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Author Topic:   On The Observability of Speciation
AustinG
Member (Idle past 3277 days)
Posts: 36
Joined: 04-06-2009


Message 1 of 17 (504950)
04-06-2009 2:38 AM


Those who refute evolution point out that speciation has not been witnissed. Altough this can be a debate in and of its self, lets save it for another time.

I seek to make this point on the subject:

Given that the population of organisms consistantly under human inspection is significantly lower than that of organism populations at large, an observation of speciation is unlikely; furthermore, the recognition of an observed speciation as such is even more unlikely.

If you were to take a trip to the San Diego zoo you would see many variety of animals like Tigers, snakes, spiders, and turtles; however, the variety and number of animals in the zoo is miniscule when compared to all of the creatures in the earthes jungles, deserts, plains, swamps, and oceans.

Likewise, organisms in labs, like bacteria, represent a small portion of wild populations. With this said, to assume speciation is something which can be readily observed is ambitious and naive, to say the least.

Chances are speciation is not going to occur in a zoo or lab; it will happen in the wild. Most newly discovered living organisms are assumed to have been simply hidden from view ant not newly evolved.

I pose this question: How will we know speciation when we see it?

Please feel free to answer my question or add your own comments or ideas.


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AdminNosy
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Message 2 of 17 (504991)
04-06-2009 9:40 AM


Thread moved here from the Proposed New Topics forum.
  
Coyote
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Posts: 6117
Joined: 01-12-2008


Message 3 of 17 (504993)
04-06-2009 9:45 AM
Reply to: Message 1 by AustinG
04-06-2009 2:38 AM


Ring species
How will we recognize speciation? Here is a perfect example from the wild--ring species. I think a few minutes study of ring species should adequately address your specific questions.

Ring species provide unusual and valuable situations in which we can observe two species and the intermediate forms connecting them. In a ring species:

  • A ring of populations encircles an area of unsuitable habitat.
  • At one location in the ring of populations, two distinct forms coexist without interbreeding, and hence are different species.
  • Around the rest of the ring, the traits of one of these species change gradually, through intermediate populations, into the traits of the second species.

A ring species, therefore, is a ring of populations in which there is only one place where two distinct species meet. Ernst Mayr called ring species "the perfect demonstration of speciation" because they show a range of intermediate forms between two species. They allow us to use variation in space to infer how changes occurred over time. This approach is especially powerful when we can reconstruct the biogeographical history of a ring species, as has been done in two cases. [b]Source


Religious belief does not constitute scientific evidence, nor does it convey scientific knowledge.
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AustinG
Member (Idle past 3277 days)
Posts: 36
Joined: 04-06-2009


Message 4 of 17 (505012)
04-06-2009 2:56 PM
Reply to: Message 3 by Coyote
04-06-2009 9:45 AM


Re: Ring species
I am aware of ring species.I'm not refuting speciation; I know it occurs. I'm more interested in how new species found in the wild can be recognized as such.

For example:

Some naturalist take a trip into Madigascar. There, they find a new species of monkey. How can they tell if the species is newly evolved or has just been "hiding" from view.

New species are found frequently. Are they newly evolved or just newly found?


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Stagamancer
Member (Idle past 3024 days)
Posts: 174
From: Oregon
Joined: 12-28-2008


Message 5 of 17 (505013)
04-06-2009 2:57 PM
Reply to: Message 1 by AustinG
04-06-2009 2:38 AM


Another instance of easily observable speciation occurs quite frequently in plants, called polyploidy. In this case, when an offspring is produced, their chromosomes do not separate during meiosis, and they receive double the genetic material from their parents. I.e., if the parents had 14 chromosomes, the offspring has 28. Therefore, when the offspring produces gametes, the games have 14 chromosomes, but the parents generation's gametes have 7, so they the offspring of that breeding would have 21 chromosomes and be triploid. Triploid organisms more often than not are not viable. So this would be a case for speciation within one generation. Granted, it doesn't involve natural selection per se, but because the polyploid individual cannot breed with it's parents' generation, it is reproductively isolated, and natural selection and genetic drift can act upon the new species to make it different from the parent species.

Another species to look at is orcas, especially the ones living off of the coasts of British Columbia and Washington. There are 3 "types" of orcas: Transient, Resident, and Off shore. Even though their ranges overlap some, they maintain themselves as very separate groups and almost never interbreed. I did a project in undergrad for a population genetics course where I went through the literature to analyze the pop. gen. data, and it's pretty evident that this different "types" of orcas are quite possibly on the road to becoming different species. This is also a very interesting case, because the populations are not separated by physical barriers, but rather by cultural barriers. The different groups eat different food, use different sounds for communication, and have different pod structures which is why they tend not to mix.


We have many intuitions in our life and the point is that many of these intuitions are wrong. The question is, are we going to test those intuitions?
-Dan Ariely
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AustinG
Member (Idle past 3277 days)
Posts: 36
Joined: 04-06-2009


Message 6 of 17 (505017)
04-06-2009 3:32 PM
Reply to: Message 5 by Stagamancer
04-06-2009 2:57 PM


interesting
Very interesting. I'll have to look into the orcas for sure.
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Stagamancer
Member (Idle past 3024 days)
Posts: 174
From: Oregon
Joined: 12-28-2008


Message 7 of 17 (505024)
04-06-2009 4:45 PM
Reply to: Message 4 by AustinG
04-06-2009 2:56 PM


Re: Ring species
How can they tell if the species is newly evolved or has just been "hiding" from view.

"Newly" is a very relative term, and all living species are equally as evolved. Except for the polyploidy example I gave, speciation does not occur within one or even a dozen generations. The best way to tell if two species have recently split is to look at genetic data and observe if they mate in the wild. Often, if two populations look similar, are genetically very similar, but don't breed regularly then they are distinct species that have recently split from a common population, like bonobos and chimpanzees.

Another good example that I just remembered are marine life (fish, shrimp, etc) on either side of the isthmus of Panama. The isthmus is a relatively new geological feature (2.5-3 million years old), and lots of population genetics studies have been done to determine that similar species on the pacific and atlantic sides of it used to be one population. This is a classic example of allopatric speciation and is well documented. http://www.ncbi.nlm.nih.gov/pubmed/19154357


We have many intuitions in our life and the point is that many of these intuitions are wrong. The question is, are we going to test those intuitions?
-Dan Ariely
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CosmicChimp
Member
Posts: 306
From: Muenchen Bayern Deutschland
Joined: 06-15-2007


Message 8 of 17 (505032)
04-06-2009 6:58 PM
Reply to: Message 4 by AustinG
04-06-2009 2:56 PM


Speciation is not Saltation
Hi AustinG,

Welcome to the forum.

Your rephrased question:

AustinG writes:

New species are found frequently. Are they newly evolved or just newly found?

Has a definite element of saltation in it. Your question is in essence not a logical question if I may be so bold as to interpret the meaning to your opening post and subsequent posts. I've included the Wiki definition of saltation it might not hurt for you to check out the Wiki articles for speciation as well. But don't get me wrong all questions are good ones. My interpretation of your question would be something like asking why don't apples taste like oranges. And of course I may be making too great an assumption as to your meaning.

Edited by CosmicChimp, : changed the post subject heading

Edited by CosmicChimp, : fixed link


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AustinG
Member (Idle past 3277 days)
Posts: 36
Joined: 04-06-2009


Message 9 of 17 (505039)
04-06-2009 8:47 PM
Reply to: Message 8 by CosmicChimp
04-06-2009 6:58 PM


Re: Speciation is not Saltation
CosmicChimp,

You bring up a good point. Let me explain what I mean by newly evolved.

Lets say an extensive expidition was conducted in the amazon during the 1800s and every species of snake living in the the jungle was documented. Lets say there were only two species of python documented (Species A and B). Species A and B can interbreed with no problem. Then, a new study in 2008 uncovered a small population of a subspecies (Species C).

After extensive research, the naturalist determined species A and B could breed, and B and C could breed; however, C can not breed with A.

One of two conclusions can be made about this research:

1. Species C always existed and simply alluded the naturalists in the 1800s.

or

2. Population C recently evolved from population B.

My hypothothesis, if you will, is that new species may have evolved since human documentation and we have simply been assuming conclusion 1. Is this plausable? I think if scientists could present enough evidence that population C evolved from population B that would be enough proof to creationists. Hence my whole point in bringing it up.


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Stagamancer
Member (Idle past 3024 days)
Posts: 174
From: Oregon
Joined: 12-28-2008


Message 10 of 17 (505043)
04-06-2009 9:21 PM
Reply to: Message 9 by AustinG
04-06-2009 8:47 PM


Re: Speciation is not Saltation
After extensive research, the naturalist determined species A and B could breed, and B and C could breed; however, C can not breed with A.

One of two conclusions can be made about this research:

1. Species C always existed and simply alluded the naturalists in the 1800s.

or

2. Population C recently evolved from population B.

My hypothothesis, if you will, is that new species may have evolved since human documentation and we have simply been assuming conclusion 1. Is this plausable?

This very improbable, especially for animals, because, unlike plants, there seem to be very rare instances of sympatric speciation occurring in the animal kingdom, which is the kind of speciation that you would require if you were to return to the same spot and find a new species that had split from another species in just 200 years. Most speciation events for animals require a significant physical barrier that lasts long enough for pre- or post-zygotic biological barriers to evolve. Some rapid speciation has been shown in insects that have switched to different host plants (where the get food and mate) and thus they stop mating with each other simply because they no longer run into each other, as it were.

quote:
Rhagoletis pomonella, the apple maggot, may be currently undergoing sympatric or, more precisely, heteropatric (see heteropatry) speciation. The apple feeding race of this species appears to have spontaneously emerged from the hawthorn feeding race in the 1800 - 1850 AD time frame, after apples were first introduced into North America. The apple feeding race does not now normally feed on hawthorns, and the hawthorn feeding race does not now normally feed on apples. This may be an early step towards the emergence of a new species.

As you can see, though, they say the "emergence of a new species," which implies that the biological reproductive barriers have probably not evolved yet.


We have many intuitions in our life and the point is that many of these intuitions are wrong. The question is, are we going to test those intuitions?
-Dan Ariely
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CosmicChimp
Member
Posts: 306
From: Muenchen Bayern Deutschland
Joined: 06-15-2007


Message 11 of 17 (505045)
04-06-2009 9:42 PM
Reply to: Message 9 by AustinG
04-06-2009 8:47 PM


Re: Speciation is not Saltation
In your last scenario it would not very likely be the case of a newly evolved snake within 200 years, due to the inadequacy of the elapsed time frame for such an event. The gradualism for speciation is not likely on that short of a time scale. But if you look at other examples your question takes on a more plausible nature. Domesticated farm animals (or pets), I think is your "best bet" as far as finding an example of initial speciation steps in vertebrates being observed my man. Also wild animals adapting to fit into a modern man-made context might be an area to focus on, like the modern foxes, coyotes, racoons, falcons, pigeons, rats and insects in cities or crop fields.

As far as humans having missed vertebrate sized animals for thousands of years, or otherwise long enough for them to have gone unnoticed as a cladogenesis event took place, highly unlikely.

At the end of the day, I think you're asking how old are the species we are living beside here.

Edited by CosmicChimp, : more examples.


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pandion
Member (Idle past 1109 days)
Posts: 166
From: Houston
Joined: 04-06-2009


Message 12 of 17 (505054)
04-07-2009 1:22 AM
Reply to: Message 4 by AustinG
04-06-2009 2:56 PM


Re: Ring species
AustinG writes:

New species are found frequently. Are they newly evolved or just newly found?


Newly found for the most part. In spite of CosmicChimp's discussion, there doesn't exist even one example of what he proposes. While saltation caused by the mutation of HOX genes or other controlling genes is plausible, at this point it is only hypothetical.

It is said that if you wish to discover a new species, you only need to shake a tree in the Amazon rain forest and describe what falls out.


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RAZD
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Message 13 of 17 (505128)
04-07-2009 10:32 PM
Reply to: Message 12 by pandion
04-07-2009 1:22 AM


Re: Ring species
While saltation caused by the mutation of HOX genes or other controlling genes is plausible, at this point it is only hypothetical.

[quibble] while not necessarily due to "HOX genes or other controlling genes" there are many examples of saltationist speciation through polyploidy, most common in plants, but not unknown in animals. Polyploidy involves the sudden duplication of chromosomes that make interbreeding between parent and daughter population impossible, thus speciation has occurred.[/quibble]

This has been observed in the field under controlled conditions, and in the lab.

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pandion
Member (Idle past 1109 days)
Posts: 166
From: Houston
Joined: 04-06-2009


Message 14 of 17 (505134)
04-08-2009 12:29 AM
Reply to: Message 13 by RAZD
04-07-2009 10:32 PM


Re: Ring species
while not necessarily due to "HOX genes or other controlling genes" there are many examples of saltationist speciation through polyploidy, most common in plants, but not unknown in animals. Polyploidy involves the sudden duplication of chromosomes that make interbreeding between parent and daughter population impossible, thus speciation has occurred.

You are correct. But I'm not a botany kind of guy. I endured my botany classes and it has affected my views of evolutionary biology. Of course polyploidy in plants can cause a new species in two generations. Sometimes it is genome duplication in a single species that produces a 3n offspring. While it is unlikely that such an offspring could breed with the parent, in self fertilizing plants, this isn't a problem. There is also the hybridization between two related species. While such crosses are generally sterile, sometimes such plants are actually inter-fertile. As I recall, wheat is the result of a cross between a 1n grass and a 2n grass, producing 3n wheat.

This has been observed in the field under controlled conditions, and in the lab.

In fact, I believe that it has been induced in the field and the lab.

However, what I had in mind was the experiment in which the genome of a shrimp was altered in a laboratory experiment. The result was that the the production of abdominal appendages (swimmerets) in offspring was suppressed. A similar mutation would be necessary in the transition from crustacean to insect and arachnid.


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pandion
Member (Idle past 1109 days)
Posts: 166
From: Houston
Joined: 04-06-2009


Message 15 of 17 (505135)
04-08-2009 12:42 AM


I can't support this from literature, I just remember reading about it somewhere.

Drosophila (fruit flies) are used used as subjects in many genetic studies. The original flies were captured in California and then propagated artificially for generations. It seems that these artificially maintained lab strains have speciated more than once. While they may be indistinguishable in appearance, there are several laboratory strains that no longer interbreed. Moreover, they no longer interbreed with the original population.

I wish I had made a note of where I read that. I have searched several times since, but have not been able to find it. It is plausible, but I can't actually cite a reliable source.


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