[Taxacom] Ladderising phylogenetic trees

[Curtis Clark]

On 3/9/2010 7:59 PM, Kenneth Kinman wrote:
> Hi Curtis,
>         I don't think that is what she meant, given that she make the
> broad statement that: "There is no evidence to support anagenesis as a
> mechanism of speciation."  She seems to be dismissing the idea of
> anagenetic speciation, be it "bad" or "good".

But in fact she is correct in that regard. I don't doubt the occurrence 
of anagenesis (there are abundant examples both from living organisms 
and from fossils), but I have yet to see evidence of anagenesis giving 
rise to a new species without lineage-splitting. Of course, if species 
are human constructs (which I reject, but it seems a majority of list 
members support), and we define species as the result of cladogenesis, 
then it is a tautology.

>         What I really worry about are the students who she might be
> negatively influencing by branding their ideas as misconceptions.   She
> seems to be branding all anagenetic evolution as a misconception (just
> as strict phylogeneticists brand all formal paraphyletic taxa as
> unnatural and/or "unscientific").

So if a student says that the existence of contemporaneous dinosaur and 
human tracks in Texas supports a recent creation of the Earth, we harm 
that student by branding it a misconception? I don't think she's 
branding anagenetic evolution as a misconception (I don't think she 
addresses it), but rather anagenetic speciation. Inasmuch as anagenetic 
speciation is largely (outside this list) regarded as a discredited idea 
of the past, one has to draw the line somewhere. We all know where 
"teaching the controversy" leads.

> P.S.  As I noted earlier this year, I am not convinced that "Humans are
> descended from monkeys" is a case of "bad" anagenesis.

Students have a modern monkey species in mind (however ill-conceived it 
might be) rather than a higher taxon. If I were instead to say "Humans 
are descended from vertebrates", the students would not "personalize" it 
so much.


-- 
Curtis Clark                  http://www.csupomona.edu/~jcclark/
Director, I&IT Web Development                   +1 909 979 6371
University Web Coordinator, Cal Poly Pomona