Lobelia sect. Rhynchopetalum (Fresen.) Bentham (1876: 552)

Rollim, Isis De Mello, Coelho, Guilherme Peres, Miotto, Silvia Teresinha Sfoggia, Iganci, João Ricardo Vieira & Oliveira, Marcelo Trovó Lopes De, 2022, Nomenclatural and taxonomic survey of the South American clade of Lobelia section Rhynchopetalum (Campanulaceae), Phytotaxa 539 (1), pp. 45-54 : 46-48

Lobelia sect. Rhynchopetalum (Fresen.) Bentham (1876: 552) .

Rhynchopetalum Fresenius (1838: 603) . Tupa sect. Rhynchopetalum (Fresen.) Richard (1850: 9) .

Type:— Lobelia rhynchopetalum Hemsl. ≡ Rhynchopetalum montanum Fresen. ≡ Tupa rhynchopetalum Hochst. ex A.Rich. Complete heterotypic synonymy in Lammers (2011).

Plants perennial or pliestesial, herbaceous phanerophytes, shrubs, treelets, or trees, with laticifers producing milky-white to yellowish latex. Stems typically robust or pachycaulous, 0.5–9 m tall, herbaceous, suffruticose, or woody, frequently fistulous, simple or branched, decumbent, ascending, or erect. Leaves simple, sessile, alternate, often apically rosulate. Flowers protandrous, resupinate, epigynous, zygomorphic, pedicellate, arranged in a terminal bracteate raceme or panicle; pedicels ebracteolate or bibracteolate. Corolla sympetalous, typically for half or more of its length, unilabiate with 5 ventral lobes or sub-bilabiate with 2 dorsal and 3 ventral lobes, of various shades of blue, purple, red, yellow, green, or white; tube curved or arcuate; lobes spreading or deflexed, as long as the tube or longer, monomorphic or scarcely dimorphic, all similar in size and shape. Stamens attached to the disc of the ovary; anthers bearded, with tufts of filiform hairs at apex of the ventral pair, or all glabrous at apex. Ovary completely or partially inferior; placentae axillar; ovules numerous. Fruit a capsule, loculicidally dehiscent by an apical pair of valves, often crowned by persistent calyx lobes, with hypanthium attached to the lower portion. Seeds small, numerous, ovoid, lenticular, commonly winged; testa striate-reticulate.

Distribution, habitat, and conservation:—The South American species are mostly concentrated in Brazil ( Fig. 1 ). Lobelia hassleri , found in the states of Rio Grande do Sul, Santa Catarina, Paraná, and São Paulo of south and southeast Brazil and the only species non-endemic to Brazil, extends its range to Misiones province of northeastern Argentina and to departments of Alto Paraná, Itapúa, Caazapá and Caaguazú of southeast Paraguay ( Lammers 2011). Some species have a very restricted distribution and are known from few localities, such as L. brasiliensis that occurs in the Distrito Federal and Goiás state, for the most part in the vicinity of Brasília; L. glazioviana is expected to be endemic to the Serra da Bocaina, of southeastern Brazil; L. hilaireana is found only in Minas Gerais state, in Serra do Ibitipoca and Serra Negra; L. langeana is endemic to the southern portion of the Serra do Mar, in the states of Paraná and Santa Catarina; and L. santos-limae is restricted to highland rocky fields of the Parque Estadual do Desengano, in Rio de Janeiro state.

The species are found mostly in the domains of the Atlantic Forest (10 spp.) and Cerrado (5 spp.), with only L. organensis also occurring in the Caatinga ( Rollim et al. 2020). They may be found at altitudes of 500–1800 m, preferring humid areas, such as swamps, gallery and ombrophilous forests, but also frequently found on high altitude grasslands and rocky fields, in dry forests, savanna formations, anthropic and disturbed areas, such as roadsides ( Vieira 2003, Rollim et al. 2020).

The natural areas of occurrence of the species of Lobelia sect. Rhynchopetalum are under constant threat by suppression of the original habitats and their conversion into agricultural and pasture lands, by soil degradation from agricultural activities and fires, and intense anthropization ( Terracap 2009, CNCFlora 2021). Nevertheless, only four of the species of L. sect. Rhynchopetalum have their official conservation status included in the Official List of Threatened Plants in Brazil ( CNCFlora 2021), with L. santos-limae assessed as Critically Endangered (CR), while L. brasiliensis , L. hilaireana , and L. langeana as Endangered (EN).

Taxonomic history:—The genus Lobelia was originally published by Plumier (1703), with a description and illustration of the polynomial L. frutescens , portulacae folia, honoring Flemish herbalist Matthias de L’Obel. Linnaeus (1753), adopting and thus validating the generic name, provided the binomial L. plumieri L. for the original species of Plumier (nowadays known as Scaevola plumieri (L.) Vahl (1791: 36) , Goodeniaceae ) and included 25 species that were previously assigned to the pre-Linnaean genera Dortmanna O.O.Rudbeck ex Hill (1756: 126) , Laurentia Adanson (1763: 134) , and Rapuntium Miller (1754: 435) .

Miller (1754, 1768), Adanson (1763), and other authors questioned Linnaeus’s circumscription of Lobelia as unnatural and even including species from two different families, resurrecting the above genera and reducing the genus exclusively to L. plumieri . Linnaeus (1771) described Scaevola Linnaeus (1771: 145) , which included L. plumieri , and maintained the Campanulaceae species in Lobelia , a circumscription that was supported by Candolle (1839) and accepted by most other authors. Differences in understanding of the concept of a valid name has produced several over the years new combinations and synonymizations ( Wimmer 1935, 1953, Lammers 2011). The taxonomic changes relevant for the South American species were treated by Presl (1836), who accepted the genus Rapuntium ; by Kuntze (1891), who recognized Dortmanna ; and Kanitz (1878), who described in Flora brasiliensis the genus Haynaldia that included all Brazilian species with robust habit.

There were several infrageneric classifications proposed for Lobelia , with the most recent those of Wimmer (1953) and Lammers (2011). Wimmer (1953) subdivided the genus into three subgenera and recognized several sections and subsections. The species treated here were allocated by him in L. subg. Tupa , L. sect. Eutupa , L. subsect. Haynadianae . Lammers (2011) divided the 415 species among 18 sections, allocating the species treated here to L. sect. Rhynchopetalum , based on a set of morphological characters, geographic distribution, and chromosome number.

Lobelia fistulosa was the first Brazilian species of L. sect. Rhynchopetalum to be described by Vellozo (1831) in a single analytical plate of his Flora fluminensis. Many studies encouraged by the Portuguese royal family contributed to the advancement of taxonomic study of L. sect. Rhynchopetalum , such as those by Pohl (1831) who described L. exaltata , based on his own specimens, and L. thapsoidea , whose authorship is also attributed to Schott. Chamisso (1833) described three species of Lobelia based on Sellow’s collections housed at B, with L. uranocoma (currently synonymous with L. fistulosa ) belonging to L. sect. Rhynchopetalum . Gardner (1845) published L. organensis based on his own collection from Serra dos Órgãos (Rio de Janeiro state).

Kanitz (1878) revised Lobeliaceae for Flora brasiliensis, describing Haynaldia exaltata var. ramosa , H. hilaireana and H. organensis var. insignis . Zahlbruckner (1896, 1907) studied the material collected by Glaziou in Brazil and by Hassler in Paraguay, publishing L. glazioviana and L. hassleri . Dúsen (1910) described L. langeana based on his own material collected during an expedition to the state of Paraná, in Brazil. Wimmer (1935) described L. imperialis and transferred the species of Haynaldia to Lobelia . Brade (1946) described L. santos-limae , collected by him and his collaborator Santos Lima, a species endemic to the municipality of Santa Maria Madalena (Rio de Janeiro state).

Braga (1946) carried out a review of the Brazilian species of Lobelia , describing L. stellfeldii based on a Stellfeld collection from Paraná. Vieira (1988) also reviewed Lobelia species for Brazil in an unpublished MSc thesis that included the most complete study of the genus, with an identification key, descriptions, and illustrations. Vieira (1988), however, did not provide or publish the necessary nomenclatural updates, suggesting two synonymizations, without a further elaboration. The most recent publication dealing with the South American clade of L. sect. Rhynchopetalum is a study by Vieira & Shepherd (1998), who described L. brasiliensis , a species endemic to Brasília (Distrito Federal).

Figures

FIGURE 1. Geographic distribution of Lobelia sect. Rhynchopetalum in South America. Species occurrences are represented by red stars.