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re: Brusatte et al. 2008
> The big question for you to ponder is this: do all these
> make sense in terms of gradualism in evolution? If
> 'sister taxa'
> don't blend morphologically from one to another,
> isn't that a red flag?
Depends. If the fossil record is complete enough, certainly. But if not, it is
not sufficient to ring the alarm bells I think.
For example, if we had a comprehensive fossil record consisting of crown-like
Trochilidae and Apodidae, with no basal cypselomorphs, _Eurotrochilus_ etc,
this would be suspicious. But for example in the case of Anhingidae vs the rest
of Anseriformes, it is OK, we simply do not have the tiniest shred of fossil
evidence near the node, and support is robust. We can *see* the gap in space
and time. There are no ?Santonian-Campanian Anseriformes that fill this gap
according to the cladogram, and neither is there anyting known that fills the
gap in contradiction to the cladogram.
On the other hand, the sister relationship between hesperornithids and
(loons+grebes) one can easily get is dubious in the face of quite some amount
of basal Neornithes to basal Neoaves fossils that simply do not fit. And as for
loons being sister to grebes, yes, you can get this easily from a cladistic
analysis too. Only if you choose your characters well (e.g. emphasize non-limb
characters) and include Palaeolodidae and flamingos and penguins and _Waimanu_,
it just as easily can be made to disappear.
Another example is "weird" placements of taxa based on mtDNA sequence analysis.
Such results cannot be automatically taken to represent the population/species
tree in addition to the maternal lineage tree rather than just the latter; you
need to see if it corresponds with a ncDNA sequence tree. If it does, it's time
to think. the Bearded Reedling is interesting in this regard; it was used as a
stand-in for parrotbills for decades, until they actually included both it and
some _Paradoxornis_ as well as numerous other Sylvioidea.
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