Evolution - diversity?

[RC Tent]

Can we explain diversity - can evolutionary biology do it? - see link

Well established theories on patterns in evolution might be wrong

Any thoughts?

 

[PloverWing]

Cool! Graham Budd is a long-term internet friend of mine, and a Christian. I'm glad to see that he's making some interesting discoveries in his research.

 

[Job 33:6]

Can we explain diversity - can evolutionary biology do it? - see link

Well established theories on patterns in evolution might be wrong

Any thoughts?

I don't see anything wrong with having open discussions on how life may or may not have diversified over time.

When we look at the fossil succession, in conjunction with genetics, we see generally how diversification has unfolded throughout time. But the specifics of why certain events unfolded in certain ways, is always up for discussion.

A populations example commonly discussed is with relation to the mammalian radiation after the k-t extinction.

The iridium layer and Yucatan crater suggest a massive asteroid destroyed the dinosaurs at the end of the Cretaceous. But we also have Deccan traps volcanism and a decline in variety of dinosaurs leading up to the k-t boundary. So it's difficult to know precisely what killed the dinosaurs. We can only really guess a combination of things involving both and perhaps even more factors beyond that.

With the mammalian radiation thereafter, it would make sense if life then had an open world to move into, thereby resulting in an expanse of variation. Which seems to be suggested as a factor or possibility considered in the paper.

Beyond that, we have other concepts weighting in, such as how much of life is captured in the succession. With the Cambrian explosion, we have arthropod tracks predating the explosion, as well as a relatively high number of soft bodied fossils. There are also fossils of shellfish, corals, sponges and other life forms before the explosion was well. this suggests that life was indeed present prior to the Cambrian explosion itself, likely in large numbers. All of this not including the ediacaran and microshellies as well, such as cloudina and sinotubilites.

But the fossil record doesn't capture a plethora of arthropod fossils before the explosion, because soft bodied fossils are a rarity by nature of fossilization.

And so the record itself doesn't necessarily capture everything, leaving us just with the succession that we have, to work with, along with genetics, biostratigraphy, comparative anatomy etc.

And so holding discussions on rates of evolution and causes for radiations or biases in our numerical recognition of fossils, is always worth examining.

 

[The Barbarian]

We actually have labs for this, provided by nature. You see, there are often places that are largely inaccessible to various organisms, and we can see what happens when a lucky group of happen to make it there. Here's some examples:

Hawaiian fruit flies. Hawaii is geologically very recent, and it was never connected to any mainland. Although genetic tests indicate that all of them are descended from one of three unremarkable species of fruit flies, those three pioneer populations have diversified into over 800 species, taking niches normally occupied by other kinds of insects (which never made it to Hawaii).

So what's so special about Hawaii? Apparently, it's too far from anything to let most insects get there. So the flies rapidly diversified and became adapted to lots of other ways of life.

Marsupials in Australia Australian marsupials ended up stranded on Australia when the continent broke off and moved away from Antarctica and South America, before the advent of placental mammals. Neither could cross Wallace's line, so Australian fauna evolved apart from everything else.

So until men arrived, there were no canids. But thylacines evolved as a wolf-like carnivore, remarkably like a wolf. There were no ungulates, so large kangaroos evolved to fill the niche normally held by grazing ungulates.

Elsewhere, marsupials are pretty much different kinds of opossums.

Darwin's Finches Darwin's finches comprise a group of 15 species endemic to the Galápagos (14 species) and Cocos (1 species) Islands in the Pacific Ocean. The group is monophyletic and originated from an ancestral species that reached the Galápagos Archipelago from Central or South America. Descendants of this ancestor on the Archipelago then colonized Cocos Island.
On the Origin of Darwin's Finches

So one major source of diversity is niche availability. Founder populations, where many niches are open, will tend to diversify to take advantage of them.

This is the key, I think, to the "Cambrian Explosion." It coincided with the evolution of complete exoskeletons. This made it possible for organisms to adopt many different ways of getting food, protection, and space to live.

But we're just beginning to get some idea of the dynamics of such evolutionary changes. So perhaps this person will be able to contribute to that understanding.

 

[The Barbarian]

But the fossil record doesn't capture a plethora of arthropod fossils before the explosion, because soft bodied fossils are a rarity by nature of fossilization.

You are perhaps familiar with the Burgess Shale, which captures a huge number of organisms just at the beginning of the Cambrian. Because it was the result of a large underwater landslide, the organisms were buried in silt, which beautifully fossilized soft parts.

Gould's "Wonderful Life" is a great introduction to the Burgess fauna, although since that was published, a few corrections, such as the reconstruction of Hallucigenia, were made since then.

 

[Job 33:6]

You are perhaps familiar with the Burgess Shale, which captures a huge number of organisms just at the beginning of the Cambrian. Because it was the result of a large underwater landslide, the organisms were buried in silt, which beautifully fossilized soft parts.

Gould's "Wonderful Life" is a great introduction to the Burgess fauna, although since that was published, a few corrections, such as the reconstruction of Hallucigenia, were made since then.

Yes that's a good book. One of my favorites! But yeah...