A taxonomic re-assessment of Ammocharis herrei and Cybistetes longifolia (Amaryllideae: Amaryllidaceae)

The infructescence of the poorly known Ammocharis herrei F.M. Leight. is similar to that which is diagnostic for Cybistetes longifolia (L.) Milne-Redh. & Schweick. In the absence of distinct morphological differences A. herrei is placed into synonymy under C. longifolia. Plants of the amplified C. longifolia have fewer, large seeds in Namaqualand and the Richtersveld and smaller, more numerous seeds in the Western Cape. This pattern is postulated to reflect divergent strategies of resource allocation in different habitats. It is suggested that the infructescence of C. longifolia. a highly derived structure suited to tumbling, evolved from the unspecialised condition in Ammocharis as an adaptation to the high winds of southwestern Africa.


INTRODUCTION
The monotypic Cybistetes Milne-Redh. & Schweick. is a Western Cape representative of Amaryllidaceae tribe Amaryllideae with a specialised infructescence in which the pedicels elongate, spread apart, stiffen and ultimately radiate equally in all directions. Its separation from the widely distributed sub-Saharan Ammocharis Herb, was based on the interpretation of Milne-Redhead & Schweickerdt (1939) that the pedicels of the infructescence and the dry. strongly ribbed capsules constitute a substantially dis tinct set of characters from the basic infructescence struc ture of Ammocharis in which the pedicels neither reflex nor elongate and the fruits remain submembranous and subglobose. This treatment, however, rendered uncertain the taxonomic position of A. herrei F.M. Leight. whose fruits have remained unknown until now.
Even in the absence of fruiting material. Milne- Redhead & Schweickerdt (1939) commented on the close resemblance of the type of A. herrei to the Western Cape species, C. longifolia (L.) Milne-Redh. & Schweick. They noted differences, however, in inflorescence characters and ovule numbers.
Several recent collections of Amaryllidaceae from the Richtersveld (Table 1). Infructescences collected near Vanrhynsdorp and Namaqualand have a greater maximum number of seeds per capsule than the fruiting material collected in the Richtersveld. The capsules from the south also tend to be longer and narrower than those in the north ( Figure 2). The differences, however, are not discrete and the increase in seed number per capsule from the north to the south appears to be continuous. There is also an inverse relationship between seed size and seed number per capsule within the species' distribution range (Table  1). Thus plants in the Richtersveld and Namaqualand tend to have especially large seeds (up to 29 mm across) whereas the seeds of those in the south are smaller (7-19 mm across) ( Figure 2). Seed size within a capsule is nevertheless variable throughout the distribution range.

DISCUSSION
In the absence of any vegetative, floral or clearly dis continuous fruiting characters to distinguish A. herrei from the variable C. longifolia, we propose that A. herrei is conspecific with C. longifolia (L.) Milne-Redh. & Schweick. but that plants of C. longifolia produce few, large seeds in the semi-arid environments of the Richtersveld and Namaqualand, and many, relatively small seeds in the more equ able south. Accordingly A. herrei is treated here as a synonym of C. longifolia.
As regards the comparative biology of individuals within the amplified C. longifolia, the most noteworthy variables are seed size and seed number. According to Harper et. al. (1970) and Stebbins (1974) seed size and seed number represent alternative strategies in the disposi tion of reproductive resources. However, due to divergent and often conflicting advantages and disadvantages of seed size versus seed number, most plant species have evolved compromise strategies which depend on various conditions of their habitat as well as their evolutionary ancestry (Stebbins 1974). In the Richtersveld the annual vegetative growth period of C longifolia is often more variable and shorter than that of plants in the Western Cape whose foliage leaves are green for five to six months throughout the winter rainfall season. The fleshy seeds of C. longifolia, which germinate immediately after being shed in autumn, are potentially susceptible to desiccation injury before the onset of winter rain. Thus within the constraints of the restricted and unpredictable growing season for C. longifolia in the semi-arid Richtersveld and Namaqualand the selection of large seeds, which have op timal reserves for their initial growth, appears to have been favoured at the expense of seed numbers. In contrast, the more reliable growing season of the Western Cape may have promoted the selection of large seed numbers over seed size to increase the probability that some seeds lodge in suitably open habitats amongst the otherwise densely vegetated communities of this region.
In several evolutionary lines Stebbins (1970) observed the transference of function of a particular structure. A notable example is the functional shift in the fruit wall from that of providing protection for developing ovules to one of effecting the dispersal of mature seeds. This pattern is paralleled in Ammocharis and Cybistetes whose indehiscent fruit walls initially protect the fleshy seeds during development, but thereafter effect divergent disper sal strategies.
The lax infructescences of Ammocharis, which favours seasonally moist habitats, initially elongate then flop to the ground, releasing their seeds close to the parent plants.
In contrast, the indehiscent fruits of Cybistetes, which in habits open, dry situations, become dry, rigid capsules, that radiate outward to form a sphere which then tumbles in the wind (Markotter 1936;Martley 1938;Milne-Redhead & Schweickerdt 1939) (Figure 1C). Following the concept of transference of function (Stebbins 1974), it is postulated that the basic protective function of the fruits has shifted to include a derived dispersive function in Cybistetes, where the entire infructescence serves as the unit of dispersal. Clearly, the specialised infructescence characters defined by Milne-Redhead & Schweickerdt (1939) as separating Cybistetes from Ammocharis are highly integrated and functionally interrelated to effect dispersal by tumbling (anemogeochory of Van der Pijl 1982). It does not seem unlikely that this syndrome of characters evolved from a most recent common ancestor within Ammocharis as an adaptation to the high winds of the Western Cape which probably date from the inception of its Mediterranean-type climate in the Late Pliocene (Deacon et al. 1992;Tankard & Rogers 1978). This in terpretation suggests that Ammocharis sensu Milne-Red head & Schweickerdt (1939) is paraphyletic and that the current classification of Cybistetes and Ammocharis war rants re-examination. Evidence of this, however, awaits a phylogenetic analysis of all the species in the generic com plex and a character analysis of the closely related and variable genus Crinum L.
In Amaryllideae anemogeochory is also known in Boophane Herb, and Brunsvigia Heist. In most taxa the infructescences detach at ground level and roll away in the wind with the scape intact. The scape, which ap proximates the length of the radiating pedicels in most species, appears to confer symmetry on the infructescence, a configuration which Maddox & Carlquist (1985) have shown ranks highly in tumbling ability. Boophane disticha (L. f.) Herb, and Boophane haemanthoides F.M. Leight. are exceptional in having infructescences which detach from the scape distally. The resultant dispersal unit lacks symmetry and appears to lose its integrity rapidly. These observations suggest that Cybistetes, Boophane and Brunsvigia offer interesting possibilities for experimental studies in wind dispersal. Bulb solitary, ovoid to globose, 100-150 mm across, extended into a neck up to 60 mm long, entirely subter ranean; outer tunics dark brown, tough and leathery; inner tunics fleshy, cream-coloured. Leaves present or absent at anthesis, 9-14, biflabellately arranged, spreading, strap shaped, more or less falcate, variable in length and width, with the inner narrower and shorter than the outer, 6-270 x 13-55 mm, glaucous, smooth; margins scarious, obscurely toothed or entire; apex truncate in mature leaves, obtuse in young leaves. Inflorescence 13-90flowered, ranging from somewhat clustered to widely spreading, 150-340 mm across; scape erect, up to 200 mm long, compressed, about 10 x 22 mm, fleshy, smooth, detaching from the bulb at ground level when dry; spathe valves 2, reflexed, broadly lanceolate, 20-30 x 40-75 mm, thinly coriaceous; bracteoles filiform: pedicels 50-110 mm long at anthesis, somewhat triangular in cross section, radiating outward, stiffening and lengthening to 100-210 mm in fruit. Perigone widely trumpet-shaped, slightly zygomorphic due to the declinate style, ivory to pink, turn ing deeper pink with age, dark reddish when collapsed. 130 sweetly scented; tube subcylindrical, widening slightly towards the mouth, 8-15 mm long, firm and fleshy; lobes oblanceolate, 40-65 x 8-15 mm, spreading and slightly recurved distally, with a raised midrib on the abaxial sur face; stamens spreading, very slightly declinate, fused to the perigone tube just below the throat, otherwise free; filaments filiform, more or less equalling the perigone lobes; anthers dorsifixed, about 12 mm long and creamcoloured before opening; pollen cream-coloured. Ovary about 10 mm long, narrowly fusiform, obscurely trian gular in cross section, placentation axile, 1-19 ovules per locule; style slender, slightly longer than the perigone lobes, declinate; stigma truncate, penicillate. Capsule indehiscent, pyriform, ovoid, ellipsoid to subfusiform, 25-100 x 10-35 mm, somewhat triquetrous, strongly 6-ribbed, bluntly beaked distally. Seeds subglobose or somewhat bluntly angled by pressure, 5-29 mm wide, fleshy, greenish; outer covering corky, pale; embryo green. Chromosome number 2n = 22 (Gouws 1949). Figure 1.

Flowering phenology
Bulbs usually produce a single inflorescence between December and March or occasionally in early April. Dis sections of mature bulbs from the wild retain evidence of many aborted inflorescences which indicates that flower ing is sporadic. Despite this irregular flowering pattern, inflorescence buds arise consistently in mature bulbs at four-leaf intervals. Each vegetative shoot consists of a non-amplexicaul bladeless prophyll, two amplexicaul foliage leaves and a non-amplexicaul foliage leaf. This leaf series is also known in Ammocharis heterostyla (Bul lock) Milne-Redh. & Schweick. and several species of Crinum but, unlike Cybistetes, two inflorescences often develop from each bulb within a few weeks of each other (Hannibal 1955). Only rarely does the bulb of C. lon gifolia produce two inflorescences simultaneously ( Figure  1A). The infructescences of C. longifolia usually mature and detach within four weeks of flowering but during rare wet autumn seasons the period from flowering to fruit dispersal may last three months. Bothalia 24,2 (1994) Vegetative phenology Foliage leaves are present only when conditions are favourable. Usually two growth flushes occur in response to alternating wet and dry sequences throughout the year. Thus leaves often appear briefly after late summer or autumn rains when the bulbs may flower, but may soon die back with the onset of a warm, dry period when the infructescences are released ( Figure ID). Thereafter suc cessive winter showers initiate rapid regrowth of the withered leaves. The leaves may persist up to six months in the wetter Western Cape (Markotter 1936), unlike the more variable pattern of growth in the semi-arid Rich tersveld. where the leaf blades may elongate and die a further two times during the year (G. Williamson pers. obs.). This growth sequence gives the leaves the truncate apices which are also found in A. coranica. Morphological studies of A. coranica have shown that the regrowth of mature leaves is due to a well-developed intercalary meristem (Troll 1954). Markotter (1936) reports that wild plants of C. lon gifolia from Stellenbosch in the Western Cape are pol linated by night-flying moths. Other visitors to flowers of C. longifolia in the Richtersveld are moths during the early morning and two common butterflies, the painted lady and green-yellow luceme butterfly during the day (G. Williamson pers. obs.). Snout beetles (Brachycerus sp.) have been observed eating all parts of C. longifolia ( Figure IB).