Ipomoea buriliae (Convolvulaceae), a new species of morning glory discovered in the Borborema Plateau, northeastern Brazil

Ipomoea buriliae (Convolvulaceae), a new species of morning glory discovered in the Borborema Plateau, northeastern Brazil Belo D.P.1,2,3,4*, Santos E.A.V.1,3 & E.C. Gasparino4 1Programa de Pós-Graduação em Biodiversidade, Departamento de Biologia, Universidade Federal Rural de Pernambuco, 52171900, Recife, Pernambuco, Brazil 2Laboratório de Sistemática Integrativa, Departamento de Biologia, Universidade Federal Rural de Pernambuco, 52171-900, Recife, Pernambuco, Brazil 3Laboratório de Anatomia Vegetal, Departamento de Botânica, Centro de Biociências, Universidade Federal de Pernambuco, 50740-570, Recife, Pernambuco, Brazil 4Laboratório de Morfologia Vegetal e Palinologia, Departamento de Biologia, Faculdade de Ciências Agrárias e Veterinárias, Universidade Estadual Paulista, 14884-900, Jaboticabal, São Paulo, Brazil *E-mail: [email protected] Abstract: Ipomoea buriliae Belo (Convolvulaceae) is described and illustrated as a new species. We provide a taxonomic treatment along with anatomical, cytogenetic, and palynological descriptions for this new species. Additionally, we include illustrations, photographs, and details about its geographical distribution and conservation status. A comparative list highlights key morphological characters of I. buriliae in relation to closely related species. It shares some morphological similarities with I. parasitica (Kunth) G.Don. However, I. buriliae is distinguished by its white corolla, spiny projections on the stem, petiole, and peduncle, as well as a campanulate corolla and tector trichomes along the filaments. Keywords: Brazilian flora, CMA/DAPI banding, Endemism, Leaf anatomy, Palynology, Taxonomy of the family in the country has expanded with the publication of several new species (e.g., Wood et al., 2017; Santos et al., 2019, 2020a, 2020b, 2021; Nepomuceno et al., 2022; Belo et al., 2023a, 2024; Pastore et al., 2023; Santos & Buril, 2024). Ipomoea L. is the most diverse genus of Convolvulaceae, comprising approximately 800 species (Wood et al., 2020; Delgado-Junior et al., 2023). Despite its morphological variability, the genus is easily recognized by several key traits: echinate and pantoporate pollen grains, an entire style, a stigma usually with two globose stigmatic lobes, and 4-valved capsules (Austin & Cavalcante, 1982; Stefanović et al., 2002). The genus has about 160 species in Brazil, of which 65 are endemic (Santos et al., 2021; Simão-Bianchini et al., 2024). Representatives of the genus are characterized by having a climbing, herbaceous, or shrubby habit, simple or compound alternate leaves, absent stipules, cymose inflorescences, funnelform, campanulate, or hypocrateriform corolla (Austin, 2004; Ferreira & Miotto, 2009; Delgado-Junior et al., 2023). The shape, proportion, indumentum, and ornamentation of the sepals are essential taxonomic characters for delimitation for species of the genus, especially when compared with vegetative characters (Wood et al., 2020; Delgado-Junior et al., 2023). Received: 28.10.2024; Revised & Accepted: 08.12.2024 Published Online: 31.12.2024 Introduction Convolvulaceae comprises about 60 genera and 1,900 species, with a cosmopolitan distribution predominantly found in tropical regions (Staples & Brummitt, 2007; POWO, 2024). In Brazil, the family is represented by 24 genera and around 430 species (including one endemic genus and approximately 200 endemic species), distributed across all phytogeographic domains (SimãoBianchini, 2024). In recent years, the knowledge Vol. 34(5): 488–505 (2024) ISSN: 0971-2313 (Print edition) ISSN: 2582-2438 (Online edition) https://dx.doi.org/10.22244/rheedea.2024.34.05.10 Rheedea Journal of the Indian Association for Angiosperm Taxonomy RESEARCH ARTICLE 489 Belo et al. Anatomical, palynological, and cytogenetic studies have been used to support the morphological delimitations of species in several plant groups, in addition to being used to describe new species (e.g., Smith & Smith, 1942; Gomes et al., 2005; Almeida et al., 2016; Santos et al., 2019, 2020a, 2020b; Nepomuceno et al., 2022; Belo et al., 2023a, 2023b, 2023c, 2024). In Convolvulaceae, anatomical characters such as the shape of the petiole, midrib, and mesophyll are informative for delimiting species of Argyreia Lour. (Traiperm et al., 2017), Camonea Raf. (Santos et al., 2024), Daustinia Buril & A.R. Simões (Alencar et al., 2024), Evolvulus L. (Ketjarun et al., 2016; Santos et al., 2020a), and Jacquemontia Choisy (Belo et al. 2023b, 2023c, 2024). During field expeditions in the Northeast region of Brazil, we encountered an unfamiliar morphotype of Ipomoea, which we studied in detail. One population of this morphotype was identified, and here we describe it as a new Ipomoea species, supported by morphological, anatomical, palynological, and cytogenetic analyses. Materials and Methods Study area Field expeditions were carried out in northeastern Brazil, between May 2023 and July 2024. The description of the new species was based on specimens collected from one population in the Areia municipality, Paraíba State, Brazil (Fig. 1). This area is part of the Borborema Plateau (BP), one of the ecoregions within the Caatinga phytogeographic domain. The BP spans an area of 43,460 km², equivalent to 2.61% of Northeastern Brazil (Silva et al., 2003). It extends across the Fig. 1. Distribution of Ipomoea buriliae Belo, sp. nov. in Brazil. 490 A new species of morning glory for Brazilian flora states of Alagoas, Pernambuco, Paraíba, and Rio Grande do Norte (Giulietti et al., 2004), with altitudes ranging from 500 to 1200 m (Silva et al., 2003; Morais Neto et al. 2009). The predominant vegetation in the BP is hypoxerophilous Caatinga (Silva et al., 2003). Morphology and conservation status Specimens of morphologically closely related species were analyzed from the following herbaria: EAC, EAN, HCES, IPA, PEUFR, and UFP (acronyms follow Thiers, 2024). The taxonomic description and terminology follow Meisner (1869), Wood et al. (2020), Harris and Harris (2001), and Ellis et al. (2009). A preliminary conservation status assessment was performed based on the IUCN Red List Categories and Criteria (IUCN, 2012, 2024). The occurrence map was generated using QGIS software 3.22 Białowieża (https://qgis.org/). Anatomical analyses of leaves For comparative anatomical analyses, three leaves from the third node of the stem were obtained from five specimens of the new species and of I. parasitica (Kunth) G.Don in the field (Table 1). These leaves were fixed in FAA 50 (formaldehyde, acetic acid, and 50% ethanol) for 48 hours (Johansen, 1940) and subsequently stored in 70% ethanol. Freehand sections were made from the median region of the leaf blade, petiole, and stem. These sections were cleared and stained with safranin-astra blue (Bukatsch, 1972). The slides were prepared following the protocols of Kraus and Arduin (1997), analyzed using a Leica DM500 photomicroscope, and deposited in the Laboratory of Integrative Systematics at the Federal Rural University of Pernambuco, in Recife, Brazil. Samples close to the leaf margins were dehydrated and prepared for scanning electron microscopy (SEM) analysis using a Hitachi SEM, model TM4000 Plus. SEM images were processed using CorelDRAW® 2021 software. Palynological analyses For pollen morphology analyses, at least five buds were nearing anthesis collected from three specimens per population to obtain a significant Table 1. Specimens used in micromorphological analyses. Taxa Locality Voucher Herbarium Anatomical analysis Palynological analysis Cytogenetic analysis Geographic coordinates (latitude, longitude) Ipomoea buriliae Belo, sp. nov. Areia, Federal University of Paraíba, Paraíba state – Brazil D. Belo &E. Barbier 740 PEUFR × × × 6° 58’ 10” S, 35° 42’ 50” W Ipomoea alba L. Areia, Campus CCA-UFPB, Paraíba state – Brazil L.P. Félix & J.P. Dantas 5000 EAN – × – 6° 58’ 08” S, 35° 43’ 01” W Ipomoea marcellia Meisn. Remígio, Paraíba state – Brazil L.P. Félixet al. 10756 EAN – × – 6° 57’ 32” S, 35° 46’ 55” W Ipomoea parasitica (Kunth) G.Don Cuité, Paraíba state – Brazil V. F. Souza s.n. HCES 722 × × – 6° 29’ 36” S, 36° 09’ 24” W Ipomoea parasitica (Kunth) G.Don Ubajara, Ceará state – Brazil J.A.A.M Lourençoet al. 98 PEUFR × × – 3° 50’ 43” S, 40° 54’ 24” W 491 Belo et al. Table 2. Comparison among Ipomoea buriliae Belo, sp. nov. (Convolvulaceae) and three morphologically similar species. Character Ipomoea buriliae Belo, sp. nov. Ipomoea alba L. Ipomoea marcellia Meisn. Ipomoea parasitica (Kunth) G.Don Stems with spiny projections Present Present Absent Present Leaf indumentum Pubescent Glabrous Velutinous to lanate Sericeous Leaf apex Caudate Acuminate Acute Acute Outer sepal shape Orbicular Lanceolate Ovate to oblong Elliptic Outer sepal apex Retuse Caudate Acute Obtuse and mucronate Corolla shape and color Campanulate, white Hypocrateriform, white Funnelform, white-yellowish Funnelform, blue Color of the abaxial mesopetal region Yellow Greenish Yellow White Tector trichomes at the base and along the filaments Present Absent Absent Absent Pollen size Very large (x = 110.8 × 109.6 μm) Large (x = 79.2 × 78.8 μm) Large (x = 92 × 91.2 μm) Very large (x = 101.1 × 100.8 μm) Number of spines 165 spines 42 spines 55 spines 703 spines Exine thickness Nexine is thicker than sexine Nexine is thicker than sexine Sexine is thicker than nexine Nexine is thicker than sexine sample of pollen material (Table 1). The pollen grains were acetolyzed following Erdtman (1960), with modifications as described by Melhem et al. (2003). Diameter measurements were taken on 25 pollen grains over one week (Salgado-Labouriau et al., 1965). Other measurements (exine thickness and apertures) were taken from ten pollen grains. The slides obtained were incorporated into the Laboratory of Plant Morphology and Palynology pollen collection at the São Paulo State University, campus Jaboticabal - UNESP/FCAV, Brazil. The pollen morphology and terminology were based on Punt et al. (2007) and Halbritter et al. (2018). Cytogenetic analyses For cytogenetic analyses, 3 mm flower buds were fixed in Carnoy’s solution (3:1 absolute ethanol/ glacial acetic acid, v/v) for 2 hours at room temperature. To prepare the slides, the flower buds were washed twice with distilled water for 5 minutes each, and the anthers were digested in an enzymatic solution containing 2% cellulase and 20% pectinase and kept in a humid chamber at 37 °C for 20 minutes. Subsequently, the anthers were fragmented on a slide in a drop of 45% acetic acid, covered with a coverslip, and crushed. The coverslip was then removed after freezing in liquid nitrogen, and the slides were air-dried and stored for three days at room temperature. The slides were stained with 10 μL of Chromomycin A3 (CMA; 0.1 mg/mL) for 1 hour, followed by 10 μL of 4’,6-diamidino-2-phenylindole (DAPI; 1 μg/ mL) for half an hour, was performed as described by Barros e Silva and Guerra (2010), and Barros e Silva et al. (2010). After washing with distilled water, the slides were air-dried and prepared in a 492 A new species of morning glory for Brazilian flora medium containing glycerol/McIlvaine buffer pH 7.0 (1:1). The slides were then stored for 3 days in a darkroom to stabilize the fluorochromes. The best cells were analyzed using a Zeiss photomicroscope with an Axio Cam MRC5 (Oberkochen, Germany) and Axiovision v.4.8 software, at the Plant Cytogenetics Laboratory at the Federal University of Paraíba, campus Areia - UFPB/CAA, Brazil. Taxonomic treatment Ipomoea buriliae Belo, sp. nov. Figs. 2,3 Ipomoea buriliae is similar to I. parasitica in having spiny projections along the stem, petiole, and peduncle, as well as cordate leaves, and prominent veins on the abaxial surface. However, I. buriliae can be distinguished by its leaves with pubescent indumentum with caudate apex (vs. sericeous with apex acute), the outer sepals orbicular with apex retuse, and the inner sepals reniform with the apex obcordate, glabrous (vs. elliptic with apex obtuse and mucronate – the outer sepals, and apex rounded and minutely mucronulate – the inner sepals, puberulent to glabrescent), white campanulate corolla (vs. blue funnelform), filaments with tector trichomes at the base and along the structure (vs. tector trichomes only at the base) (see Table 2). Type: BRAZIL, Paraíba, Areia, campus da Universidade Federal da Paraíba, 6°58’10”S, 35°42’50”W, 550 m, 20.07.2024, D. Belo & E. Barbier 740 (holo PEUFR!; iso CSTR!, EAN!, UFP!). Climbing plants; branches glabrous, striated with spiny projections; internodes 5.5–12.3 cm long. Leaves ovate, 8.5–15 × 6.1–13 cm, base cordate, margins entire, apex caudate, adaxial surface pubescent with tector and sessile peltate glandular trichomes, abaxial surface pubescent to glabrescent with tector and sessile peltate glandular trichomes, peninervea venation, simple brochidodromous type, with eight to ten pairs of secondary veins; petioles 7.2–16 cm long, glabrous to glabrescent with tector and sessile peltate glandular trichomes, striate. Inflorescence cymose, 3–8-flowered; peduncles 9.4–31 cm long, glabrescent, glabrous; bracteoles linear, 0.3–1 cm long, base rounded, apex acute, glabrous; pedicels 1–2 cm long, glabrous, striate. Sepals 5, unequal, the 2 outer ones orbicular, 6.4–6.5 × 5.8–6.2 mm, base oblique, apex retuse, glabrous, the intermediate one reniform, c. 11 × c. 10 mm, the base oblique, the 2 inner ones reniform, 11.2–12.5 × 11.2–12.6 mm, base cordate, apex obcordate. Corolla campanulate, 5.8–6.2 cm long, white, glabrous, yellow abaxial mesopetal region. Stamens 5; filaments 9.5–17.35 mm long, tector trichomes at the base and along the structure; anthers 5.8–6.9 mm long, oblong, glabrous, pollen grains monads, apolar, very large size, spheroidal, pantoporate. Ovary conical, 1.4–1.5 × 2–2.2 mm, 4-locular; style entire, 30–34.5 mm long, stigmatic lobes 2, 1.4–1.8 mm long, 2-capitate with the surface verrucose. Capsules globose, 1–2 cm long. Seeds 0.6–1 cm long, pubescent. Flowering & fruiting: Flowering from June to August and fruiting from July to September. Habitat: The new species occurs in a humid forest enclave in Paraíba state, north of the São Francisco River, Brazil, at an elevation of about 550 m. Distribution: The known distribution of I. buriliae is restricted to the type locality. Etymology: The specific epithet is named in honor of Dr. Maria Teresa Buril, acknowledging her outstanding contributions to the study of the systematics and taxonomy of Convolvulaceae, as well as to the field of botany. Beyond being a notable researcher, Dr. Buril is an exceptional mentor, committed to fostering the development of new Brazilian scientists. Additional specimens examined (Paratypes): BRAZIL, Paraíba, Areia, campus da Universidade Federal da Paraíba, 6°58’02”S, 35°42’56”W, 563 m, 21.07.2024, D. Belo & E. Barbier 741 (PEUFR!); Ibid.,, 6°58’03”S, 35°42’52”W, 570 m, 24.07.2024, D. Belo & E. Barbier 742 (PEUFR!); Ibid., 550 m, 27.08.2024, R. Silva et al. 10 (EAN!). Conservation status: According to IUCN criteria, despite occurring in an anthropic area, we consider the conservation status of I. buriliae as Data Deficient (DD) since it is known only from 493 Belo et al. Fig. 2 . Ipomoea buriliae Belo: a . Adaxial surface of the leaf blade. b . Abaxial surface of the leaf blade. c – d . Stems and petioles with spiny projections. e . Corolla shape. f – g . Inflorescence with flowers and buds. h . Sepals. i . Habit. 494 A new species of morning glory for Brazilian flora Fig. 3 . Ipomoea buriliae Belo: a . Fowering branch; b . Stem with spiny projections; c . Adaxial surface of the leaf blade. d . Abaxial surface of the leaf blade. e . Abaxial surface with trichomes f . Bracteole; g. Floral bud. h . Flower. i . Sepals [left to right - outer (2), middle (1), inner (2)]; j . Corolla–top view; k . Corolla split open showing stamens and style; l . Stamen. m . Gynoecium. n . Ovary. 495 Belo et al. the type locality. Taxonomic notes: Ipomoea buriliae resembles several species found in northeastern Brazil, such as I. alba L. and I. marcellia Meisn., which share characteristics like a white corolla, prominent veins on the leaf blade, and indumentum on the stem, leaves, petiole, and peduncle. However, reproductive characters play a significant role in distinguishing these taxa, particularly corolla shape, the color of the abaxial mesopetal region, and sepal shape (see Table 2). Anatomical notes: In the paradermic section and the frontal view, the epidermis of I. buriliae presents cells with straight anticlinal walls on the adaxial surface (Fig. 4a), and sinuous on the abaxial surface (Fig. 4b), with druses restricted to the adaxial surface (Fig. 4a). The distribution of stomata is amphihypostomatic, with paracytic and anisocytic stomata and stomatal grouping (Fig. 4c). Tector and glandular trichomes occur on both epidermal surfaces (Fig. 4a & b). In crosssection, the epidermis is uniseriate (Fig. 4d), with oval to rectangular cells and external periclinal walls covered by a smooth cuticle. The leaf blade has an asymmetric dorsiventral mesophyll (Fig. 4d), presenting biseriate palisade parenchyma and spongy parenchyma 1-3 stratum seriate. Also in the mesophyll, idioblasts containing druses (Fig. 4e), laticiferous canals (Fig. 4f), and prismatic crystals in the palisade parenchyma were observed (Fig. 4f). The main midrib, in cross-section, exhibits a biconvex contour (Fig. 4g), prominently wider on the abaxial surface. The epidermis is uniseriate, with tector trichomes. Underlying the epidermis is the lacunar collenchyma (Fig. 4h). Further internally, the fundamental parenchyma consists of isodiametric circular cells with laticiferous canals (Fig. 4h). The vascular system is bicollateral, consisting of a single U-shaped central bundle (Fig. 4g & i). The petiole in cross-section presents a concave-convex contour (Fig. 4j). The epidermis is unstratified with nectar trichomes and sessile peltate glandular trichomes. Adjacent to the epidermis, the cortical region consists of layers of angular collenchyma with druses (Fig. 4k), followed by the fundamental parenchyma with laticiferous canals. The vascular system is bicollateral, composed of five bundles – three central ones forming an arch and two adaxial accessories (Fig. 4j). Druses occur abundantly in the internal and external regions of the phloem (Fig. 4l). The leaf anatomy of I. buriliae was compared with I. parasitica, which is morphologically similar. Both species exhibit distinct vegetative morphoanatomical characters that are crucial for their delimitation. These include differences in the sinuosity of the anticlinal walls on the epidermal surface of the leaf blade, stomatal types, the number of palisade parenchyma layers in the mesophyll, the type of collenchyma in the midrib, and the shape and number of vascular bundles in the petiole (Fig. 5, Table 3). SEM images of the leaves reveal a diverse array of surface structures. The images of the leaf blade and petiole highlight the abundant presence of tector trichomes (Fig. 4m & n), which appear as thin, elongated projections. Sessile peltate glandular trichomes are distributed across the leaf blade, petiole, and stem (Fig. 4o–q). Spiny projections were observed on the stem (Fig. 4r), characterized by a robust, pointed structure with a broad base that tapers to a sharp tip. SEM images also show the presence of cuticular waxes on the adaxial surface of the leaf blade, appearing as granules (Fig. 4m) and membranous platelets (Fig. 4r). Palynological notes: The pollen grains of I. buriliae are monads, apolar and very large (x  = 110.8 × 109.6 μm), with a spheroidal shape. They are pantoporate containing approximately 90 circular pores (x  = 7.1 μm), and lack an annulus. The exine is tectate, echinate, and perforate featuring bulbous spines (x  = 15 μm), numbering around 165. These spines have a rounded apex, with a wide, polygonal base. The nexine is thicker than the sexine, and the exine is thin (total exine x  = 7.2 μm; sexine x  = 3.3 μm; nexine x  = 3.95 μm) (Fig. 6, Table 2). 496 A new species of morning glory for Brazilian flora Table 3. Anatomical comparison between Ipomoea buriliae Belo, sp. nov. and I. parasitica (Kunth) G. Don. Character Ipomoea buriliae Belo, sp. nov. Ipomoea parasitica (Kunth) G. Don Epidermal cells (adaxial wall) Straight Sinuous Epidermal cells (abaxial wall) Sinuous Sinuous Trichomes on the leaf epidermis Tector and sessile peltate glandular trichomes Tector and sessile peltate glandular trichomes Palisade mesophyll Biseriate Uniseriate Collenchyma cells of the midrib Lacunar Angular Stomata Paracytic, anisocytic stomata, and stomatal grouping. Paracytic Petiole shape Concave-convex Semicircular Vascular bundles of petiole 5, arch-shaped 13, U-shaped Cytogenetic notes: Ipomoea buriliae has a chromosome number of 2n = 30. Distinct GC-rich heterochromatic regions are observed on different chromosomes, forming 14 terminal CMA+/DAPIbands (Fig. 7). Discussion Among the Ipomoea species with a white corolla found in the Borborema Plateau (BP) of northeastern Brazil, I. buriliae is distinguished by its campanulate corolla (vs. hypocrateriform in I. alba, funnelform in I. marcellia, tubular in I. vespertilia F.D.Santos, G.C.Delgado-Junior & Buril). In the vegetative stage, the new species may be confused with I. parasitica, since they share cordate leaves, spiny projections on the stem, and occasionally on the petiole and peduncle. However, a detailed analysis of the type specimens and protologue of I. parasitica shows that the species differ mainly in the leaf apex, corolla color, peduncle size, and the sepals’ shape, apex, and indumentum. The comparative anatomical analysis revealed that the morphological delimitation of these species is strongly supported mainly by the shape of the epidermal cell walls of the adaxial surface, type of collenchyma of the midrib, types of stomata, shape of the petiole, distribution, shape, and number of vascular bundles (see Fig. 5, Table 3). Scanning electron microscopy revealed two types of epicuticular waxes: granules and membranous platelets. There is little information about the types of waxes found in Ipomoea. However, in an anatomical study of populations of Jacquemontia evolvuloides (Moric.) Meisn., Belo et al. (2023c) observed the same types of waxes, leading us to infer that it can be considered a character present in Convolvulaceae. Waxes are taxonomically important in delimitating several plant groups (Barthlott et al., 1998) and play an important functional role in reducing water loss and providing defense against pathogens (Ahmad et al., 2015). The presence of these specific waxes’ types in I. buriliae highlights the significance of anatomical features in delimiting taxonomic groups within the Convolvulaceae family. This finding provides a valuable tool for systematic studies and the identification of new species. Epidermal cells and other anatomical characters may vary according to environmental factors (Bone et al., 1985; Alencar et al., 2022). However, when characters are genetically determined and do not vary due to abiotic factors, they can be taxonomically 503 Belo et al. BELO D.P., BURIL M.T., SANTOS E.A.V., ARRUDA E. & R.B. LOUZADA 2023c. Leaf and stem micromorphology of Jacquemontia evolvuloides (Moric.) Meisn. (Convolvulaceae) populations: New insights for taxonomic classification using light and scanning electron microscopy. Microscopy Research and Technique 86(9): 1177–1196. https://doi. org/10.1002/jemt.24391 BELO D.P., LOUZADA R.B. & M.T. BURIL 2024. 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