Mating with a kin decreases female remating interval: a possible example of inbreeding avoidance |
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Authors: | Panu Välimäki Sami M Kivelä Maarit I Mäenpää |
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Institution: | (1) Department of Biology, University of Oulu, P.O. Box 3000, 90014 Oulu, Finland |
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Abstract: | Inbreeding depression is a relative decline in fitness in offspring of related parents. The magnitude of inbreeding costs
varies among taxa and may increase under stressful conditions. Inbreeding tolerance is expected to be low and selection for
inbreeding avoidance intense when both sexes invest substantially in shared offspring like in nuptial gift-giving butterflies.
This is especially true for increasing mating rate for inbreeding avoidance as nuptial feeding decreases net costs of mating
for females. We explored implications of inbreeding in the nuptial gift-giving green-veined white butterfly, Pieris napi. Compared to outbred ones, partially inbred (F = 0.25) eggs and neonate larvae had 25% lower hatching success and 30% lower survival until adult eclosion, respectively.
Inbreeding was also associated with small size. Yet, the magnitude of inbreeding depression was independent of larval conditions.
A lack of assortative mating and mating durations independent of mating type suggest that neither females nor males discriminate
close relatives (r = 0.5) as mates. Indicative of a postcopulatory mechanism to avoid inbreeding, female remating intervals decreased following
incestuous matings. Such a plastic response may affect the level of postcopulatory sexual selection as female remating interval
(time between successive matings) is necessarily negatively correlated with mating rate (matings per unit time) and mating
frequency (lifetime number of matings), and precopulatory mate choice appeared insignificant. Moreover, incest-induced shift
in the phenotype towards the adaptive peak may contribute to the evolution of female mating rates, although alternative explanations
for polyandry besides material benefits have rarely been invoked when nuptial feeding is involved. |
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