Rediscovery and first record of Octomeria romerorum (Orchidaceae, Pleurothallidinae) for Brazil

Abstract

In this article we extend the geographic distribution of a rare Octomeria species, first described from Venezuela: Octomeria romerorum is reported for the first time from Brazil. Apart from considerably extending the distribution of the species, this record also represents the first documented collections since its description in 1990. We provide a short description of the species, as well as a photographic plate, data on its ecology and distribution, and taxonomic comments.

Full text

Rediscovery and first record of Octomeria romerorum (Orchidaceae,
Pleurothallidinae) for Brazil
DAYSE RAIANE PASSOS KRAHL
1
,AMAURI HERBERT KRAHL
1
,GUY CHIRON
2
,AND
MARIO HENRIQUE TERRA-ARAÚJO
1
1
Programa de Pós-Graduação em Botânica, Departamento de Botânica, Instituto Nacional de Pesquisas da
Amazônia, Av. André Araújo, 2936, CEP: 69.060-001, Manaus, Amazonas, Brazil; e-mail:
dayseraiane@hotmail.com
2
Université de Lyon 1, Herbiers, F-69622, Villeurbanne Cedex, France
Abstract: In this article we extend the geographic distribution of a rare Octomeria species,
first described from Venezuela: Octomeria romerorum is reported for the first time from
Brazil. Apart from considerably extending the distribution of the species, this record also
represents the first documented collections since its description in 1990. We provide a short
description of the species, as well as a photographic plate, data on its ecology and distribution,
and taxonomic comments.
Keywords: Amazon Basin, Amazonas, new record, Reserva Florestal Adolpho Ducke,
taxonomy.
Octomeria R.Br. is a genus comprised of about
150 neotropical species distributed from Belize to
northern Argentina (Luer, 1986,2010;Pridgeon,
2006). More specifically the diversity centers of
the genus are the Guianas, the Amazon basin and,
particularly, Southeastern and Southern Brazil
(Forster, 2007; Forster et al., 2012). According
to Brazilian Flora Group (BFG –Brazilian Flora
Group, 2020), in Brazil, 95 species, distributed
through almost the entire country, have been re-
corded of which 71 are endemic. Among them, 22
species are found in the Brazilian Amazon and 13
are present in the state of Amazonas (BFG –
Brazilian Flora Group, 2020).
The genus is usually epiphytic, rarely
lithophytic, caespitose to creeping. Ramicauls
can be short or long, leaves sessile or petiolate,
flat to conduplicate or semiterete to terete. Inflo-
rescences are 1-flowered peduncles produced suc-
cessively or simultaneously in a fascicle from the
apex of the ramicaul (or from near of the apex).
Sepals and petals are very similar although usual-
ly of inequal sizes. Lateral sepals arefree or, more
rarely, connate. The lip can be entire or lobed and
the column is semiterete, the anther is generally
subapical, the stigma ventral, and the pollinarium
is made of eight pollinia, except in O. splendida
Garay & Dunst., which has six pollinia (Forster
et al., 2012).
In the latest molecular studies, the genus ap-
pears to be monophyletic and placed at the base of
subtribe Pleurothallidinae (Pridgeon et al., 2001;
Pridgeon, 2006; Forster, 2007; Karremans, 2016).
Two polyphyletic sections are usually recognized,
based on leaf shape, by various authors
(Rodrigues, 1882; Cogniaux, 1896; Schlechter,
1915; Pabst & Dungs, 1975;Luer,1986;
Forster, 2007). Under this circumscription, the
section Octomeria contains species with flat to
conduplicate leaves whereas the section
Teretifoliae Barb.Rodr. includes species with te-
rete to semiterete (acicular/cylindric) leaves
(Cogniaux, 1896; Luer, 1986; Pridgeon et al.,
2001;Pridgeon,2006).
In the course of an inventory of the orchid
species of the Reserva Florestal Adolpho Ducke
(RFAD), a strange species of Octomeria was col-
lected, which, after being identified as Octomeria
romerorum Carnevali & I.Ramirez, proved to be a
new occurrence for the Brazilian territory. This
species had hitherto been reported only from Ven-
ezuela (Carnevalí & Ramírez, 1990). Below, a
Brittonia, XX(X), 2022, pp. 1–5
10.1007/s12228-022-09702-2
© 2022, by The New York Botanical Garden Press, Bronx, NY 10458-5126 U.S.A.

brief description and a photo plate are given, as
well as some ecological and taxonomic comments.
Furthermore, a key to the species of the genus
Octomeria of the Brazilian Amazon is provided.
Material and methods
The specimens of O. romerorum were collected,
pressed, and dried following the usual procedures
describedinMorietal.(1989). They were then
incorporated into the INPA herbarium (acronyms
follow Thiers, 2020, continuously updated) collec-
tion of the Instituto Nacional de Pesquisas da Ama-
zônia. The taxon was identified with the protologue
published in Carnevalí and Ramírez (1990), the
revision of the genus by Forster (2007), and Luer’s
(2010) treatment. A consultation of the Virtual
Herbarium (https://www.gbif.org/species/
2816977; accessed 06 May 2021) was also made,
in which we located an image of the isotype depos-
ited in K for comparison (K000583642) (https://
api.gbif.org/v1/image/unsafe/http%3A%2F%
2Fwww.kew.org%2Fherbcatimg%2F242402.jpg).
We also provide a key to the Octomeria species of
the Brazilian Amazon, adapted from Forster
(2007) using the occurrences given by BFG
–Brazilian Flora Group (2020). The descrip-
tion was based on additional material exam-
ined (compared to the protologue), and mor-
phological terminology follows Stearn (1995)
and Harris and Harris (2001).
Taxonomic treatment
Octomeria romerorum Carnevalli &
I.Ramírez, Ann. Missouri Bot. Gard. 77(3):
551, Fig. 2 (1990). Venezuela, Territorio Fed-
eral Amazonas, Dep. Atures, carretera a
Gavilán, ca. 3 km antes del puente sobre el
Río Gavilán, Jul 1987, G. A. Romero et al.
1324 (holotype: VEN [not seen]; isotypes, K
[photo!], MO [not seen]).
Plant epiphytic, creeping. Rhizome stout, 0.5–
1 mm diameter (up to 3 mm according to Luer,
2010) between ramicauls. Ramicauls 1–2×
0.5 mm (1–2 × 0.6–0.8 mm in protologue), cylin-
dric, 1-leaved. Leaf 4–6×3–4mm(5–7 × 3.2–
3.8 mm in protologue), elliptic to ovate-elliptic,
fleshy to thick-coriaceous, flat, apex obtuse to
acute. Inflorescence 7–11 mm long, apical, 1-
flowered; floral bract 1–2 × 1 mm, deltoid, acute
at the apex. Flower whitish to white-hyaline, ped-
icellate; ovary + pedicel 4–5mmlong(4–5mmin
protologue); sepals 2–3×1mm(3–4×0.8–
1.2 mm in protologue), ovate to lanceolate, apex
acute; petals ca. 2–4×0.7mm(3–4×1mmin
protologue), ovate, apex acute; labellum ca. 1–2×
1–1.5 mm (1.2–1.3 × 1.1–1.3 mm in protologue),
broadly trullate, entire to subtrilobed, subfleshy,
warty, disc with an elliptic subglobose, 0.8–1mm
long callus; lateral lobes triangular, retrorse, con-
nected by a membranous blade, apex acute; apical
lobe ovate, apex rounded; column ca. 0.5–0.6 mm
long (0.5–0.6 mm in protologue); pollinia 8. Fruit
not observed.
Distribution and habitat.—The species occurs
in phorophytes at a height of 20–30 m; it was
found on a fallen tree in a “baixio”area (low
ground near a water course), of the “terra-firme”
forest (non-flooded forest in Brazilian Amazon)
of the RFAD. However, specimens can probably
also be found in zones of plateau and slopes. In
general, it should be considered rare in the RFAD,
since other individuals were not found. Hitherto
the species was only known from the type local-
ity, in Venezuela, Amazonas State, on the Rio
Gavilán. Thus, its distribution is extended to the
Manaus region (Brazil, AM), about 1200 km
southeastward.
Conservation status.—The species is repre-
sented by two, apparently, very small popula-
tions, with the total number of individuals less
than 50. Thus, the species may be considered
“Critically Endangered”according to criterion D
of IUCN (2012). Because of its epiphytic habit
and very small size, its observation in situ is very
difficult. According to criterion B2 –area of
occupancy less than to 500 km
2
(probably) –
and number of locations = 2, the species could
also be placed in the “Endangered”category.
However, we were not able to evaluate a possible
decline (condition b) nor any fluctuation (condi-
tion c), because of the rarity of the taxon and
difficulty observing it (two small populations en-
countered in over 30 years).
Phenology.—We observed the species
flowering in the RFAD during June (Southern
Hemisphere). The type material of Carnevali &
Ramírez (1990) was in flower in July (Northern
Hemisphere). As these authors observed, the
flowers start opening in the beginning of the
morning and partly close in the beginning of the
BRITTONIA [VOL

evening to open again the day after. The process
lasts for about four days.
Additional specimens examined.—BRAZIL. Amazonas
Manaus: Reserva Florestal Adolpho Ducke, km 26 da AM–
010, igarapé do Barro Branco, próximo à cozinha da sede,
2
°
55′48.35”S, 59
°
58′26.43”W, 0–10 m, 13 Jun 2020 [fl],A.H.
Krahl & D. R. P. Krahl 1495, 1496 (INPA); ibid.,D.R.P.
Krahl & A. H. Krahl 700, 701 (INPA).
Notes.—Octomeria romerorum (Fig. 1A–I) be-
longs to section Octomeria as it has flat to con-
duplicate leaves (Cogniaux, 1896; Luer, 1986). It
is characterized (and distinguishable) by its small
size (ca. 6–8 mm high), creeping habit, 1-
articulated ramicaul, elliptic to ovate-elliptic
leaves that are apically obtuse to acute and almost
appressed to the substrate, 1-flowered inflores-
cence, whitish to white-hyaline flowers and, es-
pecially, its entire to subtrilobed, verrucose,
broadly trullate lip with lateral pseudolobes trian-
gular, retrorse and connected by a membranous
lamina, and disc with a subglobose elliptic callus
extending through the center (Forster, 2007). In
comparison to the type population (see Carnevalí
&Ramírez,1990), the specimens collected here
vary little and bear slightly smaller leaves (4–6×
3–4vs.5–7 × 3.2–3.8 mm), slightly smaller se-
pals (2–3×1vs.3–4 × 0.8–1.2 mm), slightly
larger lip (1–2×1–1.5 vs. 1.2–1.3 × 1.1–1.3 mm),
similar lateral lobes (triangular), and the apical
lobe oval-shaped with a rounded apex (vs.
suborbicular to ovate and acute).
According to Carnevalí & Ramírez (1990)and
Forster (2007)O. romerorum is related to
O. gemmula Carnevali & I.Ramírez, which is
larger (longer ramicaules) and less creeping, with
the leaves not appressed to the substrate, the ab-
axial face of leaves purple, and the lateral lobes of
the lip antrorse. The two species also differ in the
environment they occupy, with O. romerorum
appearing to be restricted to dense forests where
it grows in tall branches, while O. gemmula grows
in shrubs of open and sandy environments.
Interestingly we should also note that
O. romerorum has a creeping habit similar to that
of some Peperomia Ruiz & Pav. (Piperaceae) spe-
cies, an uncommon condition in Octomeria
(Carnevalí & Ramírez, 1990). According to
Carnevalí & Ramírez (1990), its possessions of
rhizomes and short ramicaules, with thick, prostrate
leaves, forming small masses on the phorophyte
surface, may be associated with local environmen-
tal conditions, the type locality exhibiting a marked
dry season of approximately four months. Condi-
tions are similar in the Manaus region, where a
marked dry season lasts from August to October.
According to these authors, this kind of habit, sim-
ilar to that of Peperomia species, minimizes the loss
of water because the abaxial surface of the leaf
containing stomata is strongly appressed to the
substrate, increasing humidity between the leaf
and substrate (and thus reducing transpiration).
KeytothespeciesofOctomeria occurring in the Brazilian Amazon (based on Forster (2007))
1. Leaves flat to conduplicate.
2. Ramicaul cylindric in the basal part and flattened in the apical part....................................................................... O. grandiflora
2. Ramicaul completely cylindric.
3. Lateral sepals connate.............................................. .... ......................................... .... .................... Odontoschisma steyermarkii.
3. Lateral sepals free.
4. Plants subcespitose creeping; rhizome elongated.
5. Ramicaul ≤1 cm long..................................................................................................................................O. romerorum.
5. Ramicaul ≥5 cm long.
6. Ramicaul ≤7 cm long; leaves elliptic to elliptic-oblong...................................................................... O. graminifolia.
6. Ramicaul ≥8 cm long; leaves linear-elliptic to linear-oblong........................................................... O. guentheriana.
4. Plants distinctly cespitose; rhizome inconspicuous.
7. Lip entire to subtrilobed.
8. Leaves linear.............................................................................................................................................. O. integrilabia.
8. Leaves elliptic, narrowly elliptic, lanceolate or linear-lanceolate.
9. Leaves elliptic to na rr owly elliptic............................................................... .... .................................................. O. nana.
9. Leaves lanceolate to linear-lanceolate.
10. Margin of the clinandrium entire; sepals and petals purple or reddish brown.................................. O. lancipetala.
10. Margin of the clinandrium tenuously denticulate; sepals and petals yellow or yellow-
orange............................................................................................................................................... O. cordilabia.
7. Lip trilobed.
11. Floral bract covering the pedicel, the ovary and a part of the perianth……….…………….………….O erosilabia.
11. Floral bract covering the pedicel and the ovary completely or partially, but never the perianth.
12. Sepals and petals with a caudate apex........................................................................................................ O. setigera.
12. Sepals and petals with an acute or acuminate apex.
KRAHL ET AL.: OCTOMERIA ROMERORUM (ORCHIDACEAE)2022]

13. Leaf apex acute-apiculate; petals ≤1.5 mm long.; lateral lobes of the lip with a truncated apex; median lobe of
the lip oboval-oblong.......................................................................................................................... O. pygmaea.
13. Leaf apex emarginate or emarginate-apiculate; petals ≥1.5 mm long.; lateral lobes of the lip with an acute,
obtuse or rounded apex; medial lobe of the lip elliptical-oval, oval, oval-elliptical.
14. Leaves lanceolate to ovate-lanceolate............................................................................................. O. connellii.
14. Leaves elliptic, narrowly elliptic or elliptic-oblong.
15. Leaves distinctly petiolate................................................................................................. O. pisa tridentata.
FIG.1. Octomeria romerorum.A–B. Habit. C. Flower. D. Floral segments. E. Lip. F. Column in ventral view. G. Anther cap,
dorsal view. H. Anther cap, ventra l view. I. Pollinia. (A from A. H. Krahl & D. R. P. Krahl 1495, 1496, INPA and D. R. P. Krahl &
A. H. Krahl 700, 701,INPA;B–H from A. H. Krahl & D. R. P. Krahl 1495,INPA)
BRITTONIA [VOL

15. Leaves sessile.
16. Lip ≤3.5 mm long.; lateral lobes of the lip with suborbicular shape and rounded
apex............................................................................................................................... O. ligia sagittata.
16. Lip ≥3.5 mm long.; lateral lobes of the lip with linear-lanceolate or oval-oblong shape and acute or
obtuse apex.
17. Lateral lobes of the lip linear-lanceolate and subfalcate; medial lobe with an erose-denticulate
margin............................................................................................................................... O. flaviflora.
17. Lateral lobes of the lip ovate-oblong to suborbicular; median lobe with an entire
margin............................................................................................................................ O. crassifolia.
1. Leaves cylindric.
18. Median lobe of the lip with a rounded to obtuse apex.
19. Median lobe of the lip ovate with a rounded apex.......................................................................................... O. scirpoidea.
19. Median lobe of the lip obovate with an obtuse apex....................................................................................... O. taracuana.
18. Median lobe of the lip with a retuse to emarginate apex.
20. Median lobe of the lip ovate; petal apex acute......................................................................................... O. enothera filifolia.
20. Median lobe of the lip oblong; petal apex obtuse to rounded.................................................................... O. yauaperyensis.
Acknowledgments
The authors thank the Programa de Pós-
Graduação em Botânica (PPGBot) of the
Instituto Nacional de Pesquisas da Amazônia
(INPA) for support and logistics given throughout
the study, the Fundação de Amparo à Pesquisa
do Estado do Amazonas (FAPEAM) for the
scholarship granted to the first author, and the
team of INPA’s reserve sector (DISER) for the
collecting permit and logistical support. We also
thank the two anonymous reviewers for their
careful reading of the manuscript and for their
highly appreciated and insightful comments.
Conflicts of interest declaration
The authors declare that there are no conflicts
of interest.
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