Genetic Diversity And Biogeography Of The Genus Typha L. (Typhaceae) From China

The genus Typha L. belongs to the family Typhaceae. They are aquatic perennial herbs and the world has about 8-13 species, most of them are cosmopolitan. As one of the important distribution centers of Typha, China has 12 species, including three endemic species. However, there exists some controversies of some species. Investigations on genetic variation and interspecific hybridization in Typha were mostly conducted in North America and Europe, Asia was less. The studies on biogeographic of Typha were also less.In this study, we focused on the genus Typha of China. We collected samples throughout China to investigate its classification and distribution by using chroloplast gene fragment; compared the genetic diversity and population genetic structure among four widespread species(Typha angustifolia L., Typha latifolia L., Typha orientalis C Presl, Typha laxmannii Lepech) by using chloroplast and nuclear DNA sequences and nuclear microsatellite data; based on the combination of samples collected from the field and the materials obtained from abroad, we inferred the biogeographic history of Typha using chroloplast fragments. The main results were as follows:1) Sequences of the cpDNA rpl32-trnL fragment were obtained from 383 individuals in 272 sites. Eight species and one indeterminable species of Typha were identified in China based on their sequences and morphological characteristics. The previously recorded species were:Typha angustifolia L.? Typha latifolia L.?Typha orientalis C. Presl? Typha laxmannii Lepech.? Typha domingensis Pers.? Typha elephantina Roxb. and Typha minima Funk.. The new species was Typha xinjiangensis B. B. Zhou et Y. Dan,sp.nov.. One indeterminable species was Typha pallida Pobedimova. Two or more species co-occurred in 81 sites, of which 80 sites were located on the north of the Yangtze River and they were found more often in Xinjiang and North China. The detailed ranges were as follows:T. angustifolia was widespread throughout China; T. xinjiangensis was only founded in Xinjiang; T. latifolia disjunctively distributed among three areas, Xinjiang, Northeast China and Central China; T. laxmannii was widespread throughout the provinces on the north of the Yangtze River; T. orientalis was found to the east of the line from Northeast China to Southwest China; T domingensis disjunctively distributed between Yunnan and Xinjiang; T. elephantina was only found in Yunnan; and T. minima distributed in North China and Northwest China. As we didn't collected the specimen and experimental materials of T.pallida that had obvious features matched with the descriptions of the record in the northwest of China, we didn't discuss it temporary.2) We compared the genetic diversity and population genetic structure among four widespread species (T. angustifolia? T. latifolia? T. orientalis and T. laxmannii) of the genus Typha in China by using chloroplast and nuclear DNA sequences and nuclear microsatellite data. The experimental materials were 898 individuals collected from 120 sites in nationwide. The levels of cpDNA nucleotide diversity followed the order T. latifolia> T. laxmannii> T. angustifolia> T. orientalis, whereas the genetic diversity in nDNA and nSSR of T. laxmannii and T. angustifolia was higher than that of T. latifolia. AMOVA results indicated that In T. angustifolia, T. laxmannii and T. orientalis, more than half of genetic variation occurred within populations, and in T. latifolia, most of genetic variation occurred among populations. The variation in the levels and distributions of genetic diversity among the four species can be attributed to differences in inflorescence characteristics which either limit or enhanced outcrossing rates. The individuals of all four species formed monophyletic clades and distinct genetic clusters, suggesting no hybridization between T. angustifolia and T. latifolia in China.3) The biogeographic history of Typha were inferred by using data of seven combined chloroplast fragments based on 40 worldwide samples of 10 Typha species. In the phylogenetic tree, T. minima and T. elephantina form a clade and sister to another clade formed by other species, which is subdivided into four clades with robust support. Estimated based on fossil calibration, the crown age of the Typha genus was in the middle of Oligocene and the divergence of clades was in the middle of Miocene. Ancestral areas reconstruction showed that Typha originated in eastern Eurasia and then dispersed to the world. Ancestral character states reconstruction indicated that that female flower with bracts, gap exist between male and female inflorescence, male inflorescence longer than female inflorescence and single pollen grain were ancestral morphological characteristics.Based on the molecular evidence, eight species in the genus Typha are identified in China; substantial variation in the levels and distributions of genetic diversity among four widespread species are caused by their different breeding systems and reproduction strategies; no hybridization was found between T. angustifolia and T. latifolia in China; the Typha genus began to diverge in eastern Eurasia in the middle of Oligocene and then dispersed to the world. This study provides important basis for the taxonomic revision of the genus Typha on the molecular biology aspect and deepens understanding on the genetic variation and evolutionary history of the old aquatic plants Typha.