I was lucky enough to be one of four Te Papa Science staff to complete a 15 day multidisciplinary field study on the Snares Islands/Tini Heke in December 2013. The vascular flora of the Snares Islands is limited, at only 22 species (including one hybrid Poa). Despite this, my first impression of the main island was an island covered with lush vegetation. And there are still some botanical challenges - we failed to locate the fern Histiopteris incisa for instance. Vegetation communities on the Snares consist of five main types: forest (c.50-60% cover), tussock grassland (c.25-30%), shrubland (c.10%), herbfields (c.<1%) and herbaceous/turf seepage communities (c.1%).
Snares Island forest comprises two species of tree daisy: Olearia lyallii and Brachyglottis stewartiae, the former being the dominant species on the islands. Both have a very southern distribution between the Snares in the south (with Olearia also found on the Auckland Islands) and the Solander Islands, Foveaux Straight in the north. Shrubland contains the white-flowered variation of Veronica elliptica which occurs on the coast and on the tops, mostly bordering Olearia forest and which quickly colonise areas of forest windthrow and dieback. Tussock grassland is dominated by Poa tennantiana (wide leaved) and Poa astonii.
A major feature of sub-antarctic plant communities is the megaherbs. This feature is limited to only two sites on the main island of the Snares. They contain the impressive Stilbocarpa robusta and Anisotome acutifolia. The latter species is the only vascular plant species currently recognised as endemic to the Snares Islands. One recently described entity of Cook’s scurvy grass, Lepidium limenophylax, is also associated with these herbfields but mainly grows along the western and northern cliff tops of North East Island. Due to the limited area that they occupy, these last two species are listed as threatened. However, the populations on North East Island appear to be stable and healthy.
There are two low-lying herbaceous plants on the Snares with a New Zealand distribution limited to the sub-antarctic islands: Callitriche antarctica (which thrives in coastal and inland seepage areas) and Stellaria decipiens (glabrous native chickweed). Other species include a cushion plant (Colobanthus muscoides), a succulent herb (Crassula moschata), a small rush (Isolepis cernua) and a sedge (Carex trifida).
The islands have always been free of introduced mammals but two introduced species of plant have made it to the island. These are Stellaria media (hairy chickweed) and the grass, Poa annua. The Department of Conservation are controlling the invasive Stellaria media and we only saw scattered plants on Gull Point in Boat Harbour, North East Island.
Please see my ‘Snares Islands Flora‘ project page on Nature Watch NZ which provides more images and more information on habitat and distribution.
One objective while visiting the Snares was to collect mosses, liverworts and lichens. An overview of these collections and initial findings can be found in the Snares Islands - bryophytes and lichens blog.
Other blogs from the Te Papa Snares Islands research team:
Thank you to the Department of Conservation who made our work on the Snares Islands possible.