Intercontinental and intracontinental biogeography of the eastern Asian - Eastern North American disjunct Panax (the ginseng genus, Araliaceae), emphasizing its diversification processes in eastern Asia.

The intercontinental biogeography between eastern Asia and eastern North America has attracted much attention from evolutionary biologists. Further insights into understanding the evolution of the intercontinental disjunctions have been hampered by the lack of studies on the intracontinental biogeography in eastern Asia, a region with complex geology, geography, climates and habitats. Herein we studied the biogeographic history of the eastern Asian-eastern North American disjunct genus Panax with special emphasis on the investigation of its uneven diversification in Asia. This study reconstructs the diversification history of Panax and also emphasizes a large clade of Panax taxa, which has a wide distribution in eastern Asia, but was unresolved in previous studies. We examined the noncoding plastid DNA fragments of trnH-psbA, rps16, and psbM-trnD, the mitochondrial b/c intron of NAD1, and the nuclear ribosomal internal transcribed spacer (ITS) region of 356 samples from 47 populations. The results revealed the subtropical Northern Hemisphere origin (Asia or Asia and North America) of Panax in the Paleocene. Intercontinental disjunctions between eastern Asia and eastern North America formed twice in Panax, once estimated in early Eocene for the split of P. trifolius and another in mid-Miocene for the divergence of P. quinquefolius. Intercontinental diversifications in Panax showed temporal correlation with the increase of global temperature. The evolutionary radiation of the P. bipinnatifidus species complex occurred around the boundary of Oligocene and Miocene. Strong genetic structure among populations of the species complex was detected and the populations may be isolated by distance. The backbone network and the Bayesian clustering analysis revealed a major evolutionary radiation centered in the Hengduan Mountains of western China. Our results suggested that the evolutionary radiation of Panax was promoted by geographic barriers, including mountain ranges (Hengduan Mountains, Nanling Mountains and Wuyishan Mountains), oceans and altitudinal shifts, which further contribute to the knowledge of the uneven species diversification between eastern Asia and North America.

Genetic structure of the tree peony (Paeonia rockii) and the Qinling Mountains as a geographic barrier driving the fragmentation of a large population.

BACKGROUND: Tree peonies are great ornamental plants associated with a rich ethnobotanical history in Chinese culture and have recently been used as an evolutionary model. The Qinling Mountains represent a significant geographic barrier in Asia, dividing mainland China into northern (temperate) and southern (semi-tropical) regions; however, their flora has not been well analyzed. In this study, the genetic differentiation and genetic structure of Paeonia rockii and the role of the Qinling Mountains as a barrier that has driven intraspecific fragmentation were evaluated using 14 microsatellite markers. METHODOLOGY/PRINCIPAL FINDINGS: Twenty wild populations were sampled from the distributional range of P. rockii. Significant population differentiation was suggested (F(ST) value of 0.302). Moderate genetic diversity at the population level (H(S) of 0.516) and high population diversity at the species level (H(T) of 0.749) were detected. Significant excess homozygosity (F(IS) of 0.076) and recent population bottlenecks were detected in three populations. Bayesian clusters, population genetic trees and principal coordinate analysis all classified the P. rockii populations into three genetic groups and one admixed Wenxian population. An isolation-by-distance model for P. rockii was suggested by Mantel tests (r = 0.6074, P<0.001) and supported by AMOVA (P<0.001), revealing a significant molecular variance among the groups (11.32%) and their populations (21.22%). These data support the five geographic boundaries surrounding the Qinling Mountains and adjacent areas that were detected with Monmonier's maximum-difference algorithm. CONCLUSIONS/SIGNIFICANCE: Our data suggest that the current genetic structure of P. rockii has resulted from the fragmentation of a formerly continuously distributed large population following the restriction of gene flow between populations of this species by the Qinling Mountains. This study provides a fundamental genetic profile for the conservation and responsible exploitation of the extant germplasm of this species and for improving the genetic basis for breeding its cultivars.

Development and characterization of microsatellite markers for Panax notoginseng (Araliaceae), a Chinese traditional herb.

PREMISE OF THE STUDY: Microsatellite primers were developed for a Chinese traditional herb, Panax notoginseng, to investigate its genetic diversity and cultivar breeding. METHODS AND RESULTS: Twelve polymorphic microsatellite loci were isolated from the microsatellite-enriched genomic library of P. notoginseng. The polymorphisms were assessed in two populations and an assemblage containing individuals from the whole distribution area. The number of alleles per locus ranged from three to 12, with a mean of 5.8, and the observed and expected heterozygosity values ranged from 0.0411 to 0.8472 and from 0.0804 to 0.7653, respectively. CONCLUSIONS: These new microsatellite markers will be useful for investigation of the genetic diversity of cultivated P. notoginseng as well as assist in cultivar breeding.

Development and characterization of polymorphic microsatellite markers in Dysosma pleiantha (Berberidaceae).

PREMISE OF THE STUDY: The development of compound microsatellite markers was conducted in Dysosma pleiantha to investigate genetic diversity and population genetic structure of this threatened medicinal plant. METHODS AND RESULTS: Using the compound microsatellite marker technique, 14 microsatellite markers that were successfully amplified showed polymorphism when tested on 38 individuals from three populations in eastern China. Overall, the number of alleles per locus ranged from 2 to 14, with an average of 7.71 alleles per locus. CONCLUSIONS: These results indicate that these microsatellite markers are adequate for detecting and characterizing population genetic structure and genetic diversity in Dysosma pleiantha.

Development and characterization of microsatellite markers for Panax notoginseng (Araliaceae), a Chinese traditional herb.

PREMISE OF THE STUDY: Microsatellite primers were developed for a Chinese traditional herb, Panax notoginseng, to investigate its genetic diversity and cultivar breeding. METHODS AND RESULTS: Twelve polymorphic microsatellite loci were isolated from the microsatellite-enriched genomic library of Panax notoginseng. The polymorphisms were assessed in two populations and an assemblage containing individuals from the entire distribution area. The number of alleles per locus ranged from 3 to 12, with a mean of 5.8; the observed and expected heterozygosity values ranged from 0.0411 to 0.8472 and from 0.0804 to 0.7653, respectively. CONCLUSIONS: These new microsatellite markers will be useful for investigating the genetic diversity of this cultivated Panax notoginseng as well as assist in cultivar breeding.

[Genetic relationships among Fructus Aurantii cultivars revealed by ISSR].

OBJECTIVE: A total of 27 samples belonging to 5 cultivars of Fructus Aurantii (Citrus aurantium), i. e. cv. Xiucheng, cv. Xiangcheng, cv. Lecheng, cv. Jizicheng, and cv. Youzicheng, collected at Changfu and Huanggang, Zhangshu City, Jiangxi Province, were assayed to reveal the genetic relationship among the cultivars and the accordance between morphological and molecular markers. METHOD: Cultivar identification was based on morphology and cultivar relationship was based on Inter-simple sequence repeats (ISSR). RESULT: Twenty out of 40 ISSR primers screened generated 392 loci across all 27 samples with 315 informative loci. The UPGMA dendrogram showed that samples within cv. Xiucheng and cv. Xiangcheng from Changfu were closely related. However, samples of cv. Lecheng, cv. Jizicheng and cv. Youzicheng from Huanggang, or cv. Xiucheng and cv. Xiangcheng from both Changfu and Huanggang did not exhibited close relationships within each cultivars. CONCLUSION: Based on morphology the same cultivar grown in different plantations, or even within a single plantation sometimes do not show close genetic relationship, indicating diverse origin of the cultivars. Synonyms or homonyms are believed to common phenomenon in Fructus Aurantii production. To solve the problem ISSR markers can serve a kind of molecular markers which are preferable to partition genetic variations within and between cultivars and to establish genetic relationships among them.