Abstract
Systematists and evolutionary geneticists don't often talk to each other, and
they routinely disparage each other's work as being of little relevance to
evolution. Systematists sometimes invoke the punctuationist argument that
most evolutionary change does not occur by individual selection and hence
that within-population phenomena are largely irrelevant to evolution. They
sometimes make the pattern-c1adist contention that evolutionary processes
cannot be inferred from any observation about pattern, nor can any knowledge
of evolutionary processes inform inferences about pattern. More frequently
systematists feel, with considerable justification, that evolutionary geneticists
have simply failed to concern themselves with morphological characters and
data on differences between species. Evolutionary geneticists in tum dismiss
the idea that studies comparing species anciently diverged, using morphological
characters far removed from the level of the gene and using nonquantitative
methods, can either be sound in their inferences of pattern or can shed
much light on evolutionary processes.
Changes in the methods of collecting and analyzing data are invalidating
some of these views. Molecular data, such as nucleic acid sequences, give us
observations at the gene level that are comparable across many species, and
consideration of these data has drawn population geneticists across the species
boundary. The availability of microcomputers and digitizers is leading to
more quantitation of morphological data by systematists, and the field of
morphometries, needed to derive meaningful characters from this flood of
digitized coordinates, is expanding rapidly. My argument is that the methods
used to study the evolution of quantitative characters within populations can
profitably be used on a phylogenetic scale to illumine the connection between
pattern and process. Futuyma (29) has reached much the same conclusion; so
have Atchley (2), Shaffer (51), and of course Lande (38, 39). The moment
seems ripe to consider the matter.
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