We analyzed the phylogeny of the Diplaziumhachijoense complex using plastid trnL-F and low-copy nuclear marker AK1 DNA sequences. Based on allele constitution, triploid apogamous species of the D.hachijoense complex appeared to have originated from the hybridization of triploid apogamous species and diploid sexual species by recurrent hybridization events. These results suggested that triploid apogamous ferns can achieve hybridization with diploid sexual species by producing diploid spores with irregular meiosis in sporogenesis. Furthermore, the present study predicted the involvement of several unknown species associated with hybridization. More sampling of Callipteris species from China and adjacent areas is required to determine the relationships among unknown species and the D.hachijoense complex.
Keywords: Athyriaceae; Diplazium; Ferns; apogamous; hybridization; phylogeny.