| Research Abstract |
Reproductive isolation is one of the most important phenomena in evolutionary processes, such as species formation (speciation) and maintenance of the gene pools of incipient species. Drosophila ananassae and D. pallidosa, belonging to the Drosophila ananassae complex, are closely related and found sympatrically. Because of no postmating isolation, fertile hybrid progeny could be obtained in a laboratory. Therefore, to maintain their gene pools, premating isolation, especially sexual isolation, is essential in nature. Courtship song, generated by male wing vibration, plays an important role in sexual isolation. It is a key problem to clarify female behavior when she discriminates and accepts a courting male in the study of sexual isolation between the two species. The present study attempted to approach molecular genetic basis of female discrimination behavior. First we made intra- and inter-specific mating test using strains from three sympatric area. Copulation frequencies significantly decreased when heterospecific courtship songs exist. Next, observation of courtship behavior revealed that the female vibrated her both wings during courtship, then, immediately the male stopped courting, This observation suggests that when heterospecific songs exist, females reject males and male courtship behaviors are inhibited, resulting in significantly lower copulation. We also recorded and analyzed courtship song of the two species. Inter-pulse interval (IPI), which plays an important role in other species, did not differ between them. Burst length, number of cycles per pulse and pulse length are species specific parameters. The present study revealed female discrimination behavior and found species specific song parameters. This brings us to assay artificially generated songs by female behavior. We hope that this bioassay system enable us to clarify female discrimination in molecular genetic level.
|
