Plants

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Lepidium oligodontum

The Antipodes Islands are home to 74 native species of vascular plants, including four that are endemic to the islands. Gentianella antipoda, Puccinellia antipoda, Senecio radiolatus ssp. antipodus and Stellaria decipiens ssp. angustata are found nowhere else in the world.

The most rare and endangered species on the island is Lepidium oligodontum, which is shared with the Chatham Islands.

Few introduced weeds have been found on the islands. Four remain on the island, but have not become overly abundant or a threat to the survival of native vegetation. They include a species of tussock (Poa annua), sow thistles (Sonchus aspera and Sonchus oleraceus) and chickweed (Stellaria media). Wild turnip (Brassica rapa), pennywort (Hydrocotyle heteromeria) and yorkshire fog (Holcus lanatus) have been observed on the island, but were confined to single plants near the main huts and have since been eradicated.

The Antipodes Islands are a uniformly low fertility system. Antipodes’ soils are almost entirely composed of peat. Being supported by the ocean means their main sources of nutrients are animals that breed on the islands and the ocean that surrounds them.

The animal nutrient transfer system comes with the seabirds and marine mammals that visit the Antipodes to feed, breed or nest in colonies. Colonies of albatross and penguins leave a layer of nutrient-rich guano, while burrows dug into the landscape by petrels and prions enhance soil aeration and biota (microorganisms). Marine mammals such as elephant seals and fur seals also come ashore to breed in colonies – bringing more guano-based nutrients to the otherwise infertile landscape.

The aerosol nutrient transfer system comes from sea spray, which brings nutrient rich waters of the southern ocean to land by way of the ferocious winds that regularly affect the island. Sea spray along the coast introduces sodium and potassium to the ecosystem, which enhance plant growth and allow highly diverse plant ecosystems along the exposed cliff faces.

Outside of these hotspots, the main vegetative feature of the landscape is tussocked grasslands. Poa littorosa dominates these infertile plains where it forms large, pedastooled roots to prop itself above the islands poorly drained, peaty soil. There are also scattered areas of fernland (dominated by Polystichum vestitum), shrubland (dominated by Coprosma rugosa) and sedgelands (dominated by Carex appressa and Carex trifida in the wet depressions and seeps of the upland plains).

There are three major potential impacts upon the flora that could result from the presence of mice. These are browsing of plants, seed predation and indirect impacts resulting from impacts to fauna.

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Resources

Antipodes Flora List

Godley, E.J. (1989). The Flora of Antipodes Island. New Zealand. Journal of Botany, 27:4, 531-564, DOI: 10.1080/0028825X.1989.10414138.

Antipodes Island Flora and Fauna. Brian Rance. NZ Plant Conservaton Network. No. 137. April 2015. Read more