Evolution of oil-producing trichomes in Sisyrinchium (Iridaceae): insights from the first comprehensive phylogenetic analysis of the genus

† Background and Aims Sisyrinchium (Iridaceae: Iridoideae: Sisyrinchieae) is one of the largest, most widespread and most taxonomically complex genera in Iridaceae, with all species except one native to the American continent. Phylogenetic relationships within the genus were investigated and the evolution of oil-producing structures related to specialized oil-bee pollination examined. † Methods Phylogenetic analyses based on eight molecular markers obtained from 101 Sisyrinchium accessions representing 85 species were conducted in the first extensive phylogenetic analysis of the genus. Total evidence analyses confirmed the monophyly of the genus and retrieved nine major clades weakly connected to the subdivisions previously recognized. The resulting phylogenetic hypothesis was used to reconstruct biogeographical patterns, and to trace the evolutionary origin of glandular trichomes present in the flowers of several species. † Key Results and Conclusions Glandular trichomes evolved three times independently in the genus. In two cases, these glandular trichomes are oil-secreting, suggesting that the corresponding flowers might be pollinated by oilbees. Biogeographical patterns indicate expansions from Central America and the northern Andes to the suban