Kensuke Okada

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Inbreeding frequently leads to inbreeding depression, a reduction in the trait values of inbred individuals. Inbreeding depression has been documented in sexually selected characters in several taxa, and while there is correlational evidence that male fertility is especially susceptible to inbreeding depression, there have been few direct experimental(More)
In the stored-product beetle, the broad-horned flour beetle, Gnatocerus cornutus (Fabricius), all males possess enlarged mandibles, widened gena, and a pair of small horns on the vertex, but females lack these completely. Observations of male-male interactions of G. cornutus showed that larger individuals won male-male fights, and that the mandibles were(More)
Sexually antagonistic selection generates intralocus sexual conflict, an evolutionary tug-of-war between males and females over optimal trait values [1-4]. Although the potential for this conflict is universal, the evolutionary importance of intralocus conflict is controversial because conflicts are typically thought to be resolvable through the evolution(More)
Weapons used in male fighting can be costly to males and are often reported to trade off with other characters such as wings or spermatogenic investment. This study investigated whether increased investment into weapons can generate evolutionary changes in mating strategy for armed males. Male flour beetles, Gnatocerus cornutus, have enlarged mandibles that(More)
BACKGROUND AND AIMS As with other crop species, Al tolerance in rice (Oryza sativa) is widely different among cultivars, and the mechanism for tolerance is unknown. The Ca2+-displacement hypothesis, that is, Al displaces Ca2+ from critical sites in the root apoplast, was predicted to be the essential mechanism for causing Al toxicity in rice cultivars. If(More)
Sexually selected exaggerated traits are often coupled with modifications in other nontarget traits. In insects with weapons, enlargements of nontarget characters that functionally support the weapon often occur (i.e. supportive traits). The support of sexual traits requires developmental coordination among functionally related multiple traits-an explicit(More)
Male-male competition frequently results in the evolution of sexually selected traits used as weapons and ornaments. The expression of these traits often depends on male condition, i.e., condition dependence. Although males often have multiple sexually selected traits, to date many studies have focused on the morphological analysis of one sexual trait(More)
Although silicon (Si) is found at much higher concentrations in healthy rice crops than N, P or K, it has received far less study, particularly for upland rice. There are few reports on the existence, causes, and effects of varying Si supplies in different environments. Chemical analyses of soil, water and plant tissue samples from experiments grown on a(More)
Experience-dependent tactics of males trying to gain access to females were examined in the beetle Gnatocerus cornutus, which engages in male–male fighting for mates. In male fights, subsequent behavior is modified by winning and losing experiences. Males, therefore, may choose between several behavioral tactics to obtain a mate, based on his previous(More)
Traditional concepts of sexual selection and sexual conflict make different predictions about the costs and benefits to females of exposure to males with higher mating success. The traditional concepts of sexual selection assume that females benefit from their mate choices, whereas sexual conflict assumes that the females suffer greater costs by mating with(More)