The case of the missing ancient fungal polyploids

Polyploidy—the increase in the number of whole chromosome sets—is an important evolutionary force in eukaryotes. Polyploidy is well recognized throughout the evolutionary history of plants and animals, where several ancient events have been hypothesized to be drivers of major evolutionary radiations. However, fungi provide a striking contrast: while numerous recent polyploids have been documented, ancient fungal polyploidy is virtually unknown. We present a survey of known fungal polyploids that confirms the absence of ancient fungal polyploidy events. Three hypotheses may explain this finding. First, ancient fungal polyploids are indeed rare, with unique aspects of fungal biology providing similar benefits without genome duplication. Second, fungal polyploids are not successful in the long term, leading to few extant species derived from ancient polyploidy events. Third, ancient fungal polyploids are difficult to detect, causing the real contribution of polyploidy to fungal evolution t...多倍体（polyploidy）——即整套染色体组数量的增加——是真核生物中一项关键的进化驱动力。多倍体现象在动植物的演化历史中已被广泛证实，多项古多倍化事件被认为是引发重大进化辐射的核心驱动因素。然而真菌的演化模式却形成了鲜明反差：尽管已有大量近期形成的真菌多倍体被记录在册，但古真菌多倍体现象几乎从未被发现。本研究通过对已知真菌多倍体类群的系统性调研，证实了古真菌多倍体事件确实不存在。目前有三种假说可解释这一现象：其一，古真菌多倍体本就极为罕见，真菌生物学特性的独特之处使其无需通过基因组加倍即可获得类似的进化优势；其二，真菌多倍体类群无法在长期演化中取得演化成功，导致由古多倍化事件衍生的现存物种数量极少；其三，古真菌多倍体难以被检测识别，从而掩盖了多倍体对真菌演化的真实贡献……