New Zealand-Antarctic land bridge?

John Grehan jgrehan at SCIENCEBUFF.ORG
Wed Sep 15 08:56:56 CDT 2004

I could not resist the temptation to comment (I need to get a life). 

> Behalf Of Ken Kinman
It struck me as a strange coincidence that
> Macquarie Island (a sub-Antarctic island) supposely arose from the
> very soon afterwards.   

The island's emergence was probably strangely coincident with many other
terrestrial and extra-terrestrial events.

In my own (admittedly) peculiar way of looking at
> things, I can't help but wonder if forces which triggered Macquarie
> Island's thrust UPWARDS (whatever they were) could have also caused
> existing islands or even whole archipelagos (in this same highly
> fault zone) to have been thrust DOWNWARDS into the ocean.

In the normal run of geological affairs (asteroids aside) that would not
be unexpected.
>      What I am getting at is that a much more complete series of
> and/or archipelagos could have connected New Zealand and Antarctica
> MORE recently than we dared to imagine.  

Imagination is the right word. Anything is possible in the unknown.

Not that direct faunal and floral
> terrestrial interchange would have occurred as late as 780,000 years
> but certainly that a slightly broken land bridge could have existed in
> Miocene or even Pliocene.  

Whether or not there was once a more extensive archipelago the islands
would not necessarily function as a 'land bridge'.

Even if Antarctica completely froze over in the
> Miocene (with no surviving pockets of an ancient Antarctic flora or
> fauna), a warm period could have reopened an Antarctic corridor for
> limited faunal and floral interchange between southern South America
> New Zealand sometime in the Miocene or Pliocene.   Is it unreasonable
> contemplate such a possibility?

In the dispersalist world one may contemplate any possibilities. That is
generally what dispersalists do. For example, if one imagines a species
spreads at 10 meters each year then once can imagine that it will cross
the world in x years. If one imagines dispersal ability as the key to
biogeography then one imagines land bridges. As for Macquarie, other
islands in the region have been shown to have biogeographic elements
spatially correlated with Mesozoic tectonics (Craw, 1989). So all
imagination aside, one could say that the biota of this island was
inherited locally with an evolutionary continuity extending back to
Mesozoic times. In addition, the presence of incongruent tracks suggests
other factors for some elements, so one does not need to imagine
asteroids or other such events to consider the possibility of
interisland dispersal for some of the island's biota.

John Grehan

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