A new species of Nivenia ( Iridaceae )

Plantae 0.3-0.5(-0.8) m altae, sempervirentes, caulibus pluribus e caudice lignoso compresso elliptico, foliis distichis ensiformibus ad linearibus usitate 50-70 x 3-4 mm, inflorescentiis ex rhipidiis binatis bifloris 20-60 compositis paniculam corymbosam formantibus, spathis 3^4 mm longis, bracteis siccis papyraceis corrugatis brunneis, floribus pallide caeruleis heterostylis, tubo perianthii ± 5.5 mm longo, tepalis subpatentibus lanceolato-ellipticis 6.3-7 x 2.4-3.0 mm, filamentis ± 6 mm longis (plantis brevistylis) vel ± 2 mm longis (plantis longistylis), antheris ± 1.3 mm longis pallide caeruleis, ovario ± 1.2 mm longo, stylo ± 2 mm (plantis brevistylis) vel 6-8 mm (plantis longistylis) ex tubo exserto, lobis stigmatis ± 0.4 mm longis.


Distribution and habitat
Nivenia p a n 'iflora is restricted to the lower southern slopes of the Klein Swartberg Mountains near Ladismith in Western Cape Province, South Africa.Plants grow on rocky sandstone slopes, mostly in rock outcrops, in fynbos vegetation in a community with Protea repens L. a domi nant species.As in most species of Nivenia, flowering occurs in the late summer and autumn, March and April to early May for N. parviflora.Its close relative, N. binata, is one of only two species of the genus that flowers in the spring, August to October, the other being the taxonomically isolated N. argentea Goldblatt.

Diagnosis and relationships
Comprising 10 species, including this new species, Nivenia is one of three genera of the Iridaceae that are evergreen shrubs with truly woody stems that produce sec ondary growth.Nivenia and the two other shrubby genera.Klattia (three species) and Witsenia (one species) are a clade within subfamily Nivenioideae, one of four subfami lies of the Iridaceae, that also includes the African Aristea, the Madagascan Geosiris, and the Australasian Patersonia (Goldblatt 1990(Goldblatt , 1993) ) All three shrubby genera are re stricted to the Cape Flora Region of southern Africa.The three shrubby genera form a clade defined not only by their woody and evergreen habit, but by several other spe cialized features, including leaves with sclerenchyma strands, inflorescence units two-or one-flowered, ovules two per locule, tangentially flattened, shield-shaped seeds, and a transparent testa (Manning & Goldblatt 1991).Within this clade Nivenia has the least specialized flowers, always with a blue perianth, the majority of species are distylous, and the floral bracts are dry and papery.Out group comparison indicates that both distyly and the dry bracts are derived and thus ancestral traits for the genus.
Within Nivenia the majority of species have the indi vidual inflorescence units (binate rhipidia) arranged in co rymbose pseudopanicles and the rhipidial spathes are short and obtuse.Among these are the new Nivenia p a n iflora which has, in addition, derived dark brown and much wrinkled floral bracts and blue anthers, features shared by two other species of Nivenia, N. binata Klatt and N. stenosiphon Goldblatt.It is to these species that N. parvi flora is evidently most closely related.Both N. binata and N. stenosiphon have larger flowers with tepals 7.5-12.0mm long, and a longer perianth tube, usually 10-15 mm long in N. binata and 32-38 mm long in N. stenosiphon.Nivenia parviflora contrasts with both of these in its un usually small flowers, the tepals 5-6 mm long and the tube ± 5 .5 mm long.Because of the smaller flower and relatively short perianth tube of N. binata we suggest that N. parviflora may be most closely related to that species.Differences between them extend beyond the size and pro portions of the floral parts.The rhipidial spathes are 4-5 mm long and the floral bracts 9-10 mm long in N. binata, substantially longer than in N. parx'iflora w hich has spathes 3-4 mm long and floral bracts ± 5 mm long.The differences are presumably directly related to the smaller flowers of the species.Also presumably associated with the small flower size, the filaments and styles of N. parvi flora are shorter than those of N. binata.The filaments are either ± 2 mm or ± 6 mm long (for long-or shortstyled morphs) and the styles are either 4 mm longer or shorter than the stamens in N. par\'iflora whereas in N. binata the filaments are either 2-3 or 7-9 mm long (for long-or short-style morphs) and the styles either 5 -6 mm longer or shorter than the stamens.

Pollination and evolution
The small flower and short perianth tube of Nivenia parviflora are related to its pollination ecology.The flow ers are visited by and presumably pollinated by the medium-sized bee, Amegilla sp.(Anthophoridae), the fly Prosoeca sp.(Nemestrinidae), and the butterfly, Cynthia cardui.The flowers produce small amounts of nectar in the base of the perianth tube on which the insects feed.Mouthparts of Amegilla sp. and Prosoeca sp. are 7-8 mm and ± 10 mm long respectively.Thus both these insects are able to remove nectar from the base of the tube of N. parx'iflora which is ± 5 mm long.While foraging for nec tar in flowers of N. parviflora the bodies of these insects brush against the exserted anthers, and pollen is deposited on their bodies.Pollen of short-styled plants, thus with long stamens, is dusted on an insect's ventral and lateral thorax and abdomen but mainly on the frons in long-styled plants with short stamens.When insects visit flowers with long styles, the terminal stigmas brush against its abdomen and lower thorax thus becoming dusted with pollen from the short-styled morph.Heterostyly thus promotes outcrossing by differential pollen placement on the body of a pollinating insect and this is accompanied by contact with the complimentary stigma type.
The closest relatives of Nivenia parviflora, N. binata and N. stenosiphon are both restricted to the Swartberg Mountains, and the adjacent Touwsberg in the case of N. stenosiphon, and both are pollinated by long-tongued flies of the genus Prosoeca (Nemestrinidae) (Goldblatt & Bern hardt 1990).The difference in flower size in N. par\>iflora which is correlated with a pollination strategy different from that of its two relatives, and a difference in flowering time between N. parviflora and N. binata, presumably sis ter species, makes it desirable to recognize it as a distinct species.The ranges of the three Swartberg species of Nivenia are complimentary, N. stenosiphon occurring west of Ladismith, N. parviflora with a narrow range north of Ladismith, and N. binata, with the widest range, extends from Seweweekspoort east of Ladismith to Meiringspoort.It seems clear that both geographic and seasonal components are involved in the radiation and speciation within this clade and in differences in their pollination ecology.

History
Nivenia parx'iflora was apparently first collected by the botanist and intrepid collector, Elsie Esterhuysen in 1947 in fruiting condition.This collection, and a flowering one made in 1951, were referred to N. binata in my mono graph of the genus (Goldblatt 1993) because I thought that the specimens represented odd plants flowering out of season and with somewhat smaller flowers than normal.Additional collections show that this asssumption was wrong.The plants have a separate geographical range from that of N. binata and consistently have smaller flow ers that bloom in autumn.