期刊名称：Proceedings of the National Academy of Sciences
印刷版ISSN：0027-8424
电子版ISSN：1091-6490
出版年度：2015
卷号：112
期号：37
页码：11600-11605
DOI：10.1073/pnas.1507072112
语种：English
出版社：The National Academy of Sciences of the United States of America
摘要：SignificanceThe tempo of diversification of life can be accelerated by fortuitous ecological opportunity or by phenotypic innovation. In this study, we document how both factors are likely to have played a role in the origin and success of a major fungal lineage, the Teloschistaceae (comprising [~]1% of all fungi). Anthraquinone pigments are found in a widespread, but scattered, range of fungi and plants, but are particularly abundant in the lichen-forming Teloschistaceae, where they provide sunlight protection, especially needed when growing in arid deserts of the world. We found that anthraquinones evolved in these lichens, in conjunction with an ecological switch to exposed, rocky environments, allowing them to colonize swathes of unexploited habitats worldwide and sparking an acceleration in diversification. Adaptive radiations play key roles in the generation of biodiversity and biological novelty, and therefore understanding the factors that drive them remains one of the most important challenges of evolutionary biology. Although both intrinsic innovations and extrinsic ecological opportunities contribute to diversification bursts, few studies have looked at the synergistic effect of such factors. Here we investigate the Teloschistales (Ascomycota), a group of >1,000 lichenized species with variation in species richness and phenotypic traits that hinted at a potential adaptive radiation. We found evidence for a dramatic increase in diversification rate for one of four families within this order--Teloschistaceae--which occurred [~]100 Mya (Late Cretaceous) and was associated with a switch from bark to rock and from shady to sun-exposed habitats. This adaptation to sunny habitats is likely to have been enabled by a contemporaneous key novel phenotypic innovation: the production in both vegetative structure (thallus) and fruiting body (apothecia) of anthraquinones, secondary metabolites known to protect against UV light. We found that the two ecological factors (sun exposure and rock substrate) and the phenotypic innovation (anthraquinones in the thallus) were all significant when testing for state-dependent shifts in diversification rates, and together they seem likely to be responsible for the success of the Teloschistaceae, one of the largest lichen-forming fungal lineages. Our results support the idea that adaptive radiations are driven not by a single factor or key innovation, but require a serendipitous combination of both intrinsic biotic and extrinsic abiotic and ecological factors.
