Denisophytum R. Vig., Notul. Syst. (Paris) 13(4): 349. 1948, descr. emended E. Gagnon & G. P. Lewis

Gagnon, Edeline, Bruneau, Anne, Hughes, Colin E., de Queiroz, Luciano Paganucci & Lewis, Gwilym P., 2016, A new generic system for the pantropical Caesalpinia group (Leguminosae), PhytoKeys 71, pp. 1-160 : 29-30

6. Denisophytum R. Vig., Notul. Syst. (Paris) 13(4): 349. 1948, descr. emended E. Gagnon & G. P. Lewis Figs 11G-I , 12

Diagnosis.

Denisophytum is closely related to Tara (Fig. 3 ), but differs in having flowers with a lower cucullate sepal with an entire margin (vs. a lower cucullate sepal with a pectinate margin), and dehiscent, coriaceous, laterally compressed pods (except for Denisophytum madagascariense which has inflated fruits) (vs. indehiscent, somewhat fleshy, coriaceous pods that are slightly turgid). Morphologically, species of Denisophytum are most likely to be confused with those of Caesalpinia s.s., but no reliable diagnostic characters have been found to differentiate these two genera. The corolla of Denisophytum species is consistently yellow and the flowers are bee pollinated, whereas Caesalpinia s.s. species display a wide range of flower colour (yellow, orange, red, green and white) and pollination syndromes (chiropterophily, ornitophily, psychophily and mellitophily).

Type.

Denisophytum madagascariense R. Vig.

Emended description.

Shrubs to small trees, 0.5-2 (-5) m tall, armed with straight or curved, deflexed prickles, scattered along shoots and also in pairs at the petiole base (except Denisophytum madagascariense which is unarmed); young twigs glabrous to pubescent, eglandular. Stipules either minute or foliaceous and conspicuous, caducous (persistent in Denisophytum stuckertii ). Leaves alternate, bipinnate, ending with a pair of pinnae; petiole and rachis glabrous and eglandular, with membranous or spinulose stipels at the insertions of pinnae on the leaf rachis, occasionally also at the insertion of the leaflets on the pinnae; pinnae opposite, in 1-6 pairs per leaf; leaflets opposite, in 2-10 (-11) pairs per pinna, elliptic, obovate to orbicular, with a rounded, acuminate or emarginate apex, c. 2-25 × 3-12 mm, leaflet blades glabrous to pubescent, eglandular. Inflorescence a terminal or axillary raceme; bracts caducous (acuminate and filiform in Denisophytum stuckertii ). Flowers bisexual, zygomorphic; calyx a short hypanthium with 5 sepals, c. 4-10 mm long, eglandular, glabrous to finely pubescent, lower sepal cucullate and covering the other 4 sepals in bud, all sepals caducous, leaving a persistent free hypanthium ring on the pedicel as the fruit develops; petals 5, free, yellow, the median petal sometimes with red markings on the inner face of the blade, c. 5-10 mm long, obovate, petal claw almost absent (present in Denisophytum madagascariense ); stamens 10, free, filaments pubescent and eglandular (8-11 mm long in Denisophytum madagascariense ), anthers dorsifixed, glabrous to pubescent; ovary glabrous. Fruits coriaceous, oblong-elliptic, laterally compressed (but inflated in Denisophytum madagascariense ), glabrous, eglandular pods with a tapering, sharp beak, 18-49 × 5-15 mm, elastically dehiscent, with twisting valves. Seeds ovoid, laterally compressed.

Geographic distribution.

Denisophytum comprises nine taxa in eight species, found across North America, South America and Africa, including Madagascar, a classical highly disjunct trans-continental distribution typical of lineages occupying the succulent biome sensu Schrire et al. (2005). Three species are distributed in Mexico, Florida, and the Caribbean, one species is endemic to Paraguay and Argentina, one is endemic to northern Madagascar, and the other three occur in northern Kenya, Somalia and Arabia. An evaluation of species limits is needed in this group.

Habitat.

Low deciduous seasonally dry tropical woodland or scrubland, also in open pineland or coastal plains and foothills. Species in Madagascar and Africa grow in limestone soils.

Etymology.

There is no indication of the etymology of Denisophytum in the posthumous publication of the generic name. Nevertheless, it is quite likely that the author, René Viguier, had intended to honour his friend and collaborator, Marcel Denis, a botanist with expertise in the genus Euphorbia in Madagascar. Sadly, M. Denis passed away prematurely at the age of 33 in 1929 ( Allorge and Allorge 1930).

References.

Britton and Rose (1930); Burkart (1936: 84-86); Viguier (1949); Roti-Michelozzi (1957); Brenan (1967); Capuron (1967); Thulin (1983: 16-18; 1993: 344-347); Ulibarri (1996); Du Puy and Rabevohitra (2002); Barreto Valdés (2013).

Figures

Figure 3. A-D Phylogeny of the Caesalpinia group. Bayesian phylogram based on 312 accessions, including only accessions with two or more loci. Branch support values are indicated as follows: branches in bold indicate that maximum support has been attained in the MP, ML and Bayesian phylogenetic analyses; otherwise, posterior probabilities are indicated above in bold, with bootstrap support from ML analyses (italicised) and parsimony analyses separated by a slash below the branches; for each terminal, the species name is followed by the collector number of the corresponding voucher (see Appendix 1 for full voucher details); the suffix ** indicates that several sequences from different accessions of the same species were concatenated for analysis (see Appendix 1 for details); for major clades and genera, the names used by Gagnon et al. (2013) are indicated, as well as the corresponding new genera.

Figure 11. Caesalpinia bahamensis Lam. A inflorescence D fruits (G. P. Lewis, Cuba, Lewis 1853 (K )). Caesalpinia nipensis Urb. B flowers E fruits (G. P. Lewis, Cuba, Lewis 1838 (K )). Caesalpinia cassioides Willd. C inflorescence (C. E. Hughes, Ancash, Peru, Hughes et al. 2228 (K )). Caesalpinia pulcherrima L. (Sw.) F inflorescence (C. E. Hughes, Sonora, Mexico, unvouchered); Denisophytum pauciflorum (Griseb.) E. Gagnon & G. P. Lewis G flower and leaves (G. P. Lewis, Cuba, Lewis 1854 (K )) H branch with spine-tipped woody protuberances (B. Torke, Cuba, Torke et al. 1424 (NY )). Denisophytum madagascariense R. Vig. I flowers and fruits (G. P. Lewis, Madagascar, Lewis et al. 2158 (K )). Gelrebia trothae (Harms) E. Gagnon & G. P. Lewis J inflorescence (P. J. Cribb, Tanzania, unvouchered).

Figure 12. Denisophytum stuckertii (Hassl.) E. Gagnon & G. P. Lewis. A foliage and inflorescences B median leaflet undersurface C stipule D leaf rachis spines E bract F calyx opened out G median petal H lateral petal I stamen J gynoecium K stigma L developing ovary M infructescence, N single fruit valve after dehiscence. A, B, D-K from Renvoize et al. 3538 C, M from Venturi 7697 L from Ruiz et al. 10488 c N from Aguilar 241. Drawn by Eleanor Catherine.