The euglenids are a species-rich group of flagellates with varying modes of nutrition that can be found in diverse habitats. Phagotrophic members of this group gave rise to phototrophs and hold the key to understanding the evolution of euglenids as a whole, including the evolution of complex morphological characters like the euglenid pellicle. Yet to understand the evolution of these characters, a comprehensive sampling of molecular data is needed to correlate morphological and molecular data, and to estimate a basic phylogenetic backbone of the group. While the availability of SSU rDNA and, more recently, multigene data from phagotrophic euglenids has improved, several “orphan” taxa remain without any molecular data whatsoever. Dolium sedentarium is one such taxon: It is a rarely-observed phagotrophic euglenid that inhabits tropical benthic environments and is one of few known sessile euglenids. Based on morphological characters, it has been thought of as part of the earliest branch of euglenids, the Petalomonadida. We report the first molecular sequencing data for Dolium using single-cell transcriptomics, adding another small piece in the puzzle of euglenid evolution. Both SSU rDNA and multigene phylogenies confirm it as a solitary branch within Petalomonadida.

中文翻译：

---

无柄 Doliumsedetarium（一种花瓣单胞菌）的分子系统发育

眼虫是一群种类丰富的鞭毛虫，具有不同的营养模式，可以在不同的栖息地中找到。该类群的吞噬成员产生了光养生物，并掌握着理解眼虫整体进化的关键，包括眼虫皮膜等复杂形态特征的进化。然而，为了了解这些性状的进化，需要对分子数据进行全面采样，以关联形态学和分子数据，并估计该群体的基本系统发育主干。虽然 SSU rDNA 以及最近来自吞噬性眼虫的多基因数据的可用性有所改善，但一些“孤儿”类群仍然没有任何分子数据。Dolium sedentarium就是这样一个分类群：它是一种很少观察到的吞噬性眼虫，栖息在热带底栖环境中，也是少数已知的无柄眼虫之一。根据形态特征，它被认为是眼虫科最早的分支花瓣单胞菌属的一部分。我们利用单细胞转录组学报告了Dolium的第一个分子测序数据，为眼虫进化之谜又增添了一小部分。SSU rDNA 和多基因系统发育都证实它是花瓣单胞菌内的一个独立分支。