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Author Topic:   Galapagos finches
NosyNed
Member
Posts: 8968
From: Canada
Joined: 04-04-2003


Message 61 of 104 (85367)
02-11-2004 11:03 AM
Reply to: Message 60 by Tamara
02-11-2004 10:56 AM


Re: waiting
Would that not be an improvement? In a world "ruled" by that definition, none of us would have to waste our time arguing the finches, and could go back to having a life!

Of course. But it just doesn't cover everything. It is also, on it's own, fuzzy.

It comes down to everything about the individual is a bit unclear (and amazingly even that isn't cut and dried). The species is then next grouping of living things. It has a lot of clarity and crisp edges most of the time but not all of the time.

Again, why does it matter if there are lots of finch species or one? It doesn't seem to make any difference to anything to me.


This message is a reply to:
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Tamara
Inactive Member


Message 62 of 104 (85395)
02-11-2004 1:55 PM
Reply to: Message 61 by NosyNed
02-11-2004 11:03 AM


Re: waiting
quote:
Again, why does it matter if there are lots of finch species or one?

If only one species, then no speciation in this case. Of course, if there are other equally vivid examples, then no problem. See my new thread on Speciation examples.


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truthlover
Member (Idle past 3299 days)
Posts: 1548
From: Selmer, TN
Joined: 02-12-2003


Message 63 of 104 (85415)
02-11-2004 3:32 PM
Reply to: Message 60 by Tamara
02-11-2004 10:56 AM


Re: waiting
In a world "ruled" by that definition, none of us would have to waste our time arguing the finches, and could go back to having a life!

I'll just leave all your other assertions alone, because my answer to them is the same as this one. There are posts in this thread explaining to you why this statement isn't true.


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Tamara
Inactive Member


Message 64 of 104 (86075)
02-13-2004 11:38 AM


dog/wolf
regarding the question of dog and wolf classification, here is what my contact at the university of Guelph sent. If anyone has evidence that dogs are again a separate species, I would appreciate the reference.
---
I took a quick look on the web and found a couple of references to the re-classification of the domestic dog. The best is the University of Michigan site http://animaldiversity.ummz.umich.edu/site/accounts/information/Canis_lupus.html

While this page is about wolves, it has a number of paper and online references at the bottom of the page that may help you in your search for dog taxonomy. According to another site, the dog was reclassified in 1993 by the Smithsonian Institute and the American Society of Mammalogists. Hope this helps you!

Check out this reference; Mammal Species of the World, A Taxonomical and Geographic Reference. This is where the reclassification was originally published. As for the suggestion that the dog is once again classified as its own species, I found no reference to that in my search.


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Tamara
Inactive Member


Message 65 of 104 (86078)
02-13-2004 11:45 AM
Reply to: Message 64 by Tamara
02-13-2004 11:38 AM


Re: dog/wolf
And the wolf classification page from the university of Alberta that is referenced at the bottom of the linked article says:

"The domestic dog (Canis familiaris) is considered by some to be con-specific with the grey wolf, meaning that they are members of the same species. The dog is considered to be a domestic variant of the grey wolf and its latin name would be Canis lupus familiaris or Canis lupus var. familiaris. Despite this, the dog is still usually referred to as Canis familiaris. "


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MrHambre
Member (Idle past 632 days)
Posts: 1495
From: Framingham, MA, USA
Joined: 06-23-2003


Message 66 of 104 (86084)
02-13-2004 12:04 PM
Reply to: Message 65 by Tamara
02-13-2004 11:45 AM


Speciation
Tamara,

Again, I wonder what you're getting at. Could you tell us whether you believe speciation has ever taken place? Should all organisms be classified as the same species just because laymen aren't comfortable with the amount of ambiguity in the definition of species?

Do you have a problem with the notion of common ancestry? If so, could you tell us what it is? Do you believe that certain groups of organisms popped into existence out of thin air?

Could you please tell us what the best explanation could be for the nested hierarchies we observe in life on Earth? Or why the family trees scientists have assembled using various methods all seem to correlate to a high degree?


The dark nursery of evolution is very dark indeed.
Brad McFall

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nator
Member (Idle past 1409 days)
Posts: 12961
From: Ann Arbor
Joined: 12-09-2001


Message 67 of 104 (86249)
02-14-2004 8:27 AM
Reply to: Message 51 by truthlover
02-10-2004 9:33 AM


quote:
writes:
Maybe someone can name for me a species that varies in size and appearance as much as dogs do, yet are all considered one species (rather than one genus).

Horses.

http://www.petbypet.com/horse_breeds.htm

"The smallest horse on record, a Falabella miniature pony, stood 48 cm (19 in), or just under 5 hands, and weighed 14 kg (30 lb). The largest horse on record was a Belgian that stood 1.8 m (6 ft) tall, or 18 hands, and weighed 1,450 kg (3,200 lb)."

Remember, horse height is measured at the whithers, or the top of the shoulder blades where the back and neck meet.


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KCdgw
Inactive Member


Message 68 of 104 (87389)
02-18-2004 9:36 PM
Reply to: Message 62 by Tamara
02-11-2004 1:55 PM


Re: waiting
I think it's clear that, in the case of Darwin's Finches, we have a situation of an adaptive radiation with speciation in its very early stages. Hybridization still occurs, with about 50% of the species in the archipelago, but it is always at a very low frequency. Most of the populations of finches are reproductively isolated pre-zygotically: they mate only with birds that either look like their parents in color and size, or sing the same song as their fathers. This effectively restricts gene flow between them. At the very least, it allows for morphological differentiation to occur, which reinforces the behavioral isolation even more. However, they haven't been isolated long enough for much post-zygotic isolation to develop. In addition, the situation there is very complex, with colonization and recolonization having gone on for some time.

So, overall, I'd say Darwin's Finches are an excellent example of adaptive radiation and a wonderful example of the beginnings of speciation.

KC


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Tamara
Inactive Member


Message 69 of 104 (88864)
02-26-2004 3:10 PM
Reply to: Message 68 by KCdgw
02-18-2004 9:36 PM


margulis
I have come across a mention of the finches in Margulis & Sagan's Acquiring Genomes (pp29-32):

They accept the current species as defined, but argue that there is no evidence of incipient speciation. "The Darwinian paradigm is operating exactly as it should: Different traits (whether within species or among different species) are varying in prevalence according to the demands of the environment. Obviously, the genes that produce these traits are varying in like fashion. But there is no evidence that this process leads to speciation [among these finches].

Speciation, whether in the remote Galapagos, in the laboratory cages of the drosophilosophers, or in the crowded sediments of the paleontologists, still has never been directly traced." Goes on to describe Dobzhansky's classic 2 fly populations as "only reproductive isolation" and not speciation.

Her point, of course, is not that speciation does not go on. Her point is that the best direct cases of speciation come from the tiny critters, where two of them merge into a new organism.

Cool beans!


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Quetzal
Member (Idle past 5111 days)
Posts: 3228
Joined: 01-09-2002


Message 70 of 104 (89060)
02-27-2004 1:53 PM
Reply to: Message 69 by Tamara
02-26-2004 3:10 PM


Re: margulis
Hi Tamara,

I confess to not having "Acquiring Genomes" (although it's on my "to get around to eventually" list). You cited her as saying

quote:
Goes on to describe Dobzhansky's classic 2 fly populations as "only reproductive isolation" and not speciation.
Since reproductive isolation is the identifying feature in the most commonly accepted definition of species (i.e., the biological species concept, which in spite of its flaws - which is a whole 'nother discussion - is a pretty useful concept), the quote seems a bit odd. Could you synopsize or identify how Margulis defines "species" and "speciation"?

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truthlover
Member (Idle past 3299 days)
Posts: 1548
From: Selmer, TN
Joined: 02-12-2003


Message 71 of 104 (89070)
02-27-2004 2:58 PM
Reply to: Message 67 by nator
02-14-2004 8:27 AM


truthlover writes:

Maybe someone can name for me a species that varies in size and appearance as much as dogs do, yet are all considered one species (rather than one genus).

Schrafinator writes:

Horses

Okay, but I guess my point was that I think that if dogs were found in nature rather than in our homes, we would classify them in several species, not one. Horses would fall into exactly the same category. We have also created miniature donkeys, but I suspect there as well that if a population of miniature donkeys were found somewhere in nature and the more typical donkeys elsewhere, they'd definitely be called different species.


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Tamara
Inactive Member


Message 72 of 104 (89091)
02-27-2004 4:01 PM
Reply to: Message 70 by Quetzal
02-27-2004 1:53 PM


Re: margulis
Quetzal, she feels that the repro isolation definition of species is useful for mammals and birds. But with Dobzhansky's flies, what they had was a weird anomaly, if I recall correctly: 2 genetically identical populations that could not interbreed. I will post more if I find it.

Btw, it's well worth reading. She is pretty ethused about the subject!

[This message has been edited by Tamara, 02-27-2004]


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Sylas
Member (Idle past 4500 days)
Posts: 766
From: Newcastle, Australia
Joined: 11-17-2002


Message 73 of 104 (89110)
02-27-2004 4:51 PM
Reply to: Message 72 by Tamara
02-27-2004 4:01 PM


genetical identical but not interfertile?
Tamara writes:


Quetzal, she feels that the repro isolation definition of species is useful for mammals and birds. But with Dobzhansky's flies, what they had was a weird anomaly, if I recall correctly: 2 genetically identical populations that could not interbreed. I will post more if I find it.

Please do! I'm interested, but sceptical. My head is on the block here, but I suspect that you have misremembered something, or omitted some important details. What does genetically identical mean here anyway? Hell, even you and I are not genetically identical. I see no problem with the notion that in unusual circumstances a comparatively small amount of genetic change would be sufficient to prevent interbreeding. Dobzhansky died in 1975. He was certainly a pioneering geneticist; but genome sequencing has come a long way since his time.

Cheers -- Sylas

[This message has been edited by Sylas, 02-27-2004]


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Tamara
Inactive Member


Message 74 of 104 (89142)
02-27-2004 7:31 PM
Reply to: Message 73 by Sylas
02-27-2004 4:51 PM


Re: genetical identical but not interfertile?
Toy poodles a separate species!? What a ghastly thought.

Ok, Margulis' definition of species is: organisms with the same kinds and numbers of integrated genomes in common.

Huh? Can someone translate it into humanspeak?

Now about those pesky flies. Dobzhansky grew the same flies in two different environments -- cold and hot. The hot guys apparently lost their symbiotic mycoplasmas, and so the interbreeding of the two populations became difficult. She illustrates the same finding with weevils: 2 populations that lose their symbionts can breed as successfully as 2 groups that keep them, but a group with and a group without, they will have impaired fertility.


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NosyNed
Member
Posts: 8968
From: Canada
Joined: 04-04-2003


Message 75 of 104 (89143)
02-27-2004 7:51 PM
Reply to: Message 74 by Tamara
02-27-2004 7:31 PM


Re: genetical identical but not interfertile?
This reminds me of something else, (again no reference) where populations are separated by some kind of parasite. The article discussed this as a means to very rapid speciation

I remember no details.


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Replies to this message:
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