Calliandra, Bentham, 1840

Thulin, Mats, 2023, On Calliandra and Afrocalliandra (Fabaceae-Caesalpinioideae), Phytotaxa 595 (1), pp. 1-6 : 2

Segregates of Calliandra

Hernández (1986) segregated the species of Guinetʼs group IB as the new genus Zapoteca Hernández (1986: 757) with about 25 species in tropical America, and provided new combinations for seven of them. The remaining neotropical species plus the two species from Africa, Guinetʼs group II, formed Calliandra sensu stricto, whereas the species from Madagascar and India (Guinetʼs group IA) were said to be in need of further critical study.

Besides the palynological differences between Calliandra and Zapoteca, Hernández (1986, 1989 ) also pointed to striking differences in, for example, the cotyledons (sagittate, petiolate, fleshy, and persistent in Calliandra versus ovate, sessile, foliaceous, and ephemeral in Zapoteca ) and the shape and function of the stigmas (expanded, discoid or capitate with a wide area of polyad receptivity in Calliandra , versus cup-shaped with a narrow area of receptivity that can hold only a single polyad in Zapoteca ).

Barneby (1998), in a monograph of Calliandra , included about 130 species in the genus, all from the Neotropics, whereas all Old World species were rejected, even though he did not place them in segregate genera at this point. Over the subsequent 15 years, the majority of the Old World species of Calliandra sensu Bentham (1875) have been placed in a series of segregate genera. Viguieranthus Villiers (2002: 271) was established for 18 species mainly on Madagascar, eight of them previously in Calliandra and ten newly described. For the Asian species, C. geminata was placed in synonymy of Thailentadopsis nitida ( Vahl 1791: 103) Lewis & Schrire (2003: 492) , and the new segregate genus Sanjappa Souza & Krishnaraj in Souza et al. (2016: 6) was established to accommodate the Indian C. cynometroides as S. cynometroides (Bedd.) Souza & Krishnaraj in Souza et al. (2016: 6). The two Asian species C. griffithii and C. umbrosa , treated as a single species with two subspecies by Paul (1979), are still unplaced outside Calliandra , as is an undescribed Asian species discussed by Ringelberg et al. (2022: 52).

The African species Calliandra gilbertii and C. redacta were generally accepted as transatlantically disjunct members of Calliandra until Barneby (1998) restricted the genus to the neotropical members only. The only reason given by Barneby (1998) for excluding these two “so-called calliandras in the Old World”, apart from their African origin, was that “their acalymmate pollen is discordant”.

Souza et al. (2013), based on both nuclear and plastid markers, made the first detailed phylogenetic study of Calliandra in a wide sense. The sampling included seven species of Zapoteca , six species of Viguieranthus , and two species of Thailentadopsis Kostermans (1977: 131) . These three genera were all retrieved as well supported outside Calliandra . The 95 species sampled of Calliandra , including the two African species, formed a strongly supported clade within which was nested a sample of Guinetia tehuantepecensis Rico & Sousa in Rico Arce et al. (1999: 977).

Guinetia Rico & Sousa in Rico Arce et al. (1999: 977), a monotypic genus in Mexico, was said to differ from Calliandra by having pods initially dehiscing along one margin only. Otherwise, it agrees with Calliandra by having 8-celled polyads with a mucilaginous tail cell (“basal cell” with a “very reduced sticky appendage”), and by having sagittate, petiolate cotyledons ( Rico Arce et al. 1999: Fig. 1L). The polyads of Guinetia are calymmate ( Rico Arce et al. 1999) as in neotropical Calliandra . Given that it is deeply nested within Calliandra in their phylogeny, Guinetia tehuantepecensis was transferred to Calliandra by Souza et al. (2013), who regarded the deviating dehiscence of the pods in this species as a reversal.