Sectional Relationships in the Eurasian Bearded Iris (subgen. Iris) Based on Phylogenetic Analyses of Sequence Data

Subgenus Iris is wholly Eurasian, distributed in temperate regions from northeastern China to eastern and southern Europe where they occur in mountainous and/or dry rocky sites from near sea level to elevations of 4,500 m. These species have an easily discerned synapomorphy, a multicellular beard on each petaloid sepal. Currently two large and relatively well known and four smaller and less known sections are recognized in the subgenus. This study investigated the monophyly of circumscribed sections and relationships among these sections. Seventy-one taxa, representing each of the six sections and about 80% of the recognized species in subgen. Iris, and 11 outgroup taxa were included in the study. Also included were five Asian species that share some morphological characteristics with subgen. Iris but are typically considered in other subgenera. Phylogenetic analyses of sequence data recovered six major clades but sects. Psammiris, Pseudoregelia, and Regelia, are not monophyletic as currently circumscribed. The sister clade to subgen. Iris is comprised of I. domestica and I. dichotoma, two beardless species that occur in eastern Asia. Iris verna, a species from the eastern United States is sister to I. domestica + I. dichotoma + subgen. Iris. The sepal of I. verna has pubescence but not a beard of multicellular trichomes.