Specificity of accessory gland extracts. in three Delia fly species (Diptera: Anthomyiidae)

Abstract

Abstract. Extracts of testes and male accessory (paragonial) glands made from three species of Delia (onion fly {D.antiqua), seedcorn fly (D.platura), and cabbage fly (D.radicum)) were injected into conspecific virgin females. Extracts of paragonial glands, but not testes, from onion, seedcorn and cabbage fly males stimulated oviposition and suppressed mating when injected into conspecific virgin females. When extracts of paragonial glands from males of these species were injected into heterospecific virgin females, the extracts of D.antiqua and D.platura were fully cross‐reactive with respect to oviposition; interspecific injection stimulated oviposition at the level of the conspecific mated controls. Injection of D.radicum extract fully activated the D.antiqua and D.platura ovipositional response. D.antiqua extract caused mating inhibition and partial oviposition in D.radicum; that of D.platura had no effect on either oviposition or mating inhibition in D.radicum. These results suggest that D.antiqua and D.platura are more closely related to one another than either is to D.radicum, and agree with published anatomically‐based phylogenies and a genetic distance calculation based on eight enzyme loci. The occurrence of sex peptide cross‐reactivity, though asymmetrical, between D.radicum versus D.antiqua and D.platura indicates that, functionally, sex peptides have changed little during the evolution of this genus. An emerging pattern of broad cross‐reactivity within genera suggests that sex peptides are not an initiator of reproductive isolation.