Phylogenomics disentangles the evolutionary history of spruces (Picea) in the Qinghai-Tibetan Plateau: implications for the design of population genetic studies and species delimitation of conifers

A laborious and difficult task in current tree of life reconstruction is to resolve evolutionary relationships of closely related congeneric species that originated from recent radiations. This is particularly difficult for forest species with long generation times and large effective population sizes such as conifers. As the species diversity center of Picea, the Qinghai-Tibetan Plateau (QTP) and its adjacent areas harbor 11 species (including 5 varieties) of this genus, but evolutionary relationships of these species are far from being resolved due to recent radiation, morphological convergence, and frequent interspecific gene flow. In this study, we use these spruce species to test whether phylotranscriptomic analysis, combined with population genetic analysis, can disentangle their evolutionary relationships, and to explore whether reticulate evolution has occurred among them. Phylogenomic analyses indicate that all spruce species in the QTP and neighboring areas, except P. asperata...