Splits and Ticks (1 Viewer)

[Jim Lundberg]

Reading another thread on sub-species, it seems that birds can evolve quickly. When species are split such as Meadowlark Strunella lilianae, what consideration is given to evolution when ticking off a new species say from a 40 year-old sighting of an Eastern Meadowloark in SE Arizona? What's to say that the Eastern Meadowlark in your dusty old log book wasn't just that?

The example of Meadowlark Strunella lilianae is just what first came to mind, because I have a SE Arizona Eastern Meadowlark sighting. Maybe the pertinent sub-species differences were documented 40 years ago, and this is a poor example. But, in general, is it prudent to tick off a new species based on a sighting made before the differences were documented when, perhaps, the differences are recent evolution not recent recognition of long-term differences?

I appreciate the forum. Thank you ahead of time for your answers.

Jim

 

[Jacana]

I don't think that species are splitting at that sort of rate, it's just our awareness of what consitutes a species coupled with new techniques that weren't around 40 years ago such as genetic testing which fuel the splits and lumps.

I don't know the specific data for Lilian's Meadowlarks, but the birds that you see today would be the same as the birds seen 40, 400 even 4000 years ago, i'd like to know the acutal data if anyone has it to hand.

I hope that goes some way towards answering your question

 

[blackburnian2000]

The paper http://www.tc.umn.edu/~barke042/pdfs/Barker.et.al08-2.pdf reports a genetic divergence in cytochrome b of around 4%, which would mean the most recent common ancestor lived something like several hundred thousand to maybe 2 or 3 mya. Calibrating the avian molecular clock is somewhat controversial and filled with uncertainties at this point, though.

 

[Mysticete]

Unless you are immortal and have been birding for over 10,000 years, I don't think this is an issue.

I guess the bigger relevant issue is whether you saw a given bird that was recently split clear enough to be sure of it's identity post split to count it. When I was in Arizona I wasn't aware that the Brown-throated (I think?) House wren was a potential split, and so didn't pay much attention to them. So if House Wren was split in the future, I probably wouldn't feel comfortable about counting the birds I saw in SE Arizona. On the other hand I had no problem counting Mexican Duck for my world list when IOC split it, as I was aware of the potential split and paid attention to the major features.

 

[Jim Lundberg]

http://www.wired.com/wiredscience/2009/11/speciation-in-action/

This link to "an account of a new species" in Matt's reply in Mysticete's thread "Sub-species...are they useful", is what got me started on this line of thought. Not signicant to the Lilian's split (thank you for the explanations on divergence and interpretation of the scientific paper) it lays claim to a split, possibly, accomplished within a few generations. In which case, nobody should have old log book entries of it anyway.


Jim

 

[VATH 82]

Reading another thread on sub-species, it seems that birds can evolve quickly. When species are split such as Meadowlark Strunella lilianae, what consideration is given to evolution when ticking off a new species say from a 40 year-old sighting of an Eastern Meadowloark in SE Arizona? What's to say that the Eastern Meadowlark in your dusty old log book wasn't just that?

The example of Meadowlark Strunella lilianae is just what first came to mind, because I have a SE Arizona Eastern Meadowlark sighting. Maybe the pertinent sub-species differences were documented 40 years ago, and this is a poor example. But, in general, is it prudent to tick off a new species based on a sighting made before the differences were documented when, perhaps, the differences are recent evolution not recent recognition of long-term differences?

I appreciate the forum. Thank you ahead of time for your answers.

Jim

Jim
I think if you saw the salient features of Lilian's Meadowlark.It would be ok to tick it.

 

[Mysticete]

I think the popular press blew the "birth of new species" story out of proportion. IIRC, the authors in this paper don't consider the "new species" a valid species, they just suggest that it is undergoing the first steps towards being one.

 

[Jim Lundberg]

Does the size of a population determine stability of a species (in terms of evolution)? Does a large population, like Lilian's Meadowlarks, absorb deviations into the common gene pool? Is that the gist of the "Birth of a New Species." story?

Jim

 

[njlarsen]

One of the important issues in populations size is inbreeding. Imagine the situation on the island in Galapagos where the only remaining male was brother of the only remaining female. Their offspring would also only have one possibility, mating with individuals that were their sibling. There would therefore most likely be a large part of their DNA that the offspring were homozygous for. That is ok with most of the material, but most likely, there would be at least one recessive bad gene in there, and being homozygote for a bad gene means that you express the disease caused. When the population is larger, you can choose a partner that is not your sibling, maybe even not your cousin, and the risk that a bad gene occur in homozygosity in the offspring is less, so fewer affected individuals on average. The affected individuals in both examples might not reproduce very well, and therefore be lost from the genepool, again, this is something that has less severe consequences for the population when the population is larger and it therefore is a relatively smaller proportion of the population that have that homozygosity.

The basic argument does also apply to humans, we are all expected to carry between 1 and 10 bad recessive alleles, that mostly does not show in us and also not in our children, because they are not occurring in homozygosity.

Hope this helps
Niels

 

[Jim Lundberg]

One of the important issues in populations size is inbreeding. Imagine the situation on the island in Galapagos where the only remaining male was brother of the only remaining female. Their offspring would also only have one possibility, mating with individuals that were their sibling. There would therefore most likely be a large part of their DNA that the offspring were homozygous for. That is ok with most of the material, but most likely, there would be at least one recessive bad gene in there, and being homozygote for a bad gene means that you express the disease caused. When the population is larger, you can choose a partner that is not your sibling, maybe even not your cousin, and the risk that a bad gene occur in homozygosity in the offspring is less, so fewer affected individuals on average. The affected individuals in both examples might not reproduce very well, and therefore be lost from the genepool, again, this is something that has less severe consequences for the population when the population is larger and it therefore is a relatively smaller proportion of the population that have that homozygosity.



Hope this helps
Niels

So, because of the small population of the "New Species" of finch in the Galapagos, it has a slim chance of surviving as a new species, and the best chance of passing along their DNA is to relearn the local bird song and integrate where that uncharacteristic bill would be lost or, possibly, slightly change the local population?

Thank you, Jim

 

[njlarsen]

Jim,
I would say yes but, and the but is because nature keeps coming up with exceptions to our rules.

Niels

 

[Accentor]

I agree with everyone for the most part. However birds do evolve fairly quickly. An extreme example of this are Darwin's Finches. While I don't remember which ones they were, there was a flock of one species blown to another island. They began to breed in isolation from the parental population. After only about 15 years, there were already differences in size, bill size and even song. How much would happen after 100 years?

Birds evolve more quickly than most larger mammals because they're life cycles are often much faster. Just my two cents.

 

[Jacana]

but that doesn't make them a new species yet, if those birds were returned to the original population the features would be quickly mixed back. Natural selection can change features over just a few generations (Just look at the thousands of experiments on Drosophila to see where i'm coming from) the animals are still the same species

 

[njlarsen]

Jacana, while I am tempted to agree with you, I would like to remind that in one example of a thousand (I just made up that number but you got my gist), the change will involve the main trait that one sex uses to recognize the other, and once there is prezygotic isolation, you have essentially two species (and then it does not matter is the zygote would be viable and fertile if it was formed).

Niels

 

[Farnboro John]

Jacana, while I am tempted to agree with you, I would like to remind that in one example of a thousand (I just made up that number but you got my gist), the change will involve the main trait that one sex uses to recognize the other, and once there is prezygotic isolation, you have essentially two species (and then it does not matter is the zygote would be viable and fertile if it was formed).

Niels

Actually that is not the case, in the case you describe UNLESS another animal of the "same species" but the opposite sex has changed in the same way and "recognises" the new opposite number, no mating will take place at all (with the new type or the old type) and the change will be lost.

Fortunately million to one chances come up nine times out of ten.

John

 

[njlarsen]

Actually that is not the case, in the case you describe UNLESS another animal of the "same species" but the opposite sex has changed in the same way and "recognises" the new opposite number, no mating will take place at all (with the new type or the old type) and the change will be lost.

Fortunately million to one chances come up nine times out of ten.

John

True

Niels

 

[Alan Manson]

Actually that is not the case, in the case you describe UNLESS another animal of the "same species" but the opposite sex has changed in the same way and "recognises" the new opposite number, no mating will take place at all (with the new type or the old type) and the change will be lost.

But that does happen .... see this paper on Indigobirds.

 

[njlarsen]

Interesting paper, Alan :t:

Niels