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Author Topic:   Why Darwinism is wrong
mick
Member (Idle past 5012 days)
Posts: 913
Joined: 02-17-2005


Message 10 of 305 (202801)
04-26-2005 8:37 PM
Reply to: Message 1 by Jianyi Zhang
04-26-2005 11:57 AM


Neo-Darwinism is based on change of allele frequencies, which cannot provide explanation how allele change lead to addition, deletion of pieces of chromosome, or change of chromosomal numbers.
The theory of evolution does not claim that changes in allele frequency result in karyotype changes. Changes in karyotype may, however, affect allele frequency (i.e. if an allele is deleted or duplicated). You will need to explain how the existence of various karyotypes is meant to be a challenge to the theory.
lateral transfer in bacteria
This is no challenge to neo darwinism. It just means that our population genetics models have to be modified when we study bacteria. The existence of HGT challenges neither the existence of mutations nor the existence of natural selection. In fact HGT is rightly viewed as just another mechanism (among many) that generates genetic variability within populations, i.e. the bedrock of neoDarwinism.
polyploids in plants
I fail to understand how abnormal cell division, resulting in duplication of the genome, is meant to challenge evolutionary theory. A polyploid cell resulting from whole genome duplication isn't "instantaneous biodiversity". It's just a normal individual with twice the amount of genetic material.
generation of SARS or HIV and many virus
The molecular evolution of HIV is in fact rather well understood and you are simply wrong to say it reflects "instantaneous biodiversity". There are around five distinct forms of SIV, each associated with a different primate species, and there are chimeric forms in hybrid zones; and it's clear that human HIV evolved from SIV and didn't appear instantaneously. The molecular evolution of HIV is explained well by neoDarwinism, showing purifying selection on some regions of the viral genome and diversifying selection on others. Are you really suggesting that HIV didn't evolve from SIV?
incorporation of mitochondria by symbiosis... fall into instantaneous biodiversity, not gradual
You are way off the mark on this one. The plastid genomes of eukaryotes are highly diverse, and they are subject to ongoing evolution (i.e. http://www.ncbi.nlm.nih.gov/entrez/...).
{Shortened display form of URL, to restore page width to normal. - Adminnemooseus} They could well have arisen by multiple endosymbiotic events, not just one spontaneous event. Just compare a chloroplast or a mitochondrion to a bacterium, and look at the diversity of chloroplast structure in plants, to see that this wasn't just an instantaneous transition that has been frozen over the millenia.
atavisms, innovative organ, bottleneck effect, mosaic evolution, Cambrian explosion, rate of evolutionary change, few speciation in big mammals, RMNS mechanism poorly explains these phenomena.
I find it difficult to see what you are trying to get at here... What exactly is it about bottlenecks or different evolutionary rates that evolutionary theory can't account for? Your examples are rather odd. For example evolutionary theory (or more specifically population genetics) has a very sensible explanation for the rareness of speciation events in big mammals (hint: it has to do with generation time)
Because RMNS model has no predictory power, there is no way falsifying it,
You are just betraying your own ignorance here.
Too complicated
it's a complicated world out there.
This message has been edited by Adminnemooseus, 04-27-2005 02:03 AM

This message is a reply to:
 Message 1 by Jianyi Zhang, posted 04-26-2005 11:57 AM Jianyi Zhang has replied

Replies to this message:
 Message 20 by Jianyi Zhang, posted 04-27-2005 4:11 PM mick has replied

mick
Member (Idle past 5012 days)
Posts: 913
Joined: 02-17-2005


Message 16 of 305 (203014)
04-27-2005 1:17 PM
Reply to: Message 15 by Jianyi Zhang
04-27-2005 12:36 PM


Hi Jianyi,
For some reason you didn't reply to my post, but that of Wounded King raised similar issues, so I hope it is okay for me to jump in here.
You say that chromosomal mutations are
instantaneous processes at individual level, which occur without NS, and subject to NS effect after they are generated
.
But this also applies to any mutation (including point mutations). Point mutations are also "instantaneous processes at individual level, which occur without NS, and subject to NS effect after they are generated". Who ever said that point mutations occur "because" of NS? You are imputing a teleology to population genetics which is a misrepresentation of the theory. If point mutations are teleological, then so are chromosomal mutations. But if chromosomal mutations are not teleological, then neither are point mutations. You need to get your story straight, one way or the other.
but different species almost have different karyotic patterns, some gross mutations can not be seen by karyotypic study, as they are not big enough to be seen
The importance of chromosomal mutations is exaggerated here. There are plenty of closely related species that have identical chromosome numbers and formations, for example. I suspect that your invisible karyotypic mutations are just point mutations. If you can't identify them by karyotypic study, then how do you know they are what you say they are? The important point is that mutations such as inversions or repeats are generated by the same mechanism as any other mutation. An error in DNA replication may result in micro-level substitutions, or it may result in mid-level gene duplications, or it may result in whole genome duplications. The origin of genetic diversity in the genome doesn't make any difference to whether NS can result in speciation, as you have already pointed out NS only operates AFTER the mutation has occurred.
All of these evidences are against RMNS as the mechanism of speciation. Can you tell me how polyploids in plants occur by RMNS?
You are making the same mistake again. We already agree that NS only operates after the mutation arises. polyploidy IS a random mutation, unless you are claiming that genome duplication in plants occurs by a non-random process (which you haven't explained and haven't provided any evidence for). natural selection doesn't predict or explain why polyploidization occurs. It may have something to say about the origin of proofreading systems that correct such errors after they have occurred. But the duplication of a genome during a malfunctioned cell division happens randomly, and then NS acts on the result.
you should read some books by E. Mayr, top Darwinists
I've read some Mayr, and I think he says pretty much what I've said above. Can you elaborate?
How about virgin birth of shark in zoo?
The national geographic article you cite give some possible explanations (i.e. long-term storage of sperm, or hermaphroditism). I couldn't find any mention of this shark in the scientific literature, and note that the zookeepers have yet to carry out any genetic analysis to try to identify what happened. it's already known that hermaphroditic sharks, such as the black dogfish, exist in the wild (i.e. http://web.ukonline.co.uk/aquarium/pages/lsd.html). What's your point? What are we meant to infer re. the importance of natural selection to speciation?
Do you mean eggs give a birth to a new species?
speciation is usually considered to take longer than a single generation to occur, and I'm sure you know this. This is why reproductive isolation is necessary. But you are right, new species have arisen in oviparous clades (i.e. virtually every species of insect).
There is no way to predict anything with RMNS
here's a prediction for you: If physical barriers to gene flow are important in speciation, then we should find that "species richness" increases when the environment is variable and "patchy", compared to when it is uniform. We should also find that species richness declines for taxonomic groups that are able to travel large distances, because ability to travel will result in gene flow between divergent populations. The fact that I've made this prediction disproves your assertion.
This message has been edited by mick, 04-27-2005 01:19 PM
added in edit:
Your assertion the karyotype changes are necessary for speciation is wrong. I forgot about a useful review article that i should have mentioned. In Nature Reviews Genetics, Wu and Ting (2004, vol 5, p. 114-122) describe a number of "speciation genes" and give an overview of the theory. See Nature - Not Found
Clark et al. (Science, 2003, Vol. 302, Issue 5652) describe the variety of genes that have undergone natural selection since divergence of chimps and humans. Some of these may be "speciation genes" (though I admit it's an ugly concept). Note that this natural selection is acting irrespective of karyotype differences.
This message has been edited by mick, 04-27-2005 01:39 PM

This message is a reply to:
 Message 15 by Jianyi Zhang, posted 04-27-2005 12:36 PM Jianyi Zhang has replied

Replies to this message:
 Message 23 by Jianyi Zhang, posted 04-27-2005 7:14 PM mick has replied

mick
Member (Idle past 5012 days)
Posts: 913
Joined: 02-17-2005


Message 21 of 305 (203073)
04-27-2005 4:26 PM
Reply to: Message 20 by Jianyi Zhang
04-27-2005 4:11 PM


Jianyi,
Your post seems to rest on the idea that mutations are "caused" by natural selection. As an alternative to this view, you say
HGT is an instantaneous process, gene(s) were inserted into bacterial by viral vectors without any NS.
changes of allele frequency a gradual process, also at population level; it occurs by NS, however, duplications, deletions, inversions, amplifications and insertion are instantaneous processes at individual level, which occur without NS
Can we get it straight that mutations are not caused by natural selection? the "R" in RMNS stands for Random. That is, they are not "caused".
Now I will give you the benefit of the doubt and assume that you mean the spread of a random mutation is due to NS, but not its initial occurrence. How does this differ from the spread of a karyotype change in a population? Like a point mutation, the karyotype change occurs in a single individual. What mechanism do you have other than NS (by which I include all aspects of the modern synthesis including drift) to explain the spread of the karyotype change within a population?
mick
This message has been edited by mick, 04-27-2005 05:00 PM

This message is a reply to:
 Message 20 by Jianyi Zhang, posted 04-27-2005 4:11 PM Jianyi Zhang has replied

Replies to this message:
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mick
Member (Idle past 5012 days)
Posts: 913
Joined: 02-17-2005


Message 27 of 305 (203373)
04-28-2005 12:47 PM
Reply to: Message 23 by Jianyi Zhang
04-27-2005 7:14 PM


Hi,
Okay, I think I understand you now. Sorry if my earlier posts were slightly off-target.
There are some areas we agree on. Polyploidy in plants plays an important role in speciation. Chromosomal changes, in general, may play an important role in speciation.
What we disagree on is how a karyotypic mutation, once it occurs, spreads within a population.
You seem to be saying that the existence of a chromosomal change (often?) results in instantaneous speciation. As I understand it, this can only hold for asexually-reproducing organisms. This is probably why you keep bringing up plants. Its notable that polyploidy in plants is far more common in species with some form of vegatative propogation, because this permits the polyploidization to be spread within a large asexual lineage.
This is not the case for the vast majority of sexually-reproducing species. Perhaps this is why polyploidization is so rare in higher animals. I can think of a couple of polyploidizations in the fish, one in mammalia, a couple in reptiles, but not much more. Certainly nothing like the number of polyploidizations we can find in plants.
In a sexual species, once an individual has a chromosomal mutation resulting in reproductive isolation, it is finished, an evolutionary dead end. I imagine that this is why you brought up the virgin birth of the shark. You need mechanisms like hermaphroditism, asexuality and virgin births to explain how the mutated individual does not simply go extinct.
Unfortunately for you, hermaphroditism and virgin births are the exception rather than the rule in sexually reproducing species. (I might go so far as to say that the hermaphroditic black dogfish is a red herring )
For strictly sexual species, your model requires a multiplication of very small probabilities. First, a chromosomal change has to happen in a single individual. Then, an identical chromosomal change has to happen in a different individual of the opposite sex. Next, the two individuals have to meet each other and mate successfully with each other. All of these events are vansihingly unlikely, and the multiplication of their likelihoods has to be pretty small.
I would think a model permitting the accumulation of small chromosomal mutations with slightly negative fitness increment, in the presence of geographic isolation, would be a much more plausible hypothesis. Imagine that a small chromosomal mutation takes place. It has a slight fitness cost, or no fitness cost at all, and the individual can still reproduce. The chromosomal mutation spreads through the population by genetic drift. Many generations later, further, similarly small, mutations occur. These also spread (or not) by drift. Although none of these small changes results in reproductive isolation in and of itself, the long term accumulation of such small changes results in reproductive isolation between geographically separated populations, who have different histories of karyotype mutations that are not compatible with each other.
Unlike your model, the model I've described doesn't require the multiplication of vanishingly small probabilities, and doesn't require lots of unlikely events to occur in a single generation. All it requires is time and population genetic structure.
So I agree with you that chromosomal changes can result in speciation. But I don't agree that this happens instantaneously because of mutations resulting in complete reproductive isolation, in a single generation. And I don't agree that it is a likely general explanation for speciation in higher animals.
mick
This message has been edited by mick, 04-28-2005 01:01 PM

This message is a reply to:
 Message 23 by Jianyi Zhang, posted 04-27-2005 7:14 PM Jianyi Zhang has replied

Replies to this message:
 Message 28 by Jianyi Zhang, posted 04-28-2005 2:18 PM mick has replied

mick
Member (Idle past 5012 days)
Posts: 913
Joined: 02-17-2005


Message 29 of 305 (203459)
04-28-2005 7:33 PM
Reply to: Message 28 by Jianyi Zhang
04-28-2005 2:18 PM


Jianyi,
Thanks for responding.
In a previous post, I said that
Mick writes:
You need mechanisms like hermaphroditism, asexuality and virgin births to explain how the mutated individual does not simply go extinct.
Rather than denying my challenge, you have now added "twinning" to the mix.
Up to yet, your theory of instantaneous chromosomal speciation explains speciation in:
1. plants (but only if they reproduce asexually, for example by vegetative propogation)
2. sharks (but only in they are hermaphroditic or can have virgin births, or reproduce by vegetative propogation)
3. mammals (but only when they give birth to twins, are hermaphroditic, have virgin births or reproduce by vegetative propogation)
Why don't you give another ad hoc explanation for speciation in birds and reptiles (which don't twin and aren't hermaphroditic). Let's keep adding to the list!
And all this from somebody who criticises evolutionary theory for not being parsimnious enough!

This message is a reply to:
 Message 28 by Jianyi Zhang, posted 04-28-2005 2:18 PM Jianyi Zhang has replied

Replies to this message:
 Message 31 by Jianyi Zhang, posted 04-28-2005 8:46 PM mick has replied

mick
Member (Idle past 5012 days)
Posts: 913
Joined: 02-17-2005


Message 30 of 305 (203462)
04-28-2005 7:39 PM
Reply to: Message 28 by Jianyi Zhang
04-28-2005 2:18 PM


Usually, small animals have more species, large ones has less or none. Small animals have more siblings in the same birth. Even within mammals, mice have four siblings in the same birth; there are reports for new
speciation of mice. However, there are a few dozens billion human being in last 200,000 years, there are no signs for them, or part of them become a new species. Can any other models provide any reasonable explanation to it?
Basic population genetics tells us that population size and generation time account for such differences. Why don't you read "Why big fierce animals are rare" by Colinvaux, and read a good pop.gen textbook at the same time?

This message is a reply to:
 Message 28 by Jianyi Zhang, posted 04-28-2005 2:18 PM Jianyi Zhang has not replied

mick
Member (Idle past 5012 days)
Posts: 913
Joined: 02-17-2005


Message 32 of 305 (203503)
04-28-2005 9:32 PM
Reply to: Message 31 by Jianyi Zhang
04-28-2005 8:46 PM


Okay Jianyi,
I will await your explanation of speciation in birds, reptiles and insects.
No twinning allowed (they are oviparous; as far as I know twinning isn't physiologically possible, at least not in archaeosauria).
No polyploidization allowed (maybe not unheard of in insects, but exceedingly rare in birds and reptiles)
No virgin births allowed (none reported in the history of human science, as far as I know, in birds and reptiles; I would like to leave insects with an asexual phase in their life history out of it, just to keep it simple)
No hermaphroditism allowed (none reported in the history of science, at least in birds and reptiles, as far as I know. Though I wouldn't be surprised if it occurs in insects. Nothing about insects surprises me)
I would want an explanation that is general to archaeosauria plus insects, but also generalisable to other animals, including bacteria and viruses, in the same way that NS is universally applicable.
mick
This message has been edited by mick, 04-28-2005 09:33 PM

This message is a reply to:
 Message 31 by Jianyi Zhang, posted 04-28-2005 8:46 PM Jianyi Zhang has replied

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mick
Member (Idle past 5012 days)
Posts: 913
Joined: 02-17-2005


Message 73 of 305 (204693)
05-03-2005 2:49 PM
Reply to: Message 72 by TheNewGuy03
05-03-2005 1:52 PM


Re: LOL.
Just analyze all the evidence.
The analysis has been done, and continues as more data is gathered. If you want to argue against the common ancestry of apes and humans [sic] you will need to consider all of the evidence yourself.
Take a look at the genetic evidence, for example, and please feel free to provide evidence against common ancestry of hominidae.
Your task is to show that the genetic data are inconsistent with the idea that homo sapiens, pan troglodytes, pan paniscus, gorilla gorilla and Pongo pygmaeus form an exclusive monophyletic group.
To do this, you will first need to find a bunch of genes - say twenty or so - that have been sequenced for all of the hominid primates.
Next, you need to find the sequences for these same genes in as large a possible group of non-hominid primates. For example you would need sequences from lemurs, lorises, cebids, callitrichids, cercopithecids, etc.
Next, use a program like SeAl to align the homologous regions of each sequence, then import the alignments into Mr Bayes and generate phylogenies for each gene.
You are looking for phylogenies in which a non-hominid primate, like a lemur or macaque or baboon or something, shares a common ancestor with chimps, gorillas and orangs more recently than homo sapiens. This would be evidence for the paraphyly of hominidae, and if you could replicate it across numerous genes you would get a paper in Nature.
Good luck!
Mick
This message has been edited by mick, 05-03-2005 03:16 PM

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mick
Member (Idle past 5012 days)
Posts: 913
Joined: 02-17-2005


Message 105 of 305 (205873)
05-07-2005 4:18 PM
Reply to: Message 102 by Jianyi Zhang
05-07-2005 11:45 AM


Jianyi Zhang writes:
Can you tell me how speciation occur by RMNS, so I will start from there?
I assume you mean the genic view of speciation. Chromosomal speciation is not incompatible with genic speciation, nor with RMNS. But genic speciation appears to be incompatible with the view your are proposing. It involves genetic incompatibility between alleles of one or more genes present in divergent populations, with no chromosomal rearrangements necessary.
Wu and Ting (2004) Nature Reviews Genetics 5:114-122
"Genes and Speciation"
I have quoted a relevant passage below. You will have to pardon the references, which appears as numbers in the text. RI = reproductive isolation.
Wu and Ting writes:
The molecular genetics of speciation
To understand the molecular basis of RI, three key questions need to be addressed. First, what genes contribute to RI? Second, what are the normal functions of those genes? Third, how did these normal functions diverge among different populations, leading to RI? The fact that the genes that underlie post-mating isolation must have normal functions that are distinct from their role in RI is an important point to keep in mind. After all, the function of RI genes could not possibly be to sterilize their carriers. In this way, the analysis of RI is not unlike the study of graft rejection in organ transplantation: the biology of the major histocompatability complex, which underlies graft rejection, certainly has much wider and more profound implications than the phenomenon of graft rejection itself. In modelling the evolution of RI, the practice has been to consider only the RI phenotype without addressing the underlying function (for example, see Box 2). The reason for such a glaring omission is clear the identities of speciation genes, and so, their normal functions, have not been known until very recently.
Now, there are a handful of studies in which the identities of speciation genes have been shown: each of which we discuss. By definition, a speciation gene is one that can be shown to cause some degree of ecological, sexual or post-mating isolation between young, or even nascent, species. Although there have been other claims of speciation genes being identified, we consider the five that we discuss to be the only studies that have truly identified the molecules involved. There are many excellent studies that focus on genes that differ between species and the molecular interactions between them but that do not address their phenotypic effects on the whole organism (for example, see Ref. 23). Until these further studies have been done, such genes cannot be classified as speciation genes.
Although the definition of speciation genes includes those with strong or weak effects on ecological, behavioural or physiological differences, most of these initial studies have concentrated on genes that have large effects on physiological characteristics. Four of these five examples focus on post-mating isolation. The final example, which concerns ecological adaptation between behavioural races, is therefore of considerable interest.
Melanoma formation in Xiphophorus species hybrids (Xmrk-2). Many species in the fish genus Xiphophorus have spots on their skin that are composed of black pigment cells. In interspecific hybrids between X. maculatus (platyfish) and X. helleri (swordtail), these spots sometimes spontaneously develop malignant melanomas24-26. A two-locus Dobzhansky-Muller (DM)-type model (see Box 2) has been proposed to explain the formation of malignant melanomas. In this model, overexpression of the Tu gene causes these melanomas to form. The second locus involved, called the R gene, is a suppressor that negatively controls Tu. The platyfish contains both Tu and R genes, whereas the swordfish contains neither. In the backcross F2 hybrids, a quarter of the offspring produce melanomas owing to the presence of Tu but the absence of the R gene.
The X-linked Tu locus was subsequently mapped to a candidate gene, Xmrk-2 (Refs 27—29). Xmrk-2 encodes a transmembrane growth factor of the RECEPTOR TYROSINE KINASE SUPERFAMILY that is important in signal transduction. Its closest homologue in humans is the epidermal growth factor receptor (EGFR)30. All the features of Xmrk-2 are consistent with those of the dominant ONCOGENE that causes the melanomas in the hybrid fish. In particular, mutations at the Xmrk-2 locus abolish the Tu phenotype and the overexpression of Xmrk-2 gives rise to a high frequency of tumour formation.
In the adjacent genomic region, another EGFR homologue, Xmrk-1, was found in all Xiphophorus fish. Xmrk-1 and Xmrk-2 are therefore duplicated genes. However, Xmrk-1 transcripts can be found in all tissues, whereas Xmrk-2 transcripts are only abundant in the melanomas of the hybrids. Xmrk-2 apparently originated from non-homologous recombination between Xmrk-1 and an adjacent D locus31. So, this hybrid locus has the regulatory region from the D locus and most of the coding regions from Xmrk-1. The R gene represses Xmrk-2 as well as the D locus. Another important difference between Xmrk-1 and Xmrk-2 is the two amino-acid replacements in the extracellular domain, which shows ligand-independent activation32. So, divergence after gene duplication is important in the differentiation of these species and this might be a common feature of speciation genes (see also below).
Xmrk-2 induces tumour formation only in the hybrids in which the R gene is absent, in accordance with the classical DM model of post-mating isolation. In other species, such as the medaka, overexpression of Xmrk-2 also causes embryonic lethality. The constitutively expressed Xmrk-2 activates a transcription factor, STAT5, and subsequently upregulates several downstream targets33. So, overall, there is strong circumstantial evidence that Xmrk-2 is a speciation gene. However, the multiple alleles at each locus in the natural populations of each species, all of which cause a different degree of hybrid phenotype, require further study. It is possible that some of these alleles are not becoming fixed but rather are simply deleterious mutations in the process of being removed by purifying selection. Those deleterious alleles that are destined to be removed would not contribute to species differentiation.
Hybrid male sterility in Drosophila species (OdsH). The Odysseus (OdsH) gene from D. mauritiana causes complete male sterility when co-introgressed with the adjacent segment into D. simulans. Genetic mapping of the male sterility locus (Fig. 2a) allowed the initial identification of OdsH as this RI locus34. Recent transgenic studies have confirmed this identification35. OdsH is a homeobox gene from a family of transcription factor-encoding genes that are known to be slowly evolving. Curiously, OdsH has been evolving rapidly within the D. melanogaster subgroup even though its homologues from other species are extremely conservative.
The most direct approach to assess the normal function and the phenotypic effect of a specific gene is to knock it out. Interestingly, the deletion of OdsH from D. melanogaster results in no obvious adverse phenotype35. So, at least at this crude level of observation, OdsH is dispensable. However, a more detailed examination showed a subtle effect: males missing OdsH suffer a 40% fertility reduction when they are two days old and mate repeatedly. This fertility reduction lessens to 20% and 8% in the next two days, also under sperm-exhaustion conditions. After five days, the role of OdsH in fertility enhancement vanishes. One interpretation of these findings is that the role of OdsH is to accelerate the maturation of sperm. So, only very young males under sperm-exhaustion conditions are affected.
Comparative analyses indicate that OdsH was duplicated in the Drosophila lineage from a neuron-expressed gene, unc-4, after it diverged from the mosquito lineage. Whereas unc-4 in Drosophila has not diverged much in either sequence or expression from the ancestral state in the common ancestor it shares with mouse and C. elegans, OdsH has changed in both sequence and expression. Specifically, OdsH has been evolving away from the unc-4 pattern of embryonic and neuronal expressions to a testicular role35.
Because OdsH is divergently regulated between D. simulans and D. mauritiana, its expression in the testis of the sterile hybrids is highly misregulated. OdsH transcripts accumulate in very young spermatocytes. The pattern is not observed in either parental species or in the fertile introgression line, which differs from the sterile line by a 3-kb segment of OdsH (Ref. 34). The expression of unc-4 in the sterile introgression line is also normal. Therefore, the divergence in the sequence and the expression of OdsH might both contribute to the hybrid sterility.
Hybrid inviability in Drosophila species (Hmr). Another classical RI system in Drosophila is the hybrid incompatibility between D. melanogaster and D. simulans, two species that have been reproductively isolated more than 2.5 million years. Crosses between these species produce only inviable or sterile hybrids36-38. Five mutations that could rescue the inviable F1 hybrid progeny have been found and several were elegantly characterized for their MATERNAL or ZYGOTIC EFFECTS39-43. Given the multi-locus nature of hybrid incompatibility, it was surprising that such hybrid-rescue mutations could be identified.
Among the hybrid-rescue mutations, the X-linked Hmr (hybrid male rescue) gene, which rescues the inviable hybrid males, was mapped and cloned44, 45. Hmr was identified as a transcription factor in the myeloblastosis family44. The primary amino-acid sequence of Hmr contains two DNA-binding protein motifs that indicate its role in transcription regulation. There were many amino-acid substitutions between the sibling species in the DNA-binding domains of Hmr. So, this pattern indicates that positive selection might drive the rapid evolution of Hmr. However, the Hmr mutation that rescued hybrid viability was a P-element insertion in its 5' region that resulted in a reduction in the amount of wild-type transcript. For Hmr to be considered a true 'speciation gene', it would be necessary to show that the D. simulans and D. melanogaster alleles are functionally divergent in their rescue effect of hybrid viability. A recent transgenic study indicates that this might indeed be the case (D. Barbash, personal communication).
Hybrid inviability in Drosophila species (Nup96). Complementation mapping (Fig. 2b) has been used to analyse hybrid inviability between D. melanogaster and D. simulans. High-resolution mapping has allowed a speciation gene, Nup96, to be cloned and characterized22. The Nup96 allele from D. simulans causes inviability in the F1 hybrids if the copy from D. melanogaster is absent. Nup96, which has homologues in yeast, worm and human genomes, encodes a subunit of a nuclear-pore complex, which transports macromolecules between the nucleus and cytoplasm46 and is therefore essential for viability in flies.
An excess of non-synonymous substitutions in Nup96 between D. melanogaster and D. simulans relative to non-synonymous polymorphisms within these species (calibrated against synonymous changes with the MCDONALD AND KREITMAN TEST) indicated that this gene is under positive selection. With the sequences from D. mauritiana and D. yakuba, it was possible to map putative adaptive changes onto an evolutionary tree. Presgraves et al.22 concluded that the adaptive changes occurred in the distant past, a suggestion that is corroborated by the analysis of the extant polymorphisms in D. melanogaster and D. simulans. Had some adaptive changes occurred recently, a reduction in the amount of neutral polymorphism, which might also be accompanied by a skew towards very low- and/or very high-frequency variants, would have been expected. Neither was observed in Nup96.
Not only were Presgraves et al.22 able to map the Nup96 gene, but they were also able to locate the interacting locus in the DM model of hybrid incompatibility to the X chromosome. They did this by switching the source of the X chromosome in the hybrid males. One question to be addressed in the future is whether there are multiple loci on the X chromosome that interact with Nup96.
Ecological/behavioural races in Drosophila melanogaster (desat-2). The final example of a proven speciation gene (under our broad definition; see Box 1) provides a glimpse of the molecular genetics of ecological, and possibly behavioural, isolation. D. melanogaster from central-southern Africa around Zimbabwe and those from the rest of the world (referred to as the Z and M types, respectively) have evolved to become different ecological/behavioural races. The females of African and cosmopolitan D. melanogaster carry different forms of a specific type of non-volatile CONTACT PHEROMONES. These two forms the 5,9-heptacosadiene and 7,11-heptacosadiene forms of the 27-carbon cuticular hydrocarbons (CH)47 differ in the position of a double-bond in a long chain of saturated hydrocarbons. Two independent studies have identified the gene that controls the (5,9)/(7,11) difference to be a desaturase gene, desat2 (Refs 48,49). Although CHs often act as contact pheromones between sexes, they have also been implicated in ecological adaptations, such as heat or starvation tolerance50.
The desat2 gene apparently diverts the synthesis of 7,11-heptacosadiene into the 5,9-type. The loss of the promoter in the desat2 gene therefore results in the 7,11-type among the M flies. This observation raises the interesting possibility that loss of function of a gene has a role in this particular case of nascent speciation. The geographical distribution of the two desat2 variants (predominantly desat2+ in Africa and desat20 elsewhere) indicates that this strong differentiation must be maintained by differential selective pressure. An excess of high-frequency nucleotide mutations highlighted the influence of positive selection on the desat2 polymorphism49. Greenberg et al.17, 50 were able to show, by gene knock-out, that the loss of the desat2 gene (as in non-African M flies) results in an increase in cold tolerance and a decrease in starvation tolerance. It is plausible that, in the colder climate, a non-functional desat2 would spread through the cosmopolitan populations. So, this seems to be a case of ecological adaptation and differentiation.
An interesting aspect of the Z—M differentiation is the unidirectional sexual isolation between these forms51. Zimbabwe females, in the presence of Z and M males, do not mate with M males. (Note that the observation by itself does not indicate male or female choice.) We know that at least seven or eight genes control female or male mating behaviour, respectively13, 14. So, the question is whether desat2 is one of the loci that governs Z females' mating characteristics (for example, reduced attractiveness to M males). CH differences have been known to govern females' attractiveness in interspecific crosses52. However, it was widely thought that desat2 was not involved in female attractiveness in the Z—M system because Caribbean flies, which carry the African desat2 allele, behave like M flies. Nevertheless, recent observations have shown that, within three African populations, the presence of the African desat2 allele correlates nearly perfectly with Z-femaleness53. One possible interpretation of this pattern is that desat2 governs female attractiveness to M males and that the Caribbean population is an anomaly that results from recent admixture between African and North American flies. Although this interpretation seems to contradict the widely-accepted view that D. melanogaster males might not be discriminatory when choosing a mate54, new work indicates that M males might not court Z females as ardently as they court M females, especially when the females are not highly receptive (C.-T.T. and C.-I W., unpublished observations). If this is the case, the desat2 gene might be playing a double role in this nascent speciation through differentiation in ecological adaptation and, secondarily, through mating preference.
I hope these examples of genic speciation help.
Mick

This message is a reply to:
 Message 102 by Jianyi Zhang, posted 05-07-2005 11:45 AM Jianyi Zhang has replied

Replies to this message:
 Message 109 by Jianyi Zhang, posted 05-07-2005 6:29 PM mick has replied

mick
Member (Idle past 5012 days)
Posts: 913
Joined: 02-17-2005


Message 112 of 305 (205924)
05-07-2005 6:43 PM
Reply to: Message 109 by Jianyi Zhang
05-07-2005 6:29 PM


Hi Jianyi
Okay, here's a quick digest:
In Xiphophorus, there are differences between species in the expression level of promoters and suppressors acting on an oncogene. Hybridization between X. maculatus and X. helleri is unsuccessful because the genetically-determined difference in expression levels of promoters and suppressors in the parent species result in offspring that die of cancer. Consequently, the oncogene and its associated regulatory elements act as a reproductive isolation mechanism. The evolutionary hypothesis is that accumulated mutations in the regulatory system underlying oncogene activity result in reproductive isolation between divergent populations. Species integrity in these fish is maintained by the Xmrk-2 locus.
This is one possible mechanism by which reproductive isolation can result from small changes in single genes.
The other examples I quoted give examples of different species, different genes, and different mechanisms by which single genes, or genes plus their regulatory elements, play a role in the reproductive isolation of species. In all cases, the genes have been identified and mapped onto a chromosomal location, and their phenotypic effect has been experimentally determined.
It appears that speciation can indeed result from or be maintained by random mutation and natural selection.
Mick

This message is a reply to:
 Message 109 by Jianyi Zhang, posted 05-07-2005 6:29 PM Jianyi Zhang has replied

Replies to this message:
 Message 123 by Jianyi Zhang, posted 05-08-2005 12:50 AM mick has not replied

mick
Member (Idle past 5012 days)
Posts: 913
Joined: 02-17-2005


Message 117 of 305 (205956)
05-07-2005 8:01 PM
Reply to: Message 113 by Jianyi Zhang
05-07-2005 6:58 PM


Re: talking about mutation before
let us start wit Darwinian RMNS in speciation first, igoring others
Hi Jianyi,
After posting my last thread, I took a look at your website to examine the evidence you have against the involvement of RMNS in speciation.
First, you say that
Assuming speciation did occur by natural selection from unknown mechanism, the new species needs to find the same species at the same time in a very close geographical location along the evolutionary pathway across a few million years. If one fly were generated somewhere along the pathway, then it had to mate with another fly in the same species to have offspring. If the second fly were generated a few miles away, the chances of meeting would be dismal. If the second were generated in the following year, then they would die without reproduction. Had the speciation occurred according to Darwin’s theory, it would be mandatory to randomly generate a group of organisms with same genetic structure simultaneous in a very close geographical location. The probability for such thing is zero.
your mistake here is to think that speciation occurs in individual organisms. This is a significant misunderstanding of the conemporary view of speciation, in which speciation occurs between divergent populations of organisms. all of the references I provided in the article by Wu and Ting take this idea for granted.
let me try to explain the Xiphophorus example in a more conceptual manner. I am going to depart slightly from the description given by Wu and Ting, and give an imaginary example based on the idea of a melanin oncogene. hopefully this will make the idea clearer.
Imagine you have a population of fish which use black coloration to attract mates. The gene causing black coloration has to be expressed at a fairly precise level. Not enough black coloration leads to an absence of sexual marking, and a failure to reproduce. Overexpression of black coloration leads to melanoma, and death.
In order to control the expression of the gene that produces black coloration, the fish have two regulatory genes. One is a promoter (which encourages expression of the gene) and one is an inhibitor (which discourages expression of the gene).
Now, imagine that the population of fish becomes geographically isolated. Perhaps one group of fish swim upstream, into a lake, while another group swims downstream, into some ditches. It is very rare for a fish from the lake to accidentally find itself in the ditches, and it is very rare for a fish from the ditches to swim all the way up to the lake.
In the lake population, random mutations in the promoter gene cause slight overexpression of the gene controlling black coloration. This slightly increases the prevalence of melanoma in the population, but not to the extent that they all die of cancer. Nevertheless, any mutation causing slight overexpression of the inhibitor gene are favoured by natural selection.
In the ditch population, random mutations cause the opposite to happen. Mutations in the promoter gene reduce its biological activity, and cause slight underexpression of the gene controlling black coloration. Any mutation causing underexpression of the inhibitor gene is consequently favoured by natural selection.
Over many generations, the two populations get quite different regulatory systems operating on the same gene. One population has an extremely strong promoter and an extremely strong inhibitor. The other population has an extremely weak promoter and an extremely weak inhibitor. Both populations express the correct amount of black coloration, because the strength of promoters and inhibitors balance each other out.
Now imagine that the two populations come back into contact. When they hybridize, you end up with two unfit hybrids.
1. An offspring has an extremely strong promoter, but an extremely weak inhibitor.
2. An offspring has an extremely strong inhibitor, but an extremely weak promoter.
The first type of offspring produce too much melanin, get cancer, and die.
The second type of offspring produce not enough melanin, are unable to find mates, and do not reproduce.
As a consequence, the two populations are reproductively isolated from each other. Only if they mate "with their own kind" are they successful in producing viable young.
This is ONE idea of how speciation might occur by RMNS. It depends upon selection upon alleles in populations, not individuals.
There is not one single mechanism of how speciation might occur by RMNS. The example I have described clearly only applies for species with an oncogene that is involved in reproductive activity. But, in principle, any gene involved in reproduction and regulated by a number of loci might undergo a similar process.
Mick

This message is a reply to:
 Message 113 by Jianyi Zhang, posted 05-07-2005 6:58 PM Jianyi Zhang has replied

Replies to this message:
 Message 121 by Jianyi Zhang, posted 05-07-2005 11:45 PM mick has replied

mick
Member (Idle past 5012 days)
Posts: 913
Joined: 02-17-2005


Message 128 of 305 (206121)
05-08-2005 1:57 PM
Reply to: Message 121 by Jianyi Zhang
05-07-2005 11:45 PM


Re: talking about mutation before
Do you have any cases to support it occur at population level...This only means these authors Darwinists, or something close to that.Why does everybody else take their idea for granted?You just repeat of a typical story or imagination by current evolution theorists with Xiphophorus example
Differences in allele frequency between populations of a single species, have been demonstrated repeatedly, and empirically, in the field.
One such allele in Xiphophorus has been demonstrated to act as a reproductive isolation barrier. The gene has been characterized on a molecular level, and its phenotypic effect has been quantified in the laboratory. There is no doubt about the fact that it prevents hybridization between closely related sister species.
The Xiphophorus example is not a "story or imagination". It is a scientific fact.
Unless your theory can account for such facts in Xiphophorus and Drosophila, then you theory is simply worse than the Darwinian theory. There is no reason why Darwinists should accept a theory that performs worse than the current accepted theory.
I did not understand the remainder of your post.
Mick

This message is a reply to:
 Message 121 by Jianyi Zhang, posted 05-07-2005 11:45 PM Jianyi Zhang has replied

Replies to this message:
 Message 129 by Jianyi Zhang, posted 05-08-2005 2:39 PM mick has replied

mick
Member (Idle past 5012 days)
Posts: 913
Joined: 02-17-2005


Message 130 of 305 (206134)
05-08-2005 3:00 PM
Reply to: Message 129 by Jianyi Zhang
05-08-2005 2:39 PM


Re: talking about mutation before
You and your neighbor has different allele frequency, are you going to become different species?
This is just silly.
Jianyi, I have argued that speciation generally occurs between populations, not individuals. I would seem more apposite to ask this question of yourself. You are the only person here who believes that speciation occurs at the individual level.
In any case your suggestion that "I" have an allele frequency is statistically misguided. My allele frequencies are either 0% (don't have the allele), 50% (heterozygous) or 100% (homozygous), just like my neighbour. I suspect that we would share many allele frequencies, if the idea of statistical similarity of allele frequency is reasonable when we are talking about a sample size of 2.
Why does not my theory account for facts in Xiphophorus and Drosophila?
The paper by Wu and Ting describes evidence that reproductive isolation can occur by processes of random mutation and natural selection. In this thread you have denied this fact, based on your pet theory. This is why your theory cannot account for the phenomena in Xiphophorus and Drosophila described by Wu and Ting. If you think it can, please explain how.
I do not expect Darwinists change their faith. Who cares?
If you didn't care, you wouldn't be here. Why do you insist on talking of "faith"? I have provided references to empircal investigations that support the Darwinist hypothesis. It is only you who clings with misguided faith to a pet theory. The fact that you have made no attempts to test your theory, and just tell "stories and imagination" tells volumes.
This message has been edited by mick, 05-08-2005 03:00 PM

This message is a reply to:
 Message 129 by Jianyi Zhang, posted 05-08-2005 2:39 PM Jianyi Zhang has replied

Replies to this message:
 Message 133 by Jianyi Zhang, posted 05-08-2005 4:47 PM mick has replied

mick
Member (Idle past 5012 days)
Posts: 913
Joined: 02-17-2005


Message 135 of 305 (206179)
05-08-2005 4:56 PM
Reply to: Message 133 by Jianyi Zhang
05-08-2005 4:47 PM


Re: talking about mutation before
How about your neighbor family, town, city? Are they different? Are you going to become different species?
This is good. i think you are starting to understand. Different families, towns and cities constitute different populations. Now you are starting to agree with me. But your point is still basically silly. If you are going to persist in this tired argument about whether i am going to speciate from my neighbour, let's set things straight. The existence of widespread, cheap international travel and immigration suggests that we will not witness any future speciation events in the Homo sapiens lineage. This is because of the basic population genetic principle that gene flow reduces reproductive isolation.
If you do not understand, you need more schooling, and know some basic genetics.
Telling your opponents that they are ignorant is no way to help the conversation progress. You may wish to educate me by providing me with evidence that RMNS is NOT capable of generating reproductive isolation, with reference to the article by Wu and Ting.
Have you even bothered to read the article yet? last time, you said it was too complicated for you to understand.
Mick

This message is a reply to:
 Message 133 by Jianyi Zhang, posted 05-08-2005 4:47 PM Jianyi Zhang has replied

Replies to this message:
 Message 136 by Jianyi Zhang, posted 05-08-2005 5:08 PM mick has not replied
 Message 137 by jar, posted 05-08-2005 5:09 PM mick has replied

mick
Member (Idle past 5012 days)
Posts: 913
Joined: 02-17-2005


Message 138 of 305 (206197)
05-08-2005 5:32 PM
Reply to: Message 137 by jar
05-08-2005 5:09 PM


Re: talking about mutation before
Would we find that 100-1000 generations down the road the folk living around star A are a different species than those around star B?
Jar, under conditions of random mating and unlimited travel within planets, the number of generations required for speciation depends largely on the population sizes of each planet, because this is what determines the amount of genetic drift. The average time for fixation of a new nearly-neutral mutation in such a diploid population is in the order of 4N (where N is the population size). Beware that this distribution has an extremely high variance.
If you decide on a reasonable number of nearly-neutral mutations that might permit reproductive isolation, and settle on some initial population sizes for the two planets, you can calculate the expected number of generations prior to reproductive isolation, and you can calculate 95% confidence limits on the time (but the latter will be very wide).
In principle it is perfectly possible for a speciation event to occur in the human lineage.

This message is a reply to:
 Message 137 by jar, posted 05-08-2005 5:09 PM jar has replied

Replies to this message:
 Message 139 by jar, posted 05-08-2005 5:34 PM mick has replied

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