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Re: More on the genus problem
To me, genus and species in paleontology are just ranks which
represent the same: nested groups. Putting aside criticism to the
biological species concept, you have no way anytime soon to see who
has fertile descent with who among fossil specimens, so to group
individuals in species you have to rely uniquely on mophology, the
same as with all other larger, supraspecific groupings. No difference
Exactly. Most species concepts, and this seems to include all
interesting ones, require some kind of approximation to population
biology, and with most fossil vertebrates that is just not feasible.
I am therefore glad that the PhyloCode will let us stop pretending that
we can shoehorn every organism into a species: it will allow us to use
specimens that don't belong to a named species as specifiers in the
definitions of clade names. (And of course it does not define "belonging
to a named species"!)
So, to me, paleontology would be better stop talking about genera and
species (the latter term may still be useful regarding not-mixing of
gene pools in our times), but about (as ugly as it may sound) of
specimens referred to by their catalogue number (or perhaps given a
more aesthetic name, such as "Sue" and "Leonardo").
That's not necessary. Just name smaller and smaller clades, all the way
down to the LITUs (least inclusive taxonomic units = smallest
recognizable clades), without bothering to find out which (if any) of
them correspond to species under which species concept. Probably all
currently recognized Mesozoic dinosaur "species" -- and genera -- are
LITUs anyway, so...
(Never forget: as of February 2009, there are 147 species concepts out
there; depending on the species concept, there are from 101 to 249
endemic bird species in Mexico. All those species concepts have nothing
in common except the _word_ "species".)
I think diversity studies may be more difficult to be carried on if
abandoning usage of species as a special, and only one, accepted
rank. However, I see the same problems with their use as with the
previous use of genera and families.
I promised the references on the Phylogenetic Diversity Index long ago.
Here they are at last:
Daniel P. Faith (1992): Conservation evaluation and phylogenetic
diversity. Biological Conservation 61, 1 -- 10.
(1994a): Genetic diversity and taxonomic priorities for conservation.
Biological Conservation 68, 69–74.
(1994b): Phylogenetic pattern and the quantification of organismal
biodiversity. Philosophical Transactions of the Royal Society of London,
Series B: Biological Sciences 345, 45–58.
And here an application:
K. Nehring & C. Puppe (2004): Modelling phylogenetic diversity. Resource
and Energy Economics 26, 205–235.
The PDI uses topology and branch length to measure the uniqueness of an
OTU and the diversity represented by a tree. That's much better than
just counting species, even in the highly improbable event that they
were all named by a single person who used a single species concept