Morphological and molecular evidence for natural hybridization between Sorbus pohuashanensis and S. discolor (Rosaceae)

Abstract

In overlapping distribution areas of Sorbus pohuashanensis and S. discolor in North China (Mount Tuoliang, Mount Xiling and Mount Baihua), Sorbus individuals were found with pink fruit, which have never been recorded for the flora of China. Fourteen morphological characters combined with four chloroplast DNA markers and internal transcribed spacer (ITS) were used to analyze the origin of the Sorbus individuals with pink fruits and their relationship to S. pohuashanensis and S. discolor. PCA, SDA and one-way (taxon) ANOVA of morphological characters provided convincing evidence of the hybrid origin of Sorbus individuals with pink fruits based on a novel morphological character and many intermediate characters. Haplotype analysis based on four cpDNA markers showed that either S. pohuashanensis or S. discolor were maternal parents of Sorbus individuals with pink fruits. Incongruence of the position of Sorbus individuals with pink fruits between cpDNA and ITS in cluster trees supported by DNA sequence comparative analysis, implying former hybridization events between S. pohuashanensis and S. discolor. Multiple hybridization events between S. pohuashanensis and S. discolor might have contributed to the generation of Sorbus individuals with pink fruits. This study has provided insights into hybridization between species of the same genus in sympatric areas, which is of great significance for the study of interspecific hybridization.