Back to the brink: phylogeography and demographic history of the endangered Torreya jackii

Both natural and anthropogenic factors can negatively affect species demography and even lead to species extinction, but their relative importance in driving species rarity remains poorly understood. To this end, we investigated the phylogeography and demographic history of the endemic endangered conifer species Torreya jackii. We collected samples from all the 13 extant wild populations, and analyzed the genetic variation using 8 nuclear microsatellites and 4 chloroplast and 1 mitochondrial DNA fragments. Low genetic and nucleotide diversity was revealed, which could explain the absence of spatial and phylogeographic structure. Using a hierarchical approximate Bayesian computation technique, we identified the demographic scenario that best fit with the genetic data, where the effective population size of the plant was low at least 200,000 years ago but expanded after the last glacial maximum (LGM). The scenarios accounting for population decline during the LGM had significantly smaller...