DISTRIBUTION AND SPACING OF DROSOPHILA-MYCETOPHAGA FLIES ON BRACKET FUNGI USED AS MATING ARENAS

1. To understand the nature of male aggregations in Drosophila mycetop haga, data were collected on male and female distribution and male spa cing on bracket fungi used as mating arenas in cool rainforests of sou th-eastern Australia. 2. Both males and females appeared to be aggrega ted among bracket fungi that were used as mating arenas. Females were associated with large male aggregations. The probability of a fungus b eing occupied increased with its area. However, a multiple Poisson reg ression analysis suggested that fungus area did not affect female dist ribution when male number was controlled. 3. The presence of female br eeding and feeding resources did not determine where aggregations were formed, because there were aggregations on fungi without resources, a nd fungi with resources were not used more often than those without th em. 4. D.mycetophaga males did not select and defend territories withi n bracket fungi, and did not determine female access to areas. However , males were more evenly spaced than expected on the basis of a random distribution, suggesting that males kept apart from each other. 5. Th e distribution of the different sexes and male spacing pattern support s the interpretation that D.mycetophaga has a lek mating system.