Data from: The evolution of defense mechanisms correlate with the explosive diversification of autodigesting Coprinellus mushrooms (Agaricales, Fungi)

Bursts of diversification are known to have contributed significantly to the extant morphological and species diversity, but evidence for many of the theoretical predictions about adaptive radiations have remained contentious. Despite their tremendous diversity, patterns of evolutionary diversification and the contribution of explosive episodes in fungi are largely unknown. Here, using the genus Coprinellus (Psathyrellaceae, Agaricales) as a model, we report the first explosive fungal radiation, and infer that the onset of the radiation follows a change from a multi-layered to a much simpler defense structure on the fruiting bodies. We suggest that this change constitutes a key innovation, relaxing constraints on diversification imposed by nutritional investment into the development of protective tissues of fruiting bodies. Evidence for the impact of protective structures on diversification places our current understanding of fruiting body evolution in a new context. Fossil calibration suggests that Coprinellus mushrooms radiated during the Miocene coinciding with global radiation of large grazing mammals following expansion of dry open grasslands. In addition to diversification-rate based methods, we test the hard polytomy hypothesis, by analyzing the resolvability of internal nodes of the backbone of the putative radiation using Reversible-Jump MCMC. We discuss potential applications and pitfalls as well as how biologically meaningful polytomies can be distinguished from alignment shortcomings. Our data provide insights into the nature of adaptive radiations in general by revealing a deceleration of morphological diversification through time. The "rate" of morphological diversification was approximated by obtaining the temporal distribution of state changes in discrete traits along the trees and comparing it with the tempo of lineage accumulation. By using speciational trees, we found that the number of state changes correlate with the number of lineages, even in parts of the tree with short internal branches, and peaks around the onset of the explosive radiation followed by a slowdown, most likely because of the decrease in available niches.

物种多样化爆发对现存形态与物种多样性的贡献已得到广泛证实，但学界针对适应辐射（adaptive radiation）的诸多理论预测，相关实证始终存在争议。尽管真菌类群具有极高的物种多样性，但其演化多样化模式与爆发式演化事件的贡献程度，目前仍基本不明。本研究以小脆柄菇属（Coprinellus，粪伞科Psathyrellaceae，伞菌目Agaricales）为模型类群，首次报道了真菌的爆发式辐射演化，并推断该辐射的起始与子实体上的防御结构从多层结构简化为更简单结构的变化密切相关。我们认为该变化属于一项关键创新，缓解了因将营养资源投入子实体保护组织发育而对物种多样化造成的演化限制。防御结构对物种多样化产生影响的相关证据，为我们当前对子实体演化的认知提供了全新的研究框架。化石校准分析显示，小脆柄菇属的辐射演化发生于中新世，与干旱开阔草原扩张后全球大型植食哺乳动物的辐射演化时期高度吻合。除基于多样化速率的分析方法外，本研究还通过可逆跳跃马尔可夫链蒙特卡洛（Reversible-Jump MCMC）分析推定辐射演化主干的内部节点可解析性，以此检验硬多歧支假说（hard polytomy hypothesis）。我们还探讨了该研究的潜在应用场景与局限性，以及如何将具有生物学意义的多歧支与序列比对缺陷造成的伪多歧支加以区分。本研究通过揭示形态多样化随时间推移逐渐减速的规律，为理解适应辐射的本质提供了一般性的研究洞见。形态多样化的‘速率’通过以下方式近似估算：获取系统发育树离散性状状态变化的时间分布，并将其与谱系积累的演化速率进行对比。通过使用物种形成树（speciational trees）分析，我们发现性状状态变化的数量与谱系数量呈显著正相关，即使在内部分支较短的树结构中亦是如此；该相关性在爆发式辐射演化起始阶段达到峰值，随后逐渐放缓，这一现象很可能源于可利用生态位的不断减少。