Analysis and evaluation of morphological and molecular polymorphism in the hybridization of <i>Elaeagnus ×maritima</i> and <i>E. ×submacrophylla</i>

Abstract

The taxonomic identity of <i>Elaeagnus ×maritima</i> and <i>E. ×submacrophylla</i> (Elaeagnaceae) in Korea is unclear, yet they are presumed to be hybrid taxa based on their morphology. To determine their hybrid origins, a morphological analysis (field surveys and specimen examinations) and a molecular analysis involving two nuclear ribosomal DNA (nrDNA) regions (internal transcribed spacer and 5S non-transcribed spacer) and one chloroplast DNA (cpDNA) region (<i>matK</i>) were conducted. The morphological analysis revealed that <i>E. ×maritima</i> showed certain morphological similarities to <i>E. glabra</i>, whereas <i>E. ×submacrophylla</i> showed certain morphological similarities to <i>E. pungens</i>. However, the molecular analysis indicated that <i>E. ×maritima</i> exhibited additive species-specific sites of <i>E. glabra</i> and <i>E. macrophylla</i> in the nrDNA regions. Notably, <i>E. ×submacrophylla</i> showed various aspects, with some individuals exhibiting additive species-specific sites of <i>E. pungens</i> and <i>E. macrophylla</i> in the nrDNA and <i>E. macrophylla</i> sequences in the cpDNA regions, some individuals exhibiting <i>E. macrophylla</i> sequences in the nrDNA and <i>E. pungens</i> sequences in the cpDNA regions, and some individuals displaying <i>E. macrophylla</i> sequences in both the nrDNA and cpDNA regions, despite an intermediate morphology between <i>E. pungens</i> and <i>E. macrophylla</i>. These results indicate that these two species are of hybrid origin and frequently cross between parental and hybrid individuals.