Bidirectional natural hybridization between sympatric Ligularia vellerea and L. subspicata

Abstract

Natural hybridization has been regarded as a crucial pathway of speciation and provides the raw materials for the evolution of biodiversity. The interspecific natural hybridization of the genus Ligularia Cass. is universal and has been considered to be an important factor driving the high diversity of Ligularia species in the Hengduan Mountains, China. Although the natural hybridization between L. vellerea and L. subspicata was reported previously, the direction of hybridization was uncertain due to the limitation of sampling. Thus, in this study, we sampled more individuals and increased two fragments of chloroplast DNA on the basis of the previous study to further verify the natural hybridization between L. vellerea and L. subspicata and confirm the direction of hybridization. Based on DNA sequences (atpB-rbcL, trnL-rpl32, trnQ-5'rps16, and nuclear ribosomal internal transcribed spacer region) data, we concluded that putative hybrids were primary products of hybridization between L. vellerea and L. subspicata and the hybridization was bidirectional. Moreover, sympatric L. tongolensis was not apparently involved in the hybridization. Surprisingly, some pure L. subspicata individuals showed the disaccordance between morphology and DNA data, which might indicate that introgression occurs between L. vellerea and L. subspicata.

Keywords: ITS; Introgression; Ligularia; Natural hybridization; cpDNA.

Fig. 1

Phylogenetic relationships of the nrITS haplotypes of all Ligularia species distributed within the mixed population. Supporting rate >50% is shown above branches.

Fig. 2

Phylogenetic relationships of the three cpDNA intergenic spacer regions haplotypes of all Ligularia species distributed within the mixed population. Supporting rate >50% is shown above branches.