Convergent Evolution of the 'Homeria' Flower Type in Six New Species of Moraea (Iridaceae-Irideae) in Southern Africa

Abstract

Six new species of Moraea, all with similar small, pale to deep blue-purple flowers and reduced style branches instead of the broad petaloid style branches typical of the genus, are described from the southwest and interior west coast of southern Africa. This flower type, typical of the southern African Homeria, was previously known only in a few species of Moraea, notably sect. Polyanthes, and the flowers of the new species resemble especially those of M. crispa. However, of the new species only M. pseudospicata appears related to M. crispa. The others differ either in vegetative morphology, chromosome number, or in details of the flower, and the unusual flower seems to have evolved independently in at least three of them. Moraea graniticola, M. hexaglottis, and M. rigidifolia are each known from single populations in the southern Namib Desert of Namibia and are referred to sect. Moraea. Moraea worcesterensis, known from one site near Worcester in the southwest Cape, is probably closely related to M. algoensis of sect. Vieusseuxia. Moraea deserticola, restricted to the Knersvlakte in southern Namaqualand, is allied to M. speciosa of sect. Polyanthes. Moraea is a widespread African genus of some 115 species of seasonal, corm-bearing perennials of the Old World tribe Irideae of the large and nearly worldwide subfamily Iridoideae. It is the major genus of subtribe Homeriinae, an alliance centered in southern Africa but extending through tropical Africa into the Mediterranean and Middle East. The alliance is characterized by having an astelic corm of a single internode and distinctive, secondarily bifacial leaves (equitant isobilateral leaves are basic in Iridaceae). Moraea is the largest of the eight currently recognized genera of the subtribe and occurs almost throughout sub-Saharan Africa, but species are concentrated in highland areas of southeast tropical and southern Africa and in the winter rainfall area of southern Africa. It is relatively well known taxonomically, having been revised recently (Goldblatt, 1973, 1976b, 1977). Despite intensive study, new taxa continue to be discovered, mainly in the winter rainfall areas of South Africa and recently in southern Namibia. Some of these were described in 1982 together with a synopsis of the genus in which 105 species in five subgenera and 12 sections were recognized (Goldblatt, 1982). Several new species have been discovered since 1982, notably along the arid west coast and interior of southern Africa. The low and variable rainfall of the region is insufficient for species to flower every year, and this combined with the rugged landscape and general inaccessibility leaves this area relatively poorly known botanically. Six new species are described in this paper. Moraea graniticola, M. hexaglottis, and M. rigidifolia are each known from single populations in the southern Namib Desert of Namibia and are referred to sect. Moraea. Moraea worcesterensis, known from one site near Worcester in the southwest Cape, is probably closely related to M. algoensis of sect. Vieusseuxia. Moraea deserticola, restricted to the Knersvlakte in southern Namaqualand, is allied to M. speciosa of sect. Polyanthes, while M. pseudospicata, from the Nieuwoudtville escarpment, is closely related to the widespread Karoo species, M. crispa, also sect. Polyanthos. All six share an unusual feature, a type of flower characteristic of the related genus Homeria (Goldblatt, 1980, 198 lb) in which the style arms are narrow and inconspicuous and the tepals are similar in color, shape, and disposition. The 1 Supported by grants DEB 78-10655 and 81-19292 from the United States National Science Foundation. I thank Neil MacGregor, from Glenlyon, Nieuwoudtville, for his hospitality and assistance while in the field; John Lavranos and Inge Pehlemann, who discovered the Namib species and provided living and preserved material; Chris and Bobby van Vuuren, Rosh Pinah Mine, and Rosh Pinah, for their help in the field in southern Namibia; and Dee Snijman, from Compton Herbarium, Kirstenbosch, who rediscovered and drew my attention to the long overlooked Moraea pseudospicata and assisted me in recollecting it. I also acknowledge with thanks the drawings of Margo Branch. 2B. A. Krukoff Curator of African Botany, Missouri Botanical Garden, P.O. Box 299, St. Louis, Missouri 63166. ANN. MISSOURI BOT. GARD. 73: 102-116. 1986. This content downloaded from 157.55.39.231 on Thu, 06 Oct 2016 04:46:44 UTC All use subject to http://about.jstor.org/terms 1986] GOLDBLATT-NEW SPECIES OF MORAEA 103 flowers of the new species are similar also in being blue-purple, and, at least in four of them, small and extremely fugacious, opening in the late afternoon and fading at or shortly after dusk. This type of flower was previously known in a few taxonomically isolated species of Moraea. Despite their similarities, the flower types probably evolved independently in at least three of them. The adaptive significance of this flower is discussed after an outline of the morphology of the Moraea and Homeria flower and a review of the new species. The description of the three new species from Namibia more than doubles the number of Moraea species recorded in this country from the two admitted by Sblch (1969), M. polystachya and M. namibensis (treated as M. edulis by S6lch). Moraea carsonii has also now been found in the northeast of Namibia bringing the total species of Moraea recorded there to six, of which three are endemic. There is in addition at least one and possibly two more known new species of the genus in Namibia, both from the extreme south of the country, at present awaiting description when adequate type material can be assembled. MATERIALS AND METHODS