| Budget Amount *help |
¥41,730,000 (Direct Cost: ¥32,100,000、Indirect Cost: ¥9,630,000)
Fiscal Year 2020: ¥6,890,000 (Direct Cost: ¥5,300,000、Indirect Cost: ¥1,590,000)
Fiscal Year 2019: ¥8,710,000 (Direct Cost: ¥6,700,000、Indirect Cost: ¥2,010,000)
Fiscal Year 2018: ¥8,840,000 (Direct Cost: ¥6,800,000、Indirect Cost: ¥2,040,000)
Fiscal Year 2017: ¥17,290,000 (Direct Cost: ¥13,300,000、Indirect Cost: ¥3,990,000)
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| Outline of Final Research Achievements |
Why is the tropics so diverse? In this study, we empirically answer this question, using medaka fishes (Adrianichthyidae) as a model system. First, estimation of the comprehensive species-level phylogeny and comparisons of their sexual dimorphisms revealed that the degree of sexual dimorphisms is negatively correlated with latitudes. Second, seasonal appearance patterns of mature individuals of a tropical species (Oryzias woworae) by semi-monthly samplings from Muna Island, Indonesia, revealed that operational sex ratios are largely male-biased in the tropics where seasonality is lacking. These results indicate that sexual selection pressures are stronger in the tropics than in the temperate zone. The stronger sexual selection pressures may promote speciation rates in the tropics, resulting in the high species diversity.
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