Likely allopatric origins of Adiantum × meishanianum （Pteridaceae） through multiple hybridizations

Adiantum × meishanianum F. S. Hsu ex Y. C. Liu ＆ W. L. Chiou was regarded as an endemic species in Meishan Village, Kaohsiung, Taiwan, China and a hybrid between A. malesianum Ghatak （the maternal parent） and a sexually reproducing diploid cryptic species of A. philippense L. （the paternal parent）, as revealed by chloroplast and nuclear markers. However, morphological research revealed that A. x meishanianum is also disjunctively distributed in Yunnan and that its paternal parent is possibly A. menglianense Y. Y. Qian. Thus, this study aimed to confirm these findings by using two chloroplast regions and a low-copy nuclear marker in DNA barcoding and phylogenetic analyses, spore measurement, and flow c%cometry. Our results indicated that A. x meishanianum in Yunnan is triploid and abortive, the same as A. x meishanianum in Taiwan, and they both originated from the hybridization between the maternal parent of A. malesianum and the paternal parent of A. menglianense, but not A. philippense. In conclusion, A. x meishanianum probably originated from multiple hybridizations in Taiwan and Yunnan.