[Taxacom] Recent advances in New Caledonian biogeography

John Grehan calabar.john at gmail.com
Sat Dec 8 21:15:37 CST 2018


For anyone interested in the following article you can obtain a copy from
me or the author.

Heads, M.J. 2018. Recent advances in New Caledonian biogeography.
Biological Reviews. https://doi.org/10.1111/brv.12485

I think it provides an excellent example of why, for New Caledonia, one
might wish to imagine chance dispersals, but one really does not need to.
There is a very nice tie in with tectonics that does not create the
anomalies of chance dispersal. The paper also draws attention to the irony
that geology shows no stratigraphic evidence of complete submersion at any
one time and that geological studies cited by some biogeographers in favor
of complete submersion did not. Of the six 6 geological papers cited only
two suggested complete submersion and of these neither discussed the idea
at all or provided any evidence for it. In contrast the fact based parallel
between biogeography and tectonics is extensive and compatible with
vicariance. Chance dispersal just does not enter into the picture. If one
wants to invoke it, then fine, but why bother? There is also a nice summary
of metapopulation biogeography as an alternative to the traditional ‘island
biogeography’. Whatever your stand on such matters, you will likely find a
lot to consider in this paper.

ABSTRACT
The biota of New Caledonia is one of the most unusual in the world. It
displays high diversity and endemism, many peculiar absences, and far-flung
biogeographic affinities. For example, New Caledonia is the only place on
Earth with
both main clades of flowering plants – the endemic Amborella and ‘all the
rest’, and it also has the highest concentration of diversity in conifers.
The discovery of Amborella’s phylogenetic position led to a surge of
interest in New Caledonian
biogeography, and new studies are appearing at a rapid rate. This paper
reviews work on the topic (mainly molecular studies) published since 2013.
One current debate is focused on whether any biota survived the marine
transgressions of
the Paleocene and Eocene. Total submersion would imply that the entire
fauna was derived by long-distance dispersal
from continental areas since the Eocene, but only if no other islands (now
submerged) were emergent. A review of
the literature suggests there is little actual evidence in geology for
complete submersion. An alternative explanation for
New Caledonia’s diversity is that the archipelago acted as a refugium, and
that the biota avoided the extinctions that occurred in Australia. However,
this is contradicted by the many groups that are anomalously absent or
depauperate in
New Caledonia, although represented there by a sister group. The anomalous
absences, together with the unusual levels of endemism, can both be
explained by vicariance at breaks in and around New Caledonia. New
Caledonia has always
been situated at or near a plate boundary, and its complex geological
history includes the addition of new terranes (by accretion), orogeny, and
rifting. New Caledonia comprises ‘basement’ terranes that were part of
Gondwana, as well as
island arc and forearc terranes that accreted to the basement after it
separated from Gondwana. The regional tectonic history helps explain the
regional biogeography, as well as distribution patterns within New
Caledonia. These include endemics on the basement terranes (for example,
the basal angiosperm, Amborella), disjunctions at the West Caledonian fault
zone, and great biotic differences between Grande Terre and the Loyalty
Islands.


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