Department of Biological, Geological and Environmental Sciences-University of Bologna, via Selmi 3, 40126, Bologna, Italy.
Zoology Section, Natural History Museum of Denmark-University of Copenhagen, Universitetsparken 15, 2100, Copenhagen, Denmark.
Sci Rep. 2022 Mar 23;12(1):4931. doi: 10.1038/s41598-022-08873-y.
The class Branchiopoda, whose origin dates back to Cambrian, includes ~ 1200 species which mainly occupy freshwater habitats. The phylogeny and systematics of the class have been debated for long time, until recent phylogenomic analyses allowed to better clarify the relationships among major clades. Based on these data, the clade Anostraca (fairy and brine shrimps) is sister to all other branchiopods, and the Notostraca (tadpole shrimps) results as sister group to Diplostraca, which includes Laevicaudata + Spinicaudata (clam shrimps) and Cladoceromorpha (water fleas + Cyclestherida). In the present analysis, thanks to an increased taxon sampling, a complex picture emerges. Most of the analyzed mitogenomes show the Pancrustacea gene order while in several other taxa they are found rearranged. These rearrangements, though, occur unevenly among taxa, most of them being found in Cladocera, and their taxonomic distribution does not agree with the phylogeny. Our data also seems to suggest the possibility of potentially homoplastic, alternative gene order within Daphniidae.
枝角目，其起源可追溯到寒武纪，包括约 1200 种，主要栖息在淡水生境中。该目的系统发育和分类学长期以来一直存在争议，直到最近的系统基因组分析才更好地阐明了主要分支之间的关系。基于这些数据，鳃足亚纲（仙女虾和卤虫）是所有其他鳃足目动物的姐妹群，而无甲目（豆娘虾）则与双甲目（瓣尾类 + 栉尾类）形成姐妹群，后者包括鳃足亚纲（水蚤 + 哲水蚤）和真虾总目（枝角类 + 桡足类）。在本分析中，由于增加了分类群采样，出现了一个复杂的情况。大多数分析的线粒体基因组显示出泛甲壳动物的基因排列，而在其他几个分类群中则发现它们发生了重排。这些重排虽然在分类群中分布不均匀，但大多数发生在枝角类中，而且它们的分类分布与系统发育不一致。我们的数据似乎还表明，在盘肠溞科内部可能存在潜在的同形、替代基因排列。
