Adenocalymma darwinii L. H. Fonseca, 2026

Fonseca, Luiz Henrique M. & da Silva Ribeiro, Ricardo, 2026, Taxonomic novelties in Adenocalymma (Bignonieae, Bignoniaceae) endemic to the Atlantic Forest, Plant Ecology and Evolution 159 (1), pp. 3-11 : 3-11

2. Adenocalymma darwinii L. H. Fonseca sp. nov.

Figs 1 , 2 , 3 , 4 , Table 2

Type

BRAZIL – Espírito Santo • Santa Teresa, Cabeceira do 25 de Julho ; 17 Aug. 2005; fl.; Kollmann 8228; holotype: MBML [ MBML 00009099 ]; isotype: SPF [ SPF 00199077 ] .

Diagnosis

Adenocalymma darwinii resembles A. hirtum (Mart. ex DC.) Bureau & K. Schum. and A. salmoneum J. C. Gomes. It shares with A. hirtum the hirsute indumentum on the branches, petioles, petiolules, major veins of the leaflets, inflorescence axis, bracts, bracteoles, and calyx. However, it can be differentiated by the presence of slightly gibbous corolla with narrow aperture, and exserted anthers and stigma. It shares with A. salmoneum the slightly gibbous corolla with narrow aperture, cupular trichomes at the apex of the corolla, and exserted anthers and stigma. However, it can be differentiated by the scandent shrub-like habit (vs lianescent), the hirsute indumentum on the branches, petioles, petiolules, major veins of the leaflets, inflorescence axis, bracts, bracteoles, and calyx (vs glabrous), linear bracts (vs elliptic), yellow corolla (vs orange), and the anthers and stigma exserted or at the corolla mouth (vs included in the corolla tube).

Description

Shrub to scandent shrub, up to 3.5 m tall. Stems terete, brown, with striated bark, with elliptic lenticels; branchlets terete, hirsute, with eglandular trichomes simple or rarely branched, interpetiolar region without glandular fields; prophylls of the axillary buds narrow-elliptic, 9 × 1.3 mm, hirsute, with eglandular trichomes simple, with glandular trichomes cupular, ca 0.5 mm diam. Leaves 3 - foliolated, with the terminal leaflet not modified into a tendril; petioles 10.1–75.6 mm long; petiolules terete, with variable lengths, central petiolules ca 57 mm long, lateral petiolules ca 3 mm long, hirsute; leaflets elliptic or slightly obovate, apex acuminate to acute, base cuneate, symmetric, blade membranous, adaxial surface glabrous to slightly hirsute, with eglandular trichomes simple, abaxial surface hirsute with more trichomes on the veins, with eglandular trichomes simple, with glandular trichomes cupular sparsely distributed, first venation order pinnate, second venation order brochidodromous, third venation order reticulate, margins entire, straight, leaflets 10–24.1 × 2.3–7.0 cm. Inflorescence a branched lateral raceme, congested, main axis and pedicels hirsute, with eglandular trichomes simple or rarely branched; pedicels up to 4.8 mm long; floral bracts caducous, or covering young buds, linear, chartaceous, 9.2 × 2 mm, hirsute, with eglandular trichomes simple and glandular trichomes cupular, ca 0.8 mm diam.; bracteoles caducous, persistent covering the buds, linear, membranous, 4.8–10.2 × 0.8 mm, with glandular trichomes, ca 0.4 mm diam. Calyx green, campanulate, 5 - lobed, coriaceous, 8.9–11 × 6–7.5 mm, hirsute, with eglandular trichomes simple or branched, with glandular trichomes cupular, 0.5–0.7 mm diam. Corolla yellow, tubular to slightly gibbous, membranous, with nectar guides, 33–50.2 mm long, 8–9 mm at the portion of maximum width, 2 mm wide at the base, pubescent, with eglandular trichomes, and cupular trichomes at the apex, lobes orbicular, 3.0 × 5 mm diam. Androecium attached at 10.2 mm from the base, shorter filaments 45 mm long, longer filaments 62 mm long, staminode ca 4 mm long, glabrous, hirsute at insertion, with glandular trichomes stipitate, anthers 6 × 0.8 mm, exserted. Gynoecium ca 32–64 mm long; ovary cylindrical, 3.2 × 1.4 mm, glabrous; style ca 61 mm long, glabrous; stigma lanceolate, 2.3 × 1.5 mm, exserted. Fruit unknown.

Distribution and ecology

Adenocalymma darwinii is only known from the type locality in Espírito Santo state, Brazil (Fig. 2 ). This species is found in the understory of seasonally semi-deciduous Atlantic Forest remnants.

Phenology

The species was collected bearing flowers in August and September.

Etymology

We are describing Adenocalymma darwinii to celebrate the great British naturalist, Dr Charles Darwin. Known as one of the fathers of the theory of evolution by natural selection and the author of the book On the Origin of Species. His discoveries and insights inaugurated a new perspective on how biodiversity is perceived and understood. This tribute is also a reminder of the importance of his ideas and how influential they remain.

Preliminary IUCN conservation assessment

The species is only known from the type locality. Its conservation status is Data Deficient (DD) according to the IUCN criteria ( IUCN 2012; IUCN Standards and Petitions Subcommittee 2017) until more information about this new species is gathered during field studies and more populations are found. Meanwhile, the reduced population size and the anthropogenic pressure (see Fraga et al. 2019) at the only known locality would likely push this species towards extinction if conservation measures are not taken.

Additional material examined ( paratypes)

BRAZIL – Espírito Santo • Santa Teresa, Cabeceira do 25 de Julho , 19°50’19.2”S, 40°36’35.0”W; 302 m; 11 Sep. 2024; fl.; Ribeiro 800; VIES • Sítio Recanto Feliz ; 11 Aug. 2005; fl.; Fontana 1656; MBML [ MBML 00008654 ] .

Taxonomic notes

The state of Espírito Santo in Brazil has 16 species of Adenocalymma ( Fonseca and Lohmann 2019 a); however, A. darwinii is the only one with a hirsute indumentum and clearly differs from the morphologically similar A. hirtum by being a scandent shrub (vs liana), and by the presence of tubular corolla (vs infundibular) and exserted anthers and stigma (vs included in the corolla tube). Adenocalymma darwinii also differs from A. salmoneum by being a scandent shrub (vs liana) and by its yellow corolla (vs orange) (Table 2 ). Adenocalymma darwinii was included in the phylogenetic study and emerged as sister to A. apetiolatum L. H. Fonseca & L. G. Lohmann ( Fonseca and Lohmann 2018; Fig. 1 ). The latter species is also an endemic of seasonally semi-deciduous Atlantic Forest remnants in Espírito Santo, however, markedly differs from A. darwinii due to the presence sessile leaves and gibbous corollas.

Figures

Figure 1. Bayesian majority rule consensus tree derived from the analysis of the combined plastome and nuclear (pepC) datasets (adapted from Fonseca and Lohmann 2018). Bayesian posterior probabilities are shown above branches. Adenocalymma comosum and the new species A. darwinii are in bold.

Figure 2. Distribution of Adenocalymma comosum (red) and A. darwinii (blue) in the Brazilian Atlantic Forest.

Figure 3. Adenocalymma darwinii. A. Habit. B. Young branch. C. Old branch. D – E. Young branches covered with trichomes. F. Leaves. G – I. Inflorescence. Photos by Ricardo Ribeiro.

Figure 4. Adenocalymma darwinii. A. Flowering branch. B. Leaf. C. Detail of trichomes. D. Flower. E. Detail of corolla trichomes. F. Bracteole. G. Detail of calyx. H. Detail of calyx trichomes. I. Opened flower. J. Nectar disk, ovary, style, and stigma. K. Detail of stigma. Illustrated from Kollmann 8228 (SPF) by Klei Souza.