Understanding through Discussion


Welcome! You are not logged in. [ Login ]
EvC Forum active members: 84 (8914 total)
Current session began: 
Page Loaded: 06-18-2019 1:10 PM
33 online now:
DrJones*, dwise1, PaulK, ringo, Stile, Tangle, Tanypteryx (7 members, 26 visitors)
Chatting now:  Chat room empty
Newest Member: 4petdinos
Post Volume:
Total: 854,018 Year: 9,054/19,786 Month: 1,476/2,119 Week: 236/576 Day: 39/98 Hour: 2/1


Thread  Details

Email This Thread
Newer Topic | Older Topic
  
Author Topic:   Understanding the Genetics of Speciation
zedman963
Junior Member (Idle past 3507 days)
Posts: 3
Joined: 07-26-2009


Message 1 of 14 (519074)
08-11-2009 6:11 AM


I'm not a geneticist, only a medical student but am interested in evolution. Just to state my current stance at the moment, I believe in creation.

What I am wondering is how speciation is possible?

For the purposes of this discussion I am defining a species as two organisms who are so genetically different that if they can reproduce, then their offspring are sterile e.g. Horse + Donkey = Mule.

This is how much I understand so far:

1. One species is split into two groups due to some barrier.
2. These groups only breed within their own groups and are subjected to different pressures.
3. The variation in the gene pool means that those best suited to these pressures survive to pass on their genes to their offspring.
4. This results in two different gene pools.

It is the next step I don't understand, known as hybrid sterility:

5. For the two groups to form two separte species their gene pools have to have barriers to gene flow like horses and donkeys.

My questions:

1. Does anyone know a gene which has been shown to cause hybrid sterility between two closely related species e.g. peppered moths?

2. If a member of a the two groups does gain a mutation which confers hybrid sterility, how will he mate with any member of his isolated group in order to pass on his genes e.g. people with Down's syndrome, Klinefelter's syndrome, Turner's syndrome, etc. are all sterile? Any change in chromosome number seems to render an organism (at least humans anyway) sterile.


Replies to this message:
 Message 3 by RAZD, posted 08-11-2009 8:15 AM zedman963 has responded
 Message 4 by Wounded King, posted 08-11-2009 8:48 AM zedman963 has not yet responded

  
Adminnemooseus
Director
Posts: 3883
Joined: 09-26-2002


Message 2 of 14 (519085)
08-11-2009 7:42 AM


Thread Copied from Proposed New Topics Forum
Thread copied here from the Understanding the Genetics of Speciation thread in the Proposed New Topics forum.
    
RAZD
Member
Posts: 19871
From: the other end of the sidewalk
Joined: 03-14-2004
Member Rating: 5.3


Message 3 of 14 (519089)
08-11-2009 8:15 AM
Reply to: Message 1 by zedman963
08-11-2009 6:11 AM


simplistic version of evolution and speciation
Hi zedman963, and welcome to the fray.

What I am wondering is how speciation is possible?

Speciation is defined as the reproductive separation of daughter populations, where both descend from a parent population.

For the purposes of this discussion I am defining a species as two organisms who are so genetically different that if they can reproduce, then their offspring are sterile e.g. Horse + Donkey = Mule.

Unfortunately, that is not the definition used in biological evolution science - all that is necessary in biological evolution science is that the daughter populations fail to interbreed when provided the opportunity. The reasons for the failure could be genetic, or they could be behavioral - the daughter populations no longer see the other population as potential mates, and so do not engage in mating.

There are many instances where this occurs, ring species being the most definitive in this regard.

See http://www.zoology.ubc.ca/~irwin/GreenishWarblers.html

quote:
Greenish warblers (Phylloscopus trochiloides) inhabit forests across much of northern and central Asia. In central Siberia, two distinct forms of greenish warbler coexist without interbreeding, and therefore these forms can be considered distinct species. The two forms are connected by a long chain of populations encircling the Tibetan Plateau to the south, and traits change gradually through this ring of populations. There is no place where there is an obvious species boundary along the southern side of the ring. Hence the two distinct 'species' in Siberia are apparently connected by gene flow. By studying geographic variation in the ring of populations, we can study how speciation has occurred. This unusual situation has been termed a 'circular overlap' or 'ring species'. There are very few known examples of ring species.

There is a change in plummage and a change in mating songs, and both changes occur gradually around the ring until the point of overlap, where the difference is great enough that mating behavior is not engage in between the populations.

This is how much I understand so far:

1. One species is split into two groups due to some barrier.
2. These groups only breed within their own groups and are subjected to different pressures.
3. The variation in the gene pool means that those best suited to these pressures survive to pass on their genes to their offspring.
4. This results in two different gene pools.

Close.

They also get different random mutations, adding new variation to each gene pool and part of the total set of variations that are subject to natural and sexual selections. The end result is that there are two gene pools with different sets of variations, some are shared and some are not. If the shared genes are involved in mating and mating behavior, then the populations will likely interbreed if given the opportunity. If the non-shared genes are involved in mating and mating behavior, then the populations will likely not interbreed when given the opportunity.

It is the next step I don't understand, known as hybrid sterility:

5. For the two groups to form two separte species their gene pools have to have barriers to gene flow like horses and donkeys.

Notice that the chromosome numbers are different for horses and mules, just as they are different for humans and chimpanzees, and that this shows substantial changes to the behavior of the genes during reproduction, and thus affecting mating.

1. Does anyone know a gene which has been shown to cause hybrid sterility between two closely related species e.g. peppered moths?

Peppered moths are a good example of natural selection, however there is no evidence of reproductive isolation between the melanistic and non melanistic varieties. They are evidence of the variation possible within a gene pool, and the selection of those variations under different ecological conditions.

2. If a member of a the two groups does gain a mutation which confers hybrid sterility, how will he mate with any member of his isolated group in order to pass on his genes e.g. people with Down's syndrome, Klinefelter's syndrome, Turner's syndrome, etc. are all sterile? Any change in chromosome number seems to render an organism (at least humans anyway) sterile.

Because all the changes that add up to speciation don't occur in one individual, rather it is an accumulation, a cascade, of many mutations that end up different enough to prevent reproduction.

Look again at the Asian Greenish warblers - there are 5 varieties in the ring, each breeding with its neighbor variety, each variety being an accumulated pool of differences one from the other, but the two at the end of the ring are separated by four steps between the varieties of pools of different genetic variations - they have accumulated four times as much difference as there is between any of the other neighboring varieties.

I'm not a geneticist, only a medical student but am interested in evolution. Just to state my current stance at the moment, I believe in creation.

I suggest you study some courses, texts, whatever is at hand, material on evolution. A good place to start is:

http://evolution.berkeley.edu/evosite/evo101/index.shtml

quote:
What is evolution and how does it work? Evolution 101 provides the nuts-and-bolts on the patterns and mechanisms of evolution. You can explore the following sections:

It is easy reading and high school to university level material (depending on your schools)

Enjoy.

... as you are new here, some posting tips:

type [qs]quotes are easy[/qs] and it becomes:

quotes are easy

or type [quote]quotes are easy[/quote] and it becomes:

quote:
quotes are easy

also check out (help) links on any formatting questions when in the reply window.

For other formatting tips see Posting Tips

If you use the message reply buttons (there's one at the bottom right of each message):


... your message is linked to the one you are replying to (adds clarity). You can also look at the way a post is formatted with the "peek" button next to it.


we are limited in our ability to understand
by our ability to understand
Rebel American Zen Deist
... to learn ... to think ... to live ... to laugh ...
to share.


• • • Join the effort to solve medical problems, AIDS/HIV, Cancer and more with Team EvC! (click) • • •

This message is a reply to:
 Message 1 by zedman963, posted 08-11-2009 6:11 AM zedman963 has responded

Replies to this message:
 Message 7 by zedman963, posted 08-11-2009 1:22 PM RAZD has responded

  
Wounded King
Member (Idle past 2259 days)
Posts: 4149
From: Edinburgh, Scotland
Joined: 04-09-2003


Message 4 of 14 (519096)
08-11-2009 8:48 AM
Reply to: Message 1 by zedman963
08-11-2009 6:11 AM


1. Does anyone know a gene which has been shown to cause hybrid sterility between two closely related species e.g. peppered moths?

Not in peppered moths but in the geneticists long term workhorse Drosophila. The genes Nup160 and Nup96 which produce proteins involved in the nuclear pore complex have both been shown to cause hybrid incomaptibilites between D. simulans and D. melanogaster (Presgraves et al., 2003;Tang and Presgraves, 2009). This is an example I happen to recall, I'm sure there are others.

If a member of a the two groups does gain a mutation which confers hybrid sterility, how will he mate with any member of his isolated group in order to pass on his genes e.g. people with Down's syndrome, Klinefelter's syndrome, Turner's syndrome, etc. are all sterile? Any change in chromosome number seems to render an organism (at least humans anyway) sterile.

It is wrong to assume the incompatibilities need to be based on something as major as differences in chromosome number. As my above example shows, small alterations in one or 2 genes may be sufficient. There is a term 'Dobzhansky-Muller genes' which describes pairs of genes fulfilling a set of criteria ...

Each gene reduces hybrid fitness, has functionally diverged between the hybridizing species, and depends on the partner gene to cause HI [Hybrid Incompatibility]

One paper discussing such genes (Brideau et al., 2006) is interesting as it again describes hybrid incompatibility between D. simulans and D. melanogaster. In fact the experiments done in the Nup160/Nup96 papers were performed on hybrids which had had the incompatibility caused by the appropriately named Lethal hybrid rescue gene rescued, protecting the hybrid males from their usual fate of death.

This highlights the fact that not one but several different genetic differences have accrued between D. Simulans and D. melanogaster which have caused hybrid incompatibilities.

The point about Dobzhansky-Muller genes is that the mutation of one such gene within a population after it has diverged from its sister population will not produce incompatibility, it is in the interaction with genes in the sister population which have themselves diverged from their common ancestor that the incompatibility arises.

TTFN,

WK

Edited by Wounded King, : No reason given.


This message is a reply to:
 Message 1 by zedman963, posted 08-11-2009 6:11 AM zedman963 has not yet responded

Replies to this message:
 Message 5 by Codegate, posted 08-11-2009 11:19 AM Wounded King has responded

    
Codegate
Member
Posts: 84
From: The Great White North
Joined: 03-15-2006


Message 5 of 14 (519109)
08-11-2009 11:19 AM
Reply to: Message 4 by Wounded King
08-11-2009 8:48 AM


Are there any examples of species with differing numberer of chromosomes that continue to successfully interbreed?

Using man as an example, at some point several million years ago, we lost a chromosome from our contemporaries (chromosome 2 fusion I believe). There must have been a 'first specimen' that had this mutation, and this single ancestor must still have been able to reproduce in order to spread this mutation.

Are there any modern examples of this process occuring, where we can see a chromosomal change mutation spreading throughout a species?


This message is a reply to:
 Message 4 by Wounded King, posted 08-11-2009 8:48 AM Wounded King has responded

Replies to this message:
 Message 6 by Wounded King, posted 08-11-2009 12:09 PM Codegate has not yet responded

  
Wounded King
Member (Idle past 2259 days)
Posts: 4149
From: Edinburgh, Scotland
Joined: 04-09-2003


Message 6 of 14 (519112)
08-11-2009 12:09 PM
Reply to: Message 5 by Codegate
08-11-2009 11:19 AM


I haven't read these papers but a quick literature search turned up a few candidates.

Grishanin et al., 2006 writes:

GENETIC ARCHITECTURE OF THE CRYPTIC SPECIES COMPLEX OF ACANTHOCYCLOPS VERNALIS (CRUSTACEA: COPEPODA). II. CROSSBREEDING EXPERIMENTS, CYTOGENETICS, AND A MODEL OF CHROMOSOMAL EVOLUTION

In this paper the authors describe a series of crosses for 9 lines of Acantocyclops which had well characterised gentics and morphology and measured their comparative reproductive isolation on these bases (Grishanin et al., 2006). This set of species/subspecies showed multiple viable crosses betweeen partners with different chromosome numbers.

Buschinger and Fischer, 1990 writes:

Hybridization of chromosome-polymorphic populations of the inquiline ant,Doronomyrmex kutteri (Hym., Formicidae)

In this paper the authors describe viable hybrids from 2 subspecies of ant with differing chromosome numbers (Buschinger and Fischer, 1990). Hmm, having just looked back I don't see them actually crossing the hybrids, so maybe this paper doesn't show it at all, oops.

I'll keep looking.

TTFN,

WK


This message is a reply to:
 Message 5 by Codegate, posted 08-11-2009 11:19 AM Codegate has not yet responded

Replies to this message:
 Message 14 by sfs, posted 08-12-2009 10:53 PM Wounded King has not yet responded

    
zedman963
Junior Member (Idle past 3507 days)
Posts: 3
Joined: 07-26-2009


Message 7 of 14 (519119)
08-11-2009 1:22 PM
Reply to: Message 3 by RAZD
08-11-2009 8:15 AM


Re: simplistic version of evolution and speciation
Unfortunately, that is not the definition used in biological evolution science - all that is necessary in biological evolution science is that the daughter populations fail to interbreed when provided the opportunity. The reasons for the failure could be genetic, or they could be behavioral - the daughter populations no longer see the other population as potential mates, and so do not engage in mating.

Yes I know what the definition used in biological evolution science is.

The reason I used only the genetic component is because that is the part that is difficult to understand. How physical barriers to gene flow form.

The biological evolution science definition is just a useful way of showing how gene flow can be blocked in organisms that live in sympatry. It explains reproductive isolation in sympatry but not genetic speciation.

Therefore, for the purposes of this discussion, I have only included the genetic component in the definition.


This message is a reply to:
 Message 3 by RAZD, posted 08-11-2009 8:15 AM RAZD has responded

Replies to this message:
 Message 8 by RAZD, posted 08-11-2009 10:16 PM zedman963 has responded

  
RAZD
Member
Posts: 19871
From: the other end of the sidewalk
Joined: 03-14-2004
Member Rating: 5.3


Message 8 of 14 (519138)
08-11-2009 10:16 PM
Reply to: Message 7 by zedman963
08-11-2009 1:22 PM


Re: simplistic version of evolution and speciation
Hi again, zedman963.

The reason I used only the genetic component is because that is the part that is difficult to understand. How physical barriers to gene flow form.

But once two populations are reproductively isolated there is no restriction on the gradual modification through mutation and selection of traits that enhance the ability of individual members of each population to survive and breed.

In one population of mosquitos, one population bred during the morning and one during the evening, and this behavior difference led to reproductive isolation even though both populations occupied the same ecology and otherwise interacted as one population. They looked and behaved as one species, however it was found that one carried malaria and the other didn't: when looked at in the microscope it was discovered that the shape of the genitals had altered to such an extent that interbreeding was no longer possible and speciation had occurred.

When you look again at the Asia Greenish Warblers, there is another think to note: the hybrid zones are small in comparison to each of the habitat zones for the five varieties - implying that the hybrids as less successful in the variety zones competing with "purebred" varieties, and can only exist in the areas where there is sufficient overlap to keep producing hybrids. If these hybrids continue to have less viability and the zones continue to shrink, then a point will be reached where isolation occurs and speciation results.

My personal opinion (and I could be wrong) is that behavior changes occur first, resulting in preferential isolation, and that once that occurs, then the genetic changes that result in various levels of sterility and low viability will accumulate.

I also don't think that genetic incompatibility is important once behavior has caused the split, because once isolated, genetic changes in different directions to suit different ecologies is an open opportunity for both species to adapt to new and different ecologies. They can acquire different traits not related to breeding, and thus result in added diversity and adaptation to more opportunities.

The camel and the llama are adapted to entirely different ecosystems, separated by oceans for eons, and yet they can be artificially inseminated and develop a viable offspring. That doesn't mean that one will survive in the other habitat as well as the adapted species. Genetic incompatibility doesn't need to occur to develop different organisms adapted to different ecologies.

Enjoy.

Edited by RAZD, : .

Edited by RAZD, : ..


we are limited in our ability to understand
by our ability to understand
Rebel American Zen Deist
... to learn ... to think ... to live ... to laugh ...
to share.


• • • Join the effort to solve medical problems, AIDS/HIV, Cancer and more with Team EvC! (click) • • •

This message is a reply to:
 Message 7 by zedman963, posted 08-11-2009 1:22 PM zedman963 has responded

Replies to this message:
 Message 9 by subbie, posted 08-12-2009 12:35 AM RAZD has acknowledged this reply
 Message 10 by Wounded King, posted 08-12-2009 4:47 AM RAZD has responded
 Message 11 by zedman963, posted 08-12-2009 10:56 AM RAZD has responded

  
subbie
Member
Posts: 3509
Joined: 02-26-2006


Message 9 of 14 (519143)
08-12-2009 12:35 AM
Reply to: Message 8 by RAZD
08-11-2009 10:16 PM


The focus of this thread
I have insufficient knowledge to disagree with anything you've said, so I accept it as accurate. However, I think you are missing the point of focus that zedman intended to raise.

I have no problem with the idea that very little speciation occurs as a result of changes in chromosome numbers. But it seems that this particular mutation is the one that zedman wants to focus on. He begins with the assumption any change in chromosome number results in sterility. Obviously, there have been many such changes over the course of natural history. If his assumption is well-founded, it would present a serious problem, regardless of other types of mutation that may occur.

Wounded King purported to present one example where a change in chromosome number in fact did not result in sterility. (I don't mean to suggest that WK is wrong. I have not read his source so take him at his word that it's accurate.) At a minimum, it seems that this example is sufficient to overcome zedman's assumption that any change in chromosome number results in sterility, unless zedman can present evidence disputing WK's showing. Once this assumption is overcome, it seems that his objection that sterile offspring cannot produce a new species has been rendered irrelevant.

If my understanding of zedman's point is inaccurate, well, never mind.


Ridicule is the only weapon which can be used against unintelligible propositions. Ideas must be distinct before reason can act upon them; and no man ever had a distinct idea of the trinity. It is the mere Abracadabra of the mountebanks calling themselves the priests of Jesus. -- Thomas Jefferson

For we know that our patchwork heritage is a strength, not a weakness. We are a nation of Christians and Muslims, Jews and Hindus -- and non-believers. -- Barack Obama

We see monsters where science shows us windmills. -- Phat


This message is a reply to:
 Message 8 by RAZD, posted 08-11-2009 10:16 PM RAZD has acknowledged this reply

  
Wounded King
Member (Idle past 2259 days)
Posts: 4149
From: Edinburgh, Scotland
Joined: 04-09-2003


Message 10 of 14 (519154)
08-12-2009 4:47 AM
Reply to: Message 8 by RAZD
08-11-2009 10:16 PM


Re: simplistic version of evolution and speciation
The camel and the llama are adapted to entirely different ecosystems, separated by oceans for eons, and yet they can be artificially inseminated and develop a viable offspring. That doesn't mean that one will survive in the other habitat as well as the adapted species. Genetic incompatibility doesn't need to occur to develop different organisms adapted to different ecologies.

It is wildly misleading to put up the camel and llama as an example where 'Genetic incompatibility doesn't need to occur to develop different organisms adapted to different ecologies'. It is incredibly difficult to produce viable llama/camel hybrids there is a very high rate of spontaneous abortions and no evidence that these hybrids are fertile, these are not the hallmarks of a lack of genetic incompatibility. Indeed in their paper describing one of the successful crosses Skidmore et al. (1999) note ...

Skidmore et al., 1999 writes:

Although the diploid chromosone {sic} number of camels and guanacos is the same (2n = 74), sufficient genetic change has taken place to make the pairing of homologous chromosomes no longer possible.

Your point is good but your example fails to be an example of it.

TTFN,

WK


This message is a reply to:
 Message 8 by RAZD, posted 08-11-2009 10:16 PM RAZD has responded

Replies to this message:
 Message 12 by RAZD, posted 08-12-2009 10:28 PM Wounded King has not yet responded

    
zedman963
Junior Member (Idle past 3507 days)
Posts: 3
Joined: 07-26-2009


Message 11 of 14 (519205)
08-12-2009 10:56 AM
Reply to: Message 8 by RAZD
08-11-2009 10:16 PM


Re: simplistic version of evolution and speciation
n one population of mosquitos, one population bred during the morning and one during the evening, and this behavior difference led to reproductive isolation even though both populations occupied the same ecology and otherwise interacted as one population. They looked and behaved as one species, however it was found that one carried malaria and the other didn't: when looked at in the microscope it was discovered that the shape of the genitals had altered to such an extent that interbreeding was no longer possible and speciation had occurred.

Thank you, this is very interesting.

My personal opinion (and I could be wrong) is that behavior changes occur first, resulting in preferential isolation, and that once that occurs, then the genetic changes that result in various levels of sterility and low viability will accumulate.

I have the same opinion. It is just difficult to get my head around the next step, the genetic component.

The camel and the llama are adapted to entirely different ecosystems, separated by oceans for eons, and yet they can be artificially inseminated and develop a viable offspring. That doesn't mean that one will survive in the other habitat as well as the adapted species. Genetic incompatibility doesn't need to occur to develop different organisms adapted to different ecologies.

Also very interesting. Just for clarity, by viable offspring, do you mean fertile?

Sorry already read Wounded King's response, I withdraw my question.

Edited by zedman963, : No reason given.


This message is a reply to:
 Message 8 by RAZD, posted 08-11-2009 10:16 PM RAZD has responded

Replies to this message:
 Message 13 by RAZD, posted 08-12-2009 10:42 PM zedman963 has not yet responded

  
RAZD
Member
Posts: 19871
From: the other end of the sidewalk
Joined: 03-14-2004
Member Rating: 5.3


Message 12 of 14 (519283)
08-12-2009 10:28 PM
Reply to: Message 10 by Wounded King
08-12-2009 4:47 AM


Re: simplistic version of evolution and speciation
Thanks Wounded King, perhaps I overstated it.

It is wildly misleading to put up the camel and llama as an example where 'Genetic incompatibility doesn't need to occur to develop different organisms adapted to different ecologies'. It is incredibly difficult to produce viable llama/camel hybrids there is a very high rate of spontaneous abortions and no evidence that these hybrids are fertile, these are not the hallmarks of a lack of genetic incompatibility.

Correct, but what we have are living individual camas, a rather incredible seeming thing when we realize that they have been isolated populations for multimillion years with no chance of gene flow through intermediate species or forms, separated by an ocean as well as time.

What this shows is that the mutations and selections involved in the evolution of camels and llamas did not have to cause a prevention of the ability to interbreed for them to be better fit to their respective ecologies.

Your point is good but your example fails to be an example of it.

But it is, perhaps, an extreme example of a lot of evolution and adaptation, by two daughter populations over an extended period of time without necessarily destroying the ability to interbreed in the process, and it demonstrates that the standard of necessary genetic incompatibility is much higher than is necessary to explain the diversity of life as we know it on the planet.

Thanks.


we are limited in our ability to understand
by our ability to understand
Rebel American Zen Deist
... to learn ... to think ... to live ... to laugh ...
to share.


• • • Join the effort to solve medical problems, AIDS/HIV, Cancer and more with Team EvC! (click) • • •

This message is a reply to:
 Message 10 by Wounded King, posted 08-12-2009 4:47 AM Wounded King has not yet responded

  
RAZD
Member
Posts: 19871
From: the other end of the sidewalk
Joined: 03-14-2004
Member Rating: 5.3


Message 13 of 14 (519286)
08-12-2009 10:42 PM
Reply to: Message 11 by zedman963
08-12-2009 10:56 AM


many small steps over many generations in different ecologies
Hi again zedman963

Also very interesting. Just for clarity, by viable offspring, do you mean fertile?
Sorry already read Wounded King's response, I withdraw my question.

Yeah. At this point well just say "able to produce some living individuals with artificial breeding" and that this shows that total genetic incompatibility is not a necessary criteria for speciation.

It is just difficult to get my head around the next step, the genetic component.

So what happened in the camel and llama populations while they were separated?

Don't think of it as a single step. I can walk from Rhode Island to California, but I can't do it in one step, nor can I do it in one day: it takes many steps spread out over many days.

Each population can - and does - allow variations in the genes such that individuals each have essentially unique combinations within a population. New variations are added by mutations and old variations are eliminated by selection or by genetic drift, and the makeup of variations in the populations changes over time, generation by generation. With these generations individuals reproduce, some are infertile or miscarriages, including ones with old genes, and some are viable and robust, including ones with new genes.

Individuals only need to be able to reproduce in their generation, not with their ancestors, nor with their descendants, and a little change with each generation can add up to major change in many generations (though it does not have to, there is just the opportunity for it to do so, an opportunity that does not exist within a single population in a single generation).

Enjoy.


we are limited in our ability to understand
by our ability to understand
Rebel American Zen Deist
... to learn ... to think ... to live ... to laugh ...
to share.


• • • Join the effort to solve medical problems, AIDS/HIV, Cancer and more with Team EvC! (click) • • •

This message is a reply to:
 Message 11 by zedman963, posted 08-12-2009 10:56 AM zedman963 has not yet responded

  
sfs
Member (Idle past 698 days)
Posts: 464
From: Cambridge, MA USA
Joined: 08-27-2003


Message 14 of 14 (519287)
08-12-2009 10:53 PM
Reply to: Message 6 by Wounded King
08-11-2009 12:09 PM


quote:
In this paper the authors describe a series of crosses for 9 lines of Acantocyclops which had well characterised gentics and morphology and measured their comparative reproductive isolation on these bases (Grishanin et al., 2006). This set of species/subspecies showed multiple viable crosses betweeen partners with different chromosome numbers.

The common European shrew (Sorex araneus) has a highly variable number of chromosomes within a single species. There is some genetic isolation of karyotypic races, but also hybridization.
This message is a reply to:
 Message 6 by Wounded King, posted 08-11-2009 12:09 PM Wounded King has not yet responded

    
Newer Topic | Older Topic
Jump to:


Copyright 2001-2018 by EvC Forum, All Rights Reserved

™ Version 4.0 Beta
Innovative software from Qwixotic © 2019