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This genus is accepted, and its native range is Tropical & Subtropical America.
Ruehssia megalantha

[KBu]

Espírito Santo, F., Rapini, A., Ribeiro, P.L. et al. (2019). Phylogeny of the tribe Marsdenieae (Apocynaceae), reinstatement of Ruehssia and the taxonomic treatment of the genus in Brazil. Kew Bulletin 74: 30. https://doi.org/10.1007/s12225-019-9807-4

Morphology General Habit
Lianas, twining or climbing plants, shrubs or subshrubs, erect or prostate; white latex
Morphology Leaves
Leaves opposite, distichous or decussate, less often up to 4 leaves irregularly arranged at the nodes or in brachyblasts, sessile or petiolate, ovate, elliptic, cordate, obovate, orbicular, lanceolate, linear, rarely filiform, base cuneate, obtuse, rounded, arising, rarely truncate, apex acute, cuspidate, acuminate, emarginate or rounded, margins entire, membranous to coriaceous, glabrous or with trichomes, adaxially with 2 – 9 colleters at the base of the main vein, rarely absent
Morphology Reproductive morphology Flowers
Flowers sessile to pedicellate, tiny and discrete or large and showy; pedicels glabrous or with trichomes; sepals ovate, elliptic or orbicular, abaxially glabrous or with trichomes, margins ciliate or not, adaxially with 5 – 20 colleters at the base of the calyx, rarely absent; corolla urceolate, campanulate, tubular, hypocrateriform or rotate, generally vinaceous, greenish, white or yellowish, glabrous or with trichomes, lobes ovate, obovate, deltoid or oblong, recurved to erect, margins ciliate or not; corona with 5 lobes of different shapes, completely fused to the dorsal side of anthers or segmented with an upper free portion, occasionally exceeding the style-head; gynostegium inserted to exserted, sessile or stipitate; style-head ovoid, globose, conical or rostrate, bilobed or entire; anthers with apical membranous appendix usually oblong, ovate or suborbicular, hyaline, mostly not exceeding the apex of the style-head; corpusculum ovoid, oblong, lanceolate or linear, apex obtuse, rounded or acute, curved or erect; caudicles horizontal or ascending, distally plicate or not; pollinia erect, oblong, obovoid, elliptic, rarely reniform, attached to the caudicle by the base
Morphology Reproductive morphology Fruits
Follicles single by abortion, fusiform, elliptic, ovate or oblong, glabrous or with trichomes; seeds comose, rarely without coma.
Morphology Reproductive morphology Inflorescences
Inflorescences axillary or sub-axillary, umbelliform, glomerulate or racemiform, rarely scorpioid, fasciculate or paniculate, multi-flowered, rarely with solitary flowers, usually congested, sessile to long-pedunculate; peduncle glabrous or with trichomes
Morphology Stem
Stems corky or not, glabrous or with trichomes, usually with colleters at nodes and leaf axils
Note
Ruehssia is a heterogeneous genus and, in most cases, the identification of species is straightforward. Species such as R. altissima, R. amylacea, R. brasiliensis (Decne.) F.Esp.Santo & Rapini, R. breviramosa, R. zehntneri, R. megalantha (Goyder & Morillo) F.Esp.Santo & Rapini, R. minutiflora (F.Esp.Santo) F.Esp.Santo & Rapini, R. nana (Rapini & Fontella) F.Esp.Santo & Rapini, R. paganuccii (F.Esp.Santo & A.P.B.Santos) F.Esp.Santo & Rapini, R. rubrofusca, R. rupestris (F.Esp.Santo) F.Esp.Santo & Rapini, R. sessilifolia (E.Fourn.) F.Esp.Santo & Rapini, R. sprucei, R. thomasii (Morillo) F.Esp.Santo & Rapini and R. trisegmentata (F.Esp.Santo & A.P.B.Santos) F.Esp.Santo & Rapini have habit and /or morphology of inflorescences and /or flowers that help a safe identification. Ruehssia megalantha, for example, is one of the most extreme species morphologically within the group, and is characterised by its occurrence in rocky outcrops in Caatinga and its large and attractive flowers (c. 3.2 cm diam.), with internal structures different from all other species. However, character overlaps in other species may generate doubts and frequent errors in identifications. Among these, we can mention the complexes formed by: 1) R. amorimii (Morillo) F.Esp.Santo & Rapini, R. dorothyae (Fontella & Morillo) F.Esp.Santo & Rapini, R. montana (Malme) F.Esp.Santo & Rapini and R. paraibana (F.Esp.Santo & A.P.B.Santos) F.Esp.Santo & Rapini; 2) R. calcaria, R. phallica and R. zehntneri; 3) R. hilariana and R. lauretiana (Woodson) F.Esp.Santo & Rapini; 4) R. bergii (Morillo) F.Esp.Santo & Rapini, R. malmeana (W.Rothe) F.Esp.Santo & Rapini and R. weddellii; and 5) R. caatingae (Morillo) F.Esp.Santo & Rapini, R. loniceroides and R. otoniensis (Fontella & Morillo) F.Esp.Santo & Rapini. In these complexes, a more detailed examination of internal floral characters, particularly the shapes and dimensions of corona lobes and pollinarium, is necessary. We recognise 42 species in Brazil, Ruehssia hilariana (E.Fourn.) F.Esp.Santo & Rapini with two varieties; nine (~20%) of these species resulted from this monographic study (Espírito Santo et al. 2018a, b, c). Of these 43 taxa, 86% are endemic to Brazil, only R. altissima, R. hilariana, R. macrophylla, R. rubrofusca, R. sprucei and R. weddellii (E.Fourn.) F.Esp.Santo & Rapini occur in other South American countries, and only one, R. macrophylla, reaches Central America and Mexico. Most species are phytogeographically restricted, and the Atlantic Forest, Caatinga and Cerrado are the domains with the greatest diversity of Ruehssia. Many species are rare and / or occur only in particular habitats, such as R. breviramosa (Rapini & Fontella) F.Esp.Santo & Rapini, R. calcaria (F.Esp.Santo) F.Esp.Santo & Rapini, R. phallica (F.Esp.Santo) F.Esp.Santo & Rapini and R. zehntneri (Fontella) F.Esp.Santo & Rapini, which are endemic to limestone outcrops (Espírito Santo et al. 2018b). We estimated the extent of occurrence and the area of occupation of the species with the help of GeoCat (Geospatial Conservation Assessment Tool — Bachman et al. 2011) and classified half of them (21 species, plus one Critically Endangered variety) as threatened (10 Critically Endangered, 7 Endangered and 4 Vulnerable), 18 as Least Concern and three as Data Deficient, according to the criteria of the International Union for Conservation of Nature (IUCN 2001; IUCN Standards and Petitions Subcommittee 2016). The publication of Ruehssia had been assigned to Schlechtendal (1853) and R. purpurea Schltd. [= R. macrophylla] is the type of the genus and the only species described by him (cf. Omlor 1998). However, Ruehssia was validly published (as “Rühssia”) four years earlier by Karsten (1849), who included a description of the genus and three new species (R. estebanensis H.Karst., R. glauca H.Karst. and R. pubescens H.Karst.). He also made a new combination for Asclepias macrophylla Humb. & Bonpl. ex Schult., R. macrophylla, which is selected here as the lectotype of Ruehssia and includes Karsten’s remaining three species in its synonymy (Morillo 1978). The genus Verlotia E.Fourn. was published along with six species: V. virgultorum E.Fourn., V. suberosa E.Fourn., V. heterophylla E.Fourn., V. dracontea E.Fourn., V. macrocalyx E.Fourn. and V. 'weddellii E.Fourn.; three of these (V. heterophylla, V. dracontea and V. macrocalyx) are now under the synonymy of V. suberosa (≡ Ruehssia suberosa), which therefore is the most representative species of the group and is selected as the lectotype of Verlotia here. The genus Ruehssia includes all American species of Apocynaceae with erect pollinia, hitherto classified in Marsdenia. It covers about 110 tropical species, with three main centres of diversity, each with approximately 20 species: southeastern Mexico, representing approximately 2/3 of the Apocynaceae from Mexico (31 species; Juarez-Jaimes & Saynes 2015) and 2/3 of the flora of the Mesoamerican region (32 species; Stevens 2009), northwestern South America (Morillo 1978) and northeastern Brazil, with about half of the species of that country. This lineage originated in the Miocene (Rapini et al. 2007; Ribeiro et al. 2014; Pugliesi & Rapini 2015) and the Amazonian species R. sprucei (W.Rothe) F.Esp.Santo & Rapini appears as sister to the rest of the genus, which can be divided into two major clades, one of them diversified in South America (clade A) and the other in Mesoamerican region (clade B). Among the South American species, there is a group (clade A1), except for the Amazon R. rubrofusca (E.Fourn.) F.Esp.Santo & Rapini from “igapó” forests, which is almost restricted to seasonally dry forests, suggesting that the radiation of this lineage occurred in northeastern Brazil, dispersing from there to the savannas of Central Brazil. The other South American group (clade A 2) is widely distributed, with species such as R. altissima (Jacq.) F.Esp.Santo & Rapini and R. macrophylla (Humb. & Bonpl. ex Schult.) H.Karst. It dispersed to the north, reaching Mexico (“Marsdenia” zimapanica Hemsl.), and is especially diverse in eastern Brazil, mainly in the Atlantic forest.
Type
R. macrophylla (Humb. & Bonpl. ex Schult.) H.Karst.

Native to:

Argentina Northeast, Argentina Northwest, Belize, Bolivia, Brazil North, Brazil Northeast, Brazil South, Brazil Southeast, Brazil West-Central, Colombia, Costa Rica, Cuba, Dominican Republic, Ecuador, El Salvador, French Guiana, Guatemala, Guyana, Haiti, Honduras, Jamaica, Leeward Is., Mexico Gulf, Mexico Northeast, Mexico Southeast, Mexico Southwest, Panamá, Paraguay, Peru, Suriname, Trinidad-Tobago, Uruguay, Venezuela, Windward Is.

Ruehssia H.Karst. appears in other Kew resources:

First published in Verh. Vereins Beförd. Gartenbaues Königl. Preuss. Staaten 19: 304 (1849)

Accepted by

  • Govaerts, R., Nic Lughadha, E., Black, N., Turner, R. & Paton, A. (2021). The World Checklist of Vascular Plants, a continuously updated resource for exploring global plant diversity. https://doi.org/10.1038/s41597-021-00997-6 Scientific Data 8: 215.

Kew Backbone Distributions
The International Plant Names Index and World Checklist of Selected Plant Families 2021. Published on the Internet at http://www.ipni.org and http://apps.kew.org/wcsp/
© Copyright 2017 World Checklist of Selected Plant Families. http://creativecommons.org/licenses/by/3.0

Kew Bulletin
Kew Bulletin
http://creativecommons.org/licenses/by-nc-sa/3.0

Kew Names and Taxonomic Backbone
The International Plant Names Index and World Checklist of Selected Plant Families 2021. Published on the Internet at http://www.ipni.org and http://apps.kew.org/wcsp/
© Copyright 2017 International Plant Names Index and World Checklist of Selected Plant Families. http://creativecommons.org/licenses/by/3.0