Drosophila species (Diptera: Drosophilidae) oviposition patterns on fungi: The effect of allospecifics, substrate toughness, ovipositor structure and degree of specialisation

To determine if small-scale resource partitioning aids coexistence in fungal breeding Diptera we investigated the avoidance of interspecific larval competition by micro-resource partitioning of the host substrate in several species of Drosophila ovipositing on fungal fruiting bodies. No avoidance was detected and oviposition patterns were unaffected by the presence of allospecifics. There was a general tendency for all species to oviposit preferentially on the cap but no significant differences between species. Egg distribution was not strongly related to the sporophore's resistance to penetration measured by penetrometer and was also uncorrelated with ovipositor structure even though species had concordant suites of ovipositor characteristics with apparent specialists typified by hard and sharp ovipositors. We discuss the significance to species coexistence of the absence of micro-resource partitioning of the host.