Australia fact of the day

Comments

I find that hard to believe. Australia was part of Antarctica until about 55M years ago, well after when Archaeopteryx developed in the late Jurassic.

Read it & weep Ray Lopez:

https://www.timlow.com/where-song-began/

;)

@Ray, can you grasp the magnitude of 55 million years? Basically Antarctica was a rainforest until ~34 million years ago.

The science journalism version of the topic https://www.bbc.com/news/science-environment-12378934

The science version of the topic https://science.sciencemag.org/content/352/6281/34

Murdered with words.

Aside from the tectonic issues, there's a phylogenetic issue with your statement. The fact that a bird (not even the oldest one) evolved before Australia split from Antarctica in no way proves that THESE birds didn't all evolve from an Australian species. Perching birds are distinct from, say, emus, and it's not only plausible but likely that the younger clades evolved away from where the ultimate ancestor evolved. For why, look up allopatric speciation.

In contrast, Australia's land animals aren't very competitive on the world stage, and are in danger from outside competition like dogs and cats.

But eucalyptus trees tend to do very well for themselves in many parts of the world, taking over ecosystems where they are introduced.

Er, yes, Australian land animals definitely haven't caused all sorts of problems in places like New Zealand or Guam. Maybe some mild infestation by brushtail possums or brown tree snakes, but nothing to write home about. Not after a snake has swallowed your pen at least.

In Australia there are all sorts of creatures that have adapted to living off eucalypts but overseas they leave them all behind and so can do very well as the local pests aren't adapted to them.

"Er, yes, Australian land animals definitely haven't caused all sorts of problems in places like New Zealand or Guam."

Ah, yes, famous "world stage" locations New Zealand and Guam, which experienced even more fierce and widespread evolutionary competition than much smaller and less diverse Australia.

I don't think you get how this works. Organisms are involved in arms races with other organisms in an ecosystem. When an outside organism is introduced with characteristics other organisms haven't adapted to it can be very disruptive and become an "invasive species". It doesn't depend on "evolutionary competition". That applies to everything. The kind of competition can matter. Dodos experienced "evolutionary competition" they just didn't have any pressure towards coping with predators and now there are no more dodos.

"Organisms are involved in arms races with other organisms in an ecosystem."

Not really true in most cases. In fact, when you look at biology as a whole you find cooperation dominates. Even apparently hostile organisms--predators and prey--often benefit each other in unexpected ways.

"When an outside organism is introduced with characteristics other organisms haven't adapted to it can be very disruptive and become an "invasive species". "

This is something I think we need to think a LOT more about. What we see in the past is that most species DO NOT become invasive species (defined as species that grow at uncontrolled or nearly uncontrolled rates and which cause large disruptions in the ecosystem). The invasion of South American fauna into North America, for example, did not cause the types of ecological disruptions we associate with invasive species.

I think the key here is how full the ecosystem is. What I mean is, if there's no niche for the new species to exploit--if it's competing with other organisms that are firmly established--than it cannot become invasive. Armadillos are competing with raccoons, opossums, and a host of rodents, and therefore have a check against becoming invasive. Kudzu, on the other hand, has no such check, as it exploits an opening in the ecosystem (specifically a lack of foraging organisms). That we're seeing invasive species today is probably indicative, if not diagnostic, of the fact that we are in a mass extinction.

This is why I think the failure of marsupials to invade most territory in the Pacific is mostly due to historic contingency. They DID succeed in invading North America, but most of the megafauna was wiped out and they went along with it. And if the Australian organisms tried to invade areas with robust ecosystems there'd be no room for them.

Think of it this way: When Leaf Ericson arrived in the Americas the natives had a robust civilization and there was no room for the Vikings. They had a few outposts but were not able to establish themselves, because the area was already occupied. When Europeans tried it a few hundred years later they brought diseases with them such as smallpox. Once the diseases wiped out the native population there were ample niches for the Europeans to occupy. It has nothing to do with relative robustness of either group; it has to do with what niches are available.

"Dodos experienced "evolutionary competition" they just didn't have any pressure towards coping with predators..."

Other way 'round. They had too much pressure. The selection pressure exceeded their ability to adapt.

What really boggles the mind, once you start to grasp that concept, is that Africa retains its Pleistocene fauna despite being the cradle of humanity.

We can re-phrase Steve's point as monotremes and marsupials seem to do less then than placental mammals. Some possum-like creatures are entrenched South America, but there are no other species becoming going invasive like the Eucalyptus is.

I can't judge if that theory is right. People plant trees in their gardens from all kinds of places, but introducing new mammals (other than ones that live with us) is usually more deliberate. For all I know, kangaroos might compete quite well with deer if they were introduced onto other continents.

I would say it's wrong. If you'd been asking the same question 15,000 years ago you'd think South American marsupials were taking over, with multiple invasions of sloths, glyptodons, and the like.

Instead of an article based on the press release, why not simply cite the press release? - https://news.ufl.edu/2019/03/movement-of-the-worlds-perching-birds/

Or just skip both, and link to the actual research - https://www.pnas.org/content/116/16/7916

Then, the real Australia fact of the day is its geographical location in the last 50 million years or so, plus the location of the other continents in relation to it. Along with awareness of this, particularly in regards to land bridges and plate tectonics - https://en.wikipedia.org/wiki/Wallacea

“Why not?” Well, one might be forgiven for thinking, it’s HIS blog.

Comments for this post are closed