Phylogeography And Species Delimitation Of Three Spruce(Picea) Species

Species delimitation is an old issue that has recently attracted renewed attention. It's necessary to consider not only mutation rate but the effect of gene flow when selecting markers for species delimitation. Recent simulation studies have predicted a negative correlation between intra-and interspecific gene flow, suggesting that markers associated with the most dispersing sex should better delimitate species. Hence, species delimitation should be more effective with markers experiencing high levels of gene flow. In Picea, chloroplast genomes exhibit paternal inheritance while mitochondrial genomes exhibit maternal inheritance. Therefore, the combined pollen-and seed-mediated gene flow of cpDNA markers is greater than seed-mediated gene flow of mtDNA markers, thus cpDNA should be better suited to differentiate species.Here, we use sequence data from three cpDNA fragments and two mtDNA fragments to study the phylogeography and species delimitation of three Picea species. Ten chlorotypes and nine mitotypes were identified. For chlorotype, every species possessed its private haplotypes and P. neoveitchii fixed only one chlorotype. A star-like pattern of chlorotypes was uncovered in P. meyeri, so mismatch distribution analysis and Fu's Fs test were carried out. The mismatch analysis indicated that the distribution of pairwise differences for P. meyeri was unimodal and Fu's Fs value was significantly negative. We found that mitotypes were shared among species, that is M1 was shared between P. wilsonii and P. meyeri while M3 between P. wilsonii and P. neoveitchii. In addition, there was only one mitotype in populations of P. meyeri but a high level of differentiation among populations was found for P. wilsonii and P. neoveitchii.The results showed that P. meyeri had experienced range expansion in history and multiple refugia were maintained for P. wilsonii and P. neoveitchii during the glacial period. Furthermore, the shared Ml was the result of mitochondrial introgression and the shared M3 may be caused by historical introgression. In the last place, we further discussed about the current situation and protection strategy for P. neoveitchii.