Publications by authors named "Norihiro Yagi"

Over the past decade, the cause of sociality has been much debated. Inclusive fitness [ in Hamilton's rule ( - > 0)] has been criticized but is still useful in the organization of a framework by elucidating mechanisms through which (benefit × relatedness) becomes larger than (cost). The bee is suitable for investigation of this issue because of the sympatric occurrence of both social and solitary nesting in its populations.

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Despite being a central issue in evolutionary biology, few studies have examined the stasis of characters in populations with no gene flow. A possible mechanism of such stasis is stabilizing selection with similar peaks in each population. This study examined the evolutionary patterns of morphological characters with and without strong selection in ant populations.

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The validity of Hamilton's rule has been confirmed among cooperative breeders where helping behaviour is transient; however, Hamilton's rule has not been validated among eusocial insects where helpers commit for life. Here we conduct a direct test of Hamilton's rule using field populations of Lasioglossum baleicum bees, which inhabit sympatric solitary and eusocial nests. Our results show that the indirect fitness of sterile first-brood workers is higher than the direct fitness of solitary first-brood females, and spring foundresses achieve a large direct fitness by having helpers.

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