Research Article |
Corresponding author: Diego Santos ( fdsantosbot@gmail.com ) Academic editor: Leandro Giacomin
© 2020 Diego Santos, Raysa Valéria Carvalho Saraiva, Tiago Massi Ferraz, Emília Cristina Pereira Arruda, Maria Teresa Buril.
This is an open access article distributed under the terms of the Creative Commons Attribution License (CC BY 4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
Citation:
Santos D, Saraiva RVC, Ferraz TM, Arruda ECP, Buril MT (2020) A threatened new species of Ipomoea (Convolvulaceae) from the Brazilian Cerrado revealed by morpho-anatomical analysis. PhytoKeys 151: 93-106. https://doi.org/10.3897/phytokeys.151.49833
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A new species of Ipomoea, endemic to the Cerrado domain in Maranhão, Brazil, is described. Ipomoea maranhensis D.Santos & Buril, sp. nov. has been misidentified as I. burchellii Meisn. in several herbaria. Even though both species have oblong, pubescent leaves, they can be distinguished by morpho-anatomical characters. We present a diagnosis, complete description, illustration, taxonomic comments, conservation status and distribution map.
biodiversity, Brazilian flora, conservation, endangered species, endemic species, morpho-anatomy, South America
Ipomoea (Convolvulaceae) comprises approximately 700 species (
Among Brazilian phytogeographic domains, the Cerrado stands out as a center of diversity and endemism for several plant groups (
While analyzing Ipomoea collections from CEN, HST, HUEFS, and SLUI (acronyms follow
We consulted literature related to climbing and subshrubby species of Ipomoea from South America (
To support the morphological delimitation between this morphotype and I. burchellii, we performed a comparative anatomical analysis of the leaf, as this has been used to support the morphological delimitation of species in various plant groups (
We analyzed specimens from the following herbaria: CEN, HUEFS, SLUI (acronyms follow
For comparative anatomical analyses, three I. burchellii specimens and two vouchers of the new species were included in this study (Table
List of vouchers sampled for comparative anatomical analysis of Ipomoea maranhensis and I. burchellii.
Species/specimens | Collection point | Voucher | Herbarium |
---|---|---|---|
I. maranhensis | |||
specimen 1 | Ibipira, Mirador, Maranhão state | L.P. Felix et al. 8136 | HST |
specimen 2 | Carolina, Maranhão state | R.V.C. Saraiva 107 | SLUI |
I. burchellii | |||
specimen 1 | Canápolis, Bahia state | Yoshida-Arns, K. 557 | HUEFS |
specimen 2 | São Desidério, Bahia state | A.M. Miranda 3787 | HST |
specimen 3 | Paraiso, Goiás state | Irwin, H.S. 21745 | HUEFS |
Distribution records were obtained from herbarium sheets. The conservation status was based on IUCN guidelines and criteria (
Brazil. Maranhão: município de Mirador, Ibipira, Parque Estadual do Mirador, 06°22'01"S, 44°22'00"W, 11 April 1998 (fl.), L.P. Félix et al. 8136 (holotype HUEFS38133, isotype HST8028).
Ipomoea maranhensis differs morphologically from I. burchellii Meins. by its twining habit (vs. subshrubs), lanceolate (vs. oblong), long-acuminate (vs. acute) and densely sericeous (vs. hirsute) sepals.
Vine, internodes 1–5 cm long, latex absent; stem pubescent with whitish trichomes. Leaf blade 3.3–7 × 0.9–2.3 cm, oblong, base cuneate, rounded to subcordate, apex obtuse, acute, apiculate, margin entire, pubescent on both surfaces, discolor, whitish on abaxial face, brochidodromous, 6–10 pairs of secondary veins, main vein prominent; petiole 2–3 mm long, canaliculate, pubescent, nectary near the apex of the petiole. Inflorescence of dichasial cymes reduced, bracteolate in the axils of the upper leaves, with 3–7 flowers; peduncle 2–3 mm long, pubescent; bracts 1.7–2 × 0.5–0.8 cm, elliptical, base cuneate, apex obtuse, pubescent, foliaceous, discolor; pedicel 2–4 mm long, pubescent; bracteoles 0.9–1.6 cm long, lanceolate, oblong, base truncate, apex acute, obtuse, margin entire, pubescent. Sepals all equal, 1.7–2.3 × 0.4–0.5 cm, lanceolate, base cuneate, apex long-acuminate, margins non-membranous, densely sericeous on the adaxial surface of the sepals, whitish. Corolla ca. 4 cm long, ca. 4.5 cm diam, infundibuliform, tube ca. 1.6 cm long, rose with whitish tube, midpetaline bands area sericeous externally. Stamens ca. 3 cm long, included, unequal, pilose at the base, anthers ca. 4 mm long, oblong, white. Ovary ca. 4 mm long, conical, glabrous, 4 locule; style ca. 2 cm long, glabrous; stigma bi-globose, papillose. Fruit unknown.
Petiole epidermis uniseriate with juxtaposed cells, parenchyma with isodiametric cells, prominent/concave main rib shape, U-shaped vascular bundles. Leaf epidermis uniseriate, mesophyll dorsiventral with crystallized idioblasts (druses), palisade parenchyma with one to two layers of elongated cells more evident on the adaxial surface, spongy parenchyma with three to four layers of round cells with sinuous anticlinal walls; glandular trichomes on both leaf surfaces.
According to the anatomical analysis, we observed that I. maranhensis and I. burchellii share mesophyll with crystallized idioblasts (druses) and petiole parenchyma with isodiametric cells. However, I. maranhensis is distinguished from I. burchellii by a prominent/concave main rib shape (vs. convex/flat main rib shape in I. burchellii), U-shaped vascular bundles (vs. V-shaped), glandular trichomes spread on both leaf surfaces (vs. only on abaxial one) and dorsiventral mesophyll (vs. isobilateral) (Fig.
Comparison of morpho-anatomical characters of Ipomoea maranhensis and I. burchellii.
Characters | I. maranhensis | I. burchellii |
---|---|---|
Shape of sepals | Lanceolate | Oblong |
Apex of sepals | Acuminate | Acute |
Indumentum of sepals | Sericeous | Hirsute |
Arrangement of vascular bundles | U-shaped | V-shaped |
Glandular trichomes on leaf | Both surfaces | Abaxial surface |
Type of mesophyll | Dorsiventral | Isobilateral |
A, B Ipomoea maranhensis A arrangement of vascular bundles in U; prominent/concave main rib shape B dorsiventral mesophyll C–F I. burchellii C arrangement of vascular bundles in V; convex/flat main rib shape D mesophyll isobilateral E glandular trichomes restricted to the abaxial surface of the leaf (red arrow) F parenchymatous tissue with isodiametric cells (Photos by E. Pereira Arruda). AD: adaxial epidermis; AB: abaxial epidermis; Is: isodiametric cells; Pa: Parenchymatous tissue; Pp: palisade parenchyma; Sp: spongy parenchyma; Vb: vascular bundle; Tr: trichome.
Collected with flowers in April.
Ipomoea maranhensis is known only from two disjunct populations between the municipality of Mirador, in the Mirador State Park (area of 4370 km2) and the municipality of Carolina, in the National Park Chapada das Mesas (CMNP, area of 1600 km2) (Fig.
The specific epithet refers to Maranhão state, where the type specimens were collected.
Brazil. Maranhão: Carolina, Parque Nacional da Chapada das Mesas, 345 m elev., 7°14'14"S, 46°58'50"W, 07 April 2017 (fl.), R.V.C. Saraiva 107 (SLUI 5037); Parque Nacional Chapada das Mesas, accesso no Km 596 da BR – 230, 7 km E em estrada vicinal, 290 m elev., 7°07'33"S, 47°22'13"W, 12 April 2016 (fl.), M.F. Simon et al. 2921 (CEN 95523).
We categorized this species as Endangered (criteria EN) according to B1 (EOO < 5000 km2) and B2ab (ii, iii) (AOO < 500 km2) from
1 | Leaf blade oblong, oblanceolate, linear or obovate | 2 |
– | Leaf cordate, hastate, lobed | 5 |
2 | Leaf linear; sepals obovate, elliptic, glabrous | I. schomburgkii Meisn. |
– | Leaf oblong, oblanceolate, obovate; sepals oblong, ovate, lanceolate, sericeous, hirsute | 3 |
3 | Leaf oblanceolate to obovate; sepals ovate | I. cuneifolia A. Gray |
– | Leaf oblong; sepals oblong or lanceolate | 4 |
4 | Sepals oblong, obtuse, hirsute | I. burchellii Meisn. |
– | Sepals lanceolate, long-acuminate, sericeous | I. maranhensis |
5 | Sepals with subapical rostrum; corolla hypocrateriform | I. hederifolia L. |
– | Sepals lacking subapical rostrum; corolla funnelform | 6 |
6 | Leaf 5-lobed | I. mauritiana Jacq. |
– | Leaf hastate or cordate | 7 |
7 | Outer sepals unequal in size | I. maurandioides Meisn. |
– | Outer sepals equal in size | 8 |
8 | Sepals convex | I. goyazensis Gardner |
– | Sepals flat | I. squamosa Choisy |
The new species has been confused with I. burchellii because they share oblong, discolorous and sericeous leaves, flowers arranged in a dichasium and peduncle 2–3 mm long. However, according to the analysis of the type specimens (Burchell 8738 deposited in K [K000612855]) and protologue of I. burchellii, the new species is morphologically different from I. burchellii by its habit, shape, apex, and indumentum of sepals. Misidentifications probably occurred because both species have oblong, discolorous leaves, 2–3 mm long peduncles and inflorescence arranged in dichasium, as well as because they occur in the Cerrado domain. Anatomical analysis revealed that the morphological delimitation of these species is supported by the shape of the vascular bundles, distribution of glandular trichomes in the leaf and type of mesophyll.
These characters are considered consistent (
One of the barriers that can hinder access to knowledge about the diversity of the genus Ipomoea is that several of its new species have been described based on the morphology from one or two specimens without the without using a tool to support the morphological delimitation (
In Convolvulaceae, these characters have also been consistent and informative, such as the type of mesophyll that was used to delimit three species of Evolvulus (
We are grateful to the Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPQ) for the financial support for our field expeditions, under the project: “Sistemática de Convolvulaceae da América do Sul: construir em direção ao conhecimento global” (Process: PVE 314725/2014-8); the Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) for granting a scholarship to the first author; to Regina Carvalho for the illustrations; to the Fundação de Amparo à Pesquisa e ao Desenvolvimento Científico e Tecnológico do Maranhão (FAPEMA) for financial support, and Hannah Doerrier for English review.