Molecular Phylogeny Of The Genus Microlepia(Dennstaedtiaceae)

Microlepia C. Presl is mainly distributed in tropical and subtropical regions of Asia, representing a highly diverse genus belonging to the Dennstaedtiaceae sensu lato in eupolypods ferns. China are regarded as the distribution center of Microlepia recorded 56 species(more than 40 species in other countries) mainly from the Changjiang River area and from southern and southwestern China. Some morphological, palynological and cytological studies on Microlepia have been carried out, but molecular phylogeny remains poorly understood. So far, it is still unknown about the infrageneric system and evolutionary relationship in the Microlepia. Therefor, 4 chloroplast DNA markers(rbcL、trnL-F、psbA-trnH、rps4) are selected to construct the phylogenetic trees using the maximum likelihood(ML) and Bayesian analysis(BI) methods in this study. There are 270 samples of Microlepia and its sister genus Dennstaedtia collected from 13 provinces in China, Thailand and Indonesia. The major results are as follows:1. Evolutionary relationship among the Clade of MicrolepiaMicrolepia constitute as a monophyletic clade. Five well-supported large Clade(A, B, C, D, and E) were found in the phylogenetic topology. Based on molecular, morphological, and geographical information, we initially identified 31 clades. Unique shaped species within the genus: M. tenera(Clade A, Endemic species in China, differentiated firstly) and M. hookeriana(Clade B) are the basal taxa of Microlepia. The main characteristics of Clade C includes Fronds 3-4 pinnate, mainly 4-pinnatifid, terminal pinnules short and narrow, 11 clades are included in this Clade. Clade D Contains 7 clades, and it is distinct in the evolution correlation between each clades, the key features of which contains: Fronds 3-pinnatifid, terminal pinnules large and broad. Compared with other Clades, Clade E is relatively more complex, which involved in three kinds of fronds: 1-pinnate to 3-pinnate, but mainly in 2-pinnate and plants were small. It consists of 11 clades.2. Infrageneric species of Microlepia according to each cladesCombined with phylogenetic trees, monophyly and morphological characteristics, 31 clades of Microlepia include: M. chrysocarpa, M. lofoushanensis, M. crassa, M. trichocarpa, M. khasiyana, M. platyphylla, M. kurzii, M. firma, M. trapeziformis, M. crenata, M. subtrichosticha, and so on. In addition, our research shows that M. strigosa and M. speluncae which were considered as widespread and varied greatly, have respectively in each clade. Unlike what we previously thought, M. lofoushanensis, M. szechuanica, M. ampla, M. subspeluncae, etc, which had been treated as synonyms of other species, are in each clade. However, M. substrigosa, M. pseudo-strigosa, M. marginata var. villosa, M. marginata var. bipinnata, M. calvescens, which were characterized by obvious features and easy to identify in the classification, were not supported by phylogenetic trees.3. Possible natural hybridization in MicrolepiaIn the complex clades of the Microlepia. M. marginata(Clade E-X and E-XI) and M. hancei(Clade C-IX and C-XI) each have two independent clades relatively in sisters group. M. krameri and M. matthewii which have been suspected as origin from hybridation were included in these clades. It has been initially proved by our phylogenetic analysis for the maternal inheritance of cpDNA. In addition, we found three possible hybrids: M. marginata × M. hookeriana, M. marginata × M. trichocarpa and M. hancei×M. subtrichosticha in the aboved clades(Clade E-XI�'�C-IX). Clade E-III contains M. trichocarpa, M. herbacea and M. calvescens; Clade E-IV includes M. trichosora, M. herbacea and M. calvescens. Hybridisation is probably existed, since it is hardly difficult to distinguish them.