Genetic analysis of New World birds confirms untested evolutionary assumption

Credit: CC0 Public Domain

Biologists have always been fascinated by the diversity and changeability of life on Earth and have attempted to answer a fundamental question: How do new species originate?

An implicit assumption in the discipline of speciation biology is that genetic differences between populations of animals and plants in a given species are important drivers of formation and are a key to understanding evolution.

But that assumption has never been rigorously tested, until now, according to University of Michigan evolutionary biologist Michael Harvey, first author of a paper published online May 30 in Proceedings of the National Academy of Sciences.

Harvey and colleagues compiled and analyzed an unprecedented data set containing genetic sequences from 17,000 individuals in 173 New World , ranging from ducks and owls to swallows and sparrows.

They demonstrated that species showing faster rates of genetic between populations are more likely to produce greater numbers of species over long evolutionary timescales.

"Our results are of fundamental significance because there are researchers across the world studying speciation, and many of them investigate genetic differences between populations that are in the process of forming new species," said Harvey, a postdoctoral fellow in the Department of Ecology and Evolutionary Biology, in the laboratory of Daniel Rabosky.

"These researchers assume those genetic differences are important for evolution, but this has never been shown in a satisfactory way. We are the first to show that the differences between populations studied by speciation biologists have been fundamental determinants of the formation of the diversity of life."

The researchers measured the rate at which genetic differences accumulated between populations in each of the 173 bird species. They then compared the rate of population differentiation to the probability that each bird species would form new species over time. This probability was based on the evolutionary track record of each species: How many species did its ancestors produce over the history of avian diversity?

They found that the rate of genetic differentiation within species is positively correlated with the rate of new species formation. The two rates were more tightly linked in tropical species than in temperate species.

The study provides the first large-scale test of the link between population differentiation rates and speciation rates. The results confirm the evolutionary importance of population genetic differentiation.

However, genetic differences do not guarantee evolutionary success. Harvey and his colleagues found that the correlation between genetic differentiation and species formation was imperfect, which suggests that other factors besides differentiation may be important in determining how many new species are produced.

They also found that the emergence of new populations within a species occurs at least three times faster than new species develop, suggesting that most differences between populations will not last long enough to impact species diversity.

"Overall, however, the study confirms the long-held assumption that the between populations of a given might predict its probability of contributing to the diversity of life," Harvey said.

Other New World birds analyzed in the study include parrots, woodpeckers, toucans, hummingbirds, blackbirds, tanagers, warblers, thrushes, wrens, chickadees, jays and flycatchers.

Explore further

Long-held assumption about emergence of new species questioned

More information: Positive association between population genetic differentiation and speciation rates in New World birds, PNAS, DOI: 10.1073/pnas.1617397114 ,
Citation: Genetic analysis of New World birds confirms untested evolutionary assumption (2017, May 30) retrieved 24 July 2019 from
This document is subject to copyright. Apart from any fair dealing for the purpose of private study or research, no part may be reproduced without the written permission. The content is provided for information purposes only.

Feedback to editors

User comments

May 30, 2017
The article is willing to state that the assumption that genetic differences between populations drives speciation has never been tested until now. Yet it was always blithely given as if proved. One wonders how soon it will be before this "research" is shown to be faulty.
Note the reference to "rates of genetic differentiation". How could they even see that from the data? They are all sequences from one moment in time, a snapshot! And, if someone tries to say that they represent the spread of all possible genetic sequences in each group, that begs the question of how it is assured that that is a complete and statistically valid collection. There are, on average, only about 90 individuals from each species listed and that seems far too small.

May 30, 2017
Untested evolutionary assumption? I think this refers just about every single assumption made in the world of evolutionists. Basically nothing has been tested or verified or reproduced. It is just about all guesswork.

Scientists everywhere should be highly skeptical of such school of thought.

Julian, I don't agree with everything you write on PHYS, but you are spot on challenging evolutionary assumptions.

May 31, 2017
I never understood the anti-evolution propaganda here.

Obviously, people that are against evolution are for specific reasons. Also obviously, this idea that evolution is not supported is clearly against the vast majority of the scientific consensus. Therefore, why even bother commenting here? Why not going directly to the scientists in that specific field and exposing what are, for you, the reasons why evolution is not supported?

You have, on each article, the name and contact of each scientist working on that paper. Why not contacting them directly and exposing the ideas? That would be way more mature and productive than commenting here.

Obviously, someone who could make a valid objection to such a theory would become one the most renown scientific of all time, so why bother here? And please, don't go to the childish response about a scientific conspiracy, that would be embarrassing.

I clearly don't understand.

May 31, 2017
@julianpenrod Dunno mate, why don't you read the paper, find the error/s in their peer reviewed work, form an alternative hypothesis, test it, write a new paper rebutting this one, publish it in a peer reviewed journal, share your results with the world, increase humanity's understanding of our place in the world.

Good luck to you, hit me up when you've done it, I believe in you!

@Bart_A Ahhh, another shit posting shit poster, spreading your anti-intellectual troglodite verbal faeces wherever you go. Hope you enjoy it: it's the closest thing to human attention you'll ever get. Or are you genuinely so wrapped up in a dogma that was forced down your throat since birth that you can't even accept facts?

If only Mummy loved you as a child you wouldn't feel the need to waste your life a) making up bullshit to get a momentary rush, or b) choosing to be ignorant.

May 31, 2017
Shifting diet, poor nutrition, oxidative stress, viruses etc. cause aberrant methylation patterns that trigger deamination induced genetic errors. Cell tries to suppress faulty genes by methylating histones. This can be observed as increase of heterochromatin. Seriously damaged genes are dropped out of the genome. This leads to chromatin remodeling, smaller chromosomes and chromosome loss. Small chromosomes are combined by chromosomal recombination mechanisms during meiosis.

This phenomenon can be observed in Canidae lineage, for example. In every step of variation, information and chromosomes are lost.

Wolf 78 chromosomes
Bat-eared fox 72 chromosomes
Gray Fox 66 chromosomes
Fennec Fox 64 chromosomes
Bengal Fox 60 chromosomes
Kit Fox 50 chromosomes
Tibetan sand fox 36 chromosomes
Red Fox 34 chromosomes

Conclusions are clear. Evolution is not happening.

Jun 01, 2017
Wow, we have some very angry people on this list. They don't want to discuss real science. Only call people names, insult, and make up stories. What childish responses.

Rob---do you really want to understand? Then start by not calling things that you disagree with "propaganda". Understand that science is not "consensus". Science is science.

I have my doubts that you seriously want to engage in true scientific thought.

Jun 01, 2017
(following my previous post)

Now, I'm not a biologist, nor even a scientist. Therefore, I go with the consensus, because I trust science and his methodology. If you don't "believe" that a consensus should be followed, I guess you would have to replicate every single experiment that are supporting any idea behind any scientific fact. Obviously unfeasible.

So, considering the two facts that:
1) There's a vast consensus on evolution by scientists
2) A scientific consensus is trustworthy

Then, if you really think that evolution is wrong, or his assumptions, then I would advise you to write a paper, test your hypotheses, go to experts on that domain and do real science. I don't consider a vague conversation on a article to be real science, sorry. If you are right, you will be world renown for being the one to have destroyed such a theory. So please do.

Jun 02, 2017
Mayor, your post is hard to understand. Maybe because you don't understand what you are saying. Yes, I want to discuss real science. Don't make things up. Just go do some studying yourself first before making comments.

If people want to put forth a scientific theory, the burden is on them to go do the testing first. To quote from Wikipedia:
"A scientific theory is an explanation of some aspect of the natural world that can, in accordance with the scientific method, be repeatedly tested, using a predefined protocol of observations and experiments. Established scientific theories have withstood rigorous scrutiny and are a comprehensive form of scientific knowledge."

Sorry, Evolution does not fit into this category. So consensus comment is ridiculous. And no, consensus does not always emerge from science.

Jun 02, 2017
This is a pretty important result; it examined one of those things "everybody knows" and found out it's correct. It's one thing to logically deduce something like this from the theory; entirely another to actually go out and do the scut work and find the data to support it.

Congratulations to Dr. Harvey and team on a really good piece of science.

Jun 02, 2017
(My comment before hasn't been accepted, so I will rewrite it here)

Scientific consensus is all about science, clearly (I wanted to link to the "logic of science" page about scientific consensus, but it doesn't work...)

If you want to argue that the scientific consensus on evolution is not trustworthy, please, do so. But you have a enormous burden of proof on you. You are saying that evolution hasn't met his burden of proof. However, as stated before, the vast majority of the experts in that field do not agree with you. Why is it so? Have you been speaking with them? What was their answer? What methodology do you propose to test what's, according to you, missing?

I'm not an expert in that field, neither you are. I don't want to discuss real science, I want to do real science. And commenting on a article is not the way to do it.

Jun 02, 2017
RE: A true scientific theory may not be verified by consensuses or rhetorics alone; It must be falsifiable by empiricism unequivocally, especially for the evolutionary theory in biology nowadays!?

I think both Julianpenrod and Bart_A are not anti-evolutionaries, at all; they are just being critical to the evidence so far presented. Besides Julianpenrod does present some valid approaches that may strengthen the research study as reported above.

Meanwhile, for readers who are interested in knowing more about these scientific debate issues may find my recent comments on "Medical physiologist vs Molecular biochemist on "evolution", "junk DNA", "selfish genes", etc!?" therein: http://sandwalk.b...45288334 .

Best, Mong 6/2/17usct03:53; practical public science-philosophy critic (since 2006).

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more