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DIRECT OBSERVATION OF SEXUAL ISOLATION BETWEEN ALLOPATRIC AND BETWEEN SYMPATRIC STRAINS OF THE DIFFERENT DROSOPHILA PAULISTORUM RACES
Author(s) -
Ehrman Lee
Publication year - 1965
Publication title -
evolution
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.84
H-Index - 199
eISSN - 1558-5646
pISSN - 0014-3820
DOI - 10.1111/j.1558-5646.1965.tb03322.x
Subject(s) - allopatric speciation , sympatric speciation , biology , drosophila (subgenus) , isolation (microbiology) , reproductive isolation , evolutionary biology , zoology , genealogy , anthropology , genetics , demography , sociology , bioinformatics , history , gene , population
Dobzhansky and Spassky (1959) first suggested that Drosophila paulistorum was a cluster of species in statu nascendi, a borderline case of uncompleted speciation. Their suggestion has been borne out by much laboratory work since then. It is indeed a superspecies composed of six races or subspecies or incipient species. This situation is of interest precisely because these six may be considered about equally legitimately as very distinct races or as very closely related species. Each race inhabits a geographic area different from the others, but the distributions of some of the races do overlap. Where two or more races share a common territory (four is the maximum number of races occurring sympatrically), they seem not to interbreed, and thus they behave like full-fledged species (Dobzhansky et al., 1964). Sexual (or ethological or behavioral) isolation wherein potential mates meet but do not mate, is a most efficient isolating mechanism; it does away with the wastage of gametes, food and space for developing hybrids, etc. This sexual isolation which makes matings between the females and males of different D. paulistorum races much less likely to occur than matings within the races, is due to polygenes scattered in every one of the three pairs of chromosomes which the species possesses. These polygenes efficiently control the sexual preferences of their carriers. Their effects seem to be simply cumulative (Ehrman, 1961). A female of hybrid origin which carries a majority of the chromosomal material derived from a given race