[Taxacom] SUSPECT Re: Molecules vs Morphology

[Kipling (Kip) Will]

Possibly a species phenotypically plastic for some feature that reacts 
to the environment could become fixed for one phenotype even though the 
underlying genetics are the same. This isn’t to say that there isn’t an 
underlying genetic mechanism only that it would not have to be in 
lock-step with significant morphological change and these morphological 
changes could be phylogenetically informative. There are some 
significant works published on the subject.

Similarly a bird might learn a new song when it hears a new ring-tone 
from a cell phone and teach it to its offspring. If that song provided a 
significant advantage and was propagated through descendant generations 
it would be evolutionarily significant and be evidence for phylogenetic 
grouping even though there is was no genetic evolution directly tied to 
the song itself. Certainly it has an indirect connection to the genome 
in regard the underlying genetics behind singing and learning. But 
again, the notion of genes as a “blueprint” or one-to-one 
genotype-phenotype changes is just too simplistic.

However, I think characters of this sort are bound to be far too few and 
often too problematic to interpret to provide support for all or even 
most groups of taxa.

As you point out genetic change can also occur without obvious 
morphological change. But equating evolution to genetic change alone is 
untenable for many reasons and likewise morphology alone is not the end 
all, be all.

We are going to need all kinds of data, and there are only two kinds. 
And the kinds are *not* morphological and molecular.

The two kinds of characters are those that *correctly* mark the history 
(i.e. sister groups, for me) of the set of taxa one is investigating and 
characters that don’t (uninformative, misleading, etc.). Our job is to 
do our best to sort this out during character analysis. We always fail 
to some extent regardless of where the characters come from.

Kip


Mario Blanco wrote:
> Commonly accepted among biologists in general. That definition has 
> absolutely no conflict with morphological evolution. As I said, all 
> morphological evolution is determined by changes in the genetic
> makeup through generations. I am myself more interested in the
> morphology, but even paleontologists have to acknowledge the genetic
> basis of morphological evolution. The reason that this definition
> does not explicitly mention morphology is because you can have
> genetic change through generations without any obvious change in
> morphology or behavior. And yes, that is still evolution.
> 
> Of course, when you study evolution of extinct taxa you have to rely
> on morphological evolution and rarely (if at all) can study the
> underlying genetic changes, but that doesn't mean they didn't occur.
> The logical assumption is that all morphological changes were
> determined by genetic changes. And of course, you can have artifacts,
> like when different life stages or sexes are mistakenly taken as
> different species, always a risk with extict taxa (and any poorly
> known extant taxa for that matter).
> 
> If you define evolution in terms of morphological change, then you
> have to be careful to explicitly indicate that such change must be
> heritable (to avoid Lamarckian implications). And of course,
> "heritable change" implies that it is dictated by the genome.
> 
> 
> Bob Mesibov wrote:
>> Mario Blanco wrote:
>> 
>> "But evolution itself is defined as change in the genetic makeup of
>> a population through generations (this is a widely accepted
>> definition of evolution)."
>> 
>> Ouch. Widely accepted among phylogeneticists, maybe, but
>> paleontologists would disagree. Also all those who, like me, have a
>> rather more richly textured picture of evolutionary history than a
>> set of gene trees.
>> 
> 
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-- 
Kipling W. Will
Associate Professor/Insect Systematist
Associate Director,Essig Museum of Entomology

mail to:
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