Natural hybridization of Iris species in Mt. Palgong-san, Korea

Abstract

Series Chinensis, Genus Iris, endemic to the far regions of East Asia, consists of four species and related varieties. This series is divided into two major groups (I. rossii and I. minutiaurea complex). In this study, the ITS region and matK gene sequences within nuclear ribosomal DNA and plastid DNA were analyzed in order to investigate the phy-logenetic relationships among the I. minutiaurea complex (I. minutiaurea, I. odaesanensis, and I. koreana) and the tax-onomic identities of a putative hybrid in Mt. Palgong. In the internal transcribed spacer (ITS1, 5.8S, and ITS2) region, a total of 106 cloned genomic sequences from three taxa were obtained to study the intragenomic polymorphisms of the ITS regions. Three taxa revealed high levels of intragenomic polymorphisms, indicative of incomplete nrDNA concerted evolution. This incomplete ITS concerted evolution in the series Chinensis may be linked to the recent species divergence and frequent interspecies hybridization of the series Chinensis. In the matK gene, three taxa were fairly separated by eleven variable sites. In eight individuals collected on Mt. Palgong, putative hybrids between I. odaesanensis and I. minutiaurea were clustered in the I. minutiaurea clade in the NJ (neighbor-joining) tree based on the matK gene. However , in the ITS tree, some of them were clustered in the I. odaesanensis clade and others were clustered in the I. minu-tiaurea clade. Therefore, the individuals on Mt. Palgong were formed by the hybridization between two taxa (I. odaesanensis and I. minutiaurea) and not through the lineage of I. koreana.