Systematics of the southern African genus Ixia (Iridaceae). 1. The I. rapunculoides complex

Abstract

Field and laboratory investigation of the six varieties of Ixia rapunculoides Delile (recognized in the current revisions and flora accounts of this southern African genus of some 65 species) show that a revised taxonomy better reflects the biology of the complex. The complex is defined by the funnel-shaped perianth tube, filaments fully and anthers partly included in the perianth tube. Our conclusions indicate that  I. rapunculoides (currently var.  rapunculoides) is restricted to the western Karoo and has broad, leathery leaves, a short perianth tube, mostly 5.5-8.0 mm long, and half nodding blue-mauve flowers. Plants currently referred to I. rapunculoides var.  flaccida G.J.Lewis, include four sets of populations that we regard as two separate species. These are:  I. flaccida with small, short-tubed white- or pale blue-flushed flowers, sofl-textured leaves and corms with basal cormlets from the Olifants River Valley and nearby; and I. sobolifera from the Western and Little Karoo, which has linear leaves, nodding spikes and flowers and corms with stolons. We divide  I. sobolifera into three subspecies: subsp. carnea with pink flowers, is restricted to the Bokkeveld Plateau and nearby; subsp  sobolifera with slate-blue flowers occurs in the Klein Roggeveld and nearby; and subsp  albiflora with strongly scented white flowers occurs in the central Little Karoo. The taxon called  I. rapunculoides var.  namaquana (L.Bolus) G.J.Lewis, defined by a longer perianth tube, mostly 13-16 mm long, horizontally oriented, white, pale lilac or pink flowers and few-flowered lateral branchlets. is treated as I. namaquana, first described by H.M.L. Bolus in 1931. Plants referred to this taxon from south of its range at Hex River pass and nearby, however, have fully included anthers, a longer perianth tube. 16-20 mm. and ascending purple-pink flowers with a white cup and are referred to the new I. oxalidiflora. Two more varieties, I. rapunculoides var. subpendula G.J.Lewis and var. rigida sensu G.J.Lewis, which have upright flowers and distinctively branched stems are treated here as I. divaricata and I. contorta.  Plants in the past included in var.  rapunculoides from the Klein Roggeveld, south of the range of typical I. rapunculoides, have a longer perianth tube. 10-14 mm long, and attenuate, slightly lacerate. 5-veined. dry. rust-tipped bracts and comprise the new I. lacerata In addition, plants from streambeds in the Roggeveld that have large, white flowers, are not included in current accounts of the genus, and also represent a novel taxon, I. rivulicola. Lastly, I. rapunculoides var. robusta G.J.Lewis, the range of which falls entirely within that of var. rapunculoides and is usually sympatric with it. has pink flowers of similar structure, but four or five leaves and deep-seated corms with a collar of coarse fibres around the stem base. We raise this plant to species rank as I. robusta