Two New Edaphic Endemic Species and Taxonomic Changes in Gladiolus (Iridaceae) of Southern Africa, and Notes on Iridaceae Restricted to Unusual Substrates

Abstract

Two new species of the African and Eurasian genus Gladiolus occurring on unusual substrates are described from southern Africa. Gladiolus serpenticola is restricted to serpentine soils in the Barberton District, Mpumalanga Province, South Africa, and adjacent Swaziland and G. pavonia occurs on dolomite in Mpumalanga. Gladiolus serpenticola, unusually tall for the genus, stands 75-150 cm high, has small, dry floral bracts, and short-tubed, pale pink flowers. It appears to be most closely related to another Mpumalanga endemic, G. hollandii, and both belong to an alliance of eastern southern African species centered around the widespread G. crassifolius. Gladiolus pavonia has pale pink flowers and is most likely related to a complex of eastern southern African species, mostly of rocky habitats in montane grasslands. Three additional species of Gladiolus from Western Cape Province, South Africa, are recognized here: G. miniatus, G. caeruleus, and G. variegatus. The first is reinstated at species rank after having been reduced to a subspecies of G. floribundus. Gladiolus caeruleus and G. variegatus are raised from infraspecific rank in which they were treated as G. gracilis var. latifolius and G. debilis var. variegatus, respectively. All three of these species are restricted to limestone outcrops. Gladiolus miniatus and G. variegatus occur in the southern part of Western Cape Province, and G. caeruleus is restricted to a small area of the west coast of the Province. These five species join the small number of taxa of African Iridaceae listed here, now totaling 15, known to be endemic or largely restricted to unusual soil types. Botanists have long recognized the striking effects of such azonal substrates as limestone, dolomite, gypsum, serpentine, and heavy metal soils (Kruckeberg & Rabinowitz, 1985; Kruckeberg, 1986). These substrates often harbor unusual plant associations and endemic species, and the new species recognized here fall into this category. As far as is known, relatively few of the estimated 1750 species of the family Iridaceae are narrow edaphic endemics of these unusual substrates, and none were mentioned by Wild (1978) in his survey of daphic endemism in southern Africa. Just a handful of African Iridaceae fall into this category (Table 1), most of which belong in the genus Gladiolus L. To this short list we add five more species, two new to science and three raised from infraspecific rank. The new species are G. serpenticola, restricted to serpentine outcrops in the Barberton District, Mpumalanga Province, South Africa, and adjacent Swaziland, and G. pavonia, an apparently narrow endemic of dry dolomite slopes near Abel Erasmus Pass in the Drakensberg Mountains of Mpumalan-