Poor Knights Spleenwort On the Chatham Islands
Last week botanists Peter de Lange, John Sawyer and Amanda Baird have discovered three populations of the Acutely Threatened/Nationally Endangered Poor Knights spleenwort (Asplenium pauperequitum) at Point Somes and north of Ocean Bay in the remote north-western corner of the main Chatham (Rekohu) Island. The elusive fern, long believed endemic to the Poor Knights and Mokohinau islands located some 1280 km NNW of the Chatham Islands, was first recognised from the Chatham Island archipelago last May from fern specimens that had been collected by Mark Bellingham from the Forty-fours during February 2005.“There is nothing singular about the Forty Fours from a geological, floral or faunal perspective” said Peter de Lange, “So we always suspected that Poor Knights spleenwort, should be on the other islands of the archipelago”. De Lange who heads a team researching the taxonomic and conservation status of the Chatham Island Lepidium oleraceum complex, asked his co-workers, Wellington Department of Conservation (DoC) botanist John Sawyer and Chatham Island DoC Area Office botanist Amanda Baird to keep an eye out for the fern. “We always suspected it had to be elsewhere on the islands but that it had been overlooked, because it has a superficial similarity to shade-forms and juveniles of the very different Chatham Island endemic A. chathamense” said John Sawyer.
The first discovery was made at Point Somes, the north western most extremity of the main Chatham (Rekohu) Island. Sawyer discovered what he thought was the fern within five minutes of looking. Sure enough, the plants grew intermingled with young A. chathamense. However, the distinctive jet-black wire like stipes and rhacis, simple, scarcely divided, thick and glossy deltoid fronds, and sporangia set well back from the pinnule apices readily set this fern apart from A. chathamense. About 30 plants and numerous prothalli were soon found in two separate sites near the Point. Plants were only found on horizontally bedded Chatham schist, in the darkest overhangs. Later on last week a further smaller population in the same type of habitat was located at an unnamed point north of Ocean Bay. De Lange, Sawyer and Baird now predict that the Poor Knights spleenwort might prove to be a locally common component of the cliff and crevice vegetation in suitable areas of the main Chatham Island. Resident botanist Amanda Baird is delighted with the finds.
These discoveries are a considerable boon toward the conservation of what is still a seriously threatened fern. In its other recorded habitats the species is now believed extinct on the Mokohinau Islands, and it is not faring well on the Poor Knights Islands. These discoveries on the Chatham Islands – where nobody would have thought to look - heighten the possibility that this fern will be found elsewhere in similar rock habitats in New Zealand proper.
Posted: 18/01/2006