[Taxacom] New paper on basal angiosperm and ultramafic endemics in New Caledonia

John Grehan jgrehan at sciencebuff.org
Mon Nov 17 10:07:56 CST 2008


A copy of the following paper may be accessed at:

http://www.sciencebuff.org/heads_publications.php

 

Heads, M. 2008. Panbiogeography of New Caledonia, south-west Pacific:
basal angiosperms on basement terranes, ultramafic endemics inherited
from volcanic island arcs and old taxa endemic to young islands.

 

ABSTRACT

Aim To investigate areas of endemism in New Caledonia and their
relationship

with tectonic history.

 

Location New Caledonia, south-west Pacific.

 

Methods Panbiogeographical analysis.

 

Results Biogeographical patterns within New Caledonia are described and
illustrated with reference to eight terranes and ten centres of
endemism. The basement terranes make up a centre of endemism for taxa
including Amborella, the basal angiosperm. Three of the terranes that
accreted to the basement in the Eocene (high-pressure metamorphic
terrane, ultramafic nappe and Loyalty Ridge) have their own endemics.

 

Main conclusions New Caledonia is not simply a fragment of Gondwana but,
like New Zealand and New Guinea, is a complex mosaic of allochthonous
terranes. The four New Caledonian basement terranes were all formed from
island arc-derived and arc-associated material (including ophiolites)
which accumulated in the pre-Pacific Ocean, not in Gondwana. They
amalgamated and were accreted to Gondwana (eastern Australia) in the
Late Jurassic/Early Cretaceous, but in the Late Cretaceous they
separated from Australia with the opening of the Tasman Sea and break-up
of Gondwana. An Eocene collision of the basement terranes with an island
arc to the north-east - possibly the Loyalty Ridge - is of special
biogeographical interest in connection with New Caledonia- central
Pacific affinities. The Loyalty-Three Kings Ridge has had a separate
history from that of the Norfolk Ridge/New Caledonia, although both now
run in parallel between Vanuatu and New Zealand. The South Loyalty Basin
opened between Grande Terre and the Loyalty Ridge in the Cretaceous and
attained a width of 750 km. However, it was almost completely destroyed
by subduction in the Eocene which brought the Loyalty Ridge and Grande
Terre together again,

after 30 Myr of separation. The tectonic history is reflected in the
strong biogeographical differences between Grande Terre and the Loyalty
Islands. Many Loyalty Islands taxa are widespread in the Pacific but do
not occur on Grande Terre, and many Grande Terre/Australian groups are
not on the Loyalty Islands. The Loyalty Islands are young (2 Myr old)
but they are merely the currently emergent parts of the Loyalty Ridge
whose ancestor arcs have a history of volcanism dating back to the
Cretaceous. Old taxa endemic to the young Loyalty Ridge islands persist
over geological time as a dynamic metapopulation surviving in situ on
the individually ephemeral islands and atolls found around subduction
zones. The current Loyalty Islands, like the Grande Terre terranes, have
inherited their biota from previous islands. On Grande Terre, the
ultramafic terrane was emplaced on Grande Terre in the Eocene (about the
same time as the collision with the island arc). The very diverse
endemic flora on the ultramafics may have been inherited by the
obducting nappe from prior base-rich habitat in the region, including
the mafic Poya terrane and the limestones typical of arc and intraplate
volcanic islands.

 

 

Dr. John R. Grehan

Director of Science

Buffalo Museum of Science1020 Humboldt Parkway

Buffalo, NY 14211-1193

email: jgrehan at sciencebuff.org

Phone: (716) 896-5200 ext 372

 

Panbiogeography

http://www.sciencebuff.org/biogeography_and_evolutionary_biology.php

Ghost moth research

http://www.sciencebuff.org/systematics_and_evolution_of_hepialdiae.php

Human evolution and the great apes

http://www.sciencebuff.org/human_origin_and_the_great_apes.php

 

 




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