[Taxacom] Methodological plurality [was cladistic analysis for morphological characters -- UPGMA is not cladistics]

Kipling (Kip) Will kipwill at berkeley.edu
Mon Nov 19 11:31:47 CST 2012


On 11/19/2012 8:00 AM, David Campbell wrote:
>> Congruence or conflict across methods tells us little or nothing about
>> clade support.
>
> Although congruence across methods is not that surprising when using
> the same data set, conflict does indicate that the perceived support
> is method-sensitive.  Perhaps it's weak support; perhaps there is an
> issue with the different analysis techniques that highlight
> discrepancies in the data.  But there's good reason for caution about
> basing grand conclusions about results that are supported by one line
> of evidence (whether an analysis technique, a data set, whatever) and
> contradicted by another; conversely, if the same result pops out time
> after time, that's more convincing.
>


That line of reasoning makes using multiple methods a sensitivity 
analysis. It would be the equivalent of using only one alternative set 
of parameters. There is quite an extensive literature on sensitivity 
analyses, but I can’t recall ever seeing such a limited test of 
parameter space being considered sufficient.

In any case, conflicting resolutions can each be highly supported in 
different analyses and when they are, should we to take that to mean 
neither is highly supported?

When they agree it tells us little since we expect that or perhaps they 
are both wrong, when they disagree strongly it tells us nothing at all 
about the result (maybe something about the methods) and when they 
disagree and are each weakly supported it’s just redundant. The weak 
support measures in each analysis already told us not to be too confident.


-- 

Contact info:

Kipling W. Will
Associate Professor/Insect Systematist
Associate Director,Essig Museum of Entomology

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