Maintenance of species boundaries in three sympatric Ligularia(Senecioneae,Asteraceae)species

The key process in speciation concerns the formation and maintenance of reproductive isolating barriers between diverging lineages. Although species boundaries are frequently investigated between two species across many taxa, reproductive isolating barriers among multiple species （：〉2） that would represent the most common phenomenon in nature, remain to be clarified. Here, we use double digest restriction-site associated DNA （ddRAD） sequencing to examine patterns of hybridization at a sympatric site where three Ligularia species grow together and verify whether those patterns contribute to the maintenance of boundaries among species. The results based on the RAD SNP datasets indicated hybridization Ligularia cyathiceps x L. duciformis and L. duciformis x L. yunnanensis were both restricted toFls plus a few first-generation backcrosses and no gene introgression were identified, giving rise to strong reproductive isolation among hybridizing species. More- over, hybrid swarm simulation, using HYBRIDLAB, indicated the RAD SNP datasets had sufficient discriminatory power for accurate hybrid detection. We conclude that parental species show strong reproductive isolation and they still maintain species boundaries, which may be the key mechanism to maintain species diversity of Ligualria in the eastern Qinghai-Tibetan Plateau and adjacent areas. Moreover, this study highlights the effectiveness of RAD sequencing in hybridization studies.

ITS2,a Better DNA Barcode than ITS in Identification of Species in Artemisia L.

Objective To select a more suitable DNA barcode to identify the species in Artemisia L. Methods ITS, ITS2, and three other major universal barcode candidates（mat K, rbc L, and psb A-trn H） were evaluated in the identification efficiency using a total of 1433 sequences downloaded from Gen Bank representing 343 species in Artemisia L. ITS and ITS2 were evaluated in the PCR and sequencing rate, sequencing peak quality（Q value）, and misread rate. One hundred and twelve A. annua samples were collected from 11 populations across over China, which were amplified with universal primers on the ITS and ITS2 regions. Results ITS and ITS2 shared a higher identification efficiency and exhibited 71.43% and 64.11% detectability at the species level, respectively. The Q values of ITS and ITS2 showed that the direct PCR sequencing data were reliable for the ITS2 region and ITS exhibited poor sequencing trace quality. In certain sites, the ITS sequences exhibited reading ambiguities and errors, indicating that the misread and deletion sites in the ITS region would incorrectly inflate the identification ratio. Conclusion ITS2 is a suitable barcode for identification of species in Artemisia L., which enlarges the optimal range of divergence levels for taxonomic inferences using ITS2 sequences.