I'm deeply grateful for folks such as Dennis Paulson who have both the detailed knowledge of the species in question and the broad viewpoint necessary to put the issue into perspective. I write here only to emphasize one important point: that the relationship between information encoded in DNA and the resulting morphology is tenuous and complicated, and one should not rely overmuch on the DNA. I'm a molecular biologist by virtue of my graduate training and research, but a general biologist by virtue of my writing and the perspective I've tried to develop. I have been dismayed to see phylogenetics turning as strongly as it has to dependence on DNA, as if all of Truth could be read in nucleotide sequences. I respond with smiling approval and understanding to Brendan McGarry writing, "having participated in a project with Satin Bowerbirds where a PhD candidate who for SIX YEARS had been working with their DNA but had not been into the field with the birds and knew little about their behavior . . . I can see how something like this can happen." Similarly, Dennis's intimate, detailed knowledge of the anatomy of shorebirds gives him the perspective needed to evaluate both the molecular and morphological data, and to warn about relying too much on the molecular. For Tweets who are not biologists, I think the important take-home lesson is this: The information coded in DNA is used in a long, complicated series of developmental interactions as an animal grows from an embryo to an adult, and we are just barely coming to understand all this through the work of developmental geneticists. DNA sequences can be changed in many ways through the flip-flops that chromosomes engage in during the processes of reproduction and evolution, with unknown and at this time unpredictable effects on the structure of the resulting organisms. It is folly to try to read species boundaries, phylogenies, and patterns of evolution by relying exclusively on information from only one source. Again, my thanks to all those who have contributed their various perspectives to these discussions of gulls, shorebirds, or any other groups.

Burt Guttman
The Evergreen State College
Olympia, WA 98505 guttmanb at evergreen.edu <mailto:guttmanb at evergreen.edu>
Home: 7334 Holmes Island Road S. E., Olympia, 98503