Nematanthus exsertus Chautems, 2017

Alain Chautems & Mathieu Perret, 2017, Description and phylogenetic position of a new species of Nematanthus (Gesneriaceae) from Bahia, Brazil, Candollea 72 (2), pp. 351-359 : 355-356

Nematanthus exsertus Chautems , spec. nova ( Fig. 2 ).

Typus: BRAZIL. Bahia: Município de Wenceslau Guimarães, Estação Ecológica Estadual Nova Esperança, trilha para o Rio Agua Vermelha, 415-450 m, 13°35’43’’S 39°43’10’’W, 3.V.2007, Jardim et al. 5000 (holo-: CEPEC- 117040! ; iso-: NY!).

Nematanthus exsertus Chautems resembles N. corticola Schrad. with similar elongate pedicels, short and narrow calyx lobes and funnel-shaped, laterally compressed red corollas, but differs by a villous indumentum on stem and petioles, as well as shorter and more ventricose corollas and presence of exserted stamens and style.

Subshrub 0.5-1.2 m, epiphytic; stem ascending, sparingly branched, 3-6 mm diam., villose, especially in young parts; internodes 1.5-5 cm. Leaves strongly anisophyllous; petioles 0.5-4 cm, dark vinaceous, pubescent-hirsute; blades 2.5-5 3 0.8-2 cm (smaller ones) to 6–14 3 1.8-3 cm (larger ones), elliptic, adaxially green, pubescent, abaxially paler green, glabrescent, apex acute to acuminate, base cuneate, margin entire, 3-6 lateral veins each side of the midrib, vinaceous, pubescent. Flowers solitary, 1-3 per stem, pendent-resupinate, in leaf axils, bracts minute or early caducous; pedicels 10-18 cm long, vinaceous, pubescent. Calyx fused for 3-4 mm at base, sepals 7-8 3 2-3 mm, linear lanceolate, pubescent, vinaceous, apex acute, greenish, margin entire or remotely toothed. Corolla 3-3.5 cm long, scarlet-red, obliquely inserted in calyx, funnel-shaped, laterally compressed on ventral side before mouth, pubescent, base shortly cylindric, 4-5 mm diam., gradually enlarged to 2-2.2 cm at the opening, lobes revolute at anthesis; stamens and style exserted for about 2.5-2.8 cm beyond the corolla opening, filaments 4.5-5 cm, not coiling at the end of anthesis, white, glabrous, pollen cream; nectary gland bilobed, 3-4 3 2-3 mm, cream, ovary 4-6 mm long, vinaceous, pubescent, style 4.8-5.2 mm, white, glabrous. Fruit unknown.

Etymology. – The epithet “ exsertus ” refers to the exserted stamens and style that extend beyond the corolla opening for at least 2.5 cm.

Distribution, ecology and phenology. – Nematanthus exsertus is currently known by two collections made in the “Estação Ecológica Estadual Nova Esperança” in the municipality of Wenceslau Guimarães in the state of Bahia ( Fig. 3 ). The individuals were observed growing epiphytically on small trees at 1-2 m above the ground in the understory of a fragment of wet and dense forest on flat grounds. Specimens were collected with flowers in January and May. According to flower morphology, the species is likely pollinated by hummingbirds. Pollination by hermit hummingbirds has been documented for the related species N. crassifolia and N. brasiliensis presenting similar pendent and resupinate flowers with laterally compressed corolla ( SANMARTIN-GAJARDO & VIANNA, 2010; WOLOwSKI et al., 2013).

Conservation status. – Nematanthus exsertus is known only from a single location of a dozen individuals in an area of preservation created in 1997 and extended in 2,000, covering 2,418 ha. of Atlantic Rain Forest (“Estação Ecológica Estadual Nova Esperança”). This area is nevertheless subject to local preservation conflicts, like deforestation, illegal hunting and illegal occupation [http://www.inema.ba.gov.br/gestao-2/ unidades-de-conservacao/estacao-ecologica/estacao-ecologicade-wenceslau-guimaraes]. Therefore, with a restricted AOO, plausible threats that could rapidly push the species to “Critically Endangered”, N. exsertus is assigned a preliminary assessment of “Vulnerable” [VU D2] using the IUCN Red List Categories and Criteria ( IUCN, 2012).

Notes. – Our first thought, at the time of discovering this species, was that we had found an individual of Nematanthus corticola with ill-formed stamens and style, because this taxon occurs frequently in the southern Bahian rain forest ( Fig. 3 ). After having observed few individuals, each bearing several flowers, it was readily apparent that we had discovered a new species.

The striking exserted position of stamens and style are a unique feature in the genus Nematanthus . Nematanthus exsertus resembles N. corticola with similar pedicel, calyx lobes, corollas, but differs by a villous indumentum on stem and petioles, as well as shorter and more ventricose corollas with strikingly exserted stamens and style (see Table 1 ).

The total number of known species for the genus Nematanthus is now 32. The new species should be added to the recent checklist that established a high endemism rate of epiphytic plants within the eastern Brazilian Atlantic rain forest ( FREITAS et al., 2016). It is also an addition to the number of Gesneriaceae species that have been registered so far for the state of Bahia, the total number of registered species reaches now 29 ( CHAUTEMS, 1991; ARAUJO et al., 2017).

Paratypus. – BRAZIL. Bahia: Município de Wenceslau Guimarães, Reserva Estadual de Wenceslau Guimarães , Trilha da Petioba , 13°34’49’’S 39°42’17’’W, 411 m, 19.01.2012, Monteiro et al. 545 ( RB-536512 ).

Figures

Fig. 2. – Nematanthus exsertus Chautems. A. Habit with pendent pedicels in native habitat; B. Flowering shoots; C. Close-up of shoot showing stem and petiole indumentum; D. Close-up of corolla showing exserted stamens and style. [Jardim et al. 5000]

Fig. 3. – Distribution map of Nematanthus exsertus Chautems (star) showing also the occurrences of morphologically related species N. corticola Schrad. (circles) and N. crassifolius (Schott) Wiehler (triangles).

Tables

Table 1. – Key morphological differences between Nematanthus exsertus Chautems, N. corticola Schrad. and N. crassifolius (Schott) Wiehler; abbreviations in capital letters stands for the Brazilian states of Bahia (BA), Espírito Santo (ES),

N. corticola	N. crassifolius	N. exsertus
Stem indument	glabrous	glabrous	villose
Petiole indument	Sparsely pubescent	glabrous	villose
Pedicel length [cm]	10-20	3-10(-16)	10-18
Calyx lobes length [mm]	7-12	15-30	8-10
Calyx lobes width [mm]	2-4	4-8	2-3
Corolla length [cm]	3.8-5	4-5	3-3.5
Corolla width at max. gibbosity [cm]	1.4-2	1.8-2.4	2-2.2
Stamens position	included	included	strongly exserted
Distribution	BA in most of the southern	Montane rain forest in ES,	Restricted to one locality in
	hylea rain forest	RJ, southeastern MG and	southern BA
		marginally in SP