Plate Tectonics and Evolutionary Pressure

  • Thread starter Thread starter dedocta
  • Start date Start date
  • Tags Tags
    Plate Pressure
Click For Summary

Discussion Overview

The discussion explores the relationship between plate tectonics, continental mergers, and their potential impacts on ecosystems, particularly in the context of extinction events like the Great Dying and the evolution of marsupials and placental mammals. Participants examine historical and biological factors influencing species survival and competition.

Discussion Character

  • Exploratory
  • Debate/contested
  • Conceptual clarification

Main Points Raised

  • Some participants propose that continental mergers could lead to significant ecological disruptions, potentially resulting in mass extinctions similar to the Great Dying.
  • Others argue that the formation of land bridges, such as that between North and South America, had notable effects on species distributions, erasing endemic species like Thylacosmilus.
  • A participant questions the simplistic view that the absence of placental mammals allowed marsupials to thrive in Australia, suggesting that multiple factors must be considered.
  • There is a hypothesis that placental mammals may have competitive disadvantages for marsupials, but this is contested and not universally accepted.
  • Some participants clarify the classification of mammals into monotremes, marsupials, and placentals, discussing evolutionary implications and terminology differences.
  • Discussion includes the historical presence of placental mammals in Australia and their eventual repopulation, with debates on the impact of these species on marsupial survival.

Areas of Agreement / Disagreement

Participants express multiple competing views regarding the effects of continental mergers on ecosystems and the interactions between marsupials and placental mammals. The discussion remains unresolved, with differing opinions on the significance of these factors.

Contextual Notes

Participants acknowledge the complexity of ecological interactions and the need for nuanced understanding of historical events and species dynamics. Some claims are based on hypotheses rather than established facts, and definitions of terms like "higher mammals" vary across regions.

dedocta
Messages
11
Reaction score
3
I used to work with invasive species in the early 2000's. I saw firsthand the damage a single invasive species can wreak on an ecosystem (Emerald Ash Borer among other insects.)

After watching videos of plate tectonics, I began to wonder what would happen to ecosystems on large scales during continental mergers. Would this not lead to some sort of great dying? For that matter, what role did invasive species play in the Great Dying?
 
Earth sciences news on Phys.org
dedocta said:
Would this not lead to some sort of great dying?
The then new land bridge between North and South America erased the marsupials in the South, especially Thylacosmilus. It also erased other endemic mammals placentalia.
 
Last edited:
  • Like
Likes   Reactions: dedocta and BillTre
Is this why Australia has so many marsupials?
 
dedocta said:
Is this why Australia has so many marsupials?
This is too simple. You cannot say for sure that the absence of one kind allowed the other to thrive. One has to look at single cases and which other factors play a role, e.g. size, nutrition, etc., if there is an alternative mammal placentalia at all. But given that nearly all marsupials outside the southern hemisphere went extinct, it's probably a valid hypothesis that mammals placentalia are bad for marsupials. But it is not obvious at all, E.g. there is a wild population of kangaroos in Europe. They survived a couple of years. Time will tell whether they will vanish again. It probably will depend on the population of wolves.
 
Last edited:
  • Like
Likes   Reactions: 256bits, BillTre and dedocta
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.
 
Last edited:
  • Like
Likes   Reactions: 256bits and jim mcnamara
fresh_42 said:
, it's probably a valid hypothesis that mammals are bad for marsupials

Huh ? Last time I looked ALL marsupials ARE mammals

what did you really mean to say ? :smile:
 
davenn said:
Huh ? Last time I looked ALL marsupials ARE mammals

what did you really mean to say ? :smile:
I haven't found the correct word for "uterus animals". Should have been placentalia, sorry.
Corrected now.
 
Last edited:
  • Like
Likes   Reactions: davenn
There are three major groups of mammals:
  • the Monotremes: egg layers like the platypus and echidna (hedgehog), maternal nourishment from the egg yolk
  • the Marsupials: egg develops inside mom until something like a fetus stage, after birth, they latch onto a nipple and gain material nourishment that way
  • the Placentals: born at much later more developed stage, gain maternal nourishment through the placenta.
 
  • Informative
Likes   Reactions: davenn
BillTre said:
There are three major groups of mammals:
  • the Monotremes: egg layers like the platypus and echidna (hedgehog), maternal nourishment from the egg yolk
  • the Marsupials: egg develops inside mom until something like a fetus stage, after birth, they latch onto a nipple and gain material nourishment that way
  • the Placentals: born at much later more developed stage, gain maternal nourishment through the placenta.
Yes, I ran into "lost in translation", since the placentalia are called "higher mammals" here.
 
  • #10
fresh_42 said:
Yes, I ran into "lost in translation", since the placentalia are called "higher mammals" here.
They (Placentals) were the most recently derived in evolution.
Derived means changed from the previous more ancestral (often called primitive) versions.
"Higher" is a old-ish term (derived from a more linear view of evolutionary changes) meaning about the same thing in relation to a previously evolved form (Marsupials).
 
  • #11
fresh_42 said:
But given that nearly all marsupials outside the southern hemisphere went extinct, it's probably a valid hypothesis that mammals placentalia are bad for marsupials.

Not really. There have been placentalia in Australia long ago but they lost to the marsupials.
 
  • Skeptical
Likes   Reactions: davenn
  • #12
DrStupid said:
There have been placentalia in Australia long ago but they lost to the marsupials.

There are placental mammals in Australia today. Seen 'em myself. Bats. Big ones too.
 
Last edited:
  • Like
Likes   Reactions: davenn
  • #13
Vanadium 50 said:
There are placental mammals in Australia today. See 'em myself. Bats. Big ones too.

The original Australian placentalia died out around 20 million years ago. Than Australia has been repopulated with placental mammals in the last 5 million years. The Australian marsupial fauna never disappeared - with and without placentalia on the continent.
 
  • #14
Well, I wouldn't mess with these bats even if I were a sabre-toothed wombat.
 
  • Like
Likes   Reactions: davenn
  • #15
DrStupid said:
The original Australian placentalia died out around 20 million years ago. Than Australia has been repopulated with placental mammals in the last 5 million years. The Australian marsupial fauna never disappeared - with and without placentalia on the continent.
I just saw a documentary about it today. Is it correct that all they have is one tooth from a placentalia? This proves existence, but isn't very convincing that there had been a significant population. They said, but this was my suspicion anyway, that the climate combined with the capability to time birth were the two major factors why marsupials were (are) favored in Australia.

The real competition between the two took place in South America.
 
  • #16
Vanadium 50 said:
Well, I wouldn't mess with these bats even if I were a sabre-toothed wombat.
And not to mention messing with this other big population of placentialia.
 
  • #17
fresh_42 said:
Is it correct that all they have is one tooth from a placentalia?

I don't think so. To my knowledge there are a lot of bat fossils. Maybe they have a single tooth from a placentalia that was not a bat. But I'm not an expert.

fresh_42 said:
They said, but this was my suspicion anyway, that the climate combined with the capability to time birth were the two major factors why marsupials were (are) favored in Australia.

Yes, that's the usual explanation.
 
  • #18
The interesting part was the explanation why koalas (have to) look like teddy bears.
 
  • #19
Vanadium 50 said:
Well, I wouldn't mess with these bats even if I were a sabre-toothed wombat.

I wouldn't mess with a tasmanian devil neither.
 
  • Like
Likes   Reactions: f95toli
  • #20
DrStupid said:
The Australian marsupial fauna never disappeared - with and without placentalia on the continent.
We are placentalia, and we are still causing the biggest extinction event in the last 100 ka in Australia.
 
  • Like
Likes   Reactions: BillTre
  • #21
Too many claims, too few citations. Next claim like that gets this thread shut down. Thank you.