Evolutionary origin and systematic position of Euphorbia normannii (Euphorbiaceae), an intersectional hybrid and local endemic of the Stavropol Heights (Northern Caucasus, Russia)

• Published in: Plant systematics and evolution Vol. 307; no. 2
• Main Authors: Frajman, Božo, Geltman, Dmitry
• Format: Journal Article
• Language: English
• Published: Vienna Springer Vienna 01.04.2021; Springer Nature B.V
• Subjects: Biomedical and Life Sciences; Endemic plants; Endemic species; Endemism; Euphorbia; Flowering; Flowering plants; Genomes; Hybridization; Life Sciences; Original Article; Phylogenetics; Phylogeny; Plant Anatomy/Development; Plant diversity; Plant Ecology; Plant Sciences; Plant species; Plant Systematics/Taxonomy/Biogeography; Plants (botany); Species diversity; Northern Caucasus; Genome size; Phylogenetics; Endemism; Taxonomy; Morphology; Caucasus
• ISSN: 0378-2697; 1615-6110; 2199-6881
• DOI: 10.1007/s00606-021-01741-8

The Caucasus is one of the richest areas in the world in terms of animal and plant diversity, harbouring 6400 plant species. As a part of the Northern Caucasus, the Stavropol Heights are renowned for their local endemism, highlighted by six species of flowering plants endemic to this area. One of them is the annual species Euphorbia normannii , described in 1891, but with uncertain taxonomic position. We here used nuclear ribosomal internal transcribed spacer and plastid trn T– trn F sequences to infer the phylogenetic position of E. normannii . The nuclear data inferred its position within E. sect. Myrsiniteae , whereas the plastid data placed it within E. sect. Pithyusa , thus indicating a hybrid origin. Relative genome size (RGS) data indicate that E. normannii has the highest RGS compared to three other annual species belonging to both sections ( E. aleppica , E. gaillardotii and E. falcata ). Our data are inconclusive whether E. normannii is of allopolyploid or homoploid hybrid origin, or whether later hybridisation and plastid capture from E. sect. Pithyusa was responsible for the incongruent phylogenetic signal. Morphologically, E. normannii is distinct, as are all three before-mentioned annuals, which fall in predominately perennial sections. However, the species most similar to E. normannii is E. falcata from E. sect. Pithyusa and therefore we propose inclusion of E. normannii in this section.