Adenocalymma Mart. ex Meisn. is a Neotropical genus of lianas, shrubs and treelets with approximately 76 species (Fonseca & Lohmann, in prep.). It belongs to tribe Bignonieae, the most speciose tribe of the Bignoniaceae. The genus is centered in Amazonia and the Atlantic Forest, with most species being found at low to mid-elevations (up to 2000 m). The remaining species occur in the South American dry diagonal, wet and dry forests of Central America, Colombia, Ecuador and the Guiana Shield (Lohmann & Taylor, 2014).

The current circumscription of Adenocalymma (Lohmann & Taylor, 2014) is based on a molecular phylogeny of the whole tribe Bignonieae inferred using DNA sequences from the plastidial gene ndhF and the nuclear intron pepC (Lohmann, 2006). Under the new circumscription, Memora is synonymized under Adenocalymma, which is broadly circumscribed and characterized by cupular glandular trichomes on the prophylls of the axillary buds, floral bracts, bracteoles, calyces, and fruits, all of which are morphological synapomorphies of the genus (Lohmann, 2006, Lohmann & Taylor, 2014). More recently, a phylogeny of the “Adenocalymma-Neojobertia” clade was inferred based on a combination of nearly-complete plastome sequences and the nuclear pepC, and sampling 90% of all known species in the genus (Fonseca & Lohmann, 2018). This phylogenetic framework provided additional support for the broader circumscription of Adenocalymma adopted by Lohmann & Taylor (2014), and further indicated that Neojobertia Baill. and Pleonotoma albiflora (Salzm. ex DC.) A.H. Gentry are nested within the genus and best treated as part of Adenocalymma. The new findings are leading to an updated classification for the whole clade that recognizes a broad Adenocalymma (Fonseca & Lohmann, in prep.).

During morphological studies of the “Adenocalymma-Neojobertia” clade (Fonseca & Lohmann, in prep.), a new species from the Atlantic Forest was discovered. This is still a poorly known group, with nine new species being described for this clade only in the last decade (Udulutsch et al., 2009; Udulutsch et al., 2013; Fonseca et al., 2016; Faria et al., 2016; Fonseca & Lohmann, 2017). Two of the newly described species are endemic to the Rio Doce State Park and surroundings (Udulutsch et al., 2013), where the species described here is also found. The new taxon was sampled in the molecular phylogeny of the “Adenocalymma-Neojobertia” clade (Fonseca & Lohmann, 2018; Fig. 1), confirming its placement within the genus. The newly described species, Adenocalymma fistulosum L.H. Fonseca & L.G. Lohmann, is morphologically similar to A. apetiolatum L.H. Fonseca & L.G. Lohmann, A. sessile Udulutsch & Assis, A. subsessilifolium DC., and A. tephrinocalyx Bureau ex K. Schum., but differs in a suite of morphological characters.

Fig. 1
figure 1

Bayesian majority rule consensus tree derived of the analysis of the combined plastome and nuclear (pepC) datasets. Bayesian posterior probabilities are shown above branches. In bold are the new species, Adenocalymma fistulosum, and morphologically similar species (adapted from Fonseca & Lohmann, 2018).

Full size image

Material and methods

For this study, we examined the botanical collections deposited at the BHCB, MBML, SPF and VIC Herbaria (acronyms follow Index Herbariorum). The botanical terminology adopted here follows Hickey (1973) for leaf characters, and Weberling (1989) for inflorescence terminology. Other morphological structures follow Harris and Harris (2001) and Lohmann and Taylor (2014). Species delimitation is based on the concept proposed by Queiroz (2007), which recognizes species as independent evolutionary lineages. We are here recognizing species as independent evolutionary units that share a unique combination of features. Maps were prepared using the packages maptools (Bivand et al., unpubl.; available from http://cran.r-project.org/web/packages/maptools/index.html) and Raster (Hijmans et al., unpubl.; available from http://cran.r-project.org/web/packages/raster/index.html), both implemented in R environment (R Development core team, 2018).

Adenocalymma fistulosum L.H. Fonseca & L.G. Lohmann, sp. nov. Type: Brazil. Minas Gerais: Córrego Novo, Lagoa das Piabas, 19°51′26”S, 42°30′29”W, 260 m, 9 May 2003 [fl, fr], G.S. França 341 (holotype: SPF; isotypes: BHCB [BHCB030312], BHCB [BHCB021971]). (Fig. 2).

Fig. 2
figure 2

Adenocalymma fistulosum. A. Flowering branch. B. Detail of the hollow pith. C. Detail of inflorescence trichomes. D. Detail of young bud. E. Bract. F. Bracteole. G. Open flower. H. Detail of calyx. I. Detail of corolla showing stamen insertion. J. Nectar disk, ovary, style, and stigma. (Illustrated from the holotype).

Full size image

Diagnosis:Adenocalymma fistulosum resembles A. apetiolatum, A. sessile, A. subsessilifolium and A. tephrinocalyx, with which it shares shrubby habit, sessile leaves, and large leaflets. Adenocalymma fistulosum can be differentiated by the hollow branch and branchlet pith, narrow-elliptic prophylls of the axillary buds, villous indumenta throughout, bullate leaflet lamina, branched trichomes on the inflorescence that become olive-green when dried, small and elliptic bracts (16.4 × 6.5–8.9 mm), small and elliptic bracteoles (7.5–9 × 1.6–1.9 mm), infundibuliform yellow corolla with fields of cupular trichomes, and exserted anthers and stigmas.

Shrub, 3 m tall. Stems terete, brown, with striated bark, with lenticels elliptic; branchlets terete, villous, with eglandular trichomes simple or branched, interpetiolar region without glandular fields; prophylls of the axillary buds narrow-elliptic, 16.1 × 4.3 mm, villous and lepidote, with eglandular trichomes simple or branched, with cupular glandular trichomes ca. 1.2 mm diam. Leaves 3-foliolated, with the terminal leaflet not-modified into a tendril; petioles lacking; petiolules terete, with variable lengths, central petiolules ca. 16 mm long, lateral petiolules ca. 9 mm long, villous; leaflets elliptic or slightly obovate, apex short acuminate to acute, base cuneate, symmetric, membranous, adaxial surface pubescent, with eglandular trichomes simple or branched, abaxial surface pubescent and lepidote, with eglandular trichomes simple or branched, with glandular trichomes cupular sparsely distributed, bullate, first venation order pinnate, second venation order brochidodromous, third venation order reticulate, margins entire, straight, leaflets 0.3–38.5 × 14–16.3 cm. Inflorescence a branched lateral raceme, congested, with eglandular trichomes branched; pedicels 4.8 mm long; floral bracts persistent, covering young buds, elliptic, chartaceous, 16.4 × 6.5–8.9 mm, villous, with glandular trichomes cupular, ca. 0.8 mm diam.; bracteoles persistent, elliptic, membranous, 7.5–9 × 1.6–1.9 mm, with glandular trichomes cupular, ca. 0.3 mm diam. Calyx green, campanulate, 5-lobed, coriaceous, 6.8–8 × 6.6–8.6 mm, villous, with eglandular trichomes simple or branched, with glandular trichomes cupular, 0.6–0.8 mm diam. Corolla yellow, infundibuliform, membranous, with nectar guides, 38–40.8 mm long, tube 32.3–35.7 mm long, 10.6–14.3 mm at the portion with maximum width, 3.5–4.7 mm width at the base, pubescent, with eglandular trichomes simple or branched, without cupular trichomes, lobes orbicular, central inferior 9.6 × 10.7 mm, lateral inferior 9.8 × 8.7 mm. Androecium attached at 12.8 mm long, shorter filaments 35.2 mm long, longer filaments 41 mm long, staminode ca. 4.2 mm long, glabrous, hirsute at insertion, with glandular trichomes stipitate, anthers slightly curved backward, 5 × 0.7 mm, exerted. Gynoecium ca. 46.8 mm long, ovary cylindrical, 2.8 × 1.3 mm, glabrous, style ca. 41.7 mm long, glabrous, stigma lanceolate, 2.3 × 1.5 mm, exserted. Fruit mature, oblong, inflated, rugose, puberulent and lepidote, with eglandular trichomes simple or branched, with glandular trichomes cupular. Seeds not winged, 28–30 × 29–31 × 15–19 mm.

Distribution and ecology.—Adenocalymma fistulosum is only known from the type locality in Minas Gerais State, Brazil (Fig. 3). This species is found at 260 m elevation in seasonally semi-deciduous Atlantic forest remnants.

Fig. 3
figure 3

Distribution of Adenocalymma fistulosum and the morphologically similar A. apetiolatum, A. sessile, A. subsessilifolium, and A. tephrinocalyx in the Brazilian Atlantic Forest.

Full size image

Conservation status.—Adenocalymma fistulosum is only known from the type locality. Tentatively, its conservation status is Data Deficient [DD] according to IUCN criteria (IUCN, 2012; IUCN Standards and Petitions Subcommittee, 2017) until more information about this new species is gathered during field studies. Meanwhile, reduced population size and anthropogenic pressure on the only known locality would very likely push this species towards extinction if conservation measures are not taken seriously. Although it occurs in the surroundings of Rio Doce State Park, no populations within the Park were discovered.

Flowering and fruiting.—Adenocalymma fistulosum was collected with flower and fruit in May.

Etymology.—The specific epithet ‘fistulosum’ refers to the hollow pith of the branches and branchlets, an unusual feature within the genus.

Morphological and geographical notes.—Adenocalymma fistulosum, A. apetiolatum, A. sessile, A. subsessilifolium and A. tephrinocalyx are understory shrubs from semi-deciduous Atlantic Forest. These five Adenocalymma species are the only ones in the genus to bear sessile leaves. Although these species are superficially similar vegetatively, they differ in the type of indument, branch and branchlet pith, prophyll shape, inflorescence indument, bract and bracteole shape and size, corolla shape and color, the presence of cupular trichomes in the corolla, and anther and stigma position (Table 1).

Table 1 Morphological comparison between Adenocalymma fistulosum, A.apetiolatum, A.sessile, A.subsessilifolium, andA.tephrinocalyx
Full size table

In addition, A. fistulosum is also recognized by the bullate leaflets and olive green inflorescence indument when dried (Table 1). The bullate leaflets are shared with A. bullatum Bureau ex. K. Schum. and the olive green inflorescence indument when dried is shared, among others, with A. trifoliatum (Vell.) R.C. Laroche. As such, the new taxon is here recognized based on a unique combination of features, not found in any other species of the “Adenocalymma-Neojobertia” clade. Despite the morphological similarities among these taxa, species with sessile leaves do not form a clade (Fig. 1), indicating that the sessile condition evolved more than once within this lineage. Sessile leaves are not a very common condition within the tribe Bignonieae, being only found in a few species of Amphilophium and Anemopaegma. This condition is common among members of Crescentieae (Gentry, 1980).

The geographic distribution of the new taxon coincides with the distribution of two newly described Adenocalymma species, all of which occur in the vicinity or within the Rio Doce State Park (Udulutsch et al., 2013). All three species (A. cinereum Udulutsch & Assis, A. sessile, and A. fistulosum) are understory shrubs that are only known from a few collections around the type locality (Udulutsch et al., 2013). Adenocalymma fistulosum and A. sessile also share sessile leaves.