Thursday, 18 December 2014

A new species of Burr Marigold from Rapa in the Austral Islands, French Polynesia.


The Austral Islands are a group of eight volcanic islands to the south of the Society Islands in the southern Pacific Ocean. Rapa is the second largest of these, covering about 40 km2, and reaching about 650 m above sea-level. The island is generally rugged with many steep basalt cliffs, and a small area of cloud forest on the top of its highest peak, Mont Perau. It is also extremely remote, being nearly 1200 km southeast of Tahiti, 3700 km northeast of the north island of New Zealand, and 8500 km southwest of the Baja Peninsula in Mexico. As such it has a high rate of endemism among its plants and animals, with 238 native (i.e. not introduced by man) plants (152 flowering plants plus 86 ferns) including 85 species found only in the Austral Islands (65 flowering plants plus 20 ferns) and 73 are found only on the island of Rapa (53 flowering plants plus 20 ferns), though many of these are threatened by introduced animals, most notably Cows and Goats.

In a paper published in the journal PhytoKeys on 3 October 2014, Vicki Funk of the US National Herbarium in Washington DC and Kenneth Wood of the National TropicalBotanical Garden in Hawai’i describe a new species of Burr Marigold from Rapa. The species is was discovered by a National Geographic Society expedition to the island in March-April 2002, which included scientists from the New York Botanical Garden, the Délégationà la Recherche de la Polynésie Française and the National Tropical Botanical Garden. This expedition was originally planned to last for a month, but a delayed supply ship trapped the scientists for two months. The leader of this expedition, Timothy Motley of the New York Botanical Garden subsequently died, and the whereabouts of the majority of the specimens collected by the first expedition is unknown. A second expedition visited the island in December 2002 and collected more specimens, which were sent to the Paris Herbarium, however these also appear to have been lost.

The new species is placed in the genus Rapa, and given the specific name meyeri, in honour of Jean-Yves Meyer of the Délégation à la Recherche de la PolynésieFrançaise, for his research on the plants of Rapa and work on preserving the islands biodiversity. The species is a small sub-shrub reaching 25 cm tall with 3-4 branches reaching about 8 cm. It has fleshy, toothed leaves and yellow flowers. The species was found growing high on a cliff, and could be collected only by rope.

Bidens meyeri: Close up of a flowering plant, note the gloved finger holding the plant. Jean-Yves Meyer in Funk & Wood (2014).

Bidens meyeri is considered to be Critically Endangered under the terms of the International Union for the Conservation of Nature’s Red List of Threatened Species, as it is known from only two specimens growing on a single ledge on a northeast facing cliff 272 m above sea-level. The cliff had several small ledges with granular soil, and patches of steep slope with patches of low forest and shrubland. This environment is threatened by potential fires, habitat degradation, feral goats and competition with introduced plants.

Jean-Yves Meyer climbing with Bidens in his teeth, note yellow flowering plant on the cliff face just above his left hand. Ron Englund in Funk & Wood (2014).

See also…

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