Staurogyne Wallich (1831: 80)

Braz, Denise Monte & Monteiro, Reinaldo, 2017, Taxonomic Revision of Staurogyne (Nelsonioideae, Acanthaceae) in the Neotropics, Phytotaxa 296 (1), pp. 1-40 : 3-5

Staurogyne Wallich (1831: 80)

Lectotype (designated by Leonard 1951: 5): — S. argentea Wallich (1831: 80) .

Ebermaiera Nees von Esenbeck (1832: 75) . Type: — E. humilis Nees von Esenbeck (1832: 75) ≡ Staurogyne humilis (Nees) Kuntze (1891: 497) .

Gynocraterium Bremekamp (1939: 557) . Type: — G. guianense Bremekamp (1939: 557) ≡ Staurogyne guianensis (Bremek.) Daniel & McDade (2014:37) .

Erect or creeping herbs, shrubs, subshrubs; glandular trichomes sometimes present in the vegetative parts. Leaves opposite, usually petiolate, margin entire, membranous to chartaceous, cystoliths absent. Inflorescence a thyrse with units of one flowered opposit reduced dichasia that take the form of a raceme or a spike, cylindrical to pyramidal, rarely subcapitate, or rarely a panicle; bracteate, leafy at base or rarely all the inflorescence leafy; flowers decussate, rarely sub-opposite or alternate, each one usually accompanied by 1 bract and 2 bracteoles (4 bracteoles in S. brachiata ); bracts and bracteoles green or colored, 1-nerved, 3-nerved or 3 − 5-acrodromous veins, bracts elliptic (long-subulate with truncate base in S. guianensis ); pilosity with glandular or simple trichomes generally present on the inflorescence and other floral parts. Flowers sessile or pedicellate; calyx green or colored, deeply 5-parted, segments unequal, the posterior usually wider and longer than the others, with 3 − 7 acrodromous veins, rarely inconspicuous, lateral pair of segments usually smaller, subulate, rarely lanceolate or linear, anterior pair of segments with intermediate size, rarely equal to the lateral pair, oblong to lanceolate, rarely subulate; corolla sub-bilabiate slightly curved, infundibular white or lilac, sometimes with markings on limb and throat, sometimes tubular and yellow or red, basal tube generally well defined, 5 lobes oblong, suborbicular or subtriangular, the anterior lobe generally larger and different from the others, the 2 posterior generally smaller; stamens 4, frequently didynamous, included to sub-exserted, generally inserted in the base of the corolla; anthers bithecous, reniform to oblong, introrse, connective often expanded dorsally; staminode reduced, generally inserted between the posterior pair of stamens, filiform or expanded at apex, antheriform; nectariferous-disk inconspicuous (elongated, longitudilnally sulcate and slightly extended beyond the ovary in S. guianensis ); ovary cylindrical to sub-conical, ovules 6–36 per locule, style filiform, stigma bifid (subcrateriform in S. guianensis ), the posterior lobe divided into two segments or truncate, the anterior lobe oblong to elliptic, usually longer. Capsule cylindrical, sometimes sub-conical, sessile, usually sparsely pilose, retinacula absent; seeds 6 − 34 per locule, subglobose to slightly angled, usually hairy, smooth or with protrusions on the surface.

Distribution and habitat:— The natural limits of Staurogyne in the Neotropics extends from northwestern Mexico ( Daniel & Lott 1993), to the southern Brazil. In South America it occurs solely in very well preserved native forest vegetation and is commonly found in shady moist places, near streams, distributed in the Amazon and Atlantic Forests, and also in the gallery forests of the Cerrado domain. For other Nelsonioideae in the Neotropics, Nelsonia and Elytraria are widely distributed in South America, from the Amazon Forest, to the Brazilian Cerrado and Atlantic Forest (Profice et al. 2015). In the Caatinga domain Nelsonia and Elytraria are mostly registered in the remaining Atlantic Forest that occurs especially in isolated mountains, also called Brejos de Altitude or Florestas Úmidas (Humid Forest) ( Tabarelli & Santos 2004, IBGE 2012). Except for one collection in the State of Bahia in 1822 (L. Riedel 01,6 (LE)), Staurogyne does not ocurr in this remaining Atlantic Forest of the Caatinga domain. While Elytraria occur in dry understory, Nelsonia and Staurogyne , occur primarily near to streams or rivers. Although it is often suggested that Nelsonia is introduced in the Neotropics (Daniel & Wenk 2009, McDade et al. 2012), we reject this idea based on our extensive consultation of herbaria collections and its occurrence in natural vegetation in a great part of Brazilian territory, as well as for Elytraria and Staurogyne , as also registred by Profice et al. (2015).

Taxonomic notes:— The genus name refers to the posterior lobe of the bifid stigma which is divaricate, giving it the shape of a cross (stauros = cross; gyne = gynoecium) ( Wallich 1831) ( Figure 1A ). However, stigmas with the posterior lobe 2-divided also occur in other African Nelsonioideae genera ( Champluvier 1991) and this feature only occurs in some species of Staurogyne , many of which have the posterior lobe concave, with the two laterals slightly or deeply prolonged, or with a truncate apex. The only species with a subcrateriform stigma is Staurogyne guianensis , that also has quiet different bracts and other characteristics from those described above. Due to the difficulties in obtaining the seeds from the herbarium specimens, these have not been investigated; from those analyzed, different surfaces have been observed ( Daniel & Lott 1993, McDade et al. 2012), including some protrusions ( Figure 1B ), as also observed in other members of the Acanthaceae ( Balkwill & Campbell-Young 1999, Ruengsawang et al. 2012, Daniel & McDade 2014, Idriunas et al. 2014). Seed characters deserve further investigation. Another important aspect that merits additional study is the variation in the trichomes, which has been simplified in the present account although they show different forms (see Materials and Methods).

Figures

FIGURE 1. Staurogyne in the neotropics. A. S. parva, stigma, showing the anterior lobe slightly divided (Fernandes 2862). B.Seed of S. spraguei (Maguire &Politi 27410). (photoed by the authors)