Relationships and origins of the Dryopteris varia (L.) Kuntze species complex (Dryopteridaceae) in Korea inferred from nuclear and chloroplast DNA sequences

Abstract

The Dryopteris varia species complex belongs to D. subg. Erythrovariae sect. Variae and includes eight closely related, controversial species. In Korea, six species belong to the complex; D. varia s. str., Dryopteris pacifica, Dryopteris sacrosancta, Dryopteris bissetiana, Dryopteris saxifraga, and Dryopteris saxifragivaria. The morphology of these species is highly variable due to the frequent occurrence of agamospory, hybridization, and/or polyploidization. We analyzed sequences of the nDNA pgiC and cpDNA rbcL, trnL–trnF IGS and atpF–atpH IGS regions from all six of these species to elucidate their relationships and origins, and to investigate the parentage of the putative hybrid taxon, D. saxifragivaria. Fourteen nDNA pgiC haplotypes and five cpDNA haplotypes were obtained from accessions of the D. varia complex in Korea. In particular, all accessions examined appear to have multiple pgiC haplotypes. Maximum parsimony and Bayesian inference analyses of the nDNA and cpDNA sequence data show that the agamosporous triploids D. sacrosancta and D. pacifica are of allopolyploid origin involving interspecific hybridization. The results also indicate that agamosporous triploid individuals of D. saxifragivaria in Korea were derived from hybridization between sexual diploid individuals of D. saxifraga (maternal) and agamosporous diploid individuals of D. bissetiana (paternal). In addition, our results strongly suggest that the agamosporous triploid D. varia s. str. is probably of autopolyploid origin, and cytoplasmic gene flow has occurred from D. sacrosancta to Dryopteris chinensis of D. subg. Dryopteris.