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Proposal Summary |
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If verified, then the arrival and establishment of all land-dwelling plants and animals in the Chatham Islands has been rapid, and in biological terms, recent. This concept has major implications for understanding rates and mechanisms of dispersal and colonization over large distances, speciation, biodiversity of oceanic islands and the biological history of New Zealand The proposed research will involve geological and biological studies. It will be detective, searching for critical geological evidence of two major processes: sea level change and tectonic uplift. Biological research will compare DNA sequences from selected Chatham Islands and mainland plants and animal to explore the timing, pattern and ecological consequences of colonization and isolation. This project involves geologists and biologists working together from GNS and Massey, and Otago universities. It has the potential to establish new ways to determine island histories, rates of dispersal and rates of speciation.
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Background |
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Although the New Zealand continental landmass has subsequently subsided so that much of it, (including most of the Chatham Rise) is now submerged, it has generally been assumed that there has always been land at the Chathams supporting an ancient biota. However, identification of the remnants of a 3.6 Ma formation of deep-water limestone (Motarata limestone) exposed on Chatham Island suggests otherwise. The Motarata limestone is immediately overlain by a beach deposit (Titirangi sand). These formations indicate rapid uplift of the Chathams since deposition of the Motarata Limestone 3.6 Ma, and that the Chathams topography may be much younger than previously thought.
The Chathams may have emerged in response to a regional tectonic uplift event that affected the entire eastern end of the Chatham Rise. We shall test our null hypothesis that the Chathams did not emerge as land until the Late Pliocene, about 3.6 to 3.0 Ma. To do this, we shall examine the Chathams landscape in detail with particular regard to the origin and age of surfaces and surficial sediments. Similarly, we will use genetic data across a broad, unbiased, sample of taxa to seek evidence for ancient divergences. We shall then undertake ecological and molecular ecological studies of selected plant and animal groups, to examine in detail the depth and pattern of phylogenetic relationships amongst sister taxa from the Chathams and mainland New Zealand and compare ecological diversity (e.g. niche width). Randomisation tests comparing Chathams and mainland biotas will be used to seek evidence for common ecological characteristics of successful colonisers. The Chathams offer a splendid opportunity to determine the role of dispersal/colonization in the establishment of an island fauna and flora across 850 km of ocean. The subject relates to the wider questions of the origin and age of the mainland New Zealand biota and interpretation of historical processes in general. Further, this research has considerable international merit in the context of evolutionary theory (rates of speciation), biodiversity (generation of diversity), biogeography (efficiency of dispersal and establishment), biotic recovery and ecology (niche partitioning). 
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ChEARS 2004 Excursion |
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ChEARS 2004
excursion- team members and associates enjoying the view.
ChEARS Excursion 1: March 8-24, 2004 Objectives:
Results: All
objectives met. And,
we rediscovered on this trip the |
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| Contact Details | ||
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| Dr Steve Trewick Allan Wilson Centre for Molecular Ecology and Evolution Phone: +64 6 350 9099 x2043
Links: http://awcmee.massey.ac.nz/nzinsects/index.html
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The Chatham Islands and their biota have long been thought to be of ancient
origin. But, new evidence suggests that the Chatham Islands may have existed
for as little as 4 million years. Imagine no land there whatsoever. The
biological significance of this idea is so profound that it demands scientific
scrutiny. 
The
Chatham Islands are remote, located at 176˚W and 44°S some 850 km
due east of Christchurch, New Zealand. They are remnants of a large, extinct
stratovolcano that erupted 80-70 million years ago (Ma) in Late Cretaceous
time. When the Tasman Sea started to open about 85 Ma, the New Zealand
continental landmass rifted away from the eastern margin of Gondwanaland,
carrying with it a full complement of plants and animals. The Chathams
are thought to have been stable since then, with only minor sporadic volcanism.
Their subdued geomorphology today is thought to be the product of long,
slow erosion, and has been assumed to reflect stability.
Furthermore, there are some
prominent absences and peculiarities in the modern Chatham Islands
fauna and flora that suggest comparatively recent arrival with little
evidence of an isolated heritage of great antiquity. For example, only
2% of the Chatham Island beetle genera are endemic which is much less
than that of other island groups of similar age and size. By comparison,
beetle generic endemism on the New Zealand mainland is 70%. Furthermore,
existing genetic evidence from insect genera reveals relatively minor
Chatham-mainland divergences.
