Lotononis (DC.) Eckl. & Zeyh.

Leguminosae, various authors. Flora Zambesiaca 3:7. 2003

Morphology General Habit

Herbs.

Morphology Leaves

Leaves in Flora Zambesiaca area digitately 3-foliolate or lower ones occasionally 1-foliolate, elsewhere sometimes all 1-foliolate or up to 8-foliolate; stipules small or foliaceous, usually single at each node.

Morphology Reproductive morphology Inflorescences

Inflorescences terminal or leaf-opposed, the flowers in racemes, heads, clusters or single; bract small to foliaceous, sometimes inserted on the pedicel; bracteoles small or more often lacking.

Morphology Reproductive morphology Flowers Calyx

Calyx usually with lateral and upper lobes joined higher on either side, sometimes (sect. Oxydium) with 5 subequal lobes.

Morphology Reproductive morphology Flowers Corolla

Standard predominantly yellow, or elsewhere sometimes white, pink or blue, hairy or glabrous outside; wings shorter or longer than the keel, often hairy, generally sculptured; keel with apex rounded, pointed or somewhat beaked, often hairy.

Morphology Reproductive morphology Flowers Androecium Stamens

Stamens in a sheath open on the upper side; anthers markedly dimorphic, 4 oblong to linear and basifixed, 5 ovate and dorsifixed, the carinal one intermediate.

Morphology Reproductive morphology Flowers Gynoecium Pistil

Ovary sessile to stipitate; style tapered, with a small stigma.

Morphology Reproductive morphology Fruits

Pods linear, oblong or ovate, flat or turgid, rarely folded and twisted, usually dehiscent, few–many-seeded.

Morphology Reproductive morphology Seeds

Seeds rounded to generally oblique-cordiform, smooth to finely tuberculate.

Legumes of the World. Edited by G. Lewis, B. Schrire, B. MacKinder & M. Lock. Royal Botanic Gardens, Kew. (2005)

Note

The current state of knowledge of the Crotalarieae was reviewed by Van Wyk (1991a) and by Van Wyk & Schutte (1995a). The most conspicuous recent change has been the exclusion of the Argyrolobium group (six genera, i.e. Argyrolobium, Dichilus, Melolobium, Polhillia, Anarthrophyllum and Sellocharis), which belong in tribe Genisteae rather than in Crotalarieae, where they were previously placed (Polhill, 1981q: 399 –402). New insights into relationships within the tribe have come mainly from chemosystematic studies of alkaloids (summarised in Van Wyk & Verdoorn, 1990) and several recent generic monographs (see below).

The Crotalarieae forms part of a monophyletic clade, the ‘core genistoids’ (Fig. 36) which also includes Genisteae, Podalyrieae, Thermopsideae, Brongniartieae, Euchresteae and Sophoreae sens. strict. (Crisp et al., 2000; Pennington et al., 2000a; Kajita et al., 2001). Crotalarieae appears to be sister to the Genisteae and both are sister to the Podalyrieae (Crisp et al., 2000; Wojciechowski et al., 2004). This clade is in turn sister to the Thermopsideae and Sophoreae sens. strict. (including Euchresteae).

The Crotalarieae shares with the Podalyrieae the absence of a-pyridone alkaloids such as cytisine and anagyrine that are a typical feature of all other ‘core genistoid’ tribes. Despite a lack of defining characters, the monophyly of the tribe as circumscribed here is well supported by molecular evidence (Crisp et al., 2000; Wink & Mohamed, 2003) and by cladistic analyses of morphological, cytological and chemical characters (Van Wyk & Schutte, 1995a). The latter study suggested an early diversification of the genera with uniform anthers and lupanine-type esters of quinolizidine alkaloids (Pearsonia, Rothia and Robynsiophyton) followed by the poorly known Spartidium and then the so-called ‘Cape group of genera’ (Polhill, 1981q: 399–402), which now includes Lotononis and Crotalaria. Relationships between the seven genera of the ‘Cape group’ remains unresolved despite several recent molecular studies because sampling is still relatively poor. However, a basally branching position in the tribe of the ‘Cape group’, notably Lebeckia and Wiborgia — as considered by Polhill (1976, 1981q) — is now accepted here. The exclusion of the Argyrolobium group, based on morphological and chemical characters, is also strongly supported by DNA sequence data. Due to reticulate and overlapping patterns of character state distribution in the Crotalarieae sens. strict., generic delimitations are intricate and subject to misinterpretation. Several of the large and diverse genera appear to be either monophyletic or paraphyletic depending on the choice of characters. As currently circumscribed the tribe includes 11 genera and c. 1204 species (Fig. 37).

Considerable infrageneric variation has been accommodated in 15 sections, most of which have convincing apomorphies to support their monophyly; the relationships between sections have been explored in a series of cladistic analyses of morphological, cytological and chemical characters (Van Wyk, 1991b)

Habit

Shrubs, shrublets, suffrutices (rarely geophytic), perennial or annual herbs

Ecology

In mediterranean shrubland (dry fynbos and renosterveld), desert, xerophytic scrubland and grassland; also seasonally dry tropical to subtropical forest and woodland, usually on sand and in rocky places, more rarely in heavy or calcareous soils

Distribution

Africa, mainly in southern Africa with a few extending to (often montane) tropical Africa (c. 145 spp.); c. 5 spp. Mediterranean (S Spain, Macaronesia and N Africa [Morocco]) to W Asia, Arabia and Pakistan