Abstract
The southern African genus Ixia L. comprises ± 90 species from the winter-rainfall zone of the subcontinent. Ixia sect. Dichone (Salisb. ex Baker) Goldblatt J.C.Manning, one of four sections in the genus and currently including 10 species and three varieties, is distinguished by the following floral characters: lower part of the perianth tube filiform and tightly clasping the style; filaments not decurrent; upper part of the perianth tube short to vestigial; style branches involute-tubular and stigmatic only at the tips; and so-called subdidymous anthers. We review the taxonomy of the section, providing complete descriptions and distribution maps, and a key to the species. I. amethystina Manning Goldblatt is recognized to be a later synonym of I. brevituba G.J.Lewis. Most collections currently included under that name represent another species, here described as I. rigida. We recognize five additional species in the section: early summer-blooming I. altissima from the Cedarberg; I. bifolia from the Caledon District; I. flagellaris, a stoloniferous species from the Cedarberg; I. simulans from the western Langeberg; and I. tenuis from the Piketberg. We also raise to species rank I. micrandra var. confusa and var. minor, as I. confusa and I. minor respectively. Foliar and associated floral variation in the widespread I. scillaris has led us to recognize two new subspecies among its northern populations, broad leaved subsp. latifolia and the dwarfed, smaller flowered subsp. toximontana; subsp. scillaris is restricted to the immediate southwestern Cape, from Darling to Somerset West. Sect. Dichone now has 17 species and two subspecies.
Highlights
Restricted to the winter-rainfall zone of southern Africa, the genus Ixia L. comprises some 90 species divided among the four sections Dichone (Salisb. ex Baker) Goldblatt & J.C.Manning, Ixia, Hyalis (Baker) Diels and Morphixia (Ker Gawl.) Pax (Goldblatt & Manning 2011)
In the later account of Ixia for Flora of southern Africa, De Vos (1999) followed Lewis’s taxonomy closely but included the new species, I. collina, described by Goldblatt & Snijman (1985), and altered the arrangement of species to place those with specialized, unilateral stamens at the end of the account
We identified two further undescribed species from the Cedarberg in herbaria, namely I. altissima, an early summer blooming species of uncertain affinities and I. flagellaris, allied to I. scillaris but the only stoloniferous species in the section
Summary
Restricted to the winter-rainfall zone of southern Africa, the genus Ixia L. comprises some 90 species divided among the four sections Dichone (Salisb. ex Baker) Goldblatt & J.C.Manning, Ixia, Hyalis (Baker) Diels and Morphixia (Ker Gawl.) Pax (Goldblatt & Manning 2011). C.F Ecklon (1827) likewise treated Ixia crispa and its immediate allies in a separate genus but for which he used the name Agretta, without description His species and combinations in Agretta are currently invalid. Agretta stricta was referred by Klatt (1882) to his genus Tritonixia and the species was only transferred to Ixia 629 was later cited by Klatt (1882) under his combination Watsonia retusa, which like its basionym, I. retusa, is without a type Both Lewis (1962) and De Vos (1999) excluded I. retusa from Ixia on the basis that the protologue is inadequate to identify the species. The two genera are clearly closely allied and available molecular studies (Goldblatt et al 2006, 2008) indicate a sister relationship (with moderate bootstrap support, 80%) between the one species each of Ixia (I. latifolia D.Delaroche) and Tritonia (T. disticha (Klatt) Baker) that were sequenced. There have been no molecular studies that shed light on the relationship of Ixia and Dichone but the unstated assumption implicit in the current taxonomy is that Dichone is nested within Ixia, its status as a section of that genus
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