Studies in the Neotropical Apocynaceae LI: a new species of Laubertia (Apocynaceae) from Brazil

J. Francisco Morales

Department of Plant Systematics, University of Bayreuth, Universitätstrasse 30, 95447 Bayreuth, Germany

drjfranciscomorales@gmail.com, http://orcid.org/0000-0002-8906-8567

INTRODUCTIONTOP

Laubertia A.DC. —Apocynaceae Juss.— grows in tropical and subtropical regions of Mexico, Guatemala, and Belize, and from Colombia to Bolivia. It is composed of woody vines with milky sap, cymose inflorescences with scarious bracts, sepals without colleters at the base of the adaxial surface, corolla with an annular corona around the mouth, the tube without free corona lobes within, corolla lobes totally reflexed towards the tube during the anthesis, moniliform follicles and truncate seeds, comose at the micropylar end (Morales 2002, 2009). The first revision of Laubertia was conducted by Woodson (1936), who accepted four species, three of them restricted endemisms: L. peninsularis Woodson, L. pringlei (Greenm.) Woodson, and L. sanctae-martae (Rusby) Woodson, whereas L. boissieri A.DC. was known only from four collections from Ecuador and Peru. Shortly after, Woodson (1938) proposed L. contorta (M.Martens & Galeotti) Woodson, and reduced L. pringlei into the synonymy of that species. The most recent study (Morales 2002), accepted three species: L. boissieri —including L. sanctae-martae—, L. contorta, and L. peninsularis.

The research of phylogenetic relationships of tribe Echiteae Bartl. (Morales & al. 2017), and the revision of specimens for the Flora of Brazil (Morales in prep.) revealed a new species endemic to the Amazon basin supported by molecular data and morphological characters, which represents the first record of Laubertia for the country. This paper aims to describe this new species, including an illustration and a key to the currently accepted species of Laubertia.

MATERIAL AND METHODSTOP

Material of Laubertia of the following herbaria was reviewed: B, BM, BR, C, CIIDIR, CM, COL, CR, F, G, G-BOIS, G-DC, GH, IAN, INPA, K, LPB, MEXU, MG, MICH, MO, NY, O, P, P-HB, QCNE, RB, S, UB, US, USF, including all the type collections. The descriptions of the morphological structures follow Font Quer (1953), Radford & al. (1974), and Harris & Harris (1994).

RESULTSTOP

Key to the species of LaubertiaTOP

Description of the new speciesTOP

Laubertia brasiliensis J.F.Morales, sp. nov.

LSID: urn:lsid:ipni.org:names:77167102-1

Type: Brazil, Pará, south bank of Amazonas, ca. 2 km E of Arumanduba, 52° 27´W, 1°27´S, 27 Jul. 1961, W. Egler & H. Irwin 46037 (holo-: NY). Fig. 1.

Diagnosis.—Laubertia brasiliensis sp. nov. differs from L. contorta (M.Martens & Galeotti) Woodson by its straight corolla tube —vs. spirally contorted in L. contorta—, and from L. boissieri A.DC. by its inflorescences shorter than the subtending leaves —vs. inflorescences longer than the subtending leaves—, smaller corolla lobes —8–9 mm vs. 10–18 mm in L. boissieri—, and seeds with a smaller apical comma —0–9 mm vs. 2.5–4.8 cm in L. boissieri.

Liana. Stems with white latex; branchlets terete to subterete when old, very inconspicuously puberulent when young, glabrate at maturity; nodal colleters up to 0.4 mm long. Leaves opposite; petioles 3–9 mm long; blade 4–10.3 × 1.4–4 cm, membranaceous, ovate to ovate-elliptic, glabrous adaxially, inconspicuously puberulent along the midrib abaxially, the apex shortly acuminate, the base obtuse truncate to obtuse, the margin not revolute. Inflorescence shorter than the subtending leaves, axillary, inconspicuously puberulent, few-flowered; peduncle 7–9 mm long; pedicels 6–9 mm long; bracts 1–1.5 × 0.3–0.4 mm, linear to linear-ovate, scarious. Sepals 6–7 × 0.9–1.2 mm, narrowly ovate, acuminate, inconspicuously puberulent; corolla purple, the lobes darker towards center and orange at margins, glabrous or glabrescent externally, the tube 14–15 × 2.7–3.7 mm, not twisted around the stamens; lobes 8–9 × 2.5–3.5 mm, narrowly obovate, totally reflexed during the anthesis; anthers 5.2–5.4 mm long, glabrous dorsally, included; style head 1.9–2.1 mm long; nectary 1–1.2 mm, 5-lobed, ovary as long as the nectary. Follicles 36–38 cm × 0.3–0.6 mm, glabrous, inconspicuously moniliform; seeds 15–17 mm long, glabrous, coma up to 9 mm or absent, tan.

Distribution and habitat.—Endemic to Brazil to the states of Para and Amazonas, growing in river margins and igarapó forest, from 100 to 200 m a.s.l.

Phenology.—Flowering occurs in February and July and fruiting in July.

Additional specimen examined.—Brazil: Amazonas, Rio Solimões, Igarapé Camatiá, Sao Paulo de Olivença, 68°55´W, 03°28´S, 27 Feb. 1977, G. Prance & al. 24632 (CR, INPA, NY).

DISCUSSIONTOP

Laubertia was placed in the subtribe Prestoniinae Pichon ex M.E.Endress (Endress 2014), together with Hylaea J.F.Morales, Prestonia R.Br., and Rhodocalyx Müll.Arg., which have in common annular coronas around the corolla mouth or free corona lobes opposite to the anthers (Woodson 1936; Morales 1997, 1999; Morales & Liede-Schumann 2016). Based on the presence of an annular corona around the mouth, Laubertia had been considered as sister of Prestonia (Woodson 1936; Morales 2002), but the evidence provided by molecular data (Morales & al. 2017) showed that these genera are not even closely related and both are nested in different subtribes —Laubertinae J.F.Morales, M.E.Endress & Liede and Prestoniinae.

Laubertinae comprises Hylaea and Laubertia. The latter can be recognized from the former by its sepals without colleters on the base of the adaxial surface —vs. sepals with one colleter at the base of the adaxial surface—, corolla with an annular corona around the mouth —vs. annular corona absent— and corolla tube without free corona lobes within —vs. tube with free corona lobes.

Morales & al. (2017) published a phylogenetic study of the tribe Echiteae based on plastid —trnLF, matK-intron K, rpl16— and nuclear data —ITS—, in which L. brasiliensis sp. nov. was treated as Laubertia sp. nov. According to that study, L. brasiliensis sp. nov. is closely related to L. contorta from Mexico and northern Central America but differs by its tube corolla, not twisted, and disjunct geographical distribution. Laubertia brasiliensis sp. nov. may be distinguished from L. boissieri by its shorter inflorescences, smaller corolla lobes —lobes 8–9 mm vs. 10–18 mm—, and seeds with a smaller apical comma —0–9 mm vs. 2.5–4.8 cm.

ACKNOWLEDGEMENTSTOP

I thank the following herbaria for allow the study of their collections: B, BM, BR, C, CIIDIR, CM, COL, CR, F, G, G-BOIS, G-DC, GH, IAN, INPA, K, LPB, MEXU, MG, MICH, MO, NY, O, P, P-HB, QCNE, RB, S, UB, US, and USF. Financial support was provided in part by the University of Bayreuth Graduate School (Germany), the Deutscher Akademischer Austauschdienst (DAAD, Germany) and the Missouri Botanical Garden (United States). I grateful to one anonymous reviewer for review the English version of the manuscript.

REFERENCESTOP