Ecotype, Ecospecies, and Macroevolution

Abstract

The combined efforts of taxonomists and geneticists have succeeded to a considerable extent in solving that part of the problem of evolution which concerns the subspecific level. The detailed work of innumerable taxonomists following in the footsteps of Kleinschmidt K. Jordan, Matschie, and Rensch has shown that many species are best described as “Rassenkreise”, i.e. series, and sometimes clines (in J. Huxley’s term), of subspecies replacing each other in an orderly geographical way over the area occupied by the species’. In most cases these subspecies or geographic races do not overlap and where they meet they may form hybrid populations, as subspecies are fertile inter se. Very frequently it is possible to recognize within the subspecies local populations which are again discernable as subunits, and even these may be sometimes successfully subdivided into other distinguishable groups down to individual colonies. Though the taxonomist does not apply nomenclatural distinction to these categories below the subspecies, it is important to realize that in many cases, if not in all, further subdivisions would be possible upon the basis of still recognizable hereditary differences. A further important result of this taxonomic work, frequently forgotten by present day evolutionists, is that subspecies and even smaller units are characterized by recognizable differences which are present in every individual. This is obvious, as otherwise the taxonomist could not name and describe subspecies. When the differential characters are of a quantitative nature, the characteristics are means of quantitative series. The individual variants may or may not overlap with those of the adjoining subspecies. Furthermore, a number of such differential traits, constant within the limits of normal variation, combine to characterize the respective subspecies.

Paper read at the closing session of the International Congress of Zoology, Paris, July, 1948.