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A STUDY OF SEXUAL ISOLATION BETWEEN CERTAIN STRAINS OF DROSOPHILA PAULISTORUM
Author(s) -
MalogolowkinCohen Ch.,
Simmons A. Solima,
Levene H.
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.tb01694.x
Subject(s) - biology , isolation (microbiology) , drosophila (subgenus) , evolutionary biology , reproductive isolation , genetics , zoology , bioinformatics , demography , gene , sociology , population
The superspecies Drosophila paulistorum Dobzhansky and Pavan consists of six races or incipient species which exhibit various degrees of reproductive isolation from each other. The two principal isolating mechanisms involved are sexual (ethological) isolation and sterility of hybrid males (Dobzhansky and Spassky, 1959; Dobzhansky et al., 1964). Sexual isolation is almost certainly the more effective of the two mechanisms in preventing gene exchange between the incipient species in their natural habitats. It appears to be a general rule that where two or more of the incipient species are sympatric in the same territory, no hybrids between them are formed spontaneously, and crosses can be made in laboratory experiments only with considerable difficulty, always yielding sterile hybrids. On the other hand, socalled transitional strains are found in some territories inhabited by only one race. Thus, only the Andean-Brazilian race is found in northeastern Brazil, and some of the strains derived from the populations of that region cross to some strains of the allopatric Amazonian race and produce fertile hybrid sons (Malogolowkin, 1962, 1963; Malogolowkin et al., 1964). On the other hand, various degrees of sexual isolation have been encountered in crosses between strains of the same race from geographically remote localities (Carmody ct al., 1962). Much of the experimental work on sexual isolation in D. paulistorum has used the so-called "male choice" method. Groups of virgin females belonging to two different strains or races are confined for a certain time interval with males of one of the strains; all of the females are then