以幸存，这可能与其相对较大和复杂的身体有关，这降低了灭绝的风险。
