Abstract

Shell features are key factors for systematics and evolutionary biology studies of freshwater gastropods. Based mostly on shell morphology, 19 species of the springsnail genus Radomaniola (family Hydrobiidae) have been described. Although the scarce differentiation of various shell dimensions suggests morphological stasis, the evolutionary dynamics of shell and other anatomical structures have not yet been explored fully. By inferring a phylogeny and a time-calibrated species tree from mitochondrial (COI and 16S) and nuclear (28S) sequences of 15 recognized species, we initially examine the species diversity of the Radomaniola dataset and then, through phylogenetic comparative methods, assess the evolutionary correlation, pace and mode of 40 continuous shell and anatomical characters. By synthesizing the results of four species delimitation methods and through morphological examinations, we recognize 21 groups, for which taxonomy is discussed here. Seven new species are described. We reveal a high degree of correlated evolution between characters of the shell, which are constrained by a single morphological optimum, consistent with the morphological stasis model. Anatomical traits diverged rapidly in an unconstrained manner or toward multiple optima. These findings indicate that in order to understand the morphological evolution of springsnails, it is essential to examine different organs in detail.

中文翻译：

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蜗牛属 Radomaniola（Caenogastropoda：Hydrobiidae）的壳特征和解剖结构在 500 万年中显示出不同的进化速度和模式

摘要

贝壳特征是淡水腹足动物系统学和进化生物学研究的关键因素。主要基于贝壳形态，已经描述了 19 种春螺属Radomaniola （Hydrobiidae）。尽管各种壳尺寸的稀少差异表明形态停滞，但壳和其他解剖结构的进化动力学尚未得到充分探索。通过从 15 个已识别物种的线粒体（ COI和 16S）和核（28S）序列推断系统发育和时间校准的物种树，我们初步检查了Radomaniola的物种多样性数据集，然后通过系统发育比较方法，评估 40 个连续壳和解剖特征的进化相关性、速度和模式。通过综合四种物种划分方法的结果并通过形态学检查，我们识别出 21 个组，这里讨论了分类学。描述了七个新物种。我们揭示了壳的特征之间的高度相关进化，这些特征受单个形态最优值的约束，与形态停滞模型一致。解剖特征以不受限制的方式或向多重最优方向迅速分化。这些发现表明，为了了解蜗牛的形态进化，必须详细检查不同的器官。