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| Great Australasian Interchange | |
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| Topic Started: Jun 6 2014, 02:37 PM (3,540 Views) | |
| Spugpow | Jun 6 2014, 02:37 PM Post #1 |
Prime Specimen
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Australia is currently on a collision course with Eurasia, and, judging from similar situations in the past, this is bad news for its native fauna. The Great American Interchange was an event precipitated by the formation of the Isthmus of Panama 3 million years ago, in which the Laurasian fauna of North America largely displaced the native animals of the island continent South America. The coming faunal exchange between Australia and Asia has been anticipated by the introduction of non-native species by humans, and generally alien species have outcompeted native ones. But the American interchange wasn't entirely one-sided. A few marsupials, xenarthrans and caviomorph rodents successfully made their way into North America. Similarly, the expansion of native Australian clades like corvids in the past belies the idea that native species always lose. So the question is, assuming humans don't do much more damage than they already have, what is the fauna of Australia going to look like a few million years after colliding with Eurasia? Which native species might survive or even colonize the larger landmass? http://en.wikipedia.org/wiki/Great_American_Interchange  Edited by Spugpow, Jun 6 2014, 02:39 PM.
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| JaggerTheDog | Jul 19 2014, 08:01 AM Post #46 |
I will kill you whilst you sleep
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Well anthropic ungulates are very common on Asia. |
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| Hananas59 | Jul 19 2014, 08:04 AM Post #47 |
Traveller of the imagination
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Still the whole group of ungulates could be affected by man , pollution , overhunting the extinction events and many more reasons. It's not that ungulates are invincable and marsupials aren't invincable too but yet I think marsupials would have a big chance when they get to the mainland. |
| Treading the line between imagination and reality | |
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| JaggerTheDog | Jul 19 2014, 08:14 AM Post #48 |
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I will kill you whilst you sleep
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But still they would be outcompeted, if they survive they would occupy small niches. |
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| Hananas59 | Jul 19 2014, 08:21 AM Post #49 |
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Traveller of the imagination
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Outcompeted by what ? I just said that ungulates will be there with just a species maybe 2 or 3 while the kangaroos also come with 3 species. If it came to a clash between 3 species of ungulates and 2 species of kangaroos and a few species of wallaby then I would think marsupials would be winning. |
| Treading the line between imagination and reality | |
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| JaggerTheDog | Jul 19 2014, 10:01 AM Post #50 |
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I will kill you whilst you sleep
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Nope. 
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| Zorcuspine | Jul 19 2014, 10:26 AM Post #51 |
Enjoying our azure blue world
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I could easily see the two groups coexisting. Kangaroos seem to be doing just fine despite competition from ungulates, which suggests they hold a different niche. |
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| LittleLazyLass | Jul 19 2014, 05:11 PM Post #52 |
Proud quilt in a bag
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I see no particular reason to put placentals above marsupials based on no past evens at all. Also, I see Jagger has a new avatar. Wonder were you got that.../sarcasm. |
totally not British, b-baka! You like me (Unlike)I don't even really like this song that much but the title is pretty relatable sometimes, I guess. Me What, you want me to tell you what these mean? Read First Words Maybe | |
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| MitchBeard | Jul 20 2014, 05:31 AM Post #53 |
proud gondwanan
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There's actually a little bit of fossil evidence subtly hinting that placentals WERE on Australia when it split away from Antarctica. So oh my gosh, it's almost like it was the luck of the draw that placentals won out in the northern hemisphere. Holy Bajingos. I outright reject the hypothesis that placentals will outcompete marsupials simply because "placentals are better". There is no correlation between the introduction of placental mammals into Australia and population size or distribution of kangaroos. That's not for the lack of competition either; Australia has established feral populations of rabbits, goats, pigs, three species of deer, donkeys, horses, water buffalo and camels. The Australian government still undertakes regular culls of kangaroos, because populations get out of control. Kangaroos aren't going anywhere. Deal with it. |
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| JaggerTheDog | Jul 20 2014, 05:48 AM Post #54 |
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I will kill you whilst you sleep
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But what happens if Australia fuses with Southeast Asia, thus the climate in Australia will change rapidly. |
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| MitchBeard | Jul 20 2014, 06:01 AM Post #55 |
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proud gondwanan
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Yes, I know that Australia's climate will change. This is thing that I am taking fully into account as I think about this hypothetical situation. Also, it's not a matter of it, but when. Australia will fuse with Southeast Asia. It'll happen somewhere between 10 and 20 million years from now. As Australia moves north, coastal western Australia is becoming increasingly arid. It's something that you can plot on a map right now. The southwest tip has a really unique flora, that you can find fossils for all up the coast, but as Australia has been moving north it has been becoming increasingly restricted to the south. Australia's arid areas are not going away any time soon. Extensive desert and hummock grassland ecosystems are going to persist right up to and including at time when Australia connects to the Afro-Eurasian continents. Also as Indo-Australian plate continues to push north to northwestish into the Eurasian plate, you'll end up with Indonesia and probably Papua New Guinea turning into a massive mountain range. And where there are mountain ranges, and where they are mountain ranges, there are rain shadows. Oh look, perfect to let arid zone dominators like large bodied macropod kangaroos into the old world. |
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| MitchBeard | Jul 20 2014, 06:11 AM Post #56 |
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proud gondwanan
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The other thing you need to consider, which is often taken for granted on this website, is the flora. Australia's flora are dominated by Eucalypts. Ecologically Eucalypts are essentially giant fire weeds. The only way you get regeneration of Eucalypt forests is if you burn it. Then you get all these beautiful little euccy seedlings popping their heads out of the ash. Eucalypt actively encourage fire with their oil rich leaves and by just constantly dropping heaps of fuel onto forest floors. Bush fire comes through, cleans it all up, burns out all the competition, unlocks heaps of nutrients and trace minerals which then soak back into the soil with the next rain, hooray for new baby euccy seedlings. Australian acacias also make use of bushfires. Lots of australian acacia seed can't actually germinate until it's been exposed to searing heat. This is one reason why Australian eucalypts and acacias have become so problematic overseas. They're giant fire weeds. Australian's fauna have evolved alongside them, and have adapted to cope with this. When Australia joins the Afro-Eurasian party, Australia's lovely pyromanical flora is going spread like wildfire throughout the rest of the world, and some of the more successful groups of Australia's fauna are going to be following along after it. |
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| JaggerTheDog | Jul 20 2014, 06:46 AM Post #57 |
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I will kill you whilst you sleep
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The production of marsupial milk is also costly, as is the digestion of it within the fetus' belly. A placental mother wastes no energy passing nutrients to baby. The placenta provides the pathway to nourishing the embryo, meaning they reach a higher level of maturity prior to birth.
Edited by JaggerTheDog, Jul 20 2014, 06:51 AM.
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| JaggerTheDog | Jul 20 2014, 06:57 AM Post #58 |
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I will kill you whilst you sleep
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So you are basically saying that Australian organisms are basically superior compared to their relatives overseas, yet placentals still survive and thrive in Australia and kinda coexist with the native marsupials. You have to admit, cats, dogs and some other placentals pose a great threat to some of the native fauna, they kill native birds, and the "smaller" marsupials. |
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| MitchBeard | Jul 20 2014, 07:11 AM Post #59 |
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proud gondwanan
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I am by no means calling it a one sided fight. Marsupials are not going to come out on top. Dasyurids and Bandicoots are going to get their butts handed to them, all I'm saying is that marsupials are going to disappear outright. I know Australia is becoming wetter as it moves north. But anthropic climate change also means that swings between wet and dry periods are going to become more extreme. Animals, like macropods, have exaptations that will allow them to deal with this. This doesn't mean that Australia is going to be completely wet washed though. Australia is by no means a small place, there is still going to be vast swathes of arid and semi-arid environment. And there will be a significantly large mountain range. That's what happens when two continents collide. Every. Single. Time. A lot of marsupial species are taking a hit at the moment because of habitat degradation/destruction and the introduction of invasive species. But their are plenty of species that are THRIVING under the new regime. I am also aware of cuscus disribution throughout wallacea, but this isn't because of competition with placental mammals. Their current distribution if due to geographical barriers. WoooOOOOoooOOOoooo oogy boogy pouch rearing is inefficient. Plancental mammals have a much greater limit on how many offspring they can be producing throughout their lifetime, Marsupials can churn through a lot more young by setting up a backlog. Growing an enormous foetus inside your body puts the mother in an incredible amount of risk during pregnancy. Oh shit, my tiny peanut baby was stillborn, oh well. Marsupials will also turf their young out of their pouch if they're in a life or death interaction with a predator. I'll say it again. Marsupials are NOT going to go extinct outright when Australia connects with Afro-Eurasia. |
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| MitchBeard | Jul 20 2014, 07:18 AM Post #60 |
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proud gondwanan
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I'm not saying they're superior at all. I'm just trying to get across that they're not as inferior as most people seem to think they are. Australia has a broad suite of incredible organisms that are amazingly adapted to the driest inhabited continent with the poorest soils in the world. Australia isn't this doddery little island full of animals and plants that only survive there because the big bad placentals couldn't be bothered with it. Australia's flora and fauna are incredible, diverse, adaptable and above all enduring. Edited by MitchBeard, Jul 20 2014, 07:19 AM.
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