flora

18 posts

[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.

Chatham Island forget-me-not ([i]Myosotidium hortensia[/i]) (left) shares a common ancestry with a northern hemisphere Mediterranean herb called navel wort ([i]Omphalodes verna[/i]) (right)

New paper explores the origin of Chatham Islands native flora

A major paper (Heenan et al. 2010) examining the origin of the Chatham Islands native flora has just been published in the June 2010 issue of the New Zealand Journal of Botany. The paper written jointly by staff of Landcare Research, Department of Conservation, and Universities of Auckland, Lincoln and Otago explores the origin and diversification of 31 endemic land plants (ferns and flowering plants) of the Chatham Islands archipelago using DNA sequences pooled from a variety of independent unpublished studies.

Hooker's spleenwort ([i]Asplenium hookerianum[/i]) plants growing amongst hoho ([i]Pseudopanax chathamicus[/i]) root plate with two other ferns - maidenhair fern ([i]Adiantum cunninghamii[/i]) and [i]Rumohra adiantiformis[/i] - Waipaua Stream - Rangiauria (Pitt Island). The plants in this image represents both the finely divided frond race sometimes known as Colenso's spleenwort (A. colensoi or A. hookerianum var. colensoi) and the more common less divided frond race of Hooker's spleenwort (A. hookerianum or A. hookerianum var. hookerianum). Image: P. J. de Lange

Little fern provides cryptic proof of ongoing New Zealand to Chatham Islands plant dispersal

Hooker’s spleenwort (Asplenium hookerianum) is not a particularly common fern on the Chatham Islands.  By far the largest population the Department of Conservation knows about is one that was discovered in November 2008 along the banks of the Waipaua Stream, Pitt Island. Hooker’s spleenwort looks superficially like a smaller version […]

Typical clears vegetation of bamboo rush and swamp aster. Image: Amanda Baird/DOC

The South-West

The south-west of Chatham Island encompasses dramatic coastal scenery, a fertile farming belt and forested catchments rising to a moorish tableland containing lakes and low peaks. The south-west supports the most extensive forest on Chatham Island, expanses of upland bamboo rush & Chatham aster and important populations of threatened plants and animals. It is the only breeding sites in the world for taiko and the Chatham Island mudfish. The largest protected area occurs here with the Tuku Nature Reserve and adjoining South Chatham covenant at about 2,500 hectares.

The tableland is highly distinctive. The flat to undulating topography belies the fact it is the highest region of Chatham Island at 250-280m altitude. The island’s tallest peaks occur on the tableland’s northern edge.