Native California Roses

prepared by Barbara Ertter, 2001

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As should be evident from the historical background, a key factor in any taxonomic treatment of Rosa (or any other genus, for that matter) is the scientific philosophy underlying the particular author's decision of which units of biological diversity are worth hanging names on. Although the divergent results have been denigrated as evidence that traditional taxonomic classifications are based on personal whim rather than on "real" science, such a simplistic interpretation glosses over some serious and legitimate issues. Roses in particular provide a blatant challenge to any a priori assumption that nature should present itself in tidy, easily parsed, uniformly characterized units, however much human expectations might prefer that such be the case. In this light, any attempt to present natural diversity in the form of non-arbitrary, one-size-fits-all categories will serve to obfuscate rather than clarify the true biological complexity.

Which is far from saying that taxonomic decision-making is completely arbitrary, either. Topography provides an excellent analogy, in which mountains, hills, and valleys are by no means purely mental constructs, even in the absence of sharp, non-arbitrary boundaries separating one from the other. The best framework for explaining the taxonomic decision-making process is that provided by fuzzy (vs. crisp) logic, pioneered by UC-Berkeley mathematician Lotfi Zadeh and now an integral part of computer technology. As summarized by McNeill and Frieberger (1993) in their popularized book on fuzzy logic, "Computers forced us to take crisp boundaries seriously, and when we went searching for them, we found they didn't exist and never had" (p. 100). As an alternative to elusive searches for rigorously precise definitions and demarcations where none exist, fuzzy logic provides a mechanism whereby classification results from the summation of multiple factors, any one of which can be relatively weak if counterbalanced by the strength of others.

Within this framework, I find that "taxonomic significance" at the species level results from the "fuzzy" summation of the following five factors, of which the first two are more-or-less directly observed, the second and third are generally inferred, and the fifth is somewhere in between:

I am not so much proposing a new "fuzzy species definition" as suggesting that this is in fact exactly how traditional taxonomic decision-making has always taken place, in a non-explicit but nevertheless intellectually rigorous manner. It is, in any event, the process that underlies my own taxonomic treatments, including Rosa (Ertter, 1993).

Literature Cited:
Ertter, Barbara. 1993. Rosa. In: Hickman, J.C. (ed.) The Jepson manual: higher plants of California. University of California Press, Berkeley, CA, pp. 972--973.

McNeill, Daniel and Paul Freiberger. 1993. Fuzzy logic: the revolutionary computer technology that is changing our world. Touchstone edition, Simon & Schuster, Inc., New York, NY.