Crossing experiments within and between species of the nasuta complex of Drosophila

Abstract

Reciprocal group mating crosses were used to investigate the evolutionary status of iso-9 lines of 2 species of the nasuta complex, D. sulfurigaster atbostrigata and D. kohkoa, both collected from Continental Malaysia and Cebu. Assortative mating between iso-9 lines of these and iso-9 lines of 2 other species of the same complex, D. albomicans and D. kepulauana was also investigated using reciprocal group mating crosses. Evidence is presented of a speciation trend between populations of D. sulfurigaster albostrigata from Continental Malaysia and Cebu (Philippines). In contrast populations of D. kohkoa from these same regions show no signs of speciation. Divergence between the mate recognition systems of different species was found to be very high, however hybrids were obtained from some crosses. F1 from D. albomicans and D. kepulauana crosses were found to produce fertile offspring, suggesting a close evolutionary relationship. However, other data show that the mate recognition systems of the 2 species have diverged to such an extent that their specific identity cannot be in doubt.

Mechanisms of Speciation - A Population Genetic Approach

“…NATURE OF THE ISOLATION MECHANISMS Examples of all standard types of isolating barriers have been revealed by hybridization experiments: pre-mating isolation by ecological (205), temporal (26) or ethological (3a. , 114) barriers; post-mating but pre-zygotic isolation due to mechanical diffi culties (177) or gametic incompatibilities (236); and post-zygotic isolatiolil by F I inviability (1, 145, 232), F I sterility (1, 138, 145), and F2 or backcross breakdown (1,142,145,183,187). Often several isolating factors between species exist simultaneously (57).…”

Mate recognition in members of the Drosophila nasuta complex

“…The degree of divergence in the courtship patterns of a number of these species has been illustrated by the results of crossing experiments (Lambert 1978b). These data show that females of each species are 'tuned' only to the courtship dances of conspecific males.…”

“…The phylogenetic relationships between a number of these species deduced from polytene chromosome data (Lambert 1978a) are very similar to those suggested here. For example, both the chromosome data and crossing experiments (Lambert 1978b) show that D. kepulauana and D. albomicans are closely related. The banding sequence of D. kohkoa chromosomes is derivable from the same hypothetical species which gave rise to D. kepulauana and D. albomicans, while D. sulfurigaster can be derived through another intermediate sequence.…”

“…Courtship patterns illustrating the nature of the signal-response system have been detailed and discussed for a large number of species, for example, ten-spined sticklebacks Pygosteus pungitius (Morris 1972), the crancfly Tipu/a oleracea (Stich 1963), the frog Co!ostethus trinitatis (Wells 1980) and the oriental fruit moth Grapholitha molesta (Baker & Carde 1979). General aspects of mate recognition have been considered by Paterson (1978Paterson ( , 1980Paterson ( , 1981 and discussed for a number of specific situations by other authors including Passmore & Carruthers (1979), Lambert (1978b), Miles (1977) and Vrba (1980).…”