Dioscorea chouardii

Dioscorea chouardii (synonym: Borderea chouardii) is a herbaceous plant in the family Dioscoreaceae.[1] It is endemic to a single crag located in the Pyrenees of Aragon, Spain.[2]

Dioscorea chouardii
Scientific classification
Kingdom: Plantae
Clade: Tracheophytes
Clade: Angiosperms
Clade: Monocots
Order: Dioscoreales
Family: Dioscoreaceae
Genus: Dioscorea
Species:
D. chouardii
Binomial name
Dioscorea chouardii
Gaussen
Synonyms

Borderea chouardii (Gaussen) Gaussen & Heslot

History

A previously unknown species, Dioscorea chouardii was discovered in the 1950s growing in cracks in a limestone cliff in the Pyrenees Mountains in northeastern Spain. The fissures in which it lives are so inaccessible that it proved difficult to estimate the number of plants. At first it was thought that there were some 300 to 500 plants scattered across the rock face, but later, with the erection of some scaffolding and the help of binoculars and telescopes, individual plants could be monitored, and a total figure of around 9,000 plants was reached.[2]

Taxonomy

The plant has been described as a "living fossil"; a relict from the Tertiary period. Dioscorea chouardii is morphologically very similar to another relict species, Dioscorea pyrenaica, which has a rather wider distribution in the Pyrenees. The former grows in vertical cracks on shaded, north-facing limestone cliffs at between 730 and 850 m (2,400 and 2,800 ft) while the latter grows on limestone screes at over 1,800 m (5,900 ft). RAPD testing strongly suggests that D chouardii is not an ecotype of D. pyrenaica and that the two taxa should be considered separate species.[3]

Ecology

Dioscorea chouardii is related to the yam and grows from a tuber hidden in the rock fissure. From this it sends out a shoot each year which withers away in the autumn. The shoot leaves a scar on the tuber, which makes it possible to estimate the age of the plant from the number of scars; the oldest plants are calculated to have lived for three hundred years, and may be contenders for being the "slowest growing plants in the world". The plant reproduces by seed, pollination having been performed by ants. When fertilised, the flower-stem bends over to bury the resulting seedhead in the crack, the seeds being released when it dries. This would limit dispersal possibilities for the plant were it not for the fact that the seeds are transported by ants, which distribute them more widely.[2]

Conservation status

The European Union has classified this plant as "critically endangered" and it is protected by an EU Habitats Directive and further protected by having seven Natura 2000 sites designated for its protection.[4] However, although its range is so small, the population of this plant seems stable, and there is no particular reason why climate change should affect it adversely.[2]

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References
  1. "Dioscorea chouardii Gaussen". The Plant List. Retrieved 21 May 2019.
  2. García, María Begoña. "Secrets of some of the Pyrenees' threatened plants". Lychnos. Retrieved 21 May 2019.
  3. Mayol, Maria & Rossello, Josep A. (2001). "RAPD differentiation between Borderea pyrenaica and B. chouardii (Dioscoreaceae), two relict endangered taxa". Israel Journal of Plant Sciences. 49 (4): 259–268. doi:10.1560/3DM5-RVGT-VHKD-D5JA.
  4. "Borderea chouardii (Gaussen) Heslot". European Nature Information System. EEA. Retrieved 21 May 2019.
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