Department of Microbiology, Faculty of Science and Informatics, University of Szeged, Kozep fasor 52., H-6726 Szeged, Hungary.
Syst Biol. 2012 Jul;61(4):595-607. doi: 10.1093/sysbio/sys002. Epub 2012 Jan 4.
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 correlates with a change from a multilayered to a much simpler defense structure on the fruiting bodies. We hypothesize that this change constitutes a key innovation, probably relaxing constraints on diversification imposed by nutritional investment into the development of protective tissues of fruiting bodies. 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 of this approach 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 dynamics 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. 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.
爆发式多样化被认为对现存的形态和物种多样性做出了重大贡献，但许多关于适应性辐射的理论预测的证据仍然存在争议。尽管真菌具有巨大的多样性，但进化多样化的模式以及真菌中爆发事件的贡献在很大程度上仍不为人知。在这里，我们使用 Coprinellus 属（Psathyrellaceae，Agaricales）作为模型，报告了第一个真菌爆发辐射，并推断辐射的开始与生殖体防御结构从多层结构转变为更简单的结构有关。我们假设这种变化构成了一个关键的创新，可能会放宽对营养物质投入到生殖体保护组织发育的多样化限制。化石校准表明，Coprinellus 蘑菇在中新世辐射，与全球大型食草哺乳动物的辐射同时发生，这是由于干燥开阔草原的扩张。除了基于多样化率的方法，我们还通过使用可逆跳跃 MCMC 分析潜在辐射骨干内部节点的可解决性来检验硬多系假说。我们讨论了这种方法的潜在应用和陷阱，以及如何区分有意义的多系和对齐缺陷。我们的数据通过揭示形态多样化随时间的减速，为一般适应性辐射的性质提供了新的认识。通过获得离散特征沿树的状态变化的时间分布，并将其与谱系积累的节奏进行比较，我们可以近似形态多样化的动态。我们发现状态变化的数量与谱系的数量相关，即使在内部分支较短的树的部分也如此，并且在爆发性辐射开始时达到峰值，随后放缓，这很可能是因为可用生态位的减少。
