New Species of Aristea (Iridaceae) from South Africa and Notes on the Taxonomy and Pollination Biology of Section Pseudaristea

Abstract

Aristea teretifolia and A. cantharophila are new species from the winter-rainfall region of southern Africa. Both belong in section Pseudaristea, one of eight sections of this genus of ca. 52 species of sub-Saharan Africa and Madagascar. Aristea teretifolia has pink, mauve, or cream flowers, the inner tepals of which are longer than the outer and have a large dark blotch near the base, and stands out in the section in its very narrow linear or sometimes terete leaves. Aristea cantharophila has narrow, linear to sword-shaped leaves fairly typical of the section, and mauve or white flowers with subequal tepals, each of which has a zone of dark color near the base. In their long pedicels, oblong-trigonous ovary, large and deeply fringed stigma lobes, and woody, elongate, tardily dehiscent capsules these new species conform closely to the characteristic features of section Pseudaristea. Field observation suggests that both species are adapted for pollination by monkey beetles (Scarabidae: Rutelinae), which use the flowers of these and at least one other species of the section as sites for feeding and mating. The dark markings on the tepals appear to mimic beetles and presumably encourage visits by these insects. The Afro-Madagascan genus Aristea comprises some 52 species (Weimarck, 1940; Goldblatt, 1991, 1995a, b) currently divided among eight sections. As redefined by Goldblatt (1995a), section Pseudaristea Pax comprises five species, all of Western Cape Province, South Africa, a region of winter rainfall and summer drought. To this number we add two new species, A. cantharophila (Fig. 1A) and A. teretifolia (Fig. 1B), and exclude A. zeyheri Baker from the section. The new species are both narrow endemics of lowland sites in the southwestern part of Western Cape Province. They share all the characters that define the section and differ mainly in their unusually colored and marked flowers (Fig. 1), and in the case of A. teretifolia also in its terete or extremely narrow leaves. The defining features of section Pseudaristea are flowers with long pedicels, an oblong and three-lobed to threeangled ovary, large inflorescence spathes concealing the flower buds, prominent and deeply fringed stigma lobes, and woody, elongate, tardily dehiscent, deeply three-lobed capsules. To this list of morphological features can be added di-zonosulculate pollen grains, unique in Iridaceae (Radelescu, 1970; Schulze, 1971; Le Thomas et al., 1996), and exine with reticulate sculpturing. RELATIONSHIPS OF ARISTEA ZEYHERI Aristea zeyheri was assumed by Weimarck (1940) to accord in most of its features with those that define section Pseudaristea. New material collected since Weimarck completed his monograph of the genus in 1940, however, shows that this species has capsules with three prominent, narrow wings, 2-4 flattened, plate-like seeds per locule, and minutely trifid styles. These are exactly the apomorphic features that define section Racemosae. It seems likely that A. zeyheri is most closely related to A. racemosa Baker of that section, which it resembles closely in overall morphology, particularly the slender habit and subterete leaves. The pollen grains ofA. zeyheri are monosulcate, or in one population zonosulculate (unpublished), with rugulose exine. In its exine sculpturing and basic aperture condition, A. zeyheri also accords with section Racemosae, species of which have pollen grains with monosulcate apertures and either microreticulate or rugulose exine (Goldblatt & Le Thomas, in prep.). POLLINATION BIOLOGY OF SECTION PSEUDARISTEA Most species of Aristea have deep blue flowers, bright yellow anthers and pollen, and lack conspicuous dark markings. Preliminary observations on the pollination of the genus indicate that the blueflowered species of Aristea are pollinated by a vaNovoN 7: 137-144. 1997. This content downloaded from 157.55.39.186 on Sun, 09 Oct 2016 04:52:20 UTC All use subject to http://about.jstor.org/terms