A COMMENT ON “MATE RECOGNITION SYSTEMS“

In a recent response to a note by Ringo (1977) on "Why 300 species of Hawaiian Drosophila? ," Templeton (1979) introduced a new aspect to the discussion. This was the idea of the Mate Recognition System, or, as I now prefer to call it, the Specific-Mate Recognition System (SMRS), which I introduced in 1976. The SMRS is the essential component of a new concept of species, the Recognition Concept, which is conceptually quite distinct from the current paradigm, the Isolation Concept. According to Dobzhansky (1951, 1976), species under the latter concept are to be regarded as "adaptive devices" whose integrity is maintained through the possession of isolating mechanisms (Dobzhansky, 1935). Here I wish to comment on Templeton's use of the term "mate recognition system" because it differs fundamentally from my own. If it is not corrected at once, his usage may lead to confusion and misunderstanding when my concept is published in full. According to the recognition concept, species are incidental consequences of adaptive evolution and cannot be regarded as "adaptive devices. " The line of reasoning which leads to this conclusion runs as follows: In sexual species the achievement of syngamy is of fundamental significance. It is therefore not surprising that all sexual organisms possess adaptations which have evidently evolved to facilitate the achieving of fertilization (fertilization mechanisms). In each of these it is always possible to discern a subset, the specific-mate recognition system (SMRS). The SMRS comprises a coadapted signalresponse chain of the sort illustrated by Stitch (1963), or, in more general terms, by Desmond Morris (1956). Although under strong stabilizing selection as I have explained previously (Paterson, 1976, 1978), the SMRS is subject to modification under natural selection to improve its effectiveness should a small population become isolated in a new and distinct environment. Due to the stabilizing selection acting on the system, such adaptive change can only occur in small steps with coadaptation between male and female being re-established at each step. The evidence for these statements comes from observations on the SMRS's of species in their preferred habitats (e.g., Morton, 1975). Speciation is said to have occurred when the SMRS of the members of the daughter population has been so extensively modified that it no longer functions effectively with members of the parental or any other population. It should be said that modification of the SMRS by natural selection may be indirect, being mediated by pleiotropy. Thus, speciation occurs as an incidental consequence of the adaptation of a small isolated population to a new habitat. The SMRS, therefore, falls into the same category as other adaptive characters which are changed when a population is adjusted by natural selection to new conditions. This accounts for the common observation that modifications to the niche of members of a population generally accompanies speciation (Mayr, 1963). It is evident that a new SMRS, derived in this way, determines a new gene pool and, hence, a new species. According to the recognition concept, species are populations of individual organisms which share a common specific-mate recognition system (Paterson, 1978). Species are, thus, incidental effects of adaptive evolution. If these arguments are fully appreciated it will be obvious how greatly my ideas have been misrepresented by Templeton when he wrote (1979, p. 516): "The raison d'etre of a mate recognition system is to