SIZE-RELATED SEXUAL SELECTION AND YEAST DIET IN DROSOPHILA-BUZZATII (DIPTERA, DROSOPHILIDAE)

Size-related sexual selection (SRSS) was examined on four traits (thor ax and wing length and head and face width) in Drosophila buzzatii, by scoring male copulatory status in two mass-mating experiments. Using axenic females, experiment 1 was carried out with axenic males, and ex periment 2 with yeast-supplemented males. While there was no indicatio n of SRSS in experiment I, such selection was substantial in yeast-sup plemented males, which transmitted yeasts to mating females. Multivari ate analyses of selection indicated that face width is the measured tr ait on which directional SRSS essentially acted in yeast-supplemented males, resulting in indirect selection on body size, Because this sele ction was affected by yeast diet in males, its possible interaction wi th the yeast transmission from males to females during the courtship i s discussed.