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AW: Notarium question
> Like I
> said, you do
> the analysis to _discover_ whether this (and other
> characters) have a
> single origin or multiple origins.
> but over-emphasizing one "important" character to
> the neglect of
> others that tell a different story.
Indeed - and this is where the past experience shows it to get tricky: without
a priori assumptions, it is often be impossible to decide when some feature (I
do not say "character", because one feature may be one or several evolutionary
characters) becomes over-empathized.
I like to analyze cases where cladfistic analyses have yielded robust but wrong
results, and my conclusion is that if in doubt, it is better to split
characters rather than lumping, to the point where every suite of characters
that *might* have evolved en bloc (= as a single feature, such as a notarium)
*can* do so in the analysis, but does not *need to*.
In the case of the notarium, looking at how it differs between falcons and
flamingos for example could be helpful for character choice. (One can always
hope for some non-notarial character to provide a counterweight, but if a
notarial character can do the job, all for the better)
In molecular phylogenetics we're better off, since nobody can usually tell what
the exact consequences of a character state change (point mutation, indel) are
in the actual organism... we know that mutations in Rüppell's Vulture
hemoglobin allow the birds to breathe at extremely high altitudes, but if we
tried to elucidate phylogeny from Hb gene sequences we are still for all
practical purposes ignorant.[*]
[*] A buddy is currently working on a novel colonial protist, and lo and
behold, the preliminary phylogenetic analyses indicate that colonialism was
gained and then started to be lost again in that lineage: the new taxon is at
the base of a clade of weakly colonial species, but it itself was well as
another basal lineage are highly colonial.
Now that he has these results from his sequence data, any subsequent
morphological analysis can take them into account. And given that molecular
taxon sampling is somewhat lacking for many protist lineages, a morphological
analysis is likely to yield interesting insights in the evolutionary patterns
of protist colonialism.