Under certain circumstances evolution can be highly predictable, study shows

September 7, 2015, Liverpool School of Tropical Medicine

Researchers at Liverpool School of Tropical Medicine have shown that under certain circumstances evolution can be highly predictable, especially in terms of how creatures become resistant to dangerous toxins.

Biologists looking at the control of malaria have known for some time that mosquito populations often become resistant to insecticides designed to kill them, but in a paper published today in the journal PNAS, researchers examine the response of a variety of insects, reptiles, amphibians and mammals to a natural selection pressure in the form of cardiac glycosides - toxins produced by certain plants and toads for defence against predators.

Dr Nick Casewell, of LSTM's Alistair Reid Venom Research Unit, is one of the lead authors on the paper. Working with colleagues at the University of Liverpool and institutions in Australia and Israel, he has found that the evolution of toxin resistance in all of the different animals that eat these toxin-producing plants and toads is the result of highly similar molecular changes in one region of one particular gene, showing that responses to a selective challenge can lead to highly predictable evolutionary responses.

A fundamental debate within biology is whether evolution is unpredictable due the involvement of random variables, or can be constrained along predictable pathways. Convergent evolution, where similar changes occur in unrelated , plays a central role in that debate, but examples of convergence are rare at the molecular level and have previously been limited to groups of related species. However in this study it was found that, across all of the highly different animals studied, toxin resistance evolved because of two amino acid changes in a specific part of one gene. This particular gene produces a protein that is an essential component of the cardiac glycoside binding site, and the amino acid changes found in resistant species prevent the cardiac glycosides from binding and therefore being toxic. The fact that these changes are due to this natural selection pressure are further underlined by the reversal back to being susceptible to toxins in varanid lizards that have migrated to toad-free areas.

Dr Casewell said: "The repeatability of the process by which creatures from across the animal kingdom have become resistant to these toxins demonstrates that, in certain circumstances, evolution can be constrained along highly predicable pathways. Given the negative impact on in Australia following the introduction of the cane toad and the fact that toxic toads are now invading other toad-free biodiverse environments, our work could provide a simple method for testing the vulnerability of native species to invasive toxic toads. The repeatability of in this system will allow us to easily determine which species have the susceptible or resistant versions of the gene, thereby allowing conservationists to prioritise the protection of species at high risk and take preventative steps necessary."

Explore further: Invasive plant protects Australian lizards from invasive toad

More information: Widespread convergence in toxin resistance by predictable molecular evolution, www.pnas.org/cgi/doi/10.1073/pnas.1511706112

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14 comments

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PeterKinnon
1.6 / 5 (7) Sep 07, 2015
The evidence for directionality in nature's evolutionary machinery is overwhelming.

( But not for intentionality, with which it is often mistakenly conflated)

There is a very strong pattern of an overall increase in intricacy in the observed universe. T

A pattern traceable at least as far back as the formation of chemical elements in the first stars.

While inputs to the network are largely random, ratcheting mechanisms provide directionality.

In the case of biology, mutation is the primary random input and natural selection the ratchet.

Furthermore, as evidenced by the well documented phenomenon of convergence, there is a certain level of predictability in GROSS outcomes. An issue which is the main theme of my last book "The Intricacy Generator: Pushing Chemistry and Geometry Uphill"

A contention to which the reported experimental work lends support.
antialias_physorg
5 / 5 (6) Sep 08, 2015
The evidence for directionality in nature's evolutionary machinery is overwhelming.

No it is not. There are organisms that shed parts of their heritage as the environment allows (e.g. most all parasites)
Simplicity itself has, under certain conditions, an advantage. It allows an organism to reproduce with less energy expended i.e. faster - potentially outcompeting more complex forms. A good example are bacteria that cause acne: Splash on anti-acne cream and you're selecting for bacteria with thicker cell walls (eventually leading to a resistant population). Stop using the cream and the less hardier ones will resettle and eventually outbreed the others (since they require more of their time/energy to make these thick membranes).
There's many examples in larger animals where prey/predator relationships have gone in cycles from simple to complex back to simple.
verkle
Sep 08, 2015
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Torbjorn_Larsson_OM
5 / 5 (4) Sep 08, 2015
"The evidence for directionality in nature's evolutionary machinery is overwhelming."

I agree with antialias.

You equivocate on "machinery". 1. The organism machinery has mechanical directionality at times. 2. The evolution of organism machinery has no directionality as such, it is contingent the environment it learned from. 3. The evolutionary mechanisms has one with a local directionality - selection - but it can stall in cases (flat fitness landscapes). It has no more directionality than any other hill climbing mechanism has when it climbs.

Generally, large scale convergences are channeled by the environment, not by previous evolution as here. Say, in the cases of camera eyes or fish/whale/squid ovoid bodies. No other animal has converged on the elephant trunk say, there is nothing in the environment that constrains it.

[tbctd]
Torbjorn_Larsson_OM
5 / 5 (5) Sep 08, 2015
[ctd]

Also, there is an industry in pseudoscience convergent evolution claims. "Convergence has been associated with Darwinian evolution in the popular imagination since at least the 1940s." [ https://en.wikipe...ificance ]

******

The creationist troll has as per usual not read the article, since the research is contrasted to already known large scale (speciation scale) evolution of which there is, of course, overwhelming evidence already. And it isn't as if the discussed small scale changes are difficult to research, so overwhelmingly likely to be correct. (Though we have to wait for scientist responses if it _is_ correct.)

Trolls have to troll, and trolls have to lie. Nice way of showing that science is correct and religion is a bunch of lies propagated by a bunch of lying fools, I am sure the cult leaders are 'glad' for the 'help'.
docile
Sep 08, 2015
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docile
Sep 08, 2015
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PeterKinnon
1 / 5 (3) Sep 10, 2015
The evidence for directionality in nature's evolutionary machinery is overwhelming.

No it is not. There are organisms that shed parts of their heritage as the environment allows (e.g. most all parasites) ... etc, etc


Certainly, all this is well founded and, as such, is given due consideration in "The Intricacy Generator".

Nevertheless, although examples of such "retrograde" evolution are not uncommon, the overall characteristic of the evolutionary process is that of increasing intricacy, both in terms of structure and of diversity.

The network which comprises, for instance, a cow, is indubitably more intricate than that of a protozoan.

The intricacy of a chromium atom greater than that of the pre-stelliferous atoms, hydrogen helium or lithium.

This same general feature is found in all our observations, up to and including the evolution of technology.
PeterKinnon
1 / 5 (4) Sep 10, 2015
To address some of the more woolly comments on this subject which sink to level of "troll" accusations, I should perhaps suggest that such individual would perhaps benefit from a more careful analysis based upon the appreciation of the biological phase of the greater evolutionary process in terms of a network function rather than at the species level.

The general principle, of course, applies similarly at wider scales.
viko_mx
1 / 5 (3) Sep 10, 2015
@ PeterKinnon

Because your have overwhelming evidence for evolution, I doubt that you be snookered to give an example for the increasing of order in one physical system thanks to random events and without the the ideas, the will and the intellect of intelligent being?
The cause of the pride is ignorance.
PeterKinnon
1 / 5 (3) Sep 11, 2015
For reasons given fully in chapter 5, SHAPE, ORDER AND ORGANIZATION of "The Intricacy Generator", I carefully avoid the ambiguous concept of "order" in discussions such as this.

Similarly, the word "complexity" has become sullied by pseudo-scientific associations and can become a source of confusion.

This is why I have settled upon "intricacy" to describe the general property exhibited by evolutionary processes.

One simple example of increasing intricacy (driven by gravity and random inputs rather than "intent") is the formation of the more intricate manganese atom from primeval hydrogen.

A more complex example is the increased intricacy of minerals on this planet as nicely described by the geologist Robert M Hazen.

Many more examples, together with their contextual background will be found in my books.
viko_mx
1 / 5 (4) Sep 12, 2015
You came with the absurd idea that in our physical reality there is no order that ca be created and seen only by intelligent being? The chaos is only in your mind. If there is not order in our universe why we develop science? How things maintain their shape, structure and functionality for a long time?

The simple question is: Can you give the example for the increase of the order in one physical system without the ideas, the will and the actions of intelligent being?
If you continue to boggle and avoid calling things by their real names, you will lose credibility.
PeterKinnon
4 / 5 (4) Sep 12, 2015
I am sorry, Viko, if I had realised you were a committed creationist I would not have tried to reason. with you.

Why? I adhere to the following view rather nicely expressed by a certain Scott David Weitzenhoffer:

"Debating creationists on the topic of evolution is rather like trying to play chess with a pigeon; it knocks the pieces over, craps on the board, and flies back to its flock to claim victory."

You are, of course, free to hold your own opinions, however ill-informed they may be, but phys.org is really not the right forum for their expression.

Bye-bye
Captain Stumpy
5 / 5 (3) Sep 12, 2015
"Debating creationists on the topic of evolution is rather like trying to play chess with a pigeon; it knocks the pieces over, craps on the board, and flies back to its flock to claim victory."
this is, BY FAR, the most accurate description of viko, jvk, ren, zephir, denglish, alchie/profit, verkle, cantdrive, hannes_alfven and every other religious poster on this site!

thanks for sharing it

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