Molecular systematics of <i>Descurainia</i> (Brassicaceae) in the Canary Islands: biogeographic and taxonomic implications

Abstract

Abstract Descurainia Webb &amp; Berthel. (Brassicaceae) comprises approximately 45 species distributed throughout temperate areas of the world. In contrast to the small‐flowered herbaceous taxa which constitute the majority of the genus, the seven species endemic to the Canary Islands are relatively large‐flowered woody perennials. A molecular‐based phylogeny of Canarian Descurainia was constructed using DNA sequences from nuclear ribosomal internal transcribed spacer (ITS) and seven non‐coding chloroplast regions. The results of parsimony and Bayesian analyses suggest that species of Descurainia in the Canary Islands are recently derived via a single colonization event. The closest continental relative is D. tanacetifolia, a perennial herb from the mountains of southwestern Europe. Chloroplast data suggest that both intra‐island adaptive radiation and inter‐island colonization have played a prominent role in the evolution of Descurainia in the Canary Islands. The most likely ancestral location of the island progenitor was the lowland scrub zone on Tenerife.