| Budget Amount *help |
¥4,420,000 (Direct Cost: ¥3,400,000、Indirect Cost: ¥1,020,000)
Fiscal Year 2015: ¥520,000 (Direct Cost: ¥400,000、Indirect Cost: ¥120,000)
Fiscal Year 2014: ¥2,080,000 (Direct Cost: ¥1,600,000、Indirect Cost: ¥480,000)
Fiscal Year 2013: ¥1,820,000 (Direct Cost: ¥1,400,000、Indirect Cost: ¥420,000)
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| Outline of Final Research Achievements |
I tested the potential effect of landscape structure on the density of generalist predators (Tetragnatha spiders) in rice paddy fields mediated by food resource availability. I surveyed abundances of Tetragnatha spiders and their potential prey in 20 rice fields along a gradient from simple arable-dominated to forest-rich landscapes in Tochigi prefecture, and analyzed the relationships among landscape structure, spider abundance and prey availability. Results of landscape analysis showed that forest areas within a 200 m around study fields positively affected the abundance of spiders. Path analysis revealed that the increase in spider abundance was attributed to the increase in abundances of chironomid flies that are important alternative prey of the spiders. On the other hand, PCR-based gut-content analysis of spiders failed to detect the increase in predation rate of chironomid flies by spiders. Further improvement is needed in the evaluation method.
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