Three new species and a new synonym in Strumaria (Amaryllidaceae: Amaryllideae) from southern Africa

Newly described are three species of Strumaria Jacq. subgenus Strumaria. S. prolifera Snijman from the Kourkammaberg in Namaqualand, South Africa, is a rare species closely allied to 5. barbarae Oberm. 5. speciosa Snijman from the Sonberg, southern Namibia and S. luteoloba Snijman from Namuskluft, southern Namibia and the Richtersveld in Northern Cape, South Africa, are rare species closely related to S. phonolithica Dinter. S. gigantea D.Mull.-Doblies & U.Miill.-Doblies is formally presented as a new synonym of 5. phonolithica. A key to the species in Strumaria subgenus Strumaria is given.


INTRODUCTION
Strumaria Jacq., a genus belonging to the tribe Amaryllideae subtribe Strumariinae is endemic to the semi-arid areas of southern Africa. Most species are found in the winter rainfall region, whereas only two taxa extend into the summer rainfall karroid areas. Among southern African Amaryllidaceae, Strumaria is second only to Cyrtanthus Aiton (tribe Cyrtantheae) in terms of the natural rarity of individual species, and as many as 80% of Strumaria species have been assessed as rare and threatened (Snijman & Victor 2002).
More recently, several new collections from under explored areas of Namaqualand and southern Namibia have come to hand. Some of these were found to repre sent undescribed species that are described here for the first time. In addition, S. gigantea D.Miill.-Doblies & U.Miill.-Doblies, which was published after Strumaria was last revised in 1994, is formally presented as a new synonym of S. phonolithica Dinter.
Strumaria phonolithica and the three new species all belong to subgenus Strumaria, bringing the number of species in the subgenus to eight. Like other members of subgenus Strumaria they have strap-shaped, glabrous leaves, dorsifixed anthers and a persistent infructescence. Other features that are not consistently present in all representatives of the subgenus, but which help to characterise the group, are the three or more leaves ar ranged in a spreading fan. a sheathing cataphyll, and the apparently tubular to hypocrateriform or campanulate flowers. In addition, the pedicels often approximate the length of the flowers and the filaments are mostly fused into a basal tube divided into three nectar wells. A key to the eight species currently placed in subgenus Strumaria is given.  (-CD), 11-7-1989, Bruxns 3883 (NBG, holo.;K, PRE).
Phenology: in cultivation, S. prolifera flowers simultaneously with the bulb's newly emerging leaves in the middle of May. Several attempts have been made to study the species flowering in nature, but despite visits to the Kourkammaberg over three con secutive years in late April and May, the species has not been seen flowering in the wild. This may suggest that the bulbs flower infrequently in nature, possibly only after good autumn rains. The soft, delicate leaves remain green throughout winter but die off with the onset of hot, dry summer conditions at the end of spring.
Diagnostic features: Strumaria prolifera is easily rec ognized by its pink, funnel-shaped flowers, which enclose the stamens. Only two other species have similarly shaped flowers with short, included stamens, namely S. barbarae Oberm. from southern Namibia and the eastern Richtersveld, and S. pubescens W.F.Barker from the Roggeveld escarpment and Laingsburg District. Based on the stamen and style morphology, 5. prolifera shows greatest affinity with S. barbarae, which belongs to sub genus Strumaria. In both species the filaments form a proximal tube up to 3-5 mm long and through the fusion of the outer stamens to the three-winged style base, the tube is divided into three separate hollows, where nectar collects from the peristylar pores on the ovary dome ( Figure IE). Thus insects seeking nectar are forced to probe each hollow consecutively. Moreover, both species have drooping, scented flowers. The perigone in S. bar barae, however, is longer (28-38 mm) and mostly white when fresh, unlike the shorter (18-20 mm long), distinct ly pink perigone in S. prolifera. More divergent is S. pubescens, belonging to subgenus Gemmaria, that has spreading to erect flowers in which all six stamens are adnate to the narrowly trigonous style base. Nectar there fore discharges and collects as three small droplets in the sinuses between the inner filaments and style.
A noteworthy feature is that all the species belonging to subgenus Strumaria (S. bidentata Schinz, S. barbarae, S. hardyana D.Miill.-Doblies & U.Miill.-Doblies, S. luteoloba Snijman, S. phonolithica. S. speciosa Snijman and S. truncata Jacq.), except S. prolifera. have erect to fal cate leaves arranged in a single fan. Strumaria prolifera is unique in the subgenus in having straight, soft, oppo site leaves, which ultimately spread flat on the ground. The species is furthermore distinguished by the forma tion of bulblets and extremely thin-textured. pale green leaves.
Distribution and habitat: Strumaria prolifera is known only from the Kourkammaberg. an isolated, pre dominantly quartzite mountain on the coastal forelands of Namaqualand (Figure 2). The bulbs grow on southern slopes near the mountain's summit, where they are con fined to partial shade between large rocks (P. Desmet pers. comm.). The population consists of highly local ized colonies of up to 100 plants. Low succulent shrubs dominate the surrounding vegetation.
Etymology: the species is named prolifera for its char acteristic proliferation by offsets, which slowly give rise to dense colonies of bulbs and apparently compensate for the bulbs' infrequent flowering and fruiting.
Phenology: in cultivation the species flowers in the middle of May when the new leaves are present. The leaves remain green during winter and die back sometime in late spring at the end of the rainfall season. As yet. the species has not been recorded flowering in nature.
Diagnostic features: in its vegetative state. Strumaria speciosa is almost indistinguishable from the southern Namibian endemic, S. phonolithica Dinter. Both species have a stout bulb neck that extends well above ground level (up to 100 mm long in S. speciosa and 160 mm long in 5. phonolithica). The leaves are broad, 17-25 mm wide in 5. speciosa and 12-50 mm wide in S. phonolithica, and they curve laterally to form an outspread, erect fan which is arranged in a single plane. S. speciosa, however, is easily distinguished when flowering. The scape is recurved apically and the 30-50 mm long pedicels are firm, outspread and straight, but deflexed distally so that the campanulate flowers are nodding. Furthermore, the tepals are strongly recurved in the distal half so that the stamens protrude by almost 10 mm. In contrast, the firm, outspread pedicels in 5. phonolithica never exceed 25 mm long so that the flower cluster remains compact. The tepals also remain imbricate for about three-quarters of their length and only recurve near the tips, thus only the tips of the stamens protrude from the perigone throat. Although S. phonolithica and S. speciosa are easily distinguished, their strong morphologi cal similarities, nevertheless, emphasize a close alliance.
Distribution and habitat: Strumaria speciosa is known from only two collections on the Sonberg, a mountain range in the semi-arid, winter rainfall region of southern Namibia (Figure 4). The small, localized popu lations are found on south-facing slopes below dolomite outcrops at about 900 m. The bulbs grow in soft, loamy soil among stones and low, predominantly succulent shrubs (P.V. Bruyns pers. comm.).
Phenology: in cultivation the bulbs flower in May, before the new leaves appear. The leaves emerge shortly after flowering and remain green throughout winter until September, when they die back and the bulbs become dormant over the hot, dry summer.
Diagnostic features: the erect, fan-shaped leaf arrangement and dorsifixed anthers of S. luteoloba are sufficiently distinctive to place the species in subgenus Strumaria, but unlike most species in the subgenus, the filaments of S. luteoloba are not proximally fused into a tube. Like S. phonolithica the new species has narrow, closely imbricate tepals. However, S. luteoloba is easily recognized by the tepals being deeply channelled and sharply reflexed from ± halfway along their length, and by the outer tepal whorl reflexing 2-4 mm below the inner whorl so that the perigone has a distinctive biseriate appearance. The flower colour is also unique in the genus. The perigone is pinkish red near the base and pale lemon-to cream-coloured in the distal half. S. gemmata Ker Gawl., belonging to subgenus Gemmaria, is the only other species with lemon-or cream-coloured flowers but these are stellate and concolorous.
Distribution and habitat: Strumaria luteoloba is known only from the winter rainfall region of southern Namibia and the Richtersveld, South Africa (Figure 6). At Namuskluft, southern Namibia the plants are found in dolomite-derived soil, whereas the only other known population is on the Rooiberg (D. Hannon pers. comm.), a granite mountain massif in the Richtersveld.