V. GRANT 67 



unit, is by definition a particular type of species, a species namely 

 of hybrid origin, and is not applicable to an assemblage of hy- 

 bridizing species. The commonly used term, species group, on 

 the other hand, connotes an assemblage of related species but 

 carries no implication of natural hybridization between them, 

 and the same is true of the superspecies of Mayr (1942). 



The homogamic complex proposed by Grant (1953) for a 

 hybrid complex, the derivative forms of which are sexual, meioti- 

 cally normal, and entirely or predominantly diploid, is not en- 

 tirely suitable for our present purpose either, since this concept 

 carries the connotation of past as well as present hybridization 

 on an extensive scale. The homogamic complex is a type of phylo- 

 genetic reticulum which, at any given instant of time, may or 

 may not correspond to the group of interbreeding species. The 

 former is thus a more inclusive category than the latter, for it 

 may contain species which were formerly united by hybrid con- 

 nections but no longer actually hybridize. 



In order to find a convenient means of designating the hybrid- 

 izing species complex we must go back to the term syngameon 

 of Lotsy (1925, 1931). The syngameon was defined by Lotsy as 

 a "habitually interbreeding community" or "pairing community." 

 Thus stated, the syngameon is nothing more than the breeding 

 population or perhaps the biological species. The fact that Lotsy 

 used the term species in a very narrow sense for groups of like 

 individuals lends strength to the interpretation that his syn- 

 gameon was equivalent to what we would now call species. By 

 the context and the choice of illustrative examples, particularly 

 the European Betulas, however, it is perfectly clear that Lotsy 

 conceived the syngameon in a broader sense than the biological 

 species. His syngameon, as applied to concrete cases, was a clus- 

 ter of hybridizing species. We are justified, therefore, in taking 

 up this old, generally familiar, and etymologically appropriate 

 term for the interbreeding unit higher than the species. 



The syngameon, as redefined according to present-day con- 

 cepts, is the sum total of species or semispecies linked by fre- 

 quent or occasional hybridization in nature; a hybridizing group 

 of species; the most inclusive interbreeding population. A dia- 



