Leptotes (orchid)

Leptotes
Leptotes bicolor
Scientific classification
Domain: Eukaryota Kingdom: Plantae Division: Magnoliophyta Class: Liliopsida Order: Asparagales Family: Orchidaceae Subfamily: Epidendroideae Tribe: Epidendreae Subtribe: Laeliinae Genus: Leptotes Lindl. 1833
Type species
Leptotes bicolor Lindl. 1833
Species
L. bicolor Lindl. 1833 L. bohnkiana Campacci 2004 L. harryphillipsii Christenson 2004 L. mogyensis Krackow. ex Christenson 2004 L. pauloensis Hoehne 1934 L. pohlitinocoi V.P.Castro & Chiron 2004 L. tenuis Rchb.f. 1865 L. unicolor Barb.Rodr. 1877 L. vellozicola Van den Berg, E.C.Smidt & Marçal 2006
Synonym
None

Leptotes is a genus of orchids formed by nine small species that grow in the dry jungles of south and southeast Brazil, and also in Paraguay or Argentina. They are small epiphytic plants of caespitific growth, that sometimes resemble little Brassavola, as they share the same type of thin terete leaves, however, they are more closely related to Loefgrenianthus.

Some species of Leptotes are widely cultivated and form showy displays when completely in bloom although they are not among the easiest to grow. The majority of the species are not cultivated and some are so rare to be almost unknown; five of the species have only recently been described since 2000. Beside being cultivated for their ornamental value, there are records of the flowers and fruits of Leptotes bicolor being used as a substitute for vanilla in milk, ice cream, tea and candies.

Distribution

(CC) Photo: Dalton Holland Baptista
Sandstone cliffs covered by some remaining patches of forest close to Analândia, São Paulo State, Brazil. It is the habitat of Leptotes pauloensis.

The species of Leptotes were originally discovered in the Atlantic Forest of Brazil and are always seen living epiphytically. Two species have since been found in other countries, L. unicolor in Argentina, and L. bicolor in Paraguay. Three species show a high degree of endemism in the south of Bahia State, these do not exist in any other place. The states of southeastern Brazil can be considered the center of its distribution since they host the highest number of species and the Leptotes are most abundant there, however, the range is from the Serra da Jibóia chain of mountains, in Bahia, to the North of Rio Grande do Sul State. It is assumed that L. mogyensis is a variety collected by Krakowizer found at Mogy das Cruzes, although this has not been verified as Christenson only worked with specimens under culture in the US.

The species in the group that are characterized by wide open flowers, such as Leptotes tenuis and L. pauloensis, are more frequently found in cloud mountain forests. L. bicolor has the broadest range and can survive in both the cloud mountanin forests and the dryer woods on the plateaus of the Serra do Mar chain of mountains. Leptotes unicolor grows optimally in cooler areas, above 700 meters of altitude, and is frequently found growing on Araucaria and Podocarpus trees in the southern areas of Brazil.

Description

(CC) Image: Dalton Holland Baptista
Leptotes distribution map.

Species assigned to the genus Leptotes have a short rhizome of cylindrical section. They have small pseudobulbs that almost imperceptibly prolongate in one, rarely two, terete fleshy leaves. They have variable characteristics and can be short or long, erect or hanging, dark green or purple colors, frequently have a wrinkly surface and a deeper ridge in the face. The inflorescence is apical, generally short, and grows from the apex of the pseudobulb without a protecting spathe and bears up to seven flowers, although fewer are more common. The flowers are relatively large when compared to the overall plant dimensions, normally partially bent and in some species forming groups with a very showy aspect. They are fragrant and this perfume can last from ten to twenty days.

Floral diagram for Leptotes.

The appearance of the petals and sepals is similar, both are elongated although the petals are slightly more narrow. Flower colors are generally greenish, white or variable shades of pink and the labellum petal can be spotted in pale yellow, light purple or lilac. The labellum is located along the column and trilobated (three lobes). The lateral lobes are small and raised beside the column, although never involving it. The intermediate lobe is much bigger and quite variable between the species. They can have either lanceolate or obovate shape, occasionally be fleshy, flat or bending backwards; in some species they have denticulated edges but are smooth in others; rarely calli are present and it has claws which hold it attached to the sides of the column. The colomn is short, thick and erect, normally greenish, biauriculated, and bears six pollinia of different sizes, two larger in the center and four smaller in two pairs held by a short caudicle in an arrangement that is unique among orchids. Their fruits are rounded, succulent and have a perfume reminiscent of Vanilla.

The agent for the pollination of Leptotes has never been observed. Cássio van den Berg postulates that bees are the primary agent due to the colors and morphology of its flowers while other orchidologists suspect pollination by hummingbirds is more important.

Taxonomic notes

Original illustration published by John Lindley when he described the genus Leptotes, in 1833.

In April of 1833, an unknown species from the Serra dos Órgãos mountains of Brazil blossomed in the greenhouse of Mrs. Arnold Harrison, an English collector of orchids homaged in diverse descriptions of noted species such as Bifrenaria harrisoniae and Cattleya harrisoniana. A short time later, Mrs. Harrison sent a drawing and cutting of this plant to the botanist John Lindley, who verified it to be not only a new species but a new genus. In its description, dated the same year, Lindley suggests the name of Leptotes, from the Greek for mild, delicate, in reference to the appearance of the plants flowers. He affirmed that Leptotes was similar to Tetramicra, from which it is distinguished by the structures of the pollinarium and by the smaller lateral lobes of the lip petal; and because they have no calcar attached to the ovarium. He also differentiated it from Brassavola by the pollinia and trilobed lip. Lindley then described its type-species, Leptotes bicolor.

In 1838, Lindley received two similar but distinct plants, collected in Macaé de Cima and Ilha Grande, in Rio de Janeiro. He considered them different to the previously described species, because the lateral lobes of the lip were slightly serrated, their flowers were bigger and they occasionally had a second leaf by the pseudobulb; he proposed a new species with the name of Leptotes serrulata. Five years later, the German Count Johann Centurius von Hoffmannsegg noticed that one plant he cultivated had a different green-bluish tone to its leaves and he described the plant calling it L. glaucophylla. When reviewing all the known species of Leptotes at the time, in 1990, Carl Leslie Withner revisited the drawings published by Lindley and identified additional differences between L. bicolor and L. serrulata, describing how the latter always bears more flowers, with up to seven per inflorescence, which is also much longer. Today it is accepted, however, that both descriptions are variations of L. bicolor that coexist due to its wide dispersion and multiplicity of populations.

In 1865, Heinrich Gustav Reichenbach received, from an unknown locality in Brazil, the second described species to be accepted today. The plant was quite different from Leptotes bicolor, because of its fewer and smaller rounded flowers, with wide open pale yellowish segments and he published it as L. tenuis. Twelve years later, the third species, Leptotes unicolor, was described by Brazilian botanist João Barbosa Rodrigues. His account described a highly fragrant little species of orchid and he found some colonies with hundreds of plants living epiphyticaly along the banks of the Dourado and Sapucai rivers, nearby the city of Alfenas, in Minas Gerais. In 1881, Barbosa Rodrigues found another species, this one with longer leaves and slight differences in floral structure, and named it as L. paranaensis after Paraná State where he first found the plant, although today the location near Joinville is located in Santa Catarina. Today this species is considered to be just a variation of L. unicolor, the species he had described four years earlier.

Robert Allen Rolfe received from Brazil, also without information of locality, a plant similar to the Leptotes tenuis species described by Reichenbach over 20 years earlier. Rolfe described it as L. minuta and noted it had much thicker and shorter leaves. This new species was included in Célestin Alfred Cogniaux's revision of Brazilian orchid species, published 1903, but in doing so he was unaware of the variability within the Leptotes species. At the time Cogniaux published his book he had not had the opportunity to check the types of all the other species then described, therefore, he accepted most of them with this remark. In retrospect, it is now more clear that the variation in leaves was due to both the isolation of various populations and because of the different growth conditions in each habitat, and today L. minuta is known as a variation of L. tenuis.

(CC) Photo: Dalton Holland Baptista
Loefgrenianthus blanche-amesiae, first described under the genus Leptotes, is its closest related species.

While living in Brazil, the Swedish Botanist Johan Albert Constantin Loefgren received an Orchid from Itatiaia, Rio de Janeiro, with flowers reminiscent of the Leptotes, although its lip petal formed a pouch. He described it as Leptotes blanche-amesiae, also noting it had a pending habit and thin flat leaves. Later work on the genus by Frederico Carlos Hoehne led him to conclude that this species, despite being closely related to the Leptotes, would be better placed in another genus. He proposed the genus Loefgrenianthus, in hommage to Loefgren. In 1934, Hoehne also described a new species, Leptotes pauloensis, naming it so because it was found in São Paulo State. This species is closely related to Leptotes tenuis but its flowers have different colors. For decades taxonomists were divided on whether this should be considered a new species, partly due to the fact it was so rare, indeed, Guido Pabst considered it a synonym of L. tenuis. Recently many new colonies have been discovered and Withner now proposes that L. pauloensis should be accepted as a separate species.

Therefore in 2004 four species of Leptotes were known, three sufficiently different to each other and well stablished, L. bicolor, L. unicolor and L. tenuis, and one fourth, L. pauloensis, occasionally considered synonym of the previous one, but more frequently accepted by taxonomists. In this year, the species number doubled as other four were described. However, the history of these descriptions starts much earlier, in 1954, when one of the associates of Círculo Paulista de Orquidófilos, an orchid society in São Paulo, presented a lecture where he talked long and informally about the innumerable varieties of Leptotes that he found and gathered throughout the years and the names he particularly atributed to each. This lecture was printed and distributed in the bulletin of the association. In 2004, Eric A. Christenson, aware of this publication, found in culture in particular collections in the United States two of the several varieties mentioned in the lecture and decided to describe them formally as independent species. One of these plants, Leptotes harryphillipsii, is very similar to L. pauloensis already a problematic species by itself. The other one, L. mogyensis, is an unknown species to Brazilians, both scholar and collectors, except for the plant Christenson found in the US, supposedly originated from Mogi das Cruzes, a city nearby São Paulo.

The other two species described in 2004 belong to the affinity of Leptotes bicolor and have been both found by the same surveyor in the region of Buerarema, south of Bahia. Leptotes bohnkiana , which name is a homage to its finder, can be differentiated because of its smaller size, the other, L. pohlitinocoi, mostly by color. Finally, in 2006 Sidney Marçal de Oliveira discovered the last species to be described, also from Bahia, although inhabitant of Chapada Diamantina, Leptotes vellozicola is much diferent from all the other species.

Phylogeny

According to Cássio van den Berg et al., Leptotes is very closely related to Loefgrenianthus and both situated between Pseudolaelia and the genus which once used to be classified as Schomburgkia, by some now considered part of Laelia.

Species

(CC) Photo: Dalton Holland Baptista
Leptotes bicolor belongs to the group of species with long smooth leaves and bent elongated flowers that do not open well.

The three main characteristics that differentiate between the species of Leptotes are the general proportions of the leaves, the shape of the flowers and way the flowers open. Using these differences the species can be classified into two main groups.

One group is formed by the four species with flowers of elongated segments, which generally are not widely open. These species use to present malleable inflorescences that leave the flowers slightly or very overthrown, frequent facing down. Almost all the species of this group have long leaves, of comparatively lighter tones, generally with smooth surfaces, longer than the inflorescences.

• Leptotes unicolor is the exception in this group as it has short, wrinkly and dark leaves. Its flowers, of generally uniform pale pink, always face down. The other species of this group have flowers of stronger colors.
• Leptotes bicolor is the species with more flowers per inflorescence and with wider distribution. It is a much variable species, even tho easily recognizeable because of its bicolored flowers, of white sepals and petals and purple lip, occasionally bearing two leaves per pseudobulb. There are some records of this species living as a lithophytic.
• Leptotes bohnkiana is similar to L. bicolor, however, its flowers measure only one third of the dimensions of the second ones, with segments proportionally wider, the plant measures only one half. All the plants found had only one flower per inflorescence. It just exists in Bahia.
• Leptotes pohlitinocoi is even closer to L. bicolor but has slightly smaller flowers with all segments completely pink. It just exists in Bahia.

The other group is formed by five smaller species with more rounded flowers of wide open flatter segments and much shorter wrinkly leaves, generally very dark green or purple colored. The species of this group often have only one or two flowers each inflorescence. Four of them are much similar and sometimes difficult to distinguish.

(CC) Photo: Dalton Holland Baptista
Leptotes harryphillipsii is a member of the Leptotes group of species with short wrinkled leaves and few wide open flowers.

• Leptotes vellozicola is the only easily recognizeable species in this group as it has a thick central callus next to the lip apex. It is the only species of this group endemic of Bahia, all the other are from Southeast and South Brazil.
• Leptotes tenuis is the only Leptotes species with pale green, yellowish or white flowers and lilac lip. It is a very small and uncommon species from Southeastern States of Brazil.
• Leptotes pauloensis is a species very similar to the previous one and can be separated from it mainly by the color of the floral segments, which are inverted here, that is, pale lilac petals and sepals and white lip with a yellowish cream mark in the middle. Its distribution overlaps L. tenuis but extends much more into South.
• Leptotes harryphillipsii, another similar species to the previous, however with slightly longer lip and discrete pink stripes on the other segments, which shows a little more vibrant colors. It seems this species has been known for long time but has been always confused with the true L. pauloensis.
• Leptotes mogyensis, yet another species related to L. tenuis group but that also somewhat resembles L. unicolor although bearing white flowers with a deep purple central mark on the lip. There is no record of this plant in the wild. All information comes from a plant found under cultivation in a nursery in California, USA. It might be a rare natural hibrid of the two mentioned species.

Culture

As the roots of Leptotes rot easily with excessive humidity, the best results for their culture are achieved when they are mounted on plaques of vegetal fiber or tree cork. Watering and fertilizer must be more frequent during active growth periods and less during dormant periods. Ideal growth conditions require an intermediate temperature and exposure to filtered sunlight.