The Rhynchosia totta complex ( Phaseoleae , Fabaceae ) in Southern Africa , including the description of a new variety and new species

Rhynchosia Lour. is a member of the Fabaceae (Leguminosae) subfamily Papilionoideae (Faboideae) tribe Phaseoleae (Lackey 1981). Within the tribe Phaseoleae, taxonomic studies have been completed for a number of southern African genera, for example, Dipogon Liebm. (Stirton 1981a), Macrotyloma (Wight & Arn.) Verdc. (Verdcourt, Hooker & Halliday 1982), Bolusafra Kuntze (Moteetee & Van Wyk 2006), Dolichos L. (Moteetee & Van Wyk 2012a), Sphenostylis E.Mey. (Moteetee & Van Wyk 2012b), Ophrestia H.M.L.Forbes (Moteetee & Van Wyk 2012c), and Canavalia DC. (Moteetee 2016), while studies on other genera are ongoing. Of particular interest is the genus Rhynchosia in which taxonomic research is ongoing and several new species have already been described (Boatwright & Moteetee 2014; Germishuizen 1998, 2006, 2011; Moteetee, Boatwright & Jaca 2012, 2014). With approximately 230 species (Schrire 2005), Rhynchosia is the largest genus in the subtribe Cajaninae with the majority of species widely distributed across Africa. Some of the species are also found in warm temperate and tropical regions of Asia, Australia and America. It is closely related to Eriosema (DC.) Desv. within the Phaseoleae. Cajaninae is characterised by the presence of vesicular glands and bulbous-based hairs (Lackey 1981). It comprises eight genera, of which only four occur in southern Africa; that is, Bolusafra, Cajanus DC. (write out cultivated species), Eriosema and Rhynchosia. Comprehensive taxonomic studies of the South African species of the genus Eriosema are yet to be published; however, a number of studies have been published by Stirton (1977, 1981b, 1981c, 1994).


Introduction
have described it as a climbing, twining, ascending perennial herb with a tuberous rootstock and slender stems, with glabrescent to densely pubescent trifoliolate leaves, oblonglanceolate leaflets acute at the apex, glabrescent to silky pubescent with prominent, reticulate venation, and flowers flushed reddish that are either solitary or a few arranged in very lax inflorescences. Baker (1923) divided the species into seven variants mainly based on leaf shape and structure, as well as stem and/or leaf vestiture, but other characters such as petiole length and flower size were applied inconsistently. These are Rhynchosia totta var. brevipetiolata Baker f. (stem pilose or tomentose, petioles short), R. totta var. fenchelii Schinz (stem grey puberulous, leaves trifoliolate), R. totta var. graciliflora Harms ex Baker f. (R. graciliflora Harms) (leaves trifoliolate, linearlanceolate, pubescent or nearly glabrous), R. totta var. namaensis Schinz (leaves trifoliolate, leaflets lanceolate or ovate-lanceolate, grey puberulous), R. totta var. pilosa Harv. (stem patently pilose, leaves trifoliolate, leaflets of the lower ovate-oblong, upper linear) and R. totta var. unifoliolata Burtt Davy (leaves unifoliolate or trifoliolate, leaflets ovate, petiole short).
Having studied Rhynchosia species occurring in East Africa, Verdcourt (1971) remarked that 'three groups stand out for their difficulty, so far as Africa is concerned'. The three groups in question are: 1) the Rhynchosia minima (L.) DC. group, 2) the R. viscosa (Roth) DC. group, and 3) the R. totta (Thunb.) DC group. The R. viscosa group does not occur in South Africa, while the other two are more widely distributed in southern and tropical Africa. The R. totta group is centred in South Africa but extends through most of southern Africa ( Figure 1) and north-eastwards through East Africa as far as Somalia. Numerous South African species and infraspecific taxa in this group (herein referred to as a complex) have been described giving 'the impression that work on the group has been uninspired and that every small variant has been given a name, as the simplest way out of the particular author's immediate difficulty' (Verdcourt 1971). There are at least 17 specific and 2 varietal names that have been reduced into synonymy with R. totta over the years, possibly due to the immense variation in leaf shape and vestiture encountered across a wide distribution area. According to Verdcourt (1971), there are two extremes in East Africa (which also extend to southern Africa): there are variants with slender stems and glabrescent leaflets on the one hand (which he attributes to the typical variant) and those with thicker stems and pubescent to densely velvety leaflets on the other [R. totta var. venulosa (Hiern) Verdc. -which was recognised as a species by Baker (1923)], with several intermediates between these two. He further recognised R. totta var. elongatifolia Verdc. (Verdcourt 1971;Verdcourt et al. 2001). The development of the concept of the R. totta complex is summarised in Table 1. According to the latest checklist of southern African plants (Germishuizen and Meyer 2003), only the typical variant is currently recognised.
Here, we present results of a taxonomic study of the R. totta complex, including correct synonymy and distribution ranges of the taxa of southern Africa. We further describe a new species and a new variety.

Research method and design
Plant material representative of both R. totta and R. capensis (Burm.f.) Schinz was studied from herbarium specimens housed at GRA, JRAU, K, NH and PRE, and during field excursions. Rhynchosia capensis is the closest relative to R. totta (see the discussion under 'Diagnostic characters and relationships ' of R. totta). Herbarium acronyms are listed according to Thiers (2011). Both Baker (1923) and Verdcourt (1971) mentioned the variation in leaf structure (number and shape of leaflets) and vestiture; therefore, these were examined as well as other characters such as habit, petiole length, floral and fruit morphology. Flowers were rehydrated in boiling water and dissected under a binocular stereomicroscope.
Representative specimens examined are arranged according to the quarter-degree grid reference system (Edwards & Leistner 1971;Leistner & Morris 1976). This system is used to map distribution data of each taxon, whereby the basic unit is the one-degree square of latitude and longitude, designated by a degree reference number (i.e. degrees of latitude and longitude of the north-west corner) and the district name of that square. Some types of specimens were examined online in the JSTOR (2015) database.

Results
The examination of 562 specimens labelled as R. totta at the National Herbarium in Pretoria (PRE), and those housed in GRA, JRAU, K and NH, as well as observations made during field trips, have revealed great morphological variation. Rhynchosia totta is a scrambling perennial herb, although some of the varieties tend to be woody, particularly those occurring farther north in southern Africa.

Key to the Rhynchosia totta complex and related species
1A. Habit distinctly prostrate, stems never twining; leaflets directed upwards … R. pedunculata

Distribution and ecology
Rhynchosia totta is widespread in southern Africa, but is centred mainly in South Africa, from which it extends north through Botswana, Zimbabwe and Mozambique, westwards to Namibia and Angola, eastwards through Zambia, and http://www.abcjournal.org Open Access  across East Africa as far as Somalia (Verdcourt, Pope & Polhill 2001). In South Africa, it occurs widely in all provinces, except in the Western Cape province and is only sparsely distributed in the Northern Cape province (Figure 1). It grows in sandy soil in grasslands, burnt hillsides, rocky outcrops, near streams, and on roadside embankments.

Taxonomic notes
(i) Some of Drège's syntypes of Copisma tottum, C. paniculatum, and C. pilosum could not be found in any of the probable herbaria (B, P, UPS, W). If they were ever deposited in B, they were most probably destroyed during World War II. (ii) The K specimen of R. nervosa var. petiolata is selected because it is a better-looking specimen with multiple fruits. (iii) The K specimen of R. totta var. unifoliolata is chosen as lectotype because it is the only one available. (iv) The Z specimen of R. totta var. graciliflora is chosen as lectotype because it has both flowers and a fruit and it represents best the twining nature of the taxon.

Diagnostic characters and relationships
Rhynchosia totta resembles R. capensis in its growth form (spreading, twining or climbing herb arising from a woody rootstock), but tends to be more hairy (R. capensis tends to be glabrous or minutely downy), has leaflet margins that are not revolute (leaf margins slightly revolute in R. capensis), and peduncles that are usually laxly 1-4-flowered or sometimes 5-flowered (1-6-flowered, flowers concentrated at the tips of peduncles in R. capensis). According to Harvey (1862), R. capensis also differs from R. totta in having large resinous glands. However, glands do occur in R. totta, but they are much denser in R. capensis.

Distribution and ecology
This variety is widely distributed in South Africa (across the Eastern Cape, Free State, Gauteng, KwaZulu-Natal, Limpopo, Mpumalanga and North-West provinces), Swaziland and Lesotho (Figure 4), with two specimens found on the border of the Northern Cape province. Specimens from the latter province are sterile and could not be identified with confidence as they share similarities in appearance with R. totta var. rigidula. It grows on sandy soil in grasslands, rocky outcrops, open woodlands and forest margins.

Diagnostic characters and relationships
Rhynchosia totta var. totta differs from var. rigidula in the herbaceous habit, long rachises and leathery, glabrescent leaves (woody with short rachises and often slightly silverfelted leaves that are not leathery are found in R. totta var. rigidula). This variety also resembles the new species, R. pedunculata, but differs in the trailing, twining or spreading habit and inflorescences that are not distinctly longer than the leaves or leaves orientated horizontally (prostrate habit with inflorescences much longer than the leaves and invariably standing upright in R. pedunculata).
The typical variety includes those taxa with a woody base and herbaceous stems, and unifoliolate or trifoliolate leaves with leaflets that are ovate to lanceolate in shape. There are some specimens with long petioles and linear-lanceolate leaflets (formerly R. totta var. graciliflora), but, given the lack of any other morphological features to distinguish these collections from the typical form, the variant is included in R. totta var. totta.

Distribution and ecology
In southern Africa, this variety mostly has a northern distribution occurring from KwaZulu-Natal province north and westwards to the Northern Cape province, Botswana and Namibia ( Figure 5). The distribution may stretch into Mozambique and Zimbabwe, but no specimens in PRE were found for these areas. It is common in sandveld and brown sandy loam.

Diagnostic characters and relationships
This variety is close to R. totta var. venulosa, but differs in having relatively large flowers (12-14 mm long), elongated, linear and narrow calyx lobes and often strongly asymmetrical lanceolate-ovate leaves. In R. totta var. venulosa, the flowers are 6-10 mm long, the calyx lobes are narrowly deltoid and the leaves are less strongly asymmetrical and lanceolate in shape.

Distribution and ecology
This variety has a northern distribution extending from the central parts of the Northern Cape into KwaZulu-Natal province as well as Swaziland into Botswana, Namibia and farther northwards ( Figure 6). It grows in stony hills, welldrained, red-brown sand and banded ironstone rock.
venulosa, but differs in its symmetrical lateral leaflet bases (versus leaflet bases strongly asymmetrical in the latter), shorter peduncles (versus up to 16 mm long, opposed to 125 mm long), the relatively larger flowers (up to 18 mm long verses up to 10 mm long), and calyx that is half the length of the flower (versus calyx sometimes as long as the flower). Rhynchosia totta var. rigidula is also similar to the typical variety, but differs in its woody habit, greyish-felted, softtextured leaves and brown mottled black seeds (versus herbaceous habit, glabrescent, leathery leaves and brown seeds in R. totta var. totta).  (Figure 2a-c).

Distribution and ecology
Rhynchosia totta var. venulosa is widely distributed throughout southern and East Africa up to Ethiopia. In South Africa, it occurs in Limpopo, North-West, Gauteng, Mpumalanga, KwaZulu-Natal, and Eastern Cape provinces (Figure 7). It grows on heavy alluvium and sandy soils in floodplain grasslands, Acacia thickets and wooded grasslands.

Taxonomic notes
(v) The specimen in K is chosen as lectotype because it is the only one available. It is also possible that Burtt Davy based the description of this species on this specimen since he was based there at the time of writing his book.

Diagnostic characters and relationships
This variety differs from the typical variety in having thicker, hairier stems with a tendency of becoming woody, with pubescent to densely velvety leaflets that often have very prominent venation, and the strongly asymmetrical lateral leaflets.  Figure 8).

Additional specimens seen
Flowering time: Oct to Mar (Apr).

Distribution and ecology
A South African endemic, with populations found in the Free State, Gauteng, KwaZulu-Natal, Mpumalanga and North-West provinces ( Figure 9). It grows in grassland areas on black turf or loamy soil on dolorite or quartzite.

Diagnostic characters and relationships
Rhynchosia pedunculata is closely related to R. totta, but differs in the prostrate habit (never twining), upright leaves, long peduncles that extend beyond the leaves, and wing petals approximately equal in length to the keel. Rhynchosia totta is a trailing, climbing and twining species with leaves not distinctly erect and the peduncles not distinctly longer than the leaves (peduncles might be longer when multi-flowered), and wing petals slightly shorter and narrower than the keel. The specific epithet was chosen to honour the strikingly long peduncles by which it is differentiated from R. totta.