Rare ‘Orchid of the Falls’ Species Declared Extinct in the Wild – Verve times

The Saxicolella deniseae was discovered in 2018 by botanist Denise Molmou, endemic to a waterfall in the Konkouré River in the Republic of Guinea, West Africa. The factory’s only known site has since been flooded by water from a dam constructed some 30-40 km downstream. Credit: Denise Molmou

A team of botanists from Guinea and the Royal Botanic Gardens, Kew in the UK have sounded the death knell for a plant of the genus Saxicolella that is endemic to a single site in Guinea. The sad discovery was made by Kew botanist Dr. Martin Cheek who examined the plant’s last known coordinates using Google Earth satellite scans, following a taxonomic assessment of the genus Saxicolella published this week in the scientific journal. Kew Bulletin

The article features several new species for science, including Saxicolella deniseae, or “Denise’s Saxicolella.” Unfortunately, the most recent satellite images from November 2021 show that the plant is submerged 30-40km downstream in reservoir water from a hydroelectric dam. According to Dr. Cheek, this development actually led to the extinction of the plant.

The genus Saxicolella of eight species occurs in the family “orchids of the falls”, which contains about 300 species, mainly in the tropics. While not orchids, they are all limited to waterfalls and rapids. Officially known as Podostemaceae, these are a family of waterfall plants restricted to living in fast-moving and aerated waters, many of which are only now being described to science. The plants were featured prominently in an episode of the BBC documentary series The Green Planet earlier this year, when naturalist David Attenborough referred to the family as the ‘orchids of the falls’.

Saxicolella deniseae was believed to be endemic to a single site along the Konkouré River in the Republic of Guinea, West Africa, which is now home to several newly constructed hydroelectric dams that provide energy to the region. The only known specimen was collected by (and named after) botanist Denise Molmou in 2018 – the first and probably last scientist to have seen the species in the wild – under the Guinea Tropical Important Areas (TIPAs) program – an international effort to conserve tropical plant biodiversity in the wild.

dr. Martin Cheek, senior research leader in RBG Kew’s Africa team, says that “we know that many plant species have become extinct recently, but this case shows how unexpected and sudden extinctions can be. In Africa, species of ‘orchids of the falls’ are often limited to a single waterfall, sometimes to two, three or four on the same river. In this case, because of the dam, several waterfalls along the Konkouré, where the species may have also occurred, are now under water reservoirs, so it seems pretty certain that this species is extinct. This probably happened last year, hitherto unknown to us when we checked how close the reservoir had come to the site.”

Using satellite imagery and the Google Earth platform, Kew scientists have found the coordinates of the plant’s discovery and compared the images over the years since its discovery in 2018. Images from November 2021 indicate the area has been flooded. Credit: Google Earth

Unfortunately, the botanists have not been able to collect and store viable seeds that could preserve the genetic material of S. deniseae. The experts faced travel restrictions due to the COVID pandemic between 2020 and 2021, and Kew’s partners at the National Herbarium of Guinea were hampered by the internal turmoil of a military coup in September 2021. According to Dr. the factory would be further hampered by the exceptionally poor condition of the surrounding roads.

Denise Molmou, botanist at the UGAN National Herbarium of Guinea, says: “While it is a great honor to have a species I discovered in the wild named after me, it is really sad that it is almost certainly extinct. I’ll see if we can find it in other waterfalls, even if the chances of finding it alive aren’t very good.”

The falls on a tributary of the Konkouré River where S. deniseae was found were targeted as collections of this plant were not known along most of the river, despite the existence of multiple waterfalls visible on Google Earth. This indicated that no one had researched the biodiversity of the plant life on the falls of this river.

To prevent the extinction of biodiversity in the wild, it is critical that botanists conduct full studies of plants in waterfalls in tropical regions, especially before executing plans to build hydroelectric projects. Kew’s botanists believe it only takes an hour or two to survey a waterfall for “waterfall orchids” species, followed by additional time to determine whether they are in danger of extinction, new to science or not. Unfortunately, formal studies are rarely conducted before such projects start.

dr. Cheek says: “There is still a very slim chance that this species will survive somewhere, somehow. But since this hydroelectric project, and another project upstream, have flooded about 150 km of the length of the Konkouré River, and also the 30 km from the tributary where this species occurred, it seems very likely that this species will be lost forever.We continue to search.”

Newly described species have a higher risk of extinction

More information:

Wang, M., Molmou, D., Magassouba, S. et al. Taxonomic revision of Saxicolella (Podostemaceae), African waterfall plants highly threatened by hydroelectric projects. Kew Bulletin (2022). doi.org/10.1007/s12225-022-10019-2

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Royal Botanical Gardens, Kew

Rare species of ‘orchid of the falls’ declared extinct in the wild (2022, June 1)
collected on June 1, 2022
from https://phys.org/news/2022-06-rare-orchid-falls-species-declared.html

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