Cattleya mireileiana Menezes, Giordani & Mendes, 2022

Menezes, Euler Da Luz Fernandes, Giordani, Samuel Cunha Oliveira & Mendes, Jone Clebson Ribeiro, 2022, Cattleya mireileiana, a new species of Orchidaceae (Laeliinae) from the Southern Espinhaço Complex, Minas Gerais State, Brazil, Phytotaxa 541 (3), pp. 270-276 : 271-275

Cattleya mireileiana Menezes, Giordani & Mendes , sp. nov.

Type:— BRAZIL. Minas Gerais: Diamantina, Alto da Jacuba , 18º12.02’17.52”S, 43º32’59.8”W, 1230 m a.s.l., 5 January 2019, saxicolous in rock cracks over a rocky field, E.L.F. Menezes, C.O. Giordani & J.C.R. Mendes 154 (holotype DIAM8260 , isotypes BHCB, HDJM, RB) . Figure 1a‒k .

Cattleya mireileiana is similar to C. bradei , C. briegeri , and C. cruziana but differs in having prominent white area at the base of the labellum disc (vs. never present in C. bradei , and small in C. briegeri and barely noticeable in C. cruziana ), as well as a white central region of the labellum carina.

Plant saxicolous, caespitose, 5‒12 cm tall. Inconspicuous rhizome. Roots 0.2‒0.3 cm diameter, flexuous. Pseudobulbs with 2 internodes, obclavate, articulated, 2‒4 cm long, 1.0‒ 1.5 cm in diameter in the widest sections, with scarious amplexicaul sheaths that become papery and fragment with age, unifoliate. Leaves 2.5‒2.8 × ca. 0.6 cm, lanceolate, recurved, coriaceous, fleshy, warped lengthwise, apex acute. Spathe 1.8‒2.0 × 0.4‒0.5 cm, linear, termination oblique. Inflorescence terminal, rachis ca. 5‒11 cm long, erect, cylindrical, floral bract triangular, 2‒5 flowers distributed in the final third, simultaneous. Pedicel 3.0‒ 3.3 cm long, cylindrical, light green, but dark at the insertion of the ovary. Flowers 2.5‒3.0 cm in diameter, yellow in general appearance, fragrant, large, medium lobe of the labellum with sinuous margins. Dorsal sepal yellow, turning whitish towards the base, 2.0‒2.2 × 0.5‒0.6 cm, lanceolate, acute. Lateral sepals yellow, turning whitish towards the base, 1.6‒1.8 × 0.8‒0.9 cm, oblong-lanceolate to slightly falcate. Petals yellow, turning whitish towards the base, 1.8‒2.0 × 0.7‒0.8 cm, oblong-lanceolate to slightly falcate. Labellum yellow with a large white area at the base, moderately curved, 1.2‒1.3 × 1.3‒1.4 cm, deeply trilobed, rounded when expanded; isthmus obscure, 4 central carinas extending from the base to the first third of the median lobe in longitudinal directions, reddish violet at the base, then white to the point of insertion of the median lobe, yellow to the end; lateral lobes yellow, turning white towards the central base area, 1.1‒1.2 × 0.5‒0.6 cm, individually lunate when flattened; median lobe yellow, 0.5‒0.6 × 0.4‒0.5 cm, retroflexed, margins sinuous. Column greenish yellow, concave, 0.8‒0.85 cm long, curved dorsally, with a truncated-triangular shape when viewed in profile. Stigmatic cavity ca. 0.20‒0.25 cm long, unguiculate; anther ca. 0.1–0.11 cm wide, cucullate, whitish. Pollinia 8, 4 being smaller, discoid, yellowish.

Etymology:— The specific epithet is dedicated to Mireile São Geraldo dos Santos Souza, an orchid collector, resident of Diamantina (MG) , and former Dean and retired Professor at the Federal University of Vales do Jequitinhonha and Mucuri (UFVJM).

Distribution and habitat:— Cattleya mireileiana is only known from a population of approximately 150 individuals in Alto da Jacuba, in the municipality of Diamantina , in Minas Gerais State ( Fig. 2 ). It was found growing in shrubby vegetation on rocks with some accumulations of organic material ( Fig. 1a ). We therefore assume that this species is endemic to this region and that additional fieldwork efforts will be needed to could locate additional populations.

Phenology:— Observed flowering between January and February.

Conservation status:— Due to incomplete information on its distribution, we have assigned the new species to the category data deficient (DD), according to IUCN criteria (2012).

Taxonomic considerations: — Cattleya mireileiana it is similar to C. bradei (Pabst 1973: 332) Van den Berg (2008: 5) , C. briegeri (Blumensch. ex Pabst 1973: 367) Van den Berg (2008: 5) , and C. cruziana ( Castro & Menezes 2015: 29) Van den Berg (2019: 3) both in the vegetative aspect and in the yellow color of its flowers (see comparison in Table 1 ). However, it is separated from both congeners by the tricolor carina of the lip, reddish violet at the base, then white to the point of insertion of the middle lobe (vs. no white extension in C. bradei , C. briegeri , and C. cruziana ) and yellow from this point to the end. Other outstanding features in C. mireileiana are the yellow petals and sepals that become consistently whitish in an extension that goes from approximately the middle of these floral parts to the base (vs. absent in C. bradei , C. briegeri , and C. cruziana ).

Furthermore, C. mireileiana presents a whitish area on the lip disk, which can be well observed when it is distended. It covers an area corresponding to a semicircle with a center at the base of the distended lip and a radius corresponding to half the length of the lateral lobe. In this aspect, it can be easily separated from C. bradei and C. briegeri , where the white colored lips do not occur, and C. cruziana where some individuals may sporadically present a much smaller whitish area, with radius of at most one fourth of the length of the respective middle lobe ( Fig. 3 ).

Cattleya mireileiana can also be easily separated from both C. briegeri and C. cruziana based on the diameter of their flowers, which is 2.5‒3.0 cm (vs 3.5‒6.1 cm in C. briegeri ; and 4.0‒ 4.5 cm in C. cruziana ). The column of C. mireileiana has a uniform yellowish green color, both in the external part and in the concave internal part, and in this aspect it is not distinguished from C. briegeri and C. bradei , but it is easily distinguished from C. cruziana which always has the basal part of the dark lilac-violet color column. Regarding the vegetative aspect, C. mireileiana has pseudobulbs formed by only two nodes and is immediately distinguished from both C. bradei and C. briegeri , whose pseudobulbs are formed by three nodes and which, in this aspect, are closer to each other than in C. mireileiana . The four species are aromatic, but their fragrances differ in composition and intensity peaks, with C. briegeri , C. bradei and C. cruziana peaking in the morning and C. mireileiana in the afternoon.

In addition to the morphochromatic observations cited above, C. mireileiana features parapatric speciation in relation to C. bradei , C. briegeri , and C. cruziana , which grow in the same macro region, but not in the same rocky outcrops, and occur within an ecological context that substantially differs from that of C. bradei , as it grows in low vegetation that can protect it and provides decomposing plant material. Cattleya mireileiana never occurs on the exposed and bare rocks consistently associated with C. bradei (a notably rupicolous species). Its ecological niche is more similar to that of C. cruziana , which also shows a certain preference for areas with organic matter availability. Another characteristic linked to the ecology of the new species is its preference for areas very close to depressions in the rocks where water can accumulate in puddles during the rainy season, or run in small, semi-permanent rivulets— indicating a greater tolerance for wet or humid environments.

Figures

FIGURE 1. Cattleya mireileiana. a. Habitat; b. Habit; c. Petals and sepals; d. Flower; e. Peduncle/column/labellum in side view; f. Labellum in frontal flat view; g./h. Labellum in exploded planar view; i. Column in ventral view; j. Column in side view; k. Anther cap and pollinarium. (Photos by Euler Menezes).

FIGURE 2. Geographic distribution of Cattleya mireileiana.

FIGURE 3. Comparison among the lips of Cattleya mireileiana and similar species. a. C. mireileiana; b. C. bradei; c. C. cruziana; d. C. brigeri.