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Seasonal life cycles and resource uses of flower- and fruit-feeding drosophilids (Diptera: Drosophilidae) were studied from low to high altitudes in central Japan to understand their adaptation to seasonal changes of environmental conditions. Drosophila unipectinata and D. oshimai specialized to flowers, D. suzukii and D. subpulchrella depended almost on fruits, while D. lutescens, D. rufa, D. auraria, D. biauraria and D. sternopleuralis used both of them. It was assumed that D. unipectinata moved from low to high altitudes in June while D. oshimai, D. suzukii and D. subpulchrella in July. Migration of D. unipectinata is considered as a means to avoid summer heat or exploit early-summer resources at high altitudes. On the other hand, D. oshimai, D. suzukii and D. subpulchrella have the capacity to pass the summer at low altitudes, and therefore their migration is assumed as a means to escape from resource-poor conditions in summer at low altitudes or exploit resources at high altitudes. The generalist species, D. lutescens, D. rufa, D. auraria, D. biauraria and D. sternopleuralis, would not perform such extensive movements between low and high altitudes. They may pass the summer at low or mid altitudes depending on accidentally fallen immature fruits and/or some other resources such as decayed leaves. |
