The concept of individuality as applied to species, an important advance in the philosophy of evolutionary biology, is nevertheless in need of refinement. Four important subparts of this concept must be recognized: spatial boundaries, temporal boundaries, integration, and cohesion. Not all species necessarily meet all of these. Two very different types of pluralism have been advocated with respect to species, only one of which is satisfactory. An often unrecognized distinction between grouping and ranking components of any species concept is necessary. (...) A phylogenetic species concept is advocated that uses a grouping criterion of monophyly in a cladistic sense, and a ranking criterion based on those causal processes that are most important in producing and maintaining lineages in a particular case. Such causal processes can include actual interbreeding, selective constraints, and developmental canalization. The widespread use of the biological species concept is flawed for two reasons: because of a failure to distinguish grouping from ranking criteria and because of an unwarranted emphasis on the importance of interbreeding as a universal causal factor controlling evolutionary diversification. The potential to interbreed is not in itself a process; it is instead a result of a diversity of processes which result in shared selective environments and common developmental programs. These types of processes act in both sexual and asexual organisms, thus the phylogenetic species concept can reflect an underlying unity that the biological species concept can not. (shrink)

We argue that the logical outcome of the cladistics revolution in biological systematics, and the move towards rankless phylogenetic classification of nested monophyletic groups as formalized in the PhyloCode, is to eliminate the species rank along with all the others and simply name clades. We propose that the lowest level of formally named clade be the SNaRC, the Smallest Named and Registered Clade. The SNaRC is an epistemic level in the classification, not an ontic one. Naming stops at that level (...) because there is no currently acceptable evidence for clades within it, not because no smaller clades exist. Later, included clades may be named. They would then become the SNaRCs, while the original SNaRC would keep its original name. We argue that all theoretical tasks of biology, in evolution and ecology, as well as practical tasks such as conservation assessment, are better approached using this rankless phylogenetic approach. (shrink)

This chapter contains sections titled: Historical and Current Views of Species Return to a Darwinian View of Species Practical Implications Postscript: Counterpoint References.

Sober (1992) has recently evaluated Brandon's (1982, 1990; see also 1985, 1988) use of Salmon's (1971) concept of screening-off in the philosophy of biology. He critiques three particular issues, each of which will be considered in this discussion.

I address David Hull's theses about the process of science from the perspective of an evolutionary biologist, particularly emphasizing phylogenetic systematics, an area that has figured prominently in Hull's work as a source of both sociological data and metatheory. The goal is to carefully explore analogies and disanalogies between scientific process and comparative biology. There do seem to be remarkable analogies, indeed these lead to important insights that might not otherwise have been made, yet some possible analogies present novel problems: (...) Are "memes" like genes or like traits? What is the nature of replication in science? It is argued that the primary need is for some rigorously worked-out case studies. (shrink)

David Hull’s approach to science, which culminated in his important book Science as a Process(1988), represents an unprecedented conjunction of philosophy of science with the results and concepts of a particular science. Hull takes an evolutionary approach to the conceptual development of science, importing much of his explanatory framework from comparative biology, the discipline where his empirical observations of scientists have been made. On the surface, such a cozy relationship between data, theory, and metatheory leads to worries about circular reasoning (...) (Mishler 1989). Nevertheless, I will argue here that Hull’s approach is basically sound, and that the strength of his arguments comes precisely from his recognition of key analogies between the evolution of organisms and the conceptual evolution of scientists; however, certain disanalogies must also be taken into account.Comparative biology can be divided into two distinct (although interrelated) halves based on differing orientations and types of questions asked. (shrink)