2020 年 25 巻 2 号 p. 361-367
Recent views on the goals and methods of historical biogeography have sought support in the distinctions between three phases of biogeographic study and between three aspects of biogeographical hypotheses that were made by Ian. R. Ball in 1975 and 1990. Here it is shown that these recent perspectives on Ball’s philosophy concern misinterpretations of his views that, therefore, are incorrectly used in the development of a theoretical framework for the formation and testing of biogeographic hypotheses. This re-evaluation of Ball’s views also serves as a template for a critical appraisal of several recently published standpoints on the goals and methods of biogeography. Recent panbiogeographic studies postulate wide-spread ancestors in the explanation of present-day vicariant distributions. Wide-spread, even cosmopolitan, ancestral distributions also underlay early applications of taxon-cladistic biogeography, but this notion of primitive cosmopolitanism has been abandoned and replaced by the more realistic assumption that the ancestor had a more restricted distribution. The notion of primitive cosmopolitanism, or at least greatly widespread ancestors, has resurfaced in historical biogeographic hypotheses featuring in modern panbiogeographic studies. This explanatory model is combined with the concept of polymorphic ancestors, which may give rise to parallel evolution of descendant taxa through the process of recombination of ancestral characters. Ample parallelism is well-known in phylogenetic analyses, while it is known also from cases of relatively recent urban evolution. Recent insights into developmental genetics, character identity, and homology concur with the polytopic and polytypic biogeographic model. Progress in historical biogeography is expected to be based on calibrated timetrees and on a pluralistic approach in which the boundaries of various biogeographical hypotheses are clearly demarcated, thus delimiting the domain in which potentially falsifying observations are applicable.
