Natural Heritage

Chatham IslandsArticles by various authors on the unique natural and cultural heritage of the Chatham Islands and the ongoing efforts to conserve it.  If you'd like to contribute an article contact This email address is being protected from spambots. You need JavaScript enabled to view it.

A new highly threatened enigmatic rust recognised from Chatham Islands forget-me-not (Myosotidium hortensia) on the Chatham Islands

Chatham Island forget-me-not (Myosotidium hortensia), Kaiangaroa Point. Image: Peter J. de LangeDuring January 2007 the Auckland Botanical Society visited the Chatham Islands. During their visit the late Dr Ross Beever, then a mycologist working for Landcare Research discovered a strange, orange rust growing on cultivated plants of Chatham Islands forget-me-not (Myosotidium hortensia) within the visitor car park gardens, Department of Conservation offices, Te One, Chatham Islands (Beever 2007).

The rust Beever discovered presents somewhat of an enigma. For a start, despite much survey effort it has to date not been found anywhere else on the Chatham Islands in wild or cultivated occurrences of Chatham Islands forget-me-not. The rust has also not been found on cultivated plants in New Zealand or reported from elsewhere in the world where this plant is grown. Another oddity is that while urediniospores have been seen no teliospores have been found making accurate determination of the rust, at least on morphological grounds difficult. Finally, the new rust represents the first record of any rust infecting Chatham Islands forget-me-not, and that despite 63 species of rust fungi having now been recorded for the Chatham Islands group (McKenzie 1991; McKenzie & Johnston 1999).

Last year, the mystery rust was finally described following DNA sequencing of it, which showed that it is a species of Puccinastrum. The rust is now known as Puccinastrum myosotidii (Padamsee & McKenzie 2014), and so far the only place it has been recorded from in the whole wide world remains the visitor car park gardens, Department of Conservation offices, Te One, Chatham Islands.

 

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Sow thistle gets a name revival and a little rusty

Sonchus grandifolius just starting to flower Te Henga. Image: Peter J. de LangeLast year the Chatham Islands lost one of its unique genera. The endemic Chatham Islands sow thistle was originally described by New Zealand botanist Thomas Kirk (1828–1898) as a new species of Sonchus, S. grandifolius (Kirk 1894). Then in 1965 botanist Loufty Boulos transferred S. grandifolius and the Australian endemic S. megalocarpus to a new genus Embergeria (Eichler 1965). Later Nicholas Lander (Lander 1976) transferred the Australian Embergeria megalocarpus to another new endemic Australian genus Actites leaving the Chatham Islands E. grandifolius the sole representative of the genus Embergeria, which by default was now a Chatham Islands endemic.

Despite these moves acceptance of Embergeria has always been problematic (see comments in Webb et al. 1988) and last year Garnock-Jones (2014) relegated the genus (and another New Zealand endemic one, Kirkianella) to synonymy within Sonchus. While the decision taken could be challenged (see for example discussion on the matter by Heenan et al. 2010) for now at least it has been decided to follow this move (see http://nzflora.landcareresearch.co.nz/default.aspx?selected=NameDetails&TabNum=0&NameId=2CB14B4F-4AE0-447C-B06C-DEF50B6585A1 accessed 25 August 2015).

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New Endemic Plants for the Chatham Islands

Lepidium oblitum flowersAs progress toward the preparation of a Chatham Islands Flora continues, the number of endemic vascular plants accepted for the Chatham Islands has now increased from 38 to 42 with the formal recognition of three new scurvy grasses and one new hook sedge (oft known as bastard grass) from the islands (de Lange et al. 2013a; de Lange et al. 2013b).

Two of the three endemic scurvy grasses (Lepidium panniforme, and L. rekohuense) were first determined as distinct in the mid-1990s, while the third (L. oblitum) was discovered in 2006 during field work on Mangere Island. A fourth newly described scurvy grass, L. oligodontum is known only from the Chatham and Antipodes Islands.

 

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Sole Chatham Islands endemic lichen discovered on south Otago Coastline

Caloplaca maculata – Collected from type locality, south of Waitangi Wharf, Chatham Islands. Image: Allison KnightDespite a remarkable level of endemicity in the Chatham Islands vascular plant flora (e.g., clubmosses, whisk ferns, ferns, and flowering plants) (de Lange et al. 2011) the islands have virtually no endemic non-vascular plants (e.g., hornworts, liverworts, mosses) (de Lange et al. 2008). Currently botanists accept one endemic species of moss (Macromitriumramsayae) and one endemic variety of liverwort (Plagiochila arbuscula var. rekohuensis) (de Lange 2011a). The taxonomic status of the moss is currently under review and it seems likely that this species will at some stage be relegated into the synonym of another widespread New Zealand Macromitrium (A.J. Fife pers. comm.).

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

1. Lepidium oleraceum – Cook’s Scurvy Grass is of course not a grass but a large shrubby cress with a flavour not unlike watercress.The New Zealand scurvy grasses (Lepidium species) include the famous Cook's scurvy grass (L. oleraceum) (Fig. 1), 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 (de Lange & Norton 1996) 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').

It has long been recognised that the Chatham Islands populations of Cook's scurvy grass were variable (de Lange et al. 2010) but until they were subjected to critical study by Department of Conservation and Landcare scientists it was not realized that this variability had a firm genetic and molecular basis. A study initiated in 2005 is now drawing to its final stages prior to publication. In that work, aside from Cook's scurvy grass (known on the islands from only one 2006 Mangere Island collection), a further five species are recognised for the islands. Of these, with the exception of L. flexicaule, the other four are new and are now in the process of formal taxonomic description.

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New Checklist of the Chatham Islands Plants Published

Ferdinand von Mueller: author of the first Chatham Island Flora published by the Victoria State Government of Australia in 1864.As progress toward the preparation of the first flora of the Chatham Islands since 1864 Department of Conservation and Landcare Research scientists have published a new checklist of the plants of the Chatham Islands group (de Lange et al. 2011). The checklist not only provides the first full vouchered listing of the endemic, indigenous and naturalised flora of the islands to ever be published but also a brief history of the discovery of the Chatham Islands flora by European and later New Zealand scientists covering the period between 1840 and 2011. The checklist also describes the origins of the Chatham Island flora, and provides the first detailed discussion and assessment of the indigenous and naturalised plants to be published since the early 1900s.

The checklist accepts 875 formally described vascular plants for the island. Vascular plants are a 'catch-all' covering a diverse grouping of plants that includes clubmosses, ferns, conifers and flowering plants. The publication also notes that a further 27 plants found on the islands are new and still require formal taxonomic description. At this stage 41 formally described plants are considered endemic to the islands, a figure which includes two endemic genera, the spectacular, world famous Chatham Islands forget-me-not (Myosotidium) and Chatham Islands sow-thistle (Embergeria). There are also 400 indigenous plants and 434 that are regarded as naturalised to the islands. Of the 27 as undescribed plants, 13 are believed endemic to the islands, the remaining 11 are known also from New Zealand. A peculiar pattern that warrants further study is that many indigenous plants are known from five or less sites on the islands, and there is some evidence to suggest that the islands are still being naturally colonised by plants from New Zealand.

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Study reveals low levels of genetic diversity in Chatham Islands toetoe

Chatham Island toetoeA 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.

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.

 

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In Search of Cox’s Matipo

Unique to the Chathams, Cox's matipo (Myrsine coxii) is a tough little plant well designed to withstand the weather with small leathery leaves and usually keeping under 2m tall. Surprisingly it flowers in winter, but not that you'd notice. You might however see the odd purple berry. It doesn't appear to waste a lot of energy on flowering and fruiting though, preferring to spread by layering itself. You'll find it in boggy margins on the edge of forest, or in boggy light gaps within forest in protected areas.

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Parea - the Chatham Island pigeon

Parea - Chatham Island pigeon
Status (2008):
Population (2009):
Trend:
Critically Endangered
600 individuals
Improving
Larger and heavier than its mainland cousin, the parea or Chatham Island pigeon is today largely confined to the south-western corner of Chatham Island.  Like several other Chatham species the parea had a close brush with extinction, with the population dropping to 40-45 birds in 1989.  Fortunately, the protection of habitat and the control of predators has seen a dramatic recovery of the species and a 2009 census estimated the population to be around 600 birds.

 

 

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Chatham Island oystercatchers

Chatham Island oystercatcher (Haematopus chathamensis)
Status (2008):
Population (2010):
Trend:
Nationally critical
309 mature individuals
Stable
Many of us are familiar with New Zealand's variable oystercatcher, the black and white (or sometimes entirely black) wader with bright orange legs and bill that we encounter on beaches around the country.  What most don't know is that the Chatham Islands have their own version, the Chatham Island oystercatcher and that it narrowly escaped extinction in recent times.

The first comprehensive survey of Chatham Island oystercatcher in 1987 revealed 112 birds.  Despite the low number this was actually good news because the previous estimate, made from partial beach counts in 1970, suggested that the population may be as low as 50 birds.

The reasons behind the perilously low population were  investigated and found to be numerous.

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Chatham petrel population growing

Chatham petrel (Pterodroma axillaris)
Status (2012):
Population (2010):
Trend:
Nationally vulnerable
1,400 individuals
Improving

Probably once abundant throughout the Chatham Islands, human exploitation, habitat destruction and introduced predators saw the Chatham petrel restricted to Rangatira or Southeast Island by the time of its discovery in 1892.

Until 1961 farming activity on Rangatira resulted in the petrels being confined to small forest patches, where they competed for burrows with the similarly sized broad-billed prion. Nesting at different times of the year, many petrel chicks were ousted from their burrows by returning prions. By 1990 the Chatham petrel population was estimated to be around 1,000 birds and heavily outnumbered by some 600,000 broad-billed prions.

Studies found that while adult Chatham petrel survival was high, less than 50% of pairs were managing to fledge a chick, placing the population in peril. So, finding a way to deter prions from entering Chatham petrel burrows was a priority.

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