Abstract. Poecilogony is the intraspecific variation in developmental mode, with larvae of different types produced by the same individual, population or species. It is very rare among marine invertebrates, and in gastropods has long been described only in a few opisthobranchs. The physiological and regulatory mechanisms underlying larval evolutionary transitions, such as loss of planktotrophy that occurred repeatedly in many caenogastropod lineages, are still largely unknown. We have studied the inter- v. intraspecific variation in larval development in the north-east Atlantic neogastropod genus Raphitoma Bellardi, 1847, starting with an iterative taxonomy approach: 17 morphology-based Preliminary Species Hypotheses were tested against a COI molecular-distance-based method (ABGD), and the retained species hypotheses were eventually inspected for reciprocal monophyly on a multilocus dataset. We subsequently performed an ancestral state reconstruction on an ultrametric tree of the 10 Final Species Hypotheses, time-calibrated by fossils, revealing that the interspecific changes were planktotrophy > lecithotrophy, and all have occurred in the Pleistocene, after 2.5 million years ago. This is suggestive of a major role played by Pleistocene Mediterranean oceanographic conditions – enhanced oligotrophy, unpredictable availability of water column resources – likely to favour loss of planktotrophy. Within this group of species, which has diversified after the Miocene, we identified one pair of sibling species differing in their larval development, Raphitoma cordieri (Payraudeau, 1826) and R. horrida (Monterosato, 1884). However, we also identified two Final Species Hypotheses, each comprising individuals with both larval developmental types. Our working hypothesis is that they correspond to one or two poecilogonous species. If confirmed by other nuclear markers, this would be the first documentation of poecilogony in the Neogastropoda, and the second in the whole Caenogastropoda. Although sibling species with different developmental strategies may offer good models to study some evolutionary aspects, poecilogonous taxa are optimally suited for identifying regulatory and developmental mechanisms underlying evolutionary transitions.

中文翻译：

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Neogastropoda 中 poecilogony 的候选案例：对 Raphitoma Bellardi 属系统学的影响，1847

摘要。Poecilogony 是发育模式的种内变异，同一个体、种群或物种产生不同类型的幼虫。它在海洋无脊椎动物中非常罕见，而在腹足类动物中，长期以来仅在少数背鳃类动物中被描述过。幼虫进化转变的生理和调节机制，例如在许多 caenogastropod 谱系中反复发生的浮游生物的丧失，在很大程度上仍然是未知的。我们研究了东北大西洋新腹足动物属 Raphitoma Bellardi 幼虫发育的种间变异，1847 年，从迭代分类法开始：17 个基于形态学的初步物种假设针对基于 COI 分子距离的假设进行了测试方法（ABGD），并且最终在多位点数据集上检查了保留物种假设的相互单系性。随后，我们对 10 种最终物种假设的超测量树进行了祖先状态重建，通过化石进行了时间校准，揭示了种间变化是浮游生物 > 卵磷脂，并且都发生在 250 万年前的更新世。这表明更新世地中海海洋条件发挥了重要作用——贫营养增强、水柱资源的不可预测性——可能有利于浮游生物的丧失。在这组在中新世之后多样化的物种中，我们确定了一对在幼虫发育方面不同的同胞物种，Raphitoma cordieri (Payraudeau, 1826) 和 R. horrida (Monterosato, 1884)。然而，我们还确定了两个最终物种假设，每个假设都包含具有两种幼虫发育类型的个体。我们的工作假设是它们对应于一两个 poecilogonous 物种。如果得到其他核标记的证实，这将是新腹足类动物源源学的第一个记录，也是整个Caenogastropoda 的第二个记录。尽管具有不同发育策略的同胞物种可能为研究某些进化方面提供了很好的模型，但异源分类群最适合识别进化转变的调控和发育机制。这将是新腹足类动物源源学的第一个文献，也是整个 Caenogastropoda 中的第二个文献。尽管具有不同发育策略的同胞物种可能为研究某些进化方面提供了很好的模型，但异源分类群最适合识别进化转变的调控和发育机制。这将是新腹足类动物源源学的第一个文献，也是整个 Caenogastropoda 中的第二个文献。尽管具有不同发育策略的同胞物种可能为研究某些进化方面提供了很好的模型，但异源分类群最适合识别进化转变的调控和发育机制。