全球南方牛肝菌属系统分类学及生物地理学研究

Austroboletus is an essential group in the systematic study of the family Boletaceae, and it is widely distributed in both Northern and Southern hemisphere, with most taxa from tropical areas. Up to now, around 32 Austroboletus species has been reported worldwide, therefore, it is a relatively small genus in the family Boletaceae. However, several taxonomic issues are unsettled: 1) ubiquitous misidentify caused by the high similarity among different species accusing by convergent evolution and the relatively complex morphological characteristics make species diversity not get enough recognition; the intrageneric and intergeneric phylogenetic relationships are unclarified; and the historic origin of species, migration, differentiation and evolution are worthy to be discussed. Our preliminary study showed that some unrecognized clades and taxa are existing in China, therefore further study are needed. In this project, 1) representative samples will be accumulated as much as possible, 2) to clarify the species diversity and phylogenetic relationship of the genus, morphological and phylogenetic analysis based on 5 gene segments (ITS, LSU, ef1-a, rpb1 and rpb2) will be carried out, 3) In order to estimate the origin, specific evolution and historic distribution and analysis the specific distribution pattern, Base on the system study to further speculate the historic origin, evolution and migration of this genus, and analysis the cause of the existing distribution pattern, theory and method of molecular clock estimate and ancestor distribution area reconstruction will be used. This study would become a milestone in more comprehensively understanding the genus Austroboletus, or even the family Boletaceae.

南方牛肝菌属是牛肝菌科系统学研究的重要类群，南北半球均有分布，以热带分布为主。该属种类不多，迄今仅报道32种，但分类学问题突出，如：趋同进化导致的不同种类形态高度相似、相对复杂的形态特征仍未得到充分认识；该属在牛肝菌科中的系统发育位置及属下物种间的亲缘关系有待进一步研究；其物种的历史起源、迁移、分化及进化均值得探讨。申请人前期研究发现，该属存在一些尚未被识别的支系和物种，进一步研究将有助于对该属全面认识。本项目拟广泛收集该属全球已报道物种及数据，进行形态学及基于5个基因片段（ITS、LSU、ef1-a、rpb1和rpb2）的系统发育分析，澄清该属内物种间的系统亲缘关系，明确其物种多样性；在明确其系统发育关系的基础上，结合分子钟估算和祖先分布区域重建的理论和方法，推测该属的起源、物种演化、分布历史，解析物种分布格局。项目对全面深入认识南方牛肝菌属乃至整个牛肝菌科具有重要科学意义。

南方牛肝菌属Austroboletus (Corner) Wolfe隶属于牛肝菌目Boletales牛肝菌科Boletaceae，是牛肝菌科系统学研究中的重要类群，该类群物种主要分布在热带-亚热带地区，以南半球分布居多，常与壳斗科等植物形成外生共生关系，对维持森林生态系统稳定方面有着重要作用。世界范围内对南方牛肝菌属研究的报道并不多，且尚未开展过专门针对该类群的分子系统学与生物地理学研究，该类群物种间的亲缘关系和形态界限尚不十分明确，南方牛肝菌属的历史起源与进化演化路线尚不清晰。鉴于此，本项目开展了世界范围的南方牛肝菌属系统学研究，在国内外广泛收集南方牛肝菌属标本及相关数据信息，累计获得标本170余份，包含模式标本21份，获得分子序列180余条。对获得的标本进行了形态学观察和描述，绘制了微观结构图，拍摄了孢子扫描电镜照片，发现了一批新的分类单元，认为孢子纹饰和菌盖皮层结构可作为南方牛肝菌属物种区分的可靠分类特征，并基于形态特征和分子数据解决了部分物种的分类学问题。基于多基因序列片段重建了南方牛肝菌属及其近缘属的系统发育框架，证明南方牛肝菌属为非单系类群，将A. graclis和A. fistivus从南方牛肝菌属中分离出来，理清了南方牛肝菌属下物种间的亲缘关系。初步推算分析了南方牛肝菌属的起源与分化时间，认为该类群可能起源于6800万年前的晚白垩纪，在2500-4000万年左右得到了快速分化扩散。通过本研究对正确认识南方牛肝菌属的物种多样性与分布情况，以及该类群的系统发育与进化演化具有重要的科学意义。