Peter J. de Lange

24 posts
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.
1. Lepidium oleraceum – Cook’s Scurvy Grass is of course not a grass but a large shrubby cress with a flavour not unlike watercress.

Remarkable and unexpected diversity of scurvy grasses discovered on the Chatham Islands

The New Zealand scurvy grasses (Lepidium species) include the famous Cook’s scurvy grass (L. oleraceum), a species which has gained almost legendary status as the plant that saved Captain Cook and his crew from the depredations of scurvy. Whilst modern research has shown that this is gross exaggeration it cannot be doubted that this plant and its allies were important green foods for not only scurvy ridden sailors but iwi (who in New Zealand knew the plants collectively as ‘nau’).

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 […]

[i]Menegazzia pulchra[/i] Photo: Peter de Lange

An uncommon lichen Menegazzia pulchra found on the Chatham Islands

While our knowledge of New Zealand lichens is rapidly growing we are still unclear of what is present over large parts of the New Zealand Botanical Region. One key area of lichen ignorance is the Chatham Islands. The current lichen flora (Galloway 2007) records just 48 species for the islands. Yet despite that, the Chathams are the type locality for three species, and one of these, Caloplaca maculata, is endemic to the islands (see Galloway 2007; Johnson 2008; de Lange 2009).

In 1996 two of us, Peter de Lange & Gillian Crowcroft, visited the islands for their first time during which they collected a few lichens from the southern part of Rekohu (Chatham Island). Since then, but most especially in 2007 and 2008, Peter de Lange (mostly aided by Peter Heenan), has made a special effort to collect lichens to improve our knowledge of their diversity on the island. As a result of these gatherings, Peter de Lange and David Galloway (the author of the New Zealand Lichen flora series (Galloway 1985, 2007)) are working with the other key Chatham Islands lichen collectors Peter Johnson and Allison Knight, and lichenologist Dan Blanchon to prepare a checklist of the lichen flora for that island group (Galloway et al. in prep.). As part of that project they have been systematically working through all known collections from the island group held in New Zealand herbaria. In the process some rather interesting and at times unexpected finds are being made.

[i]Heterodea muelleri[/i] in an Australian woodland showing growth habit. Photo: Royal Botanic Garden Sydney

Apparently extinct lichen discovered on the Chatham Islands

A common woodland lichen of eastern Australia that has been recorded only twice from New Zealand in 1934 and 1976, and then only from the far north of the North Island has turned up on the Chatham Islands. The lichen, Heterodea muelleri is a leafy species that in Australia grows in moderately open woodland habitats. In New Zealand, until it was recognised from the Chatham Islands it had only ever been recorded from dune slacks somewhere on the Ninety Mile Beach and from damp sandstone ridges in light scrub near Puheke, Karikari Peninsula.

The Chatham gatherings came from the north-western end of Ocean Bay, Chatham Island and from the top of Hakepa Hill (Walkemup), Pitt Island.  At Ocean Bay the lichen grew on sandy peat and clay above schist on the margin of salt and wind blasted vegetation. In this habitat it was associated with the lichens Cladia aggregata and C. retipora, and sedge Lepidosperma australe. On Hakepa Hill specimens were gathered from amongst the dense drifts of Cladonia lichens that grow between the low, windswept fernland that covers most of that trachyte peaks summit.

Chatham Island sow thistle in flower. Image: Peter de Lange

Spectacular comeback for Chatham Island Sow-thistle

The Chatham Islands Sow-thistle or Embergeria grandifoliais one of two endemic plant genera known only from the Chatham Islands. For most of the last fifty years the sow-thistle has been in decline throughout the Chatham Islands such that at one time it was ranked by the International Union for the Conservation of Nature (IUCN) as “Endangered” meaning that if the decline wasn’t halted it would soon go extinct.

Since the late 1990s the Department of Conservation in cooperation with Chatham Islanders has been working to save this peculiar plant from extinction. While Chatham Island sow-thistle is probably not the most attractive looking of plants it is undoubtedly of world wide interest. Superficially resembling the introduced puwha/sow-thistles (Sonchus spp.), the Chatham Islands Sow-thistle is a much larger plant with flowering specimens sometimes reaching up to 1.8 m in height. The yellow-green leaves are very leathery and can be up to 1 m long, while the dense clusters of daisy-like flowers are produced in profusion and multi-coloured in shades of yellow, apricot and purple.

A plant of [i]Plagiochila arbuscula var. arbuscula[/i] growing on scoria on the Lava Caves track - Rangitoto Island. This specimen is bearing perianths. The Chatham Islands has this variety (which has long been known in New Zealand - incorrectly - as [i]P. obscura[/i]) as well as the new endemic var. [i]rekohuensis[/i]

Finally – the Chatham Islands have an endemic liverwort!

In 2005 whilst at the Allan Herbarium (CHR), Lincoln I happened to ask Dr David Glenny if anyone had examined the liverwort flora of the Chatham Islands? David told me that a few people had collected liverworts from there, including him in 1997, and so far found “nothing special”. Intrigued, I then asked if David would like me to collect hornworts and liverworts while doing vascular plant work over there, and he agreed that this would be a good idea. David also kindly gave me a checklist of the hornworts and liverworts known to be on the island, and further, he agreed to identify what I got from there.