頻繁的基因交流導致百合屬組(sections)的分類界限模糊

Abstract

To understand the evolutionary history and phylogeny of Lilium, a multilocus analysis was conducted on eight chloroplast genes and 22 nuclear loci, which were PCR amplified and sequenced based on EST libraries of Lilium formosanum and L. longiflorum. Phylogenies based on the maternally inherited cpDNA, which is merited with low or no genetic recombination, and nrDNA, a gene family regulated by concerted evolution, were consistent with the taxonomy of Lilium sections, especially after removing L. davidii var. willmottiae that caused systematic inconsistency. The tree based on the combined evidence of cpDNA genes and nrITS was deemed as the hypothetical species tree, which uncovered three groups, i.e., Cluster A (Sect. Leucolirion, Archelirion and Daurolirion), Cluster B (Sinomartagon and Archelirion), and Cluster C (Pseudolirium, Liriotypus, Martagon, Leucolirion, and Sinomartagon). Apparently, Sect. Leucolirion and Sinomartagon are paraphyletic. Nevertheless, most of the nuclear loci, up to 17 genes (85%), displayed various tree topologies inconsistent with the species tree. Given a long time period for genetic divergence, frequent systematic inconsistency is likely attributable to genetic exchanges between species / sections, as further indicated by the high levels of genetic recombination detected in the nuclear genes. Such rampant gene flow blurred the taxonomic boundaries of sections in Lilium. Nevertheless, multilocus analysis not only provide phylogenetic informations about species split, but also the status of gene flow between species.