Morphological and genetic variability of assemblages of <i>Cyclotella ocellata</i> Pantocsek/<i>C. comensis</i> Grunow complex (Bacillariophyta, Thalassiosirales)

Centric diatom taxa in the <i>Cyclotella ocellata</i> and <i>C. comensis</i> complexes show high morphological variability and often apparently continuous morphological transitions. In this study, we investigated natural assemblages of the <i>C. ocellata/C. comensis</i> complex from Hungarian and Croatian lakes and from Turkish streams using morphological and molecular methods. The studied assemblages contained cells with morphologies resembling <i>C. ocellata</i> as well as other, closely related, species: <i>C. comensis</i>, <i>C. pseudocomensis</i>, <i>C. costei</i>, and <i>C. trichnoidea</i>. The goal of our paper was to assess whether the observed morphological differences were due to intraspecific variability or suggest the existence of several, putatively distinct species.Ten morphometric characters were measured, which, either individually, or in pairs, did not differentiate the nominal taxa in our assemblages. However, multivariate discriminant analysis has revealed a group including <i>C. ocellata</i> and <i>C. trichonidea</i> morphologies could be separated from another containing <i>C. comensis</i>, <i>C. pseudocomensis</i> and <i>C. costei</i>.A nuclear (18S rDNA) and a chloroplast (<i>rbc</i>L) gene were amplified and partially sequenced from environmental DNA or from isolated cells. The sequences showed little variability among the assemblages and nominal species. Although general congruence of molecular and morphometric separation supports the species level separation of <i>C. ocellata/trichonidea</i> from the probably conspecific <i>C. comensis</i>/<i>pseudocomensis</i>/<i>costei</i>, sequence divergences between the groups are in the same range as within them, so that a conspecificity of all four taxa cannot be unequivocally excluded.

眼斑圆筛藻（Cyclotella ocellata）与科门西斯圆筛藻（C. comensis）复合群中的中心硅藻类群，展现出极高的形态变异性，且常呈现近乎连续的形态过渡。本研究采用形态学与分子生物学方法，对采自匈牙利、克罗地亚湖泊及土耳其溪流的眼斑圆筛藻/科门西斯圆筛藻复合群自然群落开展调查。所获群落中，不仅包含形态近似眼斑圆筛藻的细胞，还涵盖了其他近缘物种：科门西斯圆筛藻（C. comensis）、假科门西斯圆筛藻（C. pseudocomensis）、科斯蒂圆筛藻（C. costei）与毛状圆筛藻（C. trichnoidea）。本研究的核心目标为：探究观测到的形态差异究竟源于种内变异，还是暗示存在多个疑似独立的物种。研究共测定10项形态计量特征，无论单独使用还是两两组合，均无法区分调查群落中的命名类群。但多变量判别分析结果显示，包含眼斑圆筛藻与毛状圆筛藻（C. trichonidea）形态类群的组别，可与涵盖科门西斯圆筛藻、假科门西斯圆筛藻及科斯蒂圆筛藻的组别相区分。研究人员从环境DNA或分离得到的单胞中，扩增并部分测序了核基因18S rDNA与叶绿体基因rbcL。序列在各群落及命名类群间仅存在极微弱的变异性。尽管分子与形态计量分类结果的整体一致性，支持将眼斑圆筛藻/毛状圆筛藻类群与疑似同种的科门西斯圆筛藻/假科门西斯圆筛藻/科斯蒂圆筛藻类群划分至物种层级，但类群间的序列分化度与类群内部的分化度处于同一范围，因此无法明确排除这四个类群为同一物种的可能性。

搜集汇总

背景与挑战

背景概述

该数据集聚焦于硅藻Cyclotella ocellata和C. comensis复合体的形态与遗传变异性研究，通过分析来自匈牙利、克罗地亚和土耳其的自然群体，结合形态测量和分子测序方法，探讨了这些分类群之间的物种区分问题。研究发现，尽管形态学分析支持将C. ocellata/trichonidea与C. comensis/pseudocomensis/costei分离，但遗传序列差异较小，无法排除所有分类群为同种的可能性。