Department of Evolutionary Zoology and Human Biology, University of Debrecen, Debrecen, Hungary.
Centre for Ecological Research, Institute of Aquatic Ecology, Budapest, Hungary.
J Evol Biol. 2023 Nov;36(11):1630-1640. doi: 10.1111/jeb.14231. Epub 2023 Oct 26.
The ecological and life history drivers of the diversification of reproductive modes in early vertebrates are not fully understood. Sharks, rays and chimaeras (group Chondrichthyes) have an unusually diverse variety of reproductive modes and are thus an ideal group to test the factors driving the evolution of reproductive complexity. Here, using 960 species representing all major Chondrichthyes taxa, we reconstruct the evolution of their reproduction modes and investigate the ecological and life history predictors of reproduction. We show that the ancestral Chondrichthyes state was egg-laying and find multiple independent transitions between egg-laying and live-bearing via an intermediate state of yolk-only live-bearing. Using phylogenetically informed analysis, we also show that live-bearing species have larger body size and larger offspring than egg-laying species. In addition, live-bearing species are distributed over shallow to intermediate depths, while egg-layers are typically found in deeper waters. This suggests that live-bearing is more closely associated with pelagic, rather than demersal habitats. Taken together, using a basal vertebrate group as a model, we demonstrat how reproductive mode co-evolves with environmental conditions and life-history traits.
早期脊椎动物生殖方式多样化的生态和生活史驱动因素尚未完全了解。鲨鱼、鳐鱼和𫚉鱼（软骨鱼纲）具有非常多样化的生殖方式，因此是测试生殖复杂性进化因素的理想群体。在这里，我们使用代表软骨鱼纲所有主要分类群的 960 个物种，重建了它们的生殖方式进化，并研究了生殖的生态和生活史预测因子。我们表明，软骨鱼纲的祖先状态是产卵，并发现通过仅产蛋黄的有活力的中间状态，从产卵到有活力的生殖之间存在多次独立的转变。使用基于系统发育的分析，我们还表明，有活力的生殖物种比产卵物种具有更大的体型和更大的后代。此外，有活力的生殖物种分布在浅至中等深度，而产卵物种通常存在于更深的水域。这表明有活力的生殖与浮游生物而不是底栖生物栖息地更为密切相关。总之，使用一个基础的脊椎动物群体作为模型，我们展示了生殖方式如何与环境条件和生活史特征共同进化。
