Phylogenetic Classification in Darwin's Monograph on the Sub-Class Cirripedia

Ghiselin, M. T. and L. Jaffe (University of California, Bodega Marine Laboratory, P.O. Box 247, Bodega Bay, California 94923) 1973. Phylogenetic Classification in Darwin's Monograph on the Sub-Class Cirripedia. Syst. Zool. 22:132-140.-Darwin's barnacle monograph contains an implicit phylogeny which is reflected in the classification system. In accordance with theoretical views he expresses elsewhere, the system has no polyphyletic taxa, but it does. have paraphyletic ones. The classification also takes into account degree of difference, gaps, convenience and tradition. His general advocacy of genealogy as the basis of classification never took the form of modern cladistic views. Darwin's great Monograph on the Subclass Cirripedia (Darwin 1851a, 1854a, and, if one includes the paleontological treatises, 1851b, 1854b) has, like the rest of his works, been lavishly praised by specialists. His successor in barnacle taxonomy, Pilsbry (1916:1), says "His grasp of detail was so comprehensive and his language so lucid that one can not expect to improve upon them. In the field he covered one can not do better than imitate." Such expressions of admiration often lead to charges of hero worship. Yet what better hero? Nonetheless, this work is not alone among Darwin's writings in having been far more often praised than read, especially read with understanding. Part of the trouble has been that getting the most out of Darwin's works is almost a black art, requiring a knowledge of the man and his ideas that can take years to develop. His many volumes expound upon a coherent system of evolutionary biology, but the larger implications are not always stated explicitly (Ghiselin, 1969). One has to read between the lines, and even an expert in a branoh of knowledge upon which Darwin wrote may miss the point when he considers one work in isolation. The barnacle volumes nonetheless deserve to be known to a broader audience. They were Darwin's first major publications on evolutionary biology, and they were the first attempt to reconstitute the science of taxonomy in the light of the hypothesis of natural selection and its implications. He discusses reproductive strategies, quantitative aspects of species diversity and many other topics which interest us today. But since the Monograph was published before the Origin of Species (Darwin, 1859), our task of discovering the hidden meaning is not easy. In fact, up until very recently the evolutionary aspects of this work were virtually unknown (Ghiselin, 1969). In this paper we will present an exegesis which will help to clarify one issue of particular interest to systematists: Darwin's views on the role of phylogeny in classification. How much should a system tell us about phylogenetic trees? The issue has been raised with respect to Darwin's views by Crowson (1958), Nelson (1971) and Darlington (1972). Nelson (1971) challenged Ghiselin's (1969) interpretation of a passage in the Origin of Species, and Darlington (1972) suggested that the barnacle monograph might cast some light upon such matters. We shall show that the available evidence supports the original reading, but that the basic thesis, that Darwin advocated some kind of genealogical classification, is substantially correct. The main issue being contended has to do with the relationship between phylogenetic trees and Linnean hierarchies, especially with the issue of "monophyly" in various senses of that term. Opinion as to how phylogeny should relate to classifica-