Brief History of the Biological Species Concept

The history of the biological species concept (BSC) goes back to the early 19th century (Mayr 1955e, 1957f, 1959a, 1963b: 482-488,1980f: 33,1982d: 270-272; Grant 1994; Glaubrecht 2004; Haffer 1992, 2006). The first authors who used a biological "shared essence" (fertility of matings) for a species definition were John Ray (16271705) in 1686 and Georges Buffon (1707-1788) in 1749. However, their language indicates that species, although real entities, are essentialistically constant and invariable. Buffon's species concept was widely adopted in Europe during the late 18th and early 19th centuries including Carl Illiger (1775-1813) in Germany whose "Thoughts on the concepts species and genus in natural history" Mayr (1968i) translated into English. He cited (1942e: 156; 1963b: 483) the amazingly perceptive remarks on species and allopatric speciation by Leopold von Buch (1774-1853) in 1819 and 1825 about which Mayr may have learned from the articles by Robert Mertens (1894-1975) in 1928 or several earlier authors who had also referred to L. von Buch's theory. This theory deeply influenced Charles Darwin who had adopted a biological species concept in his notebooks during the 1830s, but later gave it up. Major contributions to the formulation of the biological species concept and the theory of allopatric speciation during the 19th century were then made by H. W. Bates, A. R. Wallace, B. Walsh, H. Seebohm and later during the early 20th century by Karl Jordan, Edward Poulton, Ludwig Plate, Erwin Stresemann and B. Rensch (Fig. 5.7).

Dobzhansky (1935,1937,1940) discussed genetic differences between every discrete group of individuals and the development of isolating mechanisms through natural selection. He proposed the most useful term "isolating mechanism" between species, but he included not only intrinsic but also extrinsic geographic barriers which, of course, are something entirely different (Mayr 1942e). According to Dobzhansky species may be conceived "statically" and "dynamically." Statically, "a species is a group of individuals fully fertile inter se, but barred from interbreeding with other similar groups by its physiological properties (producing either incompatibility of parents, or sterility of hybrids, or both)" or, in other words, "discrete non-interbreeding groups of organisms" (1935:353). His "dynamic conception" of species was less satisfactory, because species are populations, not stages in a process: "Dynamically, the species represents that stage of evolutionary divergence, at which the once actually or potentially interbreeding array of forms becomes segregated into two or more separate arrays which are physiologically incapable of interbreeding" (1935: 354). Dobzhansky's endorsement of the BSC undoubtedly contributed to its increasing popularity.

Neither Dobzhansky nor any earlier Russian scientist were the originators of the BSC, as Krementsov (1994) wrongly implied. He traced the roots of Dobzhan-sky's ideas backward to several Russian entomologists. While this is probably correct, Krementsov (l. c.) conveyed the impression that these were the first to develop the BSC. Some of his remarks read as follows: "The idea of biological species attracted little attention in the west and was not much discussed" (p. 36), "Western entomologists were generally less interested in discussing these ideas

Fig. 5.7. Interpretations of species in biology under the notions of essentialism (below) and evolutionism (above), from Haffer 2006.

The names of selected authors are indicated at their respective time levels. Solid squares refer to publications on animals in general, half-filled squares to those on plants, solid circles to insects, circled stars to mollusks and open circles to birds.

Fig. 5.7. Interpretations of species in biology under the notions of essentialism (below) and evolutionism (above), from Haffer 2006.

The names of selected authors are indicated at their respective time levels. Solid squares refer to publications on animals in general, half-filled squares to those on plants, solid circles to insects, circled stars to mollusks and open circles to birds.

[of geographical isolation as a causal factor of speciation] than were their Russian colleagues" (p. 38). "In my opinion, the essence of the biological species concept was clearly formulated in the theoretical papers of leading Russian entomologists in the prerevolutionary decades." However, they were not the first to develop the BSC, nor were E.B. Poulton or K. Jordan whose work Mayr (l.c.) discussed in detail.

Building on the work of Stresemann, Rensch, Dobzhansky, and several earlier authors mentioned above, Mayr (1942e, 1963b, 1970e) combined systematic, genetic and ecological aspects, analyzed the speciation process and thus established the theoretical BSC in all its ramifications. Through his contributions, the BSC became one of the central tenets of the modern synthetic theory of evolution. Although he was not the originator of the BSC, he demonstrated its validity more convincingly than anyone else before and proposed a superior and concise definition which has been widely adopted.

Was this article helpful?

0 0

Post a comment