POLLINATION OF MORAEASPECIES (IRIDACEAE) WITHA STAMINAL COLUMN'Peter Goldblatt2 and Peter Bernhardt;ABSTRACT The ancestral and most common flower in the African genus Moraea is Iris-like and consists of three functional units(meranthia). Each unit consists of an outer tepal opposed to a broad style branch terminating in prominent pairedcrests, together forming a gullet-like unit. However, many species in this genus of some 200 species have mechanicallyprotandrous flowers in which the three stamens form a sheath surrounding the style and the style branches are narrow,with reduced stigmatic crests, and the subequal inner and outer tepal whorls form a shallow or deep bowl sometimesfully enclosing the stamens and style branches. The flowers secrete hexose-dominant nectar and, except for M. collina,are self-incompatible. Flowers of the nine species in two sections studied comprise two different modes of pollinationbased on the presentation of the staminal column and perianth, pigmentation, scent, and edible rewards. In five species,M. collina, M. comptonii, M. elegans, M. ochroleuca, and M. vallisbelli, the perianth forms a wide or narrow bowl andproduces strong, sweet or musk-like odors, and the weakly diverging anthers are appressed to the narrow, inconspicuousstyle branches. These flowers are pollinated primarily by flower flies, scarab beetles, and honey bees that land on theperianth and brush against the anthers and/or receptive stigmas while foraging for nectar or pollen, or in the case orbeetles merely assembling on the flowers. In the second group of species, M. bifida, M. miniata, M. pseudospicata, andM. reflexa, the perianth is stellate, pink, yellow, or blue, usually without discernable scent, the filaments are unitedinto a column that is exserted from the flower, and the anthers are usually coherent. These flowers are pollinatedprimarily by polylectic bees in the families Apidae (Anthophora diversipes, Apis mellifera) and Melittidae (Redivivaspp.). The bees land on the staminal column and forage for pollen, sometimes later moving onto the perianth to takenectar present at the base of the tepals. The columns of these species are interpreted as both morphological andfunctional intermediates between pollen presenters or protostigmas (e.g., in Asterales, Campanulales, Proteales) andtrue gynostemia/gynostegia (in Asclepiadaceae, Orchidaceae, and Stylidiaceae). These flowers represent a profound shiftin the ancestral pollination strategy in the genus from one of passive pollen deposition on bees foraging for nectar onmeranthia to one of active foraging for nectar or pollen on whole flowers. Floral morphology in the Iridaceae is usuallyclosely correlated with the diversity of pollinators.For example, most species in the genera Lapeirou-sia and Nivenia have flowers with elongated floraltubes and are pollinated by nemestrinid and taba-nid flies and sphinx moths that have probosces lon-ger than their bodies and often forage for nectarwhile hovering (Vogel, 1954; Goldblatt & Bern-hardt, 1990; Goldblatt et al., 1995; Manning &Goldblatt, 1996, 1997). Conversely, North Ameri-can Sisyrinchium species, and some species of thesouthern African genera, including Aristea, Ixia,Romulea, and Sparaxis, have stellate or rotate peri-anths, the latter with reduced, often non-functionalfloral tubes. The primary pollinators of these flowersinclude small-and large-bodied bees, large scarabbeetles (Hopliinae), and short-tongued flies thatmust land on the tepals to collect nectar and/orpollen (Henderson, 1976; Cholewa & Henderson,1984; Goldblatt et al., 1998a; Goldblatt & Man-ning, 1997). In southern Africa scarab beetles alsouse the flowers as sites for assembly and mating.Genera pollinated primarily by large bees with longprobosces (e.g., Gladiolus) have zygomorphic, bi-labiate flowers in which the lower tepals form alanding platform (Vogel, 1954; Goldblatt et al.,1998b). In Iris and most species of Moraea the individualflowers comprise three functionally separate polli-nation units, or meranthia (Faegri & van der Pijl,1979). Each meranthium resembles a bilabiate gul-let flower and consists of a large outer tepal, theclaw of which is closely opposed to a flattened stylebranch that bears a transverse stigma and terminal,petal-like crests (Fig. 1). The major pollinators arelarge bees that land on the outer tepal limb and ' Support for this study by grant 5408-95 from the National Geographic Society is gratefully acknowledged. We thankH. Dombrow, Wurms, Germany, D. Barraclough, KwaZulu-Natal Museum, Pietermaritzburg, and V. Whitehead, SouthAfrican Museum, Cape Town, for identification of insects, and B.-E. van Wyk, Rand Afrikaans University, Johannesburg,for the nectar analyses. 2 B. A. Krukoff Curator of African Botany. Missouri Botanical Garden, P.O. Box 299, St. Louis. Missouri 63166,U.S.A. Biology Department, St. Louis University, St. Louis, Missouri 63103, U.S.A. ANN. MISSOURI BOT. GARD. 86: 47-56. 1999.
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