Generalized Tracks and Dispersal in Biogeography: A Response to R. M. McDowall

Abstract

McDowall (1978) presented a critique of the vicariance approach to biogeography developed by Leon Croizat and summarized by Croizat et al. (1974). His main thesis is that vicariance models are neither more nor less falsifiable than dispersal models, presumably (this is not specified by McDowall) in terms of Poper''s (1972) falsifiability criterion for the demarcation of science from non-science. McDowall also develops a number of arguments concerning the role of dispersal in biogeography, comments on problems of Southern Hemisphere biogeography, and questions the quality of Croizat''s work. This discussion is not an attempt to endorse one or the other biogeographic paradigm. The intention is to demonstrate that McDowall''s arguments about the falsifiability criterion simply reveal his basic commitment to a logical positivist philosophy of science as opposed to the Popperian approach supported by Rosen and Nelson. The major difference between McDowall, and Croizat, Nelson and Rosen is in their respective approaches to philosophy of science. The debate is only secondarily one about alternative approaches to biogeography. McDowall''s arguments about the role of dispersal in biogeography lack coherency. McDowall had misunderstood and misrepresented Croizat''s work on the important issue of the relationship between biogeography and phylogeny.