Phylogeny and Conservation

[Daniel Barker]

Russell Seymour argues phylogeny is not usually, and should not be, the
main criterion when deciding what to conserve.

For conserving ecosystems and maintaining diversity that may be of use to
man, phenotype is more relevant than phylogeny. Consider taxa A and B,
whose DNA sequences differ widely, but code for exactly the same proteins.
All the variation is of the 'silent' kind, in the 2nd and 3rd codon. Even
if A and B fall within different clades when their DNA is compared, why is
conserve both of them when, in phenotype, they are identical? Crudely, who
cares about their unexpressed differences in genotype?

This is an unrealistic example, of course, but I can imagine less extreme
cases of the failure of phylogeny to correlate with phenotype. After all,
such worries have caused UPGMA to be almost totally replaced by expressly
phylogenetic methods when studying phylogeny. In conservation, I think
phylogeny is only of interest in that it is loosely correlated with
phenotype. It would be better to replace phylogeny with expressly phenetic
clustering on the basis of phenotype (e.g. protein sequence, biochemistry,
morphology), for the same reason that UPGMA is no longer used for
phylogenetic reconstruction: similarity is not phylogeny, phylogeny is not
similarity.


Daniel Barker,
Biocomputing Research Unit,
Institute of Cell and Molecular Biology,
Swann Building,
King's Buildings,
Mayfield Road,
Edinburgh
EH9 3JR
UK