Chatham Island toetoe

Study reveals low levels of genetic diversity in Chatham Islands toetoe

A study just published in Pacific Conservation Biology reveals that the Chatham Island toetoe (Austroderiaturbaria) populations have very little significant genetic variation (Houliston et al. 2012). The discovery comes as somewhat of a worrying surprise to plant conservationists. Previously, without the ability to check levels of genetic variation the Department of Conservation has taken pains to maintain Chatham and Pitt Island populations of toetoe distinct, particularly by making sure not to mix them in cultivation or in translocations on the islands. As a further measure plants from Ocean Bay, North-Western Chatham they also kept distinct as these had a different growth habit to those seen elsewhere on the Chathams.

CI toetoe safe on pedestals just off shore - Lake Rakeinui. Image: Amanda Baird
CI toetoe safe on pedestals just off shore – Lake Rakeinui. Image: Amanda Baird/DOC

The study used a range of DNA markers and modern DNA fingerprinting techniques to examine a range of fresh tissue samples collected from the Chathams in 2008, as well as seedlings raised at the Landcare Research Campus, Lincoln, South Island from samples provided by the Department of Conservation.

The discovery suggests that either the Chatham Islands toetoe has always existed as a species with very low genetic variation or that the species gene-pool has already been so severely fragmented that all we are left with is a residual level of genetic diversity. Available evidence suggests that both situations probably apply, though it cannot be doubted that there has been tremendous loss of toetoe habitat following the colonisation of the islands by people and this has been a key factor in the genetic erosion of the species.

Whatever the cause, rather like the Chatham Islands black robin, conservation managers now have to make the best of what they have. In this respect the good news is that, of needed we can translocate (establish) new populations of toetoe in more secure sites without risking damaging existing populations. So for example if needed, we could move plants from Chatham Island to Pitt Island, or vice versa, whereas previously, as a precautionary measure this was not done fear of damaging those islands gene pools of this species.

Currently Chatham Island toetoe remains a seriously threatened plant, though its status has improved from past listings as Nationally Critical to Nationally Endangered thanks to dedicated management and protection of wild populations by islanders and the Department of Conservation.


  • Houliston G.J., Dawson M.I., de Lange P.J., Heenan PB. 2012. Using AFLP markers to inform population management of the endemic Chatham Island toetoe, Austroderiaturbaria (Poaceae). Pacific Conservation Biology 18: 33–40.

Associate Professor (Botany, Ecology, Plant Conservation, Biosystematics) at Unitec in Auckland and a former Department of Conservation scientist. Peter has been visiting the Chatham Islands since 1996 and is a current member of the Chatham Islands Conservation Board.