Key Laboratory for Plant Diversity and Biogeography of East Asia, Kunming Institute of Botany, Chinese Academy of Sciences, Kunming, P. R. China.
New York Botanical Garden, Institute of Systematic Botany, Bronx, New York, United States of America.
PLoS One. 2018 Nov 7;13(11):e0205840. doi: 10.1371/journal.pone.0205840. eCollection 2018.
Multifurca is a small genus newly established to accommodate lactarioid and russuloid species with some characters reminiscent of corticoid members of Russulaceae. It shows an amphi-pacific distribution with strong preference for the tropical zone of the Northern Hemisphere and thus has particular significance for biogeographical study. Using worldwide samples and three loci (ITS, 28S rDNA and rpb2), we demonstrated that Multifurca is split into two highly supported major clades that are here recognized at the subgeneric level: subg. Furcata subg. nov. exclusively includes lactarioid species, while subg. Multifurca includes species with a russuloid habit. Using phylogenetic species recognition and comparison of genetic distances we recognize five new and six previously described species, almost double the known number of species before this study. Molecular dating using a Bayesian method suggested that Multifurca originated in early Paleocene and diversified in the Eocene. The most recent interspecific divergences occurred both in Asia and America, roughly at the same time around the Pliocene. Ancestral area reconstruction and comparisons of genetic distances and morphology suggested an early divergence within Australasia or tropical Asia. From the early Miocene to Pliocene, multiple dispersals/migrations to Australasia and North America by island hopping or land bridge likely happened. Vicariance at the late Tertiary might be the most likely mechanism accounting for the eastern Asia-southeastern North America and Australasia-tropical Asia disjunct distributions. The shared polymorphisms in the ITS alignment, numerous degenerated base pairs in the rpb2 sequences and weak conflict between the ITS and LSU genealogies of M. subg. Furcata suggest recent speciation. Host specificity of Multifurca species or species pairs is relatively low. Host shifts are believed to have aided establishment in new territories during the dispersals and migrations.
多叉菌属是一个新建立的小属，用于容纳一些具有类似珊瑚菌科皮质成员特征的乳菇类和红菇类物种。它表现出一种环太平洋分布，强烈偏好北半球的热带地区，因此对生物地理研究具有特殊意义。使用全球范围内的样本和三个基因座（ITS、28S rDNA 和 rpb2），我们证明 Multifurca 分为两个高度支持的主要分支，在这里被认作亚属水平：亚属 Furcata 亚属。nov. 专门包括乳菇类物种，而亚属 Multifurca 包括具有红菇类习性的物种。使用系统发育物种识别和遗传距离比较，我们识别了五个新物种和六个以前描述过的物种，几乎是这项研究之前已知物种数量的两倍。使用贝叶斯方法进行分子定年表明，Multifurca 起源于早古新世，并在始新世多样化。最近的种间分歧发生在亚洲和美洲，大致在更新世同时发生。祖先区重建以及遗传距离和形态比较表明，在澳大利亚或热带亚洲早期就已经发生了分歧。从中新世到上新世，通过岛屿跳跃或陆桥向澳大利亚和北美洲的多次扩散/迁移可能发生。晚第三纪的隔离可能是解释东亚-东南北美和澳大利亚-热带亚洲间断分布的最可能机制。ITS 序列比对中的共享多态性、rpb2 序列中大量退化碱基对以及 Multifurca 亚属 Furcata 的 ITS 和 LSU 系统发育之间的微弱冲突表明最近发生了物种形成。Multifurca 物种或物种对的宿主特异性相对较低。在扩散和迁移过程中，宿主转移被认为有助于在新领土上建立新的种群。
