Data from: The genus Gennadas (Benthesicymidae: Decapoda): morphology of copulatory characters, phylogeny, and co-evolution of genital structures

Species within Gennadas differ from each other largely only in male (petasma) and female (thelycum) copulatory characters, which were restudied in scanning electron microscopy and used as a basis for phylogenetic analyses. Twenty-six petasma characters and 49 thelycum characters were identified. All sixteen recognized species of Gennadas and Aristaeomorpha foliacea (outgroup) were included as terminals. Four robust monophyletic clades were retrieved, described and diagnosed as new species groups. The thelycum characters had greater impact on tree topology and supported deeper nodes than did the petasma characters. We hypothesize that aspects of the thelycum evolved first followed by aspects of the petasma. Relatively more conservative characters include parts of the anterior sternites of the thelycum and of the petasma, while the scuti and protuberances on the thelycum and the shape and subdivisions of the petasma lobes are evolutionary plastic. We identified two groups of copulatory characters, which are likely coupled functionally and interlinked evolutionarily: (1) the external part of the petasma and the posterior part of the thelycum and (2) the internal part of the petasma and anterior part of the thelycum. We reconstruct possible mating position during copulation for each of the new species groups presented here. We also present an updated key to species of Gennadas.Gennadas属内各物种间的差异，主要仅体现于雄性（petasma，雄性交接器）与雌性（thelycum，雌性交接器）的交配器官特征。本研究通过扫描电子显微镜（scanning electron microscopy）对上述特征开展了重新研究，并以此作为系统发育分析的基础。 本次研究共鉴定出26个雄性交接器特征与49个雌性交接器特征。纳入分析的终端类群涵盖Gennadas属目前已确认的全部16个物种，以及外类群Aristaeomorpha foliacea（叶形樱虾）。 本研究检索得到4个支持度较高的单系演化支（monophyletic clades），并将其描述、界定为新的物种组。相较于雄性交接器特征，雌性交接器特征对系统树拓扑结构的影响更为显著，且能够更好地支撑更深层级的系统发育节点。我们推测，雌性交接器的相关特征演化早于雄性交接器。 相对保守的特征包括雌性交接器的前腹甲部分以及雄性交接器的相关结构；而雌性交接器上的盾片（scuti）与突起，以及雄性交接器叶瓣的形态与细分方式则具有演化可塑性。 我们鉴定出两类可能在功能上偶联、演化上相互关联的交配器官特征：（1）雄性交接器的外部区域与雌性交接器的后部区域；（2）雄性交接器的内部区域与雌性交接器的前部区域。 针对本文提出的各新物种组，我们重建了其交配过程中可能的交配体位。此外，本研究还更新了Gennadas属物种的分类检索表。