Loricalepis Brade has been up until now a monotypic genus in Melastomataceae (Melastomateae) known only from white sand vegetation along the upper Rio Negro basin, in the state of Amazonas, Brazil (Brade 1938; Goldenberg and Michelangeli 2019a), and in the nearby Río Guainía basin, in the department of Guainía, Colombia. It has been collected only three times: twice in Brazil, the type in 1936 (Ducke 35,068, US, RB) and a recent collection quite near the type locality in 2009 (Hopkins 1904, INPA, UPCB), and only once in Colombia, in 2006 (Cárdenas 20,309, NY), always on white sand vegetation. These last collections brought some light to this otherwise elusive genus, including photos and silica-dried leaf samples. Several morphological characters, such as the ovary crowned with a few setae, and the capsular fruits with cochleate, tuberculate seeds, suggest that it is a member of pantropical Melastomateae sensu stricto or “core Melastomeae” sensu Michelangeli et al. (2013) and Veranso-Libalah et al. (2017)., i.e. excluding Rhexieae, Microlicieae (Fritsch et al. 2004) and Marcetieae (Rocha et al. 2018).

The original diagnosis of Loricalepis is very vague, poorly distinguishing it from Tibouchina Aubl. s.l. by the glabrous hypanthium and 1-nerved leaves, with the secondary transversal nerves immersed in the leaf blade tissue (Brade 1938). On the other hand, the combination of these characters with small tree habit, scalariform indumentum on the stems and leaves, thick-cartilaginous, crenulate-serrulate and paleaceous-ciliate leaf margins, 4-merous flowers, persistent acute and seta-tipped sepals, petals with glandulose-ciliate margins, glabrous and subisomorphic stamens, these with the connective not at all or shortly prolonged but ventrally bilobed, the ovary apex with a crown of scaly setae surrounding the style, and dry, capsular fruits (Fig.1) make Loricalepis hardly similar to any other genus of Melastomateae s.s. Indeed, Guimarães et al. (2019) suggested that it may be sister to the remainder of the tribe Melastomateae s.s.

Fig. 1
figure 1

Loricalepis duckei. A. Habit. B. Branch with an open flower. C. Detail of a branch node with a pair of petioles and transversal nodal ridge between them. D. Detail of leaf apex, adaxial view. E. Detail of leaf apex, abaxial view. F. Flower bud, lateral view. G. Branch with young fruits. H. Detail of a young fruit, apical view. (All photographs by Mike Hopkins of Hopkins et al. 1904.)

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One of the most striking features in Loricalepis duckei is the scalariform indumentum on vegetative organs. The scale-like trichomes, from now on called “scales”, are similar to the ones described as “leaf scales, proximally attached” and “leaf scales, with basal ear” by Wurdack (1986). Wurdack mentioned that these scales were found mostly in Tibouchina s.l., in species that are now either in the newly re-circumscribed Tibouchina s.s. or in Andesanthus P.J.F.Guim. & Michelang. (Guimarães et al. 2019), and only in one species of Pterolepis (DC.) Miq. Apart from these three genera, such scales are not found elsewhere in Neotropical Melastomateae (Michelangeli et al. 2013; Meyer 2016). Loricalepis can be distinguished from Tibouchina s.s. and Andesanthus by the combination of characters listed above (see also: Guimarães et al. 2019) and from Pterolepis by the absence of pennicellate projections on its hypanthia (see Renner 1994).

In a recent discovery, we became aware of a specimen in the CEPEC herbarium (Larceda 191) from the white sand vegetation of coastal Bahia that shares most, but not all, of the diagnostic features of Loricalepis duckei, The discovery of this apparently closely related species is especially remarkable given the 3000 km distance separating its collection locality from those of L. duckei in the upper Rio Negro, although both species appear to be restricted to a similar vegetation type. Subsequently, we revisited the collection site in Bahia and obtained silica-dried leaf samples of the species, but for the last two years, in spite of several attempts, we have been unable to obtain DNA sequences in order to ascertain its generic placement. Nevertheless, we describe the new species here in Loricalepis based on its morphological similarity to L. duckei, with the hope that our hypothesis will be tested in the future by phylogenetic analysis of molecular data.

Materials and methods

The descriptions and illustrations of the new species are based on field collections and the examination of herbarium specimens housed in the CEPEC, NY and UPCB herbaria. Information concerning plant height, habit, leaf blade surfaces, sepals, petals, fruits and other informative features were noted while examining fresh material in the field, or was transcribed from the collection labels of herbarium specimens. For examination by scanning electron microscopy (SEM), samples of leaves and seeds were placed on stubs, sputter-coated, and photographed in a Quanta 250 (Fei Company) Scanning Electron Microscope in the Microscopy Electronic Center (CME) at Santa Cruz University, Ilhéus, Bahia, Brazil.

A distribution map was generated using the web-based application SimpleMappr (Shorthouse 2010). Geographical coordinates of collection localities were obtained from field GPS determinations or from the online databases speciesLink (http://www.specieslink.org.br) or JABOT (http://www.jbrj.gov.br/jabot).

Taxonomic treatment

Loricalepis atlantica Amorim, Michelang. & R.Goldenb., sp. nov.—Type: Brazil. Bahia: Mun. Itacaré, Rodovia Ilhéus-Itacaré, Campo Cheiroso, 14°22′50″S, 39°02′23″W, 100–125 m, 21 Nov 2015 [bud, fl, fr], A. M. Amorim, C. S. Pessoa, C. C. de Paula, D. S. Lisboa & J. L. Paixão 9900 (holotype: CEPEC; isotypes: HUEFS, INPA, K, MBM, NY, P, RB, SPF, UESC, UPCB). (Figs. 2–3, 4A–E.)

Fig. 2
figure 2

Loricalepis atlantica. A. Flowering branch, with a detail of leaf margins in abaxial view (left) and adaxial view (right), showing the scales. B. Leaves from the base of the stem. C. Floral bud in lateral view. D. Detail of a sepal, adaxial view, showing the apex and trichomes. E. Flower, lateral view. F. Antesepalous stamen, lateral view. G. Antepetalous stamen, lateral view. H. Hypanthium, longitudinal section with a detail of the ovary apex. I. Mature fruit, lateral view. (A–H, based on Amorim et al. 9990; I, based on Amorim et al. 9528.)

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Fig. 3
figure 3

Loricalepis atlantica. A. Old stem. B. Flowering branch. C. Detail of a young stem. D. Detail of the leaf margin, abaxial surface. E. Detail of a pair of petioles, with transversal ridge between them. F. Flower bud, lateral view. G. Open flower, with detail of ovary apex crowned with setae. H. Detail of androecium (the stamens damaged by bees) and style. I. Old and young fruits. J. Detail of ovary apex of a young fruit, lacking setae. (All photographs by André Amorim of Amorim et al. 9990.)

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Fig. 4
figure 4

SEM images of the Loricalepis species. A–E. L. atlantica [from Amorim et al. 9900 (CEPEC)]. A. Adaxial view of leaf surface. B. Abaxial view of leaf surface with detail of stomata. C. Detail of scales. D, E. Seeds in lateral view. F–H. L. duckei [from Hopkins et al. 1904 (UPCB)]. F. Abaxial view of leaf surface. G. Detail of scales on abaxial leaf surface. H. Detail of scales on midrib.

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Diagnosis: Loricalepis atlantica differs from L. duckei Brade by its 5-merous flowers (vs. 4-merous in L. duckei), hypanthium covered with minute scales (vs. glabrous), light-pink petals (vs. white), purple anthers (vs. white) and 5-celled ovary (vs. 4-celled).

Shrub to small tree, 3–6 m tall; trunk 3–7 cm diam. at breast height, the bark sulcate, and splitting longitudinally in narrowly oblong, pale-gray to brownish in older branches, glabrous stripes; young branches terete, occasionally pendulous, brown, the nodes with a thick transversal ridge joining the opposite petioles, the surface moderately to densely (particularly immediately below the nodes) covered with thick, appressed, deltoid to lanceolate or rounded scales 0.1–0.6 × 0.1–0.4 mm, with lacerate-ciliate margins and an acute to rounded apex, the scales partially caducous and becoming sparser in older branches. Leaves opposite, isomorphic; petiole (3.3–)4.7–8.8(−13.2) mm, adaxially canaliculate, with the same dense scales as the nodes of young branches; lamina 4.9–8.5(−15.5) × (2.4–)3.1–5.6(−9.8) cm, ovate, obovate to orbiculate, rarely oblong, subcoriaceous, base rounded to obtuse, sometimes rounded-attenuate, apex rounded or rarely obtuse-retuse, margin thick-cartilaginous, slightly crenulate to minutely serrulate in the upper half, and paleaceous-ciliate on the teeth, the scales on the margins 0.4–0.6 mm long, larger and thicker than those on the leaf surfaces, main veins 3, basal, sometimes with an additional, faint, submarginal, confluent (i.e. joining the lateral veins before reaching the leaf base) pair, the midrib slightly impressed, laterals slightly raised, transversal veins barely visible or slightly raised, reticulation not visible on adaxial surface, the midrib slightly raised, laterals plane, not raised, transversal veins barely visible or slightly raised, reticulation not visible on abaxial surface, adaxial leaf surface dark-green, sparsely covered with minute, hyaline, appressed, deltoid to rounded scales 0.1–0.3 × 0.1–0.3 mm, these scales sunken and more easily distinguished in pickled or fresh leaves than in dried samples, the scales on the base of the veins larger, up to ca. 0.5 × 0.4 mm, abaxial leaf surface pale-green, with similar sparse scales, but these on a flat surface and not sunken. Inflorescence usually cymose, with up to 3 dichasia, 3–7 flowers, 3–4.6 cm long (including flowers), terminal; bracts 0.8–1.4(−4.8) × 0.6–2(−4.5) cm, foliaceous, sessile, concave, ovate, oblanceolate to orbiculate, apex rounded or acute and seta-tipped, margins ciliate, adaxial surface with small scales as in the leaves, abaxial surface with scales as in the young branches; bracteoles 2, persistent at anthesis, 3.7–5 × 1.3–1.4 mm, thick, concave, oblong-lanceolate, apex acute and seta-tipped, margins ciliate, adaxial surface glabrous, abaxial surface with scales as in the young branches; pedicels green, 2.5–3.6 mm long. Flowers bisexual, 5-merous; hypanthium green, 1.2–1.4 × 0.8–1 cm, terete to narrowly campanulate, densely covered with adpressed, deltoid to lanceolate scales 0.1–0.6 × 0.1–0.4 mm, torus glabrous; calyx tube 1–2 mm long, at anthesis partially tearing at the apex between the lobes, lobes 5.6–6.4 × 4.2–5 mm, persistent in fruit, deltoid, apex acute and seta-tipped, the seta up to 1.4 mm long, margins membranaceous and ciliate, cilia up to 0.5 mm long, adaxial surface reddish at the base, pale green at the apex, glabrous, abaxial surface green, with scales as in the hypanthium; petals light-pink, 2–2.3 × 1.4–2 mm, obovate and slightly uncinate, apex rounded-retuse, both surfaces glabrous, margin glandulose-ciliate, the glandular heads caducous, slightly more persistent toward the base of the petal; stamens 10, subisomorphic, filaments light-pink, 1–1.4 cm long, glabrous, connectives cream-colored, not prolonged below the thecae, ventrally bilobed, the lobes 0.5–0.6 mm long, obovate, glabrous, anthers (from pre-anthesis flower buds) purple, 9.8–11.5 mm long, long-subulate, the pore ventral; ovary ca. 8 mm long, superior, but with longitudinal trabeculae joined to the surface of the hypanthium for ca. 90% of the ovary length (or in an alternative interpretation, 90% inferior with longitudinal pockets—each filled with a curved stamen in bud—that reach the ovary base), 5-locular, the free apical portion with a narrow crown of scales 1–1.3 mm long, these thickened at the base and subulate distally, and rows of smaller (but similar) scales 0.3–0.6 mm long along the furrowed sutures between carpels, both sets of scales caducous after anthesis and not seen in young fruits, style light-pink, 2–2.4 cm, filiform, sigmoidal, glabrous, stigma punctiform. Capsule persisting on plants for long periods, green to brownish or pale-gray, 18–23(−25) × 11–13.4 mm, campanulate, coriaceous to strongly lignified at maturity, densely covered with appressed, deltoid to lanceolate scales, the scales partially caducous and becoming sparser in maturity, sepals persistent. Seeds ca. 1.9 × 0.6 mm, 9–11 per locule, cochleate, testa tuberculate.

Distribution and habitat.––Loricalepis atlantica is endemic to the Atlantic Forest domain in Bahia state (Fig. 5A), where it is known from a single locality in the Municipality of Itacaré. The species occurs exclusively in “mussununga” vegetation (see comments below) on white sand soils (Fig. 5B). This area, locally known as Campo Cheiroso, comprises 160 ha and is located about 3 km from the coastline, at about 120 m elevation. The species grows in the border of forest remnants with open scrub physiognomies (Fig. 5C).

Fig. 5
figure 5

Distribution and habitat of Loricalepis atlantica, endemic to southern Bahia, Brazil. A. Geographic distributions of the two species of Loricalepis. B. Typical “mussununga” vegetation on white sand. C. Locality where L. atlantica was collected, in “Campo Cheiroso”, Mun. Itacaré, Bahia, Brazil. (Photographs by André Amorim.)

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Conservation status.— Loricalepis atlantica is known only from the type locality, which is not part of a protected area. The locality has been disturbed for coconut (Cocos nucifera L.) cultivation, which involves burning of the vegetation to clear the ground for planting. Following the IUCN Red List categories and criteria (IUCN 2012), this species can be considered critically endangered (CR). Its area of occupancy is < 10 km2, and there is only a small number of mature individuals [B2ab(ii)+D]. All of the specimens of the new species were collected within the last nine years.

Phenology.— Plants were found in flower in November and March (just one inflorescence), young fruits in November and March, and mature fruits in March and June.

Etymology.—The specific epithet refers to the species’ occurrence in the Brazilian Atlantic Forest.

Additional specimens examined. BRAZIL. Bahia: Mun. Itacaré, Rodovia Ilhéus–Itacaré, Campo Cheiroso, 14°22′50″S, 39°02′23″W, 100–125 m, 12 Jun 2011 (fr), V. D. Lacerda 191 (CEPEC); 14 Mar 2015 (fl, fr), A. M. Amorim et al. 9528 (CEPEC, HUEFS, K, MBM, NY, P, RB, SPF, UPCB); 18 Mar 2017 (fr), R. P. Asprino et al. 159 (CEPEC, RB, UPCB, US).

Loricalepis atlantica and L. duckei are both shrubs or small trees that share similar scalariform indumentum covering the stems and leaves (the minute scales on the hypanthium of L. atlantica also curiously similar to the scales on the vegetative parts of L. duckei); young stem nodes with a transversal ridge joining the opposite petioles; thick-cartilaginous, crenulate-serrulate and paleaceous-ciliate leaf margins; persistent acute and seta-tipped sepals; petals with glandulose-ciliate margins; glabrous and subisomorphic stamens, these with the connectives not at all or little prolonged and ventrally bilobed; the ovary apex with a crown of scales surrounding the style; and dry, capsular fruits. As detailed in the diagnosis, they differ in flower merosity, hypanthium indument, petals and anther color, and ovary division.

Despite the great distance separating the geographical distributions of Loricalepis duckei and L. atlantica, the two species may experience similar ecological conditions. Loricalepis duckei has been found growing in igapó vegetation (fide Hopkins 1904) and in white sand vegetation (i.e. “Amazonian caatinga”, fide Ducke 35,068, and “sabana natural de arenas blancas”, fide Cárdenas 20,309). Igapó is a semi-aquatic Amazonian forest type occurring on river floodplains that are periodically inundated by oscillating water levels (Junk et al. 2011). It frequently occurs on patches of white sand soils, which often support open vegetation types, locally known as campinas and campinaranas. One of the possible explanations for these big white sand deposits in the Rio Negro basin is that they may result from leaching of alluvial deposits, these products of erosion of sandstones from the Guiana Shield (Capurucho et al. 2020). Similarly, in the Atlantic Forest Domain, Loricalepis atlantica occurs in vegetation known as mussunungas and campos nativos (Saporetti-Junior et al. 2012) that grow on isolated patches of white sands distant from the coast. The occurrence of these white sands can be explained by the uplifting of river beaches, imprisonment of water in periods of higher sea levels or ancient lakes (Araujo et al. 2008), or by deposition from the weathering of sandstone rocks and/or podzolization due to water table fluctuation (Anderson 1981). Thus, the white sand soils along the Brazilian coast may have been structured by aquatic transgression events (Rossetti et al. 2013), as is the case for similar Amazonian phytophysiognomies. Regardless of the origins of the white sand deposits, whether in the Rio Negro basin or in the mussunungas in coastal Bahia, the vegetation in both grow on poor-nutrient soils with low water retention capacity, and that are subject to high precipitation. In both, the physiognomy is more or less similar, with a gradient from dense and tall shrubs or small trees (up to ca. 4 m) to more open grasslands. These facts may help explaining the extensive disjunction between the two species of Loricalepis.

Disjunctions between the Atlantic Forest in Bahia and Amazonia are quite frequent in Melastomataceae. For example, what were thought to be exclusively Amazonian species Graffenrieda intermedia Triana and Votomita guianensis Aubl. were recently discovered in Bahia (Jardim 2010 and Goldenberg and Michelangeli 2019b, respectively), making these the only species of their respective genera found in the Atlantic Coastal Forest. Similarly, the clade comprising the former genus Conostegia is common in northern South America and Central America, but there is one species, Miconia subhirsuta (DC.) M.Gómez [formerly Conostegia icosandra (Sw.) Urb.], with a disjunct population in Bahia (Kriebel 2016).