Cliff Swallows may be evolving to dodge traffic (2 Viewers)

[jaco]

You can beg to differ all you like, but your example, without a demonstration of heritability, is absolutely nothing like what the authors of the swallow paper are suggesting.

Oh well. I'll drop it.

 

[Snapdragyn]

I think what's being missed, KenM, is that an individual swallow won't 'grow' longer wings in response to a change in flight style (so far as we are aware). Thus, a change to shorter wings in the population must reflect a change in frequency of an inherited characteristic.

An individual human, on the other hand, may most certainly develop larger muscles & increase bone density in response to exercise. Thus there is the question of whether the thicker joints seen in the individuals who departed this island were a result of heredity or simply a lifetime of a particular exercise regime. The first would represent natural selection & thus parallel the findings of the swallow study - but the second would merely point toward a potential new fitness fad waiting to be born.

It would be interesting to see if any similar measurements were done of the first generation born off the ancestral island.

 

[KenM]

I think what's being missed, KenM, is that an individual swallow won't 'grow' longer wings in response to a change in flight style (so far as we are aware). Thus, a change to shorter wings in the population must reflect a change in frequency of an inherited characteristic.

Same prayer sheet.

An individual human, on the other hand, may most certainly develop larger

muscles & increase bone density in response to exercise. Thus there is the question of whether the thicker joints seen in the individuals who departed this island were a result of heredity or simply

a lifetime of a particular exercise regime.

That's putting it mildly


The first would represent natural selection & thus parallel the findings of the swallow study - but the second would merely point toward a potential new fitness fad waiting to be born.

I think survival ''fad'' of the fittest might be more appropriate?


It would be interesting to see if any similar measurements were done of the first generation born off the ancestral island.

I can't see any logical reason as to why they wouldn't have inherited their ''immediate'' ancestors structure.

 

[KenM]

You can beg to differ all you like, but your example, without a demonstration of heritability, is absolutely nothing like what the authors of the swallow paper are suggesting.

Oh well. I'll drop it.

My anecdotal recollection is a little ''misty'' in the sands of time....however the ''material'' differences in the relative joint measurements (which in all good faith I accept, and have no reason to doubt), can be explained by....?

Yawn...

 

[jaco]

I can't see any logical reason as to why they wouldn't have inherited their ''immediate'' ancestors structure.

The same reason my kid wouldn't inherit my large muscles if I took up weightlifting.

The same reason a Jewish kid isn't born circumcised.

 

[Richard Klim]

Birdwatch

Birdwatch News, 21 Mar 2013: Shorter winged swallows dodge cars.

 

[KenM]

Birdwatch News, 21 Mar 2013: Shorter winged swallows dodge cars.

Thanks for that Richard...does make you wonder if and how the shorter wing might impact during migration. Would a shorter wing result in less glide..more flaps..equalling more energy expense. The fact that the colony appears to be thriving, might suggest that the shorter wing has no negative impact on the species ability to sustained migration.

 

[KenM]

The same reason my kid wouldn't inherit my large muscles if I took up weightlifting.

The same reason a Jewish kid isn't born circumcised.

I'll ignore the last comment!...your quite right on the first..however over a number of generations, as has been shown with the new world slaves...circa several hundred years. The athletes drawn from this "pool" invariably from a performance perspective, exceed those from "the old world"...euphemism for Africa.

 

[Ian Lewis]

Thanks for that Richard...does make you wonder if and how the shorter wing might impact during migration. Would a shorter wing result in less glide..more flaps..equalling more energy expense. The fact that the colony appears to be thriving, might suggest that the shorter wing has no negative impact on the species ability to sustained migration.

Isn't this a case of dynamic equilibrium? A longer wing would improve migratory performance, most long distance migrants have longer wings than their short distant relatives, eg Willow Warbler vs Chiffchaff, but shorter wings improve manouverability and hence avoidance of predators or traffic. Thus selection acting on both factors produces an intermdiate wing length that will change over the generations as selection pressures change.

Ian

 

[nicklittlewood]

There is a close parallel in this topic with work done on Garden Tiger moths in the UK (published 2008).

As the population and range have declined, hindwings have become longer and narrower and forewings narrower proportional to length (measured from specimens collected over the past century). It is suggested that habitat fragmentation and increased suitability of northerly sites may explain selection of increasingly dispersive individuals.

Paper here (but not sure whether or not it is accessible without a subscription):
http://onlinelibrary.wiley.com/doi/10.1111/j.1365-2311.2008.01013.x/pdf

Nick

 

[njlarsen]

Isn't this a case of dynamic equilibrium? A longer wing would improve migratory performance, most long distance migrants have longer wings than their short distant relatives, eg Willow Warbler vs Chiffchaff, but shorter wings improve manouverability and hence avoidance of predators or traffic. Thus selection acting on both factors produces an intermdiate wing length that will change over the generations as selection pressures change.

Ian

That is the correlation true for e.g., thrushes, where American Robin (migratory) has relatively longer wings then the relative Red-legged Thrush which is a resident species in the Caribbean

Niels

 

[Kirk Roth]

Or one swell coupe? 3

Didn't see that coming! And here I've been steeling myself for some sort of "Dodge Ram" joke...

 

[bitterntwisted]

The same reason my kid wouldn't inherit my large muscles if I took up weightlifting.

The same reason a Jewish kid isn't born circumcised.

Exactly. Lamarckism... http://en.wikipedia.org/wiki/Lamarckism