The symbiotic relationships between ectomycorrhizal fungi (EcM) and host plants are vital for the survival and diversification of each group. Here we introduce the Suillus / Pinaceae model system to address evolutionary relationships between EcM fungi and host plants. Genus Suillus has higher host specificity than other groups of EcM fungi, associating almost exclusively with Pinaceae. Discoveries from this study reveal evolutionary or even coevolutionary relationships between EcM fungi and host plants. This study provides the first comprehensive multigene datasets (ITS, 28S, TEF1, RPB1 and RPB2) of Suillus. Over 95% of sequences other than ITS were generated during this study. The sampled diversity covered c. 80% of known Suillus species. Species recognition by GCPSR, concatenation and coalescence was applied and compared. A total of c. 92 OTUs were recognized from the ITS phylogeny, of which 71 species were identified using coalescent analyses and GCPSR. The diversity of Suillus has been well sampled in North America and Europe, but a broad sampling gap still existed in East Asia where Pinaceae diversity is rich. Intensive field sampling for Suillus in East Asia led to the discovery of 26 new species and 5 new reports for East Asia. The phylogeny derived from the concatenated sequence data (28S, TEF1, RPB1 and RPB2) resolved basal relationships of Suillus and supported the recognition of 5 subgenera and 2 sections. Suillus originated in the Eocene associated with Larix in the circumboreal region. Subgenus Boletinus is sister to other subgenera. By the end of the Eocene, Suillus diverged into two basal subgenera Boletinus and Spectabilis associated with Larix in northern Eurasia and eastern North America. Another monophyletic lineage distributed broadly across Eurasia and North America further diversified into other subgenera and switched hosts to Pinus and Pseudotsuga. Subg. Larigni associated with Larix in northern Eurasia and Indo-Pacific. In the Oligocene Suillus subg. Douglasii switched host to Pseudotsuga in western North America (WNA). In contrast, the ancestor of Larix and Pseudotsuga originated in NORTH AMERICAand the two genera diverged in the Paleogene. In the early Oligocene Suillus switched host to Pinus subg. Strobus sect. Quinquefoliae in the Indo-Pacific or subtropical East Asia. The association with Quinquefoliae in the Indo-Pacific lasted at least c. 10 million years after the divergence of sections Suillus and Diversipes. Throughout the Miocene, four independent host switches to subg. Pinus occurred. Pinus divergence into four sections with distinct geographic ranges, and this divergence predated Suillus’ host switching to Pinus. In summary, discordance rather than coevolution can better explain the evolutionary relationship between Suillus and its hosts Larix, Pseudotsuga and Pinus. The evolutionary history of Suillus differed in space and time from its hosts. Additionally, no diversification rate shifts were detected in Suillus or Pinaceae. A new calibration scenario was proposed that identified the earliest EcM fossil as potentially being associated with Suillus subg. Suillus. The supplementary information from all chapters is compiled into one file in pdf format. The supplementary document includes 1 method description, 9 tables and 13 figures.

Last modified

• 02/22/2019

Creator

• Rui Zhang

DOI

• https://doi.org/10.21985/N2QZ0P

Subject

• Plant Biology and Conversation

Keyword

• host shift speciation
• biogeography
• systematics
• phylogeny
• evolutionary history
• Suillus

Date created

• 2018-01-01

Resource type

• Dissertation

Rights statement

• In Copyright