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The saga of the spurges: a review of classification and relationships in the Euphorbiales

1987; Oxford University Press; Volume: 94; Issue: 1-2 Linguagem: Inglês

10.1111/j.1095-8339.1987.tb01036.x

1095-8339

Grady L. Webster,

Botany, Ecology, and Taxonomy Studies

The order Euphorbiales, defined by Lindley in 1836, has undergone many vicissitudes to the present day. Over 30 families have been referred to the Euphorbiales by various authors, but most of them no longer appear closely related to the Euphorbiaceae. Several families commonly referred to Euphorbiales (or Tricoccae) in the 19th century now appear better located in other orders: Buxaceae in Hamamelidales (sensu lato), Empetraceae in Ericales, and Callitrichaceae in Lamiales. Several putatively related families, including the Aextoxicaceae, Stackhousiaceae, and Dichapetalaceae, appear to be of Celastralean affinity. The Simmondsiaceae, a problematical family once referred to the Buxaceae, have been included in the Euphorbiales in recent classifications, but the evidence for this is still inconclusive. Thymelaceaceae show a number of similarities to Euphorbiaceae, but share a greater number of distinctive characters with Malvales. The Euphorbiales show affinities to both the Malvales and Geraniales (sensu lato), and separation of these three orders between two major dicotyledon subclasses (Dilleniidae and Rosidae) appears questionable. The evidence does not support recognizing segregate families from the Euphorbiaceae such as the Bischofiaceae, Picrodendraceae and Stilaginaceae; the Euphorbiales are therefore best construed as containing a single major family, the Euphorbiaceae, as suggested by Hutchinson; the small family Pandaceae is also included in the Euphorbiales but may not be separable from the Euphorbiaceae. The recent classifications of Airy Shaw and Webster agree in many respects, and areas of disagreement indicate the need for additional data gathering and analysis.