The German botanist Rudolf
Schlechter published Orchidaceae Perrierianae, a description of all then known
species of Orchids from Madagascar, including 332 new species based upon
material supplied by the French plant-collector Joseph Marie Henry Alfred Perrier de la Bâthie. One
specimen mentioned in this volume was a leafless orchid lacking chlorophyll,
which Schlester assigned to the genus Gastrodia,
but did not assign to a specific genus due to the limited material available.
Unfortunately Schlechter died shortly after this volume was published, leaving
much material supplied by Perrier de la Bâthie undescribed. In 1939 and 1942 Perrier
de la Bâthie published his own description of this material in the two volume
work Flore de Madagascar, including a description of chlorophyll-less Orchid
under the name Gastrodia madagascariensis.
However Perrier de la Bâthie’s description was in French, in breach of then
requirements of the International Code of Nomenclature which required
descriptions in Latin, and much of the material was subsequently destroyed the
bombing of the Berlin Herbarium in March 1943, leaving the status of Perrier de
la Bâthie’s Orchid in limbo.
In a paper published in the
journal Phytotaxa on 28 July 2015, Florent Martos, Steven Johnson and Benny Bytebier of the School of Life Sciences at the University of KwaZulu-Natal, describe new specimens of a parasitic Orchid from Madagascar,
which they believe to be the same species as Perrier de la Bâthie’s Orchid, and
formally redescribe this as Gastrodia
madagascariensis.
Gastrodia madagascariensis is a slender leafless Orchid reaching
100-300 mm in height, with a dark brown or blackish stem. It produces 3-12
light or reddish brown in colour, darkening to blackish at the apex, with
yellow-orange and emerald green markings. It was growing as an understory plant
in the humid evergreen Ambodiriana Forest, at altitudes below 200 m.
Gastrodia madagascariensis. (A)
Growing plant; note the dark colour of the peduncle contrasting with the
whitish pedicels, and the dark colour of the perianth tube at the apex. (B)
Open flower, front view; note the perianth tube spreading towards the apex, and
the reddish brown (bottom half) and light brown (top half) colour of the
perianth tube on the inner surface. (C). Open flower, three quarter view; note
the emerald green colour of the lip tip and of two tubercular calli borne on
the column-foot (also seen on B). D. Dehiscent capsules borne on elongated fruiting
pedicels. (E) Fusiform rhizome with fine adventitious roots. A Charbouillot and
Jean-Michel Hervouet in Martos et al. (2015).
All terrestrial plants survive by
forming symbiotic relationships with mycorrhizal fungi, which absorb minerals
and nutrients from the soil and pass them on to the plant roots in return for
sugars produced by photosynthesis. However in a few groups of plants some
members have developed the ability to live parasitically upon these fungi,
absorbing both minerals and sugars produced by other plants through their roots.
These plants do not produce chlorophyll or photosynthesize themselves.
In 1953 Victor Summerhayes suggested
that Perrier de la Bâthie’s Orchid should be placed in the genus Didymoplexis, due to its elongated
fruiting pedicles, and though since this time other members of the genus Gastrodia have been found with elongated
fruiting pedicles, it has not been possible to resolve the precise generic
position of Perrier de la Bâthie’s Orchid with the limited material available. Perrier
de la Bâthie collected his specimens in 1912, and no further specimens of
either genus were discovered on Madagascar until 2005, when specimens of Didymoplexis were found growing on the
island; since this time two new members of that genus have been described from
Madagascar, and one southern African species has also been found on the island,
and while none of these could be connected directly to Perrier de la Bâthie’s
Orchid, they did lend support to the idea that this could also be a member of
the genus Didymoplexis.
The Orchids discovered by Martos et al. were found growing in Ambodiriana
Forest near Manompana, near to the river Manompana and its tributaries. This is
less than 10 km from the location given by Perrier de la Bâthie for his Orchid,
in the basin of the river Fandrarazana. Martos et al.’s Orchid flowers in the cooler dryer season (the forests of
east Madagascar do not have a dry cool or dry season) in July to August and
produces fruits in August to September, while Perrier de la Bâthie collected
his Orchid’s in September, when they were in fruit. It cannot be asserted
conclusively that Martos et al.’s and
Perrier de la Bâthie’s Orchids are the same species without DNA barcoding,
however this would involve destroying the very limited material remaining from Perrier
de la Bâthie’s Orchid, and could not be guaranteed to produce results anyway,
as this material is over 100 years old and current DNA barcoding techniques are
notoriously unreliable for Orchid’s at the best of times.
Map of Madagascar showing the distribution of the various observations
of Gastrodieae on the island. Didymoplexis avaratraensis and Didymoplexis recurvata, both endemic to Madagascar, co-occur in the northern province
of Antsiranana, in evergreen wet forest at mid elevation. Didymoplexis verrucosa, also known from South Africa, was recently
photographed in the western province of Mahajanga, in deciduous seasonally dry
forest. Gastrodia madagascariensis
occurs in the eastern province of Toamasina opposite the island Nosy Boraha, in
evergreen wet forest at low elevation. Filled triangles: flowers observed. Open
triangle: only fruits observed. Martos et
al. (2015).
The Ambodiriana Forest is a protected forest controlled by the Association de Défense de la Forêt d’Ambodiriana, however like other forests of east Madagascar, protected or
otherwise, it is considered vulnerable to slash-and-burn agriculture, with
fields currently reaching within 2 km of the forest’s border. All of the known
plants of Gastrodia madagascariensis were found growing within an area of 2.25
km2, with less than 50 plants observed in the 2013 growing season.
It is also likely that the plant needs to be associated with particular mycorrhizal
fungi for carbon-uptake. For this reason Martos et al. recommend that it be listed as Critically Endangered under
the terms of the International Union for the Conservation of Nature’s Red List of Threatened Species.
See also…
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Balanophora coralliformis: A new species of parasitic plant from Luzon Island in the Philippines.Balanophoras, Balanophoraceae, are parasitic plants related to Sandlewoods and Mistletoes found in tropical and temperate...
A new species of parasitic Orchid from Takeshima Island, Japan.
Orchids of the genus Gastrodia are found across temperate and tropical Asia, Oceania and Madagascar. They are mycoheterotrophs; parasitic plants which obtain nutrients and sugars from Mycorrhizal Fungi (Fungi which normally form symbiotic...