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Research shows that pre-extinction disruption of food webs makes ecosystems more fragile, susceptible

Jonathan Mitchell, a Ph.D. student on the University of Chicago's Committee on Evolutionary Biology, Peter Roopnarine of the California Academy of Sciences, and Kenneth Angielczyk of the Field Museum have collaborated to produce a fascinating simulations-based analysis of the factors that helped dinosaurs go extinct en masse at the close of the Cretaceous era.

The authors used a food web program they wrote, which looked at dozens of species.  They looked to lay to rest debates about dinosaurs' diet (e.g. did T. rex eat Triceratops, Duck-Billed dinosaurs, or a mixture of both?) by carrying out a number of simulations with each possibility considered.  A total of 17 food webs, based on species alive at the time, were inspected

What they found was that the precise diet of dinosaurs mattered less than the relative diversity of one ecosystem versus another.  Comments Professor Angielczyk, "Using modern food webs as guides, what we have discovered is that this uncertainty is far less important to understanding ecosystem functioning than is our general knowledge of the diets and the number of different species that would have had a particular diet."

The researchers suggest that climate change in the Cretaceous led to a number of changes, including the drying of a sea in North America.  The net result was a loss of diversity.

Creataceous food web
Lower food web diversity made the dinosaurs more vulnerable to mass-extinction a new study claims. [Image Source: PNAS]

This meant that while the ecosystem was still flourishing, it was respectively more fragile than its equivalent, 13 million years before the meteorite impact at Chicxulub on the Yucatan Peninsula.  Comments Mr. Mitchell, "The ecosystems collapsed because of the asteroid impact, and nothing in our study suggests that they would not have otherwise continued on successfully.  Unusual circumstances, such as the after-effects of the asteroid impact, were needed for the vulnerability of the communities to become important."

In fact, the authors argue that the dinosaurs would likely have survived the calamity, had the meteorite hit 13 million years earlier, during the period of greater diversity.

Meteorite
If the meteorite hit 13 million years earlier, the dinosaurs might not have gone extinct.
[Image Source: D. Davis]

The authors say their analysis provides cautionary hints to help assess current ecosystems for vulnerability.  States Professor Rooparine, "Besides shedding light on this ancient extinction, our findings imply that seemingly innocuous changes to ecosystems caused by humans might reduce the ecosystems' abilities to withstand unexpected disturbances."

However, the authors are also careful to note that their study did not indicate more species was a significant safeguard; rather they argue it's the amount of genetic diversity across species that's important -- in other words, saving a lot of similar species may not help as much as conserving species that play unique roles in the ecosystem.

The study was published in the prestigious peer-reviewed journal Proceedings of the National Academy of Sciences (PNAS).

Sources: Eurekalert, PNAS



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RE: Ignorance perpetuates
By conquistadorst on 10/30/2012 3:21:41 PM , Rating: 4
Yes folks, and that's why there aren't any species of animals that lay eggs on the ground today. It's because of those mammal egg-stealing whippersnappers. That's also why there aren't any mammals that can climb trees, it's too hard for mammals to do that and evolution is unable to find a way to help them. It's a proven fact that eggs in high places cannot be reached.

I assure you, absolutely no dinosaurs were harmed by the meteor that hit our Earth 65 million years ago and created a 180km crater. Absolutely none! You know, the 1000m high tsunamis, blotting out the sun from the sky disrupting photosynthesis for months, globally igniting wild fires, earthquakes, and volcanoes. That's all child's play, no effect on dino mortality!


RE: Ignorance perpetuates
By retrospooty on 10/30/2012 3:47:46 PM , Rating: 1
I don't think you are understanding the point. Populations were already on the decline, severely when it hit... Therefore the effect was extinction. Had there been higher #'s with the conditions that existed millions of years prior, it probably would not have led to extinction.


RE: Ignorance perpetuates
By conquistadorst on 10/30/2012 4:10:40 PM , Rating: 2
No, I followed his point and I was poking fun at it. He bluntly said:

quote:
Dinosaurs didnt die because of a meteor.


You also cannot simply take a line graph and extrapolate it over time and say "yes, definitely extinction due to egg stealing. No other plausible explanation. Everyone else is ignorant tee hee!". That's not even science. And yes, it's certainly plausible it was the culmination of many events together that led to their extinction. But that was certainly not what he said.


RE: Ignorance perpetuates
By retrospooty on 10/30/2012 5:37:27 PM , Rating: 2
ok... I was more referring to the fact that population was already declining, that they can tell. How and why could be debatable/


RE: Ignorance perpetuates
By docinct on 10/30/2012 5:36:03 PM , Rating: 2
"That's also why there aren't any mammals that can climb trees"
I assume that is a joke otherwise the lemurs, squirrels, rats, possums, mice, gibbons, etc. of the world will be insulted.


RE: Ignorance perpetuates
By Azethoth on 10/30/2012 7:39:12 PM , Rating: 2
No it is not a joke. It is sarcasm. May as well be sarcastic since the OP is either trolling or a special brand of ignorant.


RE: Ignorance perpetuates
By conquistadorst on 10/30/2012 8:10:36 PM , Rating: 2
quote:
I assume that is a joke otherwise the lemurs, squirrels, rats, possums, mice, gibbons, etc. of the world will be insulted.

Yes it was most certainly trying to drown it in sarcasm. I was mocking the OP and pointing out just how preposterous his theory sounds where walking dinosaur's went extinct just because mammals were so good at stealing their eggs. Perhaps I didn't make my reply as painfully obvious as I had thought.


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