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(Last Modified On 12/17/2016)
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Description:
Deciduous (rarely evergreen) geophytes. Corm globose to depressed-globose, axial in origin, tunics of fine or coarse fibres, leathery or woody, rarely papery. Catapylls 3, pale and membranous. Stem well developed, usually terete or rarely angled or slightly winged, simple or branched, often flexuouse, rarely scabrid to velvety. Leaves solitary to several, mostly basal and forming a 2-ranked fan or some cauline, rarely borne on a separate shoot, sometimes dry at flowering, blade sometimes reduced or lacking and leaves thus entirely sheathing, unifacial, usually with a definite midrib, plane and linear to lanceolate, rarely round to oval in section, occasionally the margins or midrib raised or winged and leaves thus X- or H-shaped in section, sometimes terete and longitudinally 4-grooved, cauline leaves usually few and reduced, rarely scabrid to velvety or pubescent; margin with vascular bundle and epidermal cells unspecialized. Inflorescence a spike, usually secund or in two ranks; bracts green and soft or firm, sometimes dry above, usually large, inner smaller than outer and 2-toothed or notched apically. Flowers usually zygomorphic, rarely radially symmetric, long-lived, bilabiate and funnel–salver-shaped or rarely rotate, variously coloured but often pink to mauve, lower tepals usually with contrasting nectar guides, unscented or variously scented, often closing at night, with nectar from septal nectaries; perianth tube funnel-shaped or cylindric, short or long; tepals subequal or unequal with dorsal largest and arched to hooded over the stamens, the lower three narrower and forming a lip, sometimes clawed and shortly united. Stamens usually unilateral and arcuate, rarely symmetrically disposed; filaments inserted well below top of perianth tube, included or exserted. Ovary globose; style filiform, usually unilateral and arcuate, 3-branched distally, branches oblanceolate-conduplicate, and expanded above, often bilobed. Capsules leathery, usually slightly inflated and raltively large, ovoid to ellipsoid, segments recurving strongly after dehiscence. Seeds discoid with a broadly circumferetial papery wing, rarely wing obsolete, then subglobose or angled, domed on seeed body and concave on wing. Pollen monosulcate-operculate, operculum 2-banded, exine perforate-scabrate. Basic chromosome number x = 15, other numbers 14, 12, 11.
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Etymology:
from the Latin, gladiolus, diminutive of gladius, sword, for the sword-shaped leaves.
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General Notes:
Species about 270, mainly sub-Saharan Africa and Madagascar, also Europe and the Middle East, about 169 in southern Africa, centred in the winter-rainfall zone of southwestern Western Cape, with secondary centres of diversity in the eastern African highlands and in Shaba Province of Congo. As in most genera of Iridaceae with a significant representation of species in both summer- and winter-rainfall southern Africa there is minimal overlap among the species from the two rainfall regimes or in those from tropical Africa. Gladiolus species are most common in temperate habitats, mainly grasslands and open savanna in areas of summer rainfall and fynbos and other shrublands in the winter-rainfall region.
Gladiolus is highly variable in both floral and vegetative morphology but most species have characteristic ovoid, leathery, somewhat inflated capsules and distinctive seeds with a broad circumferential wing. The style is also diagnostic, with oblanceolate-conduplicate branches that are expanded above into broad, bilobed tips. The basic chromosome number, x = 15, indicates that the genus is palaeopolyploid. Most species are diploid, 2n = 30 but the almost pan African G. dalenii is heteroploid, with tetraploid, hexaploid, and occasionally diploid populations.
The affinities of Gladiolus have long been uncertain but molecular phylogenetic analyses suggest that the genus is most closely allied to the monospecific Melasphaerula of the southern African winter-rainfall zone. The two genera have little morphological similarity. A molecular phylogenetic genetic analysis of Gladiolus, with an emphasis on the southern Arican and Mediterranean species, proposes an origin for the genus in southern Africa during the Miocene, followed by range extensions into tropical Africa, Madagascar and the Mediterranean. The high diversity in the southern African winter-rainfall region is interpreted as a result of the long history of the genus in the region, combined with comparatively low rates of extinction and higher rates of ecological speciation.
The large number of generic synonyms reflects the floral diversity in the genus, much of which is now understood to represent adaptation to various specialized pollination systems. Pollination by large anthophorine bees foraging for nectar is the most common system in the genus but many southern African species have long-tubed white to pink flowers adapted for pollination by long-proboscid flies. Bird pollination is frequent in southern and tropical African species, as is moth pollination by large settling moths or hovering sphinx moths. Other species are pollinated by large butterflies, notably in southern Africa, where red-flowered species are pollinated largely or exclusively by the satyrid butterfly, Aeropetes. Radial symmetry has evolved in a handful of species in both southern and tropical Africa, and these species appear mostly to be pollinated by female bees foraging for pollen.
The floral diversity is matched by numerous vegetative adaptations, notably reduction in leaf number and the development of winged midribs and/or margins, or reduction of the entire leaf blade. In some species flowering occurs before the leaves are produced or after they have dried, thereby separating the growth and reproductive phases of the life cycle.
The current classification of Gladiolus in southern Africa recognizes seven sections, distinguished by the insertion of the foliage leaves on the stem, the shape and thickening of the blades, the shape and number of the flowers, and the shape and size of the capsules. The molecular phylogenetic analysis of the genus by Valente is only partially congruent with this classification and some marked anomalies make it difficult to interpret. However, many of the series or species groups recognized by Goldblatt & Manning are retrieved in their phylogeny, providing independent support for species relationships at these lower taxonomic levels. Provisionally, therefore, the slightly modified version of Goldblatt & Manning's classification by proposed by Manning & Goldblatt (2009) is followed here.
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