Department of Botany, Faculty of Science, Charles University, Benátská 2, CZ-12800, Prague, Czech Republic.
Institute of Botany, The Czech Academy of Sciences, Zámek 1, CZ-25243, Průhonice, Czech Republic.
J Phycol. 2019 Aug;55(4):912-923. doi: 10.1111/jpy.12882. Epub 2019 Jun 24.
The evolution of phenotypes is highly understudied in protists, due to the dearth of morphological characters, missing fossil record, and/or unresolved phylogeny in the majority of taxa. The chrysophyte genus Mallomonas (Stramenopiles) forms species-specific silica scales with extraordinary diversity of their ornamentation. In this paper, we molecularly characterized three additional species to provide an updated phylogeny of 43 species, and combined this with evaluations of 24 morphological traits. Using phylogenetic comparative methods, we evaluated phylogenetic signal in traits, reconstructed the trait evolution, and compared the overall phylogenetic and morphological diversity. The majority of traits showed strong phylogenetic signal and mostly dynamic evolution. Phylogenetic relatedness was often reflected by the phenotypic similarity. Both V-rib and dome are very conservative structures that are presumably involved in precise scale overlap and bristle attachment, respectively. Based on modern species, it seems the dome firstly appeared on apical and/or caudal scales, and only later emerged on body scales. Bristle was presumably present in the common ancestor and gradually elongated ever since. However, most other morphological traits readily changed during the evolution of Mallomonas.
由于形态特征缺乏、化石记录缺失和/或大多数分类群的系统发育未解决，原生动物中的表型进化研究还很不充分。金藻门的卵囊藻属（不等鞭毛类）形成具有特殊装饰性的种特异性硅质鳞片。在本文中，我们对另外三个物种进行了分子鉴定，为 43 个物种的更新系统发育提供了依据，并将其与 24 个形态特征的评估相结合。利用系统发育比较方法，我们评估了特征的系统发育信号，重建了特征进化，并比较了总体的系统发育和形态多样性。大多数特征显示出强烈的系统发育信号和动态进化。形态相似性通常反映了系统发育上的亲缘关系。V 肋和圆顶都是非常保守的结构，分别用于精确的鳞片重叠和刚毛附着。基于现代物种，圆顶似乎首先出现在顶部和/或尾部鳞片上，然后才出现在身体鳞片上。刚毛可能存在于共同祖先中，并自此逐渐延长。然而，在卵囊藻属的进化过程中，大多数其他形态特征很容易发生变化。
