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.

研究背景：传统上，学界普遍认为无尾目（Anura）动物的陆生繁殖演化源自水生繁殖的祖先类群，这一观点已被相关文献广泛认可。然而，部分依赖水环境的过渡类群的存在——例如将卵产在近水区域（如洞穴）而非自然水体中的物种——为“繁殖方式向更严格陆生方向逐步、有序演化”的假说提供了支撑。但这一传统观点近年来受到了部分无尾目类群研究的挑战。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，不同支系间的水环境依赖程度差异显著。本研究针对细趾蟾亚科验证了“陆生繁殖演化具有渐进性与有序性”的假说，包括验证半陆生繁殖策略这类强制性过渡阶段的存在性；同时探讨了繁殖模式与形态、生态特征之间的关联。

研究结果：祖先性状重建分析结果显示，尽管在细趾蟾属（Leptodactylus）与腺蛙属（Adenomera）的演化历程中，存在从水生繁殖向陆生繁殖的性状转变，但从陆生繁殖转回水生繁殖的频率几乎与之相当。本研究结果还表明，半陆生蝌蚪的繁殖模式并非必然是水生与陆生繁殖之间的过渡类型。繁殖模式与其他生活史性状的相关性分析显示，蝌蚪生存环境、产卵量、婚刺以及卵的色素沉着存在协同演化关系，且受水环境依赖程度的驱动。

研究结论：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性证据。我们观察到从陆生蝌蚪发育转回水生繁殖的演化逆转现象，且未发现半陆生繁殖策略这类强制性过渡阶段的存在证据。同时本研究证实了繁殖模式与受水环境依赖驱动的其他生活史性状之间存在相关性：水生繁殖模式与更高的产卵量、静水环境，以及婚刺和卵色素沉着的存在显著相关。