Today East Asia harbors many “relict” plant species whose ranges were much larger during the Paleogene-Neogene and earlier. The ecological and climatic conditions suitable for these relict species have not been identified. Here, we map the abundance and distribution patterns of relict species, showing high abundance in the humid subtropical/warm-temperate forest regions. We further use Ecological Niche Modeling to show that these patterns align with maps of climate refugia, and we predict species’ chances of persistence given the future climatic changes expected for East Asia. By 2070, potentially suitable areas with high richness of relict species will decrease, although the areas as a whole will probably expand. We identify areas in southwestern China and northern Vietnam as long-term climatically stable refugia likely to preserve ancient lineages, highlighting areas that could be prioritized for conservation of such species.

Fossil ectomycorrhizae were found recently among permineralized plant remains in the middle Eocene Princeton chert of British Columbia. The ectomycorrhizae are associated with roots of Pinus and have a Hartig net that extends to the endodermis, a pseudoparenchymatous mantle, and contiguous extramatrical hyphae that are simple-septate. The mycorrhizal rootlets lack root hairs and dichotomize repeatedly to form large, coralloid clusters. Reproductive structures are absent. Based on the morphological characteristics, and the identity of the host, the closely related basidiomycete genera Rhizopogon and Suillus are suggested as comparable extant mycorrhizal fungi. These exquisitely preserved specimens represent the first unequivocal occurrence of fossil ectomycorrhizae and demonstrate that such associations were well-established at least 50 million years ago.

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Aim The East Asia endemic Taiwania cryptomerioides Hayata is an iconic and relictual monotypic conifer whose main extant populations are now restricted to the Yunnan-Myanmar border, northern Vietnam and Taiwan. It has also been reported from several localities in Guizhou, Hubei and Fujian Provinces, China. Its fossil record indicates that, while it was more widely distributed in the Northern Hemisphere and grew under a range of different ecological conditions, it has remained almost unchanged in its morphology for over 100 Myr. We investigate whether these remaining extant, disjunct populations have diverged genetically; when such a divergence may have occurred; and which, if any, of the extant populations exhibit refugial characteristics.Location East Asia.Methods Sequences of five chloroplast DNA markers (petG-trnP, trnH-psbA, trnV-trnM, trnC-ycf6 and trnL-trnF) from all extant populations of T. cryptomerioides were analysed to reveal their phylogeography. Molecular clock models with fossil calibrations were used to estimate divergence times between extant populations.Results Extremely low nucleotide diversity was found in the overall population (p = 0.00077) with only nine haplotypes distinguished. The mainland Asia populations share one major ancestral haplotype. The insular populations in Taiwan all possess a unique haplotype with at least an eight-mutational-step difference to the mainland Asia haplotype. Molecular clock estimations demonstrated that the mean divergence time between the predominant insular population haplotype and the mainland Asia haplotype occurred at c. 3.23-3.41 Ma, followed by a split into Vietnamese and Yunnan-Myanmar populations (c. 1.0-1.39 Ma).Main conclusions Strong genetic differentiation exists between insular (Taiwan) and mainland Asia populations. The split between insular and mainland haplotypes can be dated back to the end of the Pliocene. The Yunnan-Myanmar border area, northern Vietnam and Taiwan are identified here as potential refugia for T. cryptomerioides. Other populations in mainland China are unlikely to be the result of historical fragmentation and their origins require further investigation.

Hemlock, Tsuga (Pinaceae), has a disjunct distribution in North America and Asia. To examine the biogeographic history of Tsuga, phylogenetic relationships among multiple accessions of all nine species were inferred using chloroplast DNA sequences and multiple cloned sequences of the nuclear ribosomal ITS region. Analysis of chloroplast and ITS sequences resolve a clade that includes the two western North American species, T. heterophylla and T. mertensiana, and a clade of Asian species within which one of the eastern North American species, T. caroliniana, is nested. The other eastern North American species, T. canadensis, is sister to the Asian clade. Tsuga chinensis from Taiwan did not group with T. chinensis from mainland China, and T. sieboldii from Ullung Island did not group with T. sieboldii from Japan suggesting that the taxonomic status of these distinct populations should be reevaluated. The Himalayan species, T. dumosa, was in conflicting positions in the chloroplast and ITS trees, suggesting that it may be of hybrid origin. Likelihood-based biogeographic inference with divergence time estimates infers an Eocene basal crown group diversification and an initial widespread circumpolar distribution with subsequent vicariance and extinction events leading to the current disjunct distribution.