Data from: Ancestral reconstruction of reproductive traits shows no tendency toward terrestriality in Leptodactyline frogs

Background:Traditionally, the evolution of terrestrial reproduction in anurans from ancestors that bred in water has been accepted in the literature. Still, the existence of intermediate stages of water dependency, such as species that lay eggs close to water (e.g., in burrows) instead of in bodies of water, supports the hypothesis of an ordered and gradual evolution in the direction of a more terrestrial form of reproduction. However, this conventional view has recently been challenged for some anurans groups. Leptodactylinae frogs are a remarkable example of anurans with an outstanding diversity in terms of reproductive features, with distinct water dependency among lineages. Here, we tested the hypothesis of a gradual and ordered tendency towards terrestriality in Leptodactylinae, including the existence of obligatory intermediate stages, such as semi-terrestrial reproductive strategies. We also addressed the association between reproductive modes and the morphological and ecological features. Results: An ancestral reconstruction analysis indicated that even though shifts from aquatic to terrestrial breeding occurred throughout the history of Leptodactylus and Adenomera, shifts from terrestrial to aquatic reproduction happened at almost the same frequency. Our results also demonstrated that reproductive modes for semi-terrestrial tadpoles were not necessarily an intermediate form between aquatic and terrestrial breeds. Correlations among reproductive modes and other life-history traits suggested that tadpole environment, clutch size, nuptial spines, and egg pigmentation were co-evolving and driven by water dependency. Conclusions: Our results found no evidence of evolutionary tendencies toward terrestriality in Leptodactylinae. We found reversals from terrestrial to aquatic tadpole development and no evidence of obligatory intermediate stages, such as semi-terrestrial reproductive strategies. We also found correlations between reproductive modes and other life-history traits driven by water dependence. Aquatic reproductive modes are associated with higher clutch sizes, lentic waters, and the presence of nuptial spines and egg pigmentation.

背景：传统上，学界普遍认为无尾目（Anura）的陆生繁殖演化起源于水生繁殖的祖先类群。不过，仍存在一类对水具有中等依赖程度的过渡阶段类群——例如将卵产在水域附近（如洞穴中）而非水体内部的物种，这支持了“繁殖方式向更陆生方向有序且渐进演化”的假说。但近年来，这一传统观点受到了部分无尾目类群相关研究的挑战。细趾蟾亚科（Leptodactylinae）蛙类是无尾目中繁殖特征多样性极为突出的类群，不同演化支之间的水依赖程度差异显著。本研究针对细趾蟾亚科验证了“陆生繁殖趋势具有渐进性与有序性”的假说，其中包括半陆生繁殖策略这类必需的过渡阶段。此外，本研究还探讨了繁殖模式与形态、生态特征之间的关联。结果：祖先特征重建（ancestral reconstruction）分析显示，尽管在细趾蟾属（Leptodactylus）和腺趾蟾属（Adenomera）的演化历史中，存在从水生繁殖向陆生繁殖的转变，但从陆生繁殖转向水生繁殖的频率几乎与之相当。研究结果还表明，半陆生蝌蚪的繁殖模式未必是水生繁殖与陆生繁殖之间的过渡形式。繁殖模式与其他生活史性状（life-history traits）之间的相关性分析显示，蝌蚪生存环境、产卵量（clutch size）、婚刺（nuptial spines）以及卵的色素沉着存在协同演化关系，且受水依赖程度驱动。结论：本研究未发现细趾蟾亚科存在向陆生繁殖方向演化的趋势。我们观察到从陆生蝌蚪发育向水生发育的逆转现象，且未发现存在诸如半陆生繁殖策略这类必需的过渡阶段的证据。此外，本研究还发现繁殖模式与受水依赖程度驱动的其他生活史性状之间存在关联：水生繁殖模式与更高的产卵量、静水环境（lentic waters），以及婚刺和卵色素沉着的存在相关联。