title: Phylogeographic study reveals the origin and evolutionary history of a Rhododendron species complex in Taiwan.
abstract: This study infers a single origin and a once-widespread distribution of the Rhododendron pseudochrysanthum species complex in Taiwan based on chloroplast DNA (cpDNA) variation. In total, 124 individuals from five endemic Rhododendron species were used for amplifications of two chloroplast intergenic spacers: trnL-trnF and atpB-rbcL. The haplotype and nucleotide diversities were much lower for the R. pseudochrysanthum complex, comprised of the species R. pseudochrysanthum, R. morii, Rhododendron rubropunctatum, and Rhododendron hyperythrum, than for Rhododendron formosanum. Two measures of pairwise population differentiation, N(ST) and F(ST), consistently revealed mostly non-significant levels of genetic divergence between populations of the R. pseudochrysanthum complex. No genetic difference was found among the four species of the R. pseudochrysanthum complex by analysis of molecular variance (AMOVA), which is concordant with the parsimonious topology of cpDNA haplotypes for the complex. Nested clade analysis (NCA) of the cpDNA haplotypes indicated that restricted gene flow with isolation-by-distance characterized the recolonization pattern of the R. pseudochrysanthum complex. In contrast, the NCA analysis indicated a contiguous range expansion for cpDNA haplotypes of R. formosanum. This research suggests a once-widespread distribution of the R. pseudochrysanthum complex probably via north-to-south colonization of mid-elevations during low-temperature periods of the Pleistocene. Population fragmentation followed the warmer climate which began in the Holocene and resulted in the present-day range contraction into high elevations.
authors.affiliation: Division of Silviculture, Taiwan Forestry Research Institute, 53 Nanhai Road, Taipei 10066, Taiwan.
authors.forename: Jeng-Der
authors.initials: JD
authors.lastname: Chung
authors.forename: Tsan-Piao
authors.initials: TP
authors.lastname: Lin
authors.forename: Yu-Ling
authors.initials: YL
authors.lastname: Chen
authors.forename: Yu-Pin
authors.initials: YP
authors.lastname: Cheng
authors.forename: Shih-Ying
authors.initials: SY
authors.lastname: Hwang
mesh_terms: D018742:DNA, Chloroplast / Q000737:chemistry / Q000235:genetics*; D019143:Evolution, Molecular; D014644:Genetic Variation; D005843:Geography; D006239:Haplotypes / Q000235:genetics; D008969:Molecular Sequence Data; D010802:Phylogeny; D029793:Rhododendron / Q000145:classification / Q000235:genetics*; D017422:Sequence Analysis, DNA; D013624:Taiwan
chemical_list: D018742:DNA, Chloroplast