金牛肝菌属的起源与区域物种分化研究

The species of the genus Aureoboletus, belonging to the family Boletaceae, are edible mushrooms and always form ectomycorrhizal symbiosis with the plants of Fagaceae and Pinaceae. They have important values in economy and ecology. Being different from the knowledge available, our preliminary study indicated that clearly geographic distribution patterns exist in Aureoboletus, which promotes a further research on the origin and evolution of Aureoboletus. Although this small to medium-sized genus does not harbor many species, it is widely distributed in the six continents, namely Africa, Asia, Europe, North America, South America and Oceania. Could such distribution patterns be resulted from the vicariance due to its early origin, or from long distance dispersal in recent historic events, or both? When and where did this genus originate? How are the relationships between its speciation and its coevolution with host plants in different continents? By means of molecular phylogenetical analyses on DNA sequences of five to seven DNA markers, including nuclear and mitochondrial genes, of about 150 collections from ca. 30 species, this project is 1) to clarify the species diversity and their phylogenetic relationships, and to provide morphological criteria for species delimitation and identification; 2) to infer the origin time and speciation history of this genus, and to elucidate the possible causes of the geographic distribution patterns of the current species with molecular biogeographical methods including ancestral range reconstruction and molecular clock analysis. This research will contribute to the knowledge of the origin, evolution and dispersal of the species of Aureoboletus, and its allied genera as a whole.

金牛肝菌属隶属于牛肝菌科，该属真菌不仅可食，而且与壳斗科、松科植物形成菌根共生关系，故该属真菌具有生态和经济价值。与过去的认知不同，申请人前期初步研究发现该属的物种有着明显的地理分布样式，是开展物种起源与演化研究的理想材料。该属虽非大属但却全球分布，这是否是因为该属起源早并在在各大洲隔离分化，还是近期通过长距离扩散所致？还是二者兼有？其何时何地起源？各大洲的物种分异与宿主植物的协同演化关系如何？本项目拟对该属约30个物种的150份标本开展5-7个基因片段（包括核基因和线粒体基因）的DNA测序并进行分子系统发育分析，澄清属下各支系间的系统亲缘关系，结合形态解剖特征提出分种标准，认识该属物种多样性；利用祖先分布区域重建和分子钟等分子生物地理学研究手段，进一步推断该属的起源时间和各物种的分化历史，解析现有物种分布格局的可能成因。本研究对认识该属及其近缘属的物种起源、演化和扩散有较重要的科学意义。

金牛肝菌属隶属真菌界牛肝菌目牛肝菌科。该属真菌常与壳斗科和松科的植物形成外生菌根共生关系，对维护森林生态系统的稳定有着重要作用。此外，该类群某些物种还是非常重要的食用真菌。前期初步研究发现该属的物种有着明显的地理分布样式，是开展物种起源与演化研究的理想材料。通过本项目的执行，首先发现金牛肝菌属物种多样性一度被低估，已由原来的13种扩充到了42种，其中半数以上为新种，并且发现东亚是该属的物种多样性中心。第二，经多基因联合分子系统发育分析，金牛肝菌属大体可以分为五大分支，基部分支分布于我国热带地区，而在其余分支中，东亚-北美，欧洲-东亚-北美间断分布的“种对”非常普遍。第三，经物种分化时间推算和祖先分布区重建推断，由于金牛肝菌属基部支系的物种均来自东亚的热带地区，属于古热带，故推测该属的物种可能在晚白垩世时期（约68 Mya）起源于古热带，随后可能在古新世时期（约58 Mya）通过白令陆桥或北大西洋路桥，扩散至北美地区，后一直南下至哥伦比亚。始新世、中中新世至晚中新世时期的持续降温均加速了金牛肝菌属的物种形成，并通过白令陆桥随着宿主在东亚和北美之间进行频繁的物种交流。另外，横断山在该时期的快速隆升也促进了该属物种在中国西南地区的快速辐射演化。本研究对认识牛肝菌物种起源与演化、揭示现有物种分布格局成因和其与植物的协同演化有着较重要的科学意义。