Molecular Phylogeny Of Aspidistra Ker-Gawl.(Asparagacea)

Aspidistra Ker-Gawl. is one of the most special groups in monocotyledon, with high species riches and varieties of flower structures. It has the largest number of species in tribe Convallarieae (Liliaceae), with104species formally described. According to the molecular phylogenetic evidences, Aspidistra has been classified in Nolinoideae (Asparagaceae) in2009by the Angiosperm Phylogeny Group (APG). Despite ideal subjects for the study of floral evolution in monocotyledon, little is known about their genetic background. The investigation of molecular phylogeny of Aspidistra can help us uncover the relationships among the different groups and understand the pattern and consequences of speciation in monocotyledon.In this study, nine different genes (cpDNA trnL-F, rbcL, rpl16, trnK; nrDNA ITS; nDNA RLCKVII, MS, RPB2, GLO-like) are sequenced for reconstructing the phylogenetic relationships within the genus Aspidistra, using the genera of tribe Convallarieae as outgroups. Here, the major effects of hybridization and polyploidization in the evolutionary history of Aspidistra were inferred from molecular data. The main results are summarized as follows:1. Phylogenetic relationships of nuclear genes are consistent with the result of chloroplast gene. The relationships between genera of Convallarieae support the results from the previous phylogenetic analyses of this group. Among those genera, Tupistra is the closest relative of Aspidistra, and Campylandra should be transferred to Rohdea.2. The well supported clade of the genus of Aspidistra shows a species radiation in the phylogenetic trees. Molecular phylogenies cannot support the previous infrageneric classification of Aspidistra based on morphology characters. Inferred from the molecular clock of chloroplast genes, the species radiation should be a recent event, which may occur in the past10myr.3. The analysis of nuclear genes in Aspidistra reconstructs its reticulate evolution. More than seventy percent species of the genus have somehow experienced autopolyploidy and allopolyploidy. Since the genus Aspidistra are speculated as ancient polyploidy of2n=18or20, the genus of Aspidistra has probably experienced more episodes of allopolyploidization frequently, followed by a rapid diploidization process. Thus, the multiple origins lead to the more perplexing relationships of reticulate evolution in Aspidistra.4. In this study, three of four nDNA are single-copy genes and RPB2is the only one who has two copies. The cloning sequences of these nuclear genes are useful tools in reconstructing the reticulate evolutionary history of the genus of Aspidistra. Also, it suggests that RPB2had duplicated predating the radiation of the genus, even before the early diversification of Convallarieae.5. Rapid radiation makes it hard to identify the relationships among species, while in some highly supported clades, interspecific relationships can still be confirmed. For example, being very close to each other in different phylogenetic trees, those samples from Taiwan are probably come from A. elatior.6. The floral transcriptome of A. saxicola was obtained by next-generation sequencing (NGS). Our results have demonstrated the efficient use of NGS to generate large numbers of transcriptome sequences for the discovery of microsatellite markers in the species of Aspidistra. Further investigation of subset of these SSR markers can offer abundant SSRs for deeper analysis, especially for the phylogeographic distribution pattern and relationships within the genus.