Tuesday 13 February 2024

Thonningia alba: A new species of Parasitic Plant from Madagascar.

The Balanophoraceae is a family of obligate root-parasitic plants (which is to say, Plants which tap into the root systems of other Plants for nutrients, and carry out little-or-no photosynthesis for themselves) in the order Santalales, which also includes Sandalwoods and Mistletoes. Six species of these plants, in five genera, are known from Africa, while three are found in Madagascar, Ditepalanthus malagasicus and Thonningia malagasica (sometimes known as Langsdorfa malagasica), which are endemic to the island, and  Balanophora abbreviata, which is also found in Southeast Asia.

In a paper published in the Kew Bulletin on 25 January 2024, Leandro Jorge Telles Cardoso and João Marcelo Alvarenga Braga of the Instituto de Pesquisas Jardim Botânico do Rio de Janeiro, describe a new species of Balanophoraceaen Parasitic Plant from the Masoala Peninsula of northeastern Madagascar.

Cardoso and Braga first came across this species as specimens in the collections of the Missouri Botanical Garden and Muséum National d'Histoire Naturelle, which were identified as belonging to Thonningia malagasica, but which appeared more similar to Thonningia sanguinea, a species known from West and Southern Africa, but never previously recorded in Madagascar. Closer examination of this material and comparison to specimens of all known species of Thonningia and Langsdorfa led Cardoso and Braga to conclude that the material did in fact represent a new species.

The new species is named Thonningia alba, where 'alba' means 'white' in reference to the colour of the flowers. Known specimens of the species have a single branch with 1-3 clusters of inflorescences. Leaves are reduced to a few 3-5 whorls of scales around the base of these inflorescences. Inflorescences can be male or female, and reach a maximum diameter of about 3 cm in diameter. Flowers are tubular, with male flowers reaching 12-16 mm in length, while female flowers are 9-12 mm long.

Thonningia alba. Male inflorescence, Masoala Peninsula, Madagascar, 15°41'43.55"S, 49°57'50.63"E, 270 m above sealevel, September 2018. Neek Helme in Cardoso & Braga (2024).

Thonningia alba has been found growing in tropical rainforests on the Masoala Peninsula at altitudes of between 110 and 650 m above sealevel, and appears to flower between July and November, with fruit being produced in November; although the limited number of observations of the species in the wild mean that this cannot be stated with absolute confidence. It is clearly parasitic in nature, but the identity of its host Plant is unclear. 

The Masoala Peninsula is considered to be a mega-diverse region of global biodiversity importance, and is covered by a mosaic of protected areas, the largest of which is the Masoala National Park, which includes large expanses of rainforests and coastal landscapes. Specimens of Thonningia alba were collected in 1986, 1993, and 1994, and the species was observed in the wild in September 2018. All observations were within the Masoala National Park, at two locations separated by about 16 km. While the park itself is a protected area, the surrounding area is home to a growing Human population, which is at least partially dependent on collecting wild resources from the area's forests. For this reason, Cardoso and Braga recommend that the species be treated as Endangered under the terms of the International Union for the Conservation of Nature’s Red List of Threatened Species.

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