Systematics and floral evolution in Fraxinus (Oleaceae)

Abstract

Oleaceae is a family of about 600 species in 24 extant genera (Wallander & Albert 2000). Th ey occur all over the world in tropical, subtropical and temperate climates. Phylogenetically, the family is near the base in the order Lamiales. Th e largest genus in the family is Jasminum with about 200 species. Other well-known genera in the family are Forsythia (11 spp.), Ligustrum (45 spp.), Syringa (20 spp.), Olea (40+ spp.) and Fraxinus. Th e species are trees, shrubs or woody climbers with opposite, simple or compound leaves without stipules. Th e fl owers are hypogynous (petals and sepals attached under the ovary) and four-merous, generally with two stamens, but four stamens occur in some species. Th e corolla is actinomorphic (radial symmetric) and usually sympetalous. Free petals occur in Chionanthus and Fraxinus, and apetalous fl owers occur in Nestegis, Forestiera, and wind-pollinated species of Fraxinus. Th e ovary is syncarpous (carpels fused), consisting of two carpels. Fruit types range from loculicidal capsules (with two locules), woody schizocarps (a dry fruit type that splits in two parts), and samaras to berries and drupes. Most of the species in the family are insectpollinated with petaliferous, fragrant and nectariferous fl owers (e.g. Jasminum, Forsythia, Ligustrum, Syringa, Chionanthus). Six of the genera in the family contain species with wind-pollinated fl owers (Fraxinus, Forestiera, Priogymnanthus, Nestegis, Phillyrea and Olea). Systematics and fl oral evolution in Fraxinus (Oleaceae)