Sibling cannibalism in the ladybird beetleHarmonia axyridis: Fitness consequences for mother and offspring |
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Authors: | Naoya Osawa |
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Institution: | (1) Laboratory of Entomology, Faculty of Agriculture, Kyoto University, 606 Kyoto, Japan |
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Abstract: | Summary The adaptive significance of sibling cannibalism was analyzed in the ladybird beetleHarmonia axyridis at two prey densities. Possible costs and benefits were considered from three points of view: the mother, the cannibal and
the victim. Cannibals ate both infertile and fertile eggs, thereby increasing in body length and survival rate with the intensity
of sibling cannibalism. The cannibalistic trait was clearly beneficial to the cannibal when aphid density was low. However,
it was not always beneficial when aphid density was high and the victims were full siblings. The altruistic behavior of being
a victim was beneficial only when the victim was cannibalized by full siblings at low aphid density. The mother attained almost
equal fitness at low aphid density, regardless of the intensity of sibling cannibalism. This suggests that sibling cannibalism
is not maladaptive for the mother. At high aphid density, however, mother’s fitness decreased with the intensity of sibling
cannibalism, indicating that sibling cannibalism is maladaptive for the mother when larval food availability is high. |
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Keywords: | sibling cannibalism kin selection fitness ladybird beetle Harmonia axyridis |
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