Department of Forest Mycology and Pathology, Swedish University of Agricultural Sciences, PO Box 7026, S-75007 Uppsala, Sweden.
Mol Ecol. 2010 Nov;19(22):4979-93. doi: 10.1111/j.1365-294X.2010.04873.x. Epub 2010 Oct 22.
We investigated two hypotheses for the origin of the root rot fungus Heterobasidion annosum species complex: (i) that geology has been an important factor for the speciation (ii) that co-evolutionary processes with the hosts drove the divergence of the pathogen species. The H. annosum species complex consists of five species: three occur in Europe, H. annosum s.s., Heterobasidion parviporum and Heterobasidion abietinum, and two in North America, Heterobasidion irregulare and Heterobasidion occidentale; all with different but partially overlapping host preferences. The evolution of the H. annosum species complex was studied using six partially sequenced genes, between 10 and 30 individuals of each species were analysed. Neighbour-joining trees were constructed for each gene, and a Bayesian tree was built for the combined data set. In addition, haplotype networks were constructed to illustrate the species relationships. For three of the genes, H. parviporum and H. abietinum share haplotypes supporting recent divergence and/or possible gene flow. We propose that the H. annosum species complex originated in Laurasia and that the H. annosum s.s./H. irregulare and H. parviporum/H. abietinum/H. occidentale ancestral species emerged between 45 and 60 Ma in the Palaearctic, well after the radiation of the host genera. Our data imply that H. irregulare and H. occidentale were colonizing North America via different routes. In conclusion, plate tectonics are likely to have been the main factor influencing Heterobasidion speciation and biogeography.
我们研究了导致根腐菌 Heterobasidion annosum 种复合体起源的两个假说：（i）地质一直是物种形成的重要因素；（ii）与宿主的协同进化过程驱动了病原体物种的分歧。H. annosum 种复合体由五个物种组成：三个在欧洲，即 H. annosum s.s.、Heterobasidion parviporum 和 Heterobasidion abietinum，两个在北美洲，即 Heterobasidion irregulare 和 Heterobasidion occidentale；它们都有不同但部分重叠的宿主偏好。使用六个部分测序的基因研究了 H. annosum 种复合体的进化，对每个物种的 10 到 30 个个体进行了分析。为每个基因构建了邻接树，并为组合数据集构建了贝叶斯树。此外，构建了单倍型网络来说明物种关系。对于三个基因，H. parviporum 和 H. abietinum 共享支持近期分化和/或可能基因流的单倍型。我们提出 H. annosum 种复合体起源于劳亚古陆，H. annosum s.s./H. irregulare 和 H. parviporum/H. abietinum/H. occidentale 祖先物种在古北极出现于 45 到 60 Ma 之间，远在宿主属辐射之后。我们的数据表明，H. irregulare 和 H. occidentale 是通过不同的途径殖民北美的。总之，板块构造可能是影响 Heterobasidion 物种形成和生物地理学的主要因素。
