Use of Phylogenies

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The comments on aspects of phylogenetic inference posted to PaleoNet are
very interesting and certainly reflect the wide (and therefore healthy)
diversity of opinion that exists out there.  My own bias in this area
presently comes down on the side of using morphologic data to infer the
phylogeny (via cladistics) and then comparing those results to the
stratigraphy.  If everything works out, great.  If not, then some decision
has to be made as to which dataset (or combination of data) to believe.
Almost everyone knows of examples where the exclusive focus on aspects of a
group's morphology can be misleading (especially if these are analyzed in
isolation from other morphologic characters).  Unfortunately, it is not as
widely appreciated that stratigraphy can also be a very misleading
indicator of phylogenetic relationship due to the existence of diachronous
species ranges, differential preservation potentials, hiatuses, allopatric
speciation, etc., etc., etc.  These complicating factors cut across the
fossil records of all organismal groups and, to me, it seems highly
questionable to assume that any fossil group (even marine microfossils) are
automatically immune from either morphologic or stratigraphic noise when it
comes to phylogenetic inference.  Efforts are currently underway to
directly incorporate stratigraphic data into the parsimony algorithms that
lie at the heart of most approaches to cladistics, but it remains an open
question as to how well this can be accomplished either in principle or in
practice.

That having been said, however, my original comment was not primarily
targeted at eliciting a discussion of the merits of particular approaches
to phylogenetic inference (though this is an important topic and I do
encourage the PaleoNet discussion of it to proceed).  Of equal interest (at
least to me), is the question of how we use a phylogenetic tree (regardless
of how it is derived) in addressing other paleontologically-important
questions. Last year I published a paper in Marine Micropaleo. in which I
used a cladogram to make inferences about the nature of adaptive radiation
within a planktic foraminiferal lineage.  In conducting that study I was
impressed by the increased resolution that the incorporation of
phylogenetic information can bring to the study of adaptation.  I also have
a (as yet unpublished) study in which I and Ken Rose use autocorrelation
analysis to remove phylogenetic covariance within some mammalian
morphometric data originally collected to address a question in functional
morphology.  In both instances the incorporation of phylogenetic
information was very useful in clarifying and interpreting the
paleoecological and morphometric/functional data that had been collected.
Of course, we, as paleontologists, rhetorically subscribe to the idea that
the only proper way to view our data is within the context supplied by
evolutionary theory.  However, in the last few years it has struck me that
we tend to treat phylogeny as an end in itself (which, of course it can be)
when we could also be using it as a means to better achieve other ends.  I
agree that the neontologists and vertebrate paleontologists are a bit
further along this road than invertebrate and micropaleontologists.  But I
also think that the latter can reap many benefits by incorporating a more
explicitly phylogenetic approach to the analysis of what are
"non-phylogenetic" questions.  Even biostratigraphy (perhaps the most
Baconian of all paleontological disciplines) can reap benefits in this
area.

Two recently published books that I would recommend to anyone who wishes to
explore this topic in detail are:

Harvey and Pagel (1991) The Comparative Method in Evolutionary Biology. Oxford.
Brooks and McLennan (1991) Phylogeny, Ecology, and Behavior. Chicago Univ. Pr.

Comments??


Norm MacLeod


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Norman MacLeod
Senior Research Fellow
N.MacLeod@nhm.ac.uk (Internet)
N.MacLeod@uk.ac.nhm (Janet)

Address: Dept. of Palaeontology, The Natural History Museum,
                     Cromwell Road, London, SW7 5BD

Office Phone: 071-938-9006
Dept. FAX:  071-938-9277
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