| Budget Amount *help |
¥3,500,000 (Direct Cost: ¥3,500,000)
Fiscal Year 2004: ¥1,100,000 (Direct Cost: ¥1,100,000)
Fiscal Year 2003: ¥1,000,000 (Direct Cost: ¥1,000,000)
Fiscal Year 2002: ¥1,400,000 (Direct Cost: ¥1,400,000)
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| Research Abstract |
Drosophilid flies occur mainly in woodlands from tropical to arctic regions. However, the distribution rage of single species is not so wide, and the distribution of tropical species is almost restricted in tropical regions and that of temperate species in temperate regions. This study focuses on the question why tropical species are not distributed in temperate regions and temperate species are not present in tropical regions. According to the present study with 30 drosophilid species from Japan, tropical species are not cold tolerant, and this inhibits them to colonize temperate regions. It has been reported in many organisms that cold-adapted species have higher metabolic rates than species from warmer regions. However, such tendency was not observed in drosophilid flies. On the other hand, the absence of cold-tolerant species in warmer regions suggests that the acquisition of cold tolerance resulted in the loss of adaptability to warmer regions. Here, walking speed and the rate of pupal development were compared for 28 drosophilid species. If walking speed is reduced, they would become vulnerable to predators. If the rate of pupal development is retarded (i.e., pupal period is prolonged), they would also become vulnerable to predators, parasitoids and infectious microorganisms. In our experiments, cold-tolerant species had lower walking speed and lower rate of pupal development, suggesting that cold-tolerant species are disadvantageous in warmer regions than cold-intolerant species. However, little is known on predators, parasitoids or infectious microorganisms of drosophilids. In this study, we made a survey on parasitoid wasps of drosophilid flies in Japan and recorded about 20 species. It is needed to examine whether or not cold-tolerant species are more heavily attacked by parasitoids than cold-intolerant species.
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