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Author Topic:   On The Observability of Speciation
Stagamancer
Member (Idle past 3088 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
This message is a reply to:
 Message 1 by AustinG, posted 04-06-2009 2:38 AM AustinG has responded

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Stagamancer
Member (Idle past 3088 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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 Message 4 by AustinG, posted 04-06-2009 2:56 PM AustinG has not yet responded

    
Stagamancer
Member (Idle past 3088 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
This message is a reply to:
 Message 9 by AustinG, posted 04-06-2009 8:47 PM AustinG has not yet responded

    
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