Tom Ames

Molecular data is afforded special status in systematics (relative to morphological data) for at least four reasons that I can think of off the top of my head:
<ol type="1">[*]The coding of the character state is unambiguous. If, say, a clade of snake has between 5 and 10 scales in a particular location, there are a number of ways to code, and treat, those data. Nucleotide or amino acid identity does not have this problem[*]The characters themselves are (potentially) unambiguous. Morphologists may define the same feature differently. Unless the alignment is screwy, determinations of homologous sequence characters can be less of a problem.[*]There is a lot more molecular data available, especially on a per dollar basis[*]The models of molecular evolution (for neutral sites at least) are more rational than those for morphological character evolution. Likelihood methods are thus better applied to molecular data[/list=a]

I could probably come up with another half dozen reasons if I tried hard. None of these reasons would be religious or mystical.

seanie

Motorcycle Mama

If I were you I'd edit your profile.

I'm not sure you are a diest.

Motorcycle Mama

No argument with the above points. I take exception to three aspects of molecular data. First is the vagueness of molecular data as expressed in many equally valid results from one analysis or the exisistence of ambiguities in those results. Second, the results achieved after an analysis of molecular data will differ depending on the program used or the assumptions built into the analysis, e.g., outgroup. Third the supposed superiority of molecular over morphological data are never demonstrated analytically. It seems to me that molecular, or any other kind of data when used systematically, is first and foremost a problem in data analysis and the principles of data analysis should be applied. By and large they are not in studies involving molecular data.
Motorcycle Mama

Motorcycle Mama

A deist, in my lexicon, is someone who believes God created the basic units of the universe (energy [matter being transformed energy] and the laws of nature). What we now see in the universe is the result of the natural events that followed from the existence of energy and the laws of nature. This is Lamarck's argument; he used the term Supreme Author for God and Nature for energy and the laws of nature. Or as I used to say in a class I taught, God created Nature and then retired to the grandstand with a celestial six-pack and a tamale dispenser to watch the physical world unfold. Being a deist is an easy way to avoid original sin when addressing the physical world.
Motorcycle Mama

seanie

Fine.

What's a diest believe?

That doG created the universe?

Peez

This limitation is well-known to systemitists, and is not present in all studies. This sounds a lot like the first "aspect", and the same rebuttal applies. What do you mean? As has been explained, there are a number of advantages of DNA data over morphological measurements. Do you disagree with one or more of these advantages? Why do you think this?

Peez

Motorcycle Mama

Peez,
I don't know how to get all your quotes into one response so I'll try to respond to your questions. The first two points I raised about ambiguity in molecular data are related, but not of necessity; you can get many equally valid results within which there are no ambiguities or only one valid result replete with ambiguities. The problem I have with ambiguous results, and a problem that molecular systematists seem not to concern themselves with, is what those ambiguous results mean in terms of the data. I don't know of any detailed studies on the types of analyses that molecular systematists use but when other multivariate techniques give vague results it means there are no strong trends in the data. If there are no strong trends in the data then it seems to me that one would want to know why. Are the relationships among the individuals being analyzed unclear or are the data themselves unclear?
I could go on at length but shall not, both of us have better things to do with their time.
Motorcycle Mama

Motorcycle Mama

Duvenoy,
You're right, the name of the game is understanding. The belief system in molecular studies comes from the belief that such lead to a deeper, more profound, more meaningful, etc., understanding.
Also, molecular studies are not cheap. Some labs. in the dept. from which I am retired spend $20,000 a year, granted those are $.70 Canadian dollars, on chemicals to do their molecular research. I've not spent that much on privately supported morphological research in 10 years.
Also, molecular studies, because they are expensive, cannot adequately evaluate variation. Often a species, or even a genus, is represented by a very limited number of organisms.
Also, molecular studies cannot evaluate within organism variation for two reasons. First is the one mentioned above, cost, and the second is that, at least now, most molecular studies assume DNA is constant throughout an organism. This, however, may change.
And lastly, and perhaps most importantly, when you do morphological studies you have an excuse to go to pretty places, in my case central Washington, central Oregon and northeastern Oregon, so you can get adequate samples to study variation with and among species.


doov[/QB][/QUOTE]

Me, I wouldn't have the patience for it.

doov[/QB][/QUOTE]

Me neither, and I have technological fingers of death to boot.

Motorcycle Mama

scigirl

MM -

What I think they mean is, you spelled deist wrong. it's D - E - I - S - T not DIEST.

Hey don't worry I spelled atheist wrong in my profile for a while!

scigirl

Tom Ames

All of these criticisms apply equally to morphological studies. And techniques for analyzing molecular data (and evaluating uncertainty in the results) have progressed beyond your impression of the state of the art.