Genetic Structure And Phylogeography Studies On Croomia

The genus Croomia (Stemonaceae) comprises three herbaceous perennial species which distributed in temperate-deciduous forests in Southeastern North America (C. pauciflora) and East Asia (C. japonica, C. heterosepala). This small family has attracted much interest of plant taxonomists and phylogeographers. It played an important role in the phylogeny of monocotyledon and the plants with reticulate vein. We investigated genetic diversity and population structures, phylogeography, determined inter- and intraspecific relationships and divergence patterns and glacial refugia based on chloroplast DNA (cpDNA), single-copy nuclear gene and microsatellite. The main results of our study are as follows:1 Phylogeographic study based on cpDNA and single-copy nuclear geneThirty-four populations (201 individuals) were analyzed using cpDNA psbA-trnH, trnL-F and trnD-E intergenic spacer. A total of 27 cpDNA haplotypes were detected. Twenty-seven populations (112 individuals) were analyzed using single-copy nuclear gene Agt1 intergenic spacer. A total of 20 cpDNA haplotypes were detected. At the genus-wide scale, cpDNA data revealed high calculates of haplotype diversity (h=0.742). Nucleotide diversity (π(× 10-3)=3.88), as Agtl data (h=0.898,π(×10-3)=13.72). Analysis of molecular variance (AMOVA) demonstrated that tiny genetic diversity was found within populations. High genetic differentiation was detected among the specics of Southeastern North America (C. pauciflora) and East Asia (C. japonica, C. heterosepala) and even among populations within species.2 Microsatellite polymorphisms and genetic structureWe isolated and characterized eleven polymorphic microsatellite loci from Croomia using a PCR method. The results showed that the average of number of alleles per locus (k) was 31.36, the average of observed and expected heterozygosities (Ho) and (HE) and polymorphic information content (PIC) were 0.579,0.811 and 0.792, respectively. Structure analysis and PCoA analysis revealed three major phylogeographical groups:East China and Ryukyu Archipelago, Main Japanese islands and Southeastern North America. High genetic differentiation was detected within populations (FST=0.33189). Croomia have not undergone bottleneck according to the Wilcoxon sink-rank test in TPM.3 Refugia existed during the glaciationCroomia of different origin had high genetic diversity and come from different cluster thought the unrooted TCS network on cpDNA data and genetic structure on SSR. The refugia of Croomia in China concentrated on Mt. Huaiyu and Mt. Tianmushan. In Japan, the refugia were distributed in central region of Main Japanese islands. At least one refugium was inferred in USA.