dedocta said:
For that matter, what role did invasive species play in the Great Dying?
The Great Dying usually refers to the
end of the Permian when huge numbers of both marine and terrestrial species went extinct:
The
Permian–Triassic extinction event, also known as the
P–Tr extinction,
[2] the
P–T extinction,
[3] the
End-Permian Extinction,
[4] and colloquially as the
Great Dying,
[5] formed the boundary between the
Permian and
Triassic geologic periods, as well as between the
Paleozoic and
Mesozoic eras, approximately 252 million years ago. It is the
Earth's most severe known
extinction event, with up to 96% of all
marine species[6][7] and 70% of
terrestrial vertebrate species becoming
extinct.
[8] It was the largest known mass extinction of
insects. Some 57% of all
biological families and 83% of all
genera became extinct.
Probably the most favored candidate for a cause of the end Permian extinction is super massive volcanic eruptions (the Siberian Traps), which would have modified the atmosphere by releasing large amounts of gases.
Pangea (a single large continent, instead of several separated continents as we have now) had already formed during the Permian and therefore is not a good candidate for the extinction cause.
The formation of Pangea is thought to have had effects on species, but not to such a great effect.
By putting all the land together, climate patterns were changed and particular environments reduced or eliminated. Different species could have been outcompeted the continents came together, but it would seem to be a much smaller effect then the end Permian extinction was. There was less shoreline (a productive area) and a dry interior in the giant continent. Shore between continents went away as they merged.
(This reminds me of a bumper sticker I saw recently: "
Reform Pangea!")
In general, more ancient species, which originated earlier can persist in
refugia where more recently evolved species (presumably more more adaptive in some way) are not able to access (geographically or otherwise).
In biology, a
refugium (plural:
refugia) is a location which supports an isolated or
relict population of a once more widespread species.
The common underlying idea would be that older, in some way less adaptive, animal designs that originated first were less adaptive in some way and would be replaced by newer, more efficient or adaptable designs, which evolved later in other places could have out competed them if they could have gotten to their location.
There are many
examples of continental scale refugia.
An understanding of when various continents were in different places, is informative about the timing of these events:
Extinctions can come in different sizes and result from different causes.
A species invading a new area might kill off an native species in some way (predation, out competing for resources).
An invading species (or other cause, like environmental changes) might also cause the indirect death of many species but braking the the function of the ecosystem in some way (and thus the flow of energy through the interacting network of organisms in an environment). Taking out a single "
keystone species" in some way might effect an whole environment (many species).
Something like the Chicxulub impact that ended the dinosaurs would very rapidly completely destroy local environments and kill species and ecosystems directly. (The rapidity of this extinction event is usual among large extinctions.) But it also had significant short term and long term global environmental consequences.
Large volcanic eruptions would probably be similarly global, but with a slower time course.
