|3. Trans-Pacific Biotic Disjunctions
The precise regions that unite along the matching outlines
(e.g. Tasmania and South-central Chile) share hundreds of
poor-dispersing sister taxa found nowhere else in the world.
The following are just a few of the biogeographical
problems that this presents to plate tectonics:
|3a. These taxa cannot cross oceans.
Countless narrow-range, sister taxa that are rejoined in expanding
Earth paleomaps are separated by vast oceans in plate tectonics.
These taxa include purely freshwater fish; terrestrial vertebrates;
shallow, bottom dwelling marine taxa that cannot survive in the
deep ocean; weakly-flying birds; even lumbering dinosaurs.
Not only would all of these taxa have to manage a jump-dispersal
event across the full-breadth of a superocean -- a feat otherwise
unknown in these types of organisms -- they then would have had
to never end-up anywhere else. For some reason, the taxa would
have had to prefer jaunts between regions that were juxtaposed on
expanding Earth paleomaps. To mention one of hundreds of
examples: the closest relatives of the Fijan banded (right) occur in
California and Mexico. No other iguanas inhabit any other island in
the Central or West Pacific.
|3b. The Oceanic Island /Wide-Ranging Problem
Taxa that are able to cross large marine gaps are
wide-ranging and appear on other oceanic islands.
For example, all species of plants on Pitcairn are from
wide-ranging ancestors, distributed throughout the Pacific.
Pitcairn, unlike New Zealand, does not exclusively share
any plant with South America -- even though Pitcairn is
roughly half as far away from S. America as New Zealand.
Quite simply, taxa that can reach remote oceanic islands
can reach nearer ones too. This empirically challenges
hypotheses of cross-ocean dispersal currently used to
explain narrow-range, trans-Pacific biotic disjunctions.
In other words, if the poor-dispersing taxa shared by South
America and New Zealand, New Caledonia, and Fiji really
are capable of cross-ocean dispersal, they should appear on
at least a few of the 25,000 other islands in the Pacific, and
they do not.
|3c. The Ancient Island Problem
Of more than 25,000 islands in the Pacific, only three
are old enough to have once been in proximity with
South America according to expanding Earth
paleomaps: New Zealand, New Caledonia, Fiji. All
problematic disjunctions of narrow-range taxa occur on
those three islands -- or the more ancient continental
regions of Australia, New Guinea and Indonesia. None
of the other islands in the Pacific boast problematic
disjunctions of poor-dispersing taxa with the Western
Americas. (Hawaii, which is merely 3900 km from the
nearest continent, has no native, non-volant terrestrial
vertebrates at all -- let alone all from one particular
narrow region 7000 km away.)
|Coming soon: The Mozambique Channel and the Torres Strait provide a more
significant barrier to dispersal than Panthalassa; all arguments used by Wegener are
also valid for the Pacific; Index of similarity analyses from the Upper-Triassic.