Postmating sexual selection: the effects of male body size and recovery period on paternity and egg production rate in a water strider |
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Authors: | Arnqvist Goran; Danielsson Ingela |
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Institution: | a
Department of Animal Ecology, University of
Ume, SE-901 87
Ume, Sweden
b
Animal Ecology, Department of Zoology, Göteborg
University, Box 463, SE-405 30 Göteborg,
Sweden |
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Abstract: | The role of male body size in postmating sexual selection wasexplored in a
semiaquatic insect, the water strider Gerris lateralis.To separate
effects of male size per se from those due to numericsperm competition, male
recovery period (shown here to be proportionalto ejaculate size) was
manipulated independently of body sizein a factorial experiment where virgin
females were mated firstwith sterile males and then with focal males. Both
relativemale fertilization success and female reproductive rate were
measured.The number of sperm transferred increased with male recoveryperiod,
an effect that was mediated by longer copulation duration,but there were no
effects of body size on ejaculate size. Neithermale size nor recovery period
had any significant direct effectson male fertilization success. However,
copulation durationinfluenced relative fertilization success, suggesting that
malesable to transfer more sperm also achieved higher fertilizationsuccess.
Females exercised cryptic female choice by modulatingtheir reproductive rate
in a manner favoring large males andmales that were successful in terms of
achieving high relativefertilization success. Thus, successful males gained a
twofoldadvantage in postmating sexual selection. This study has important
implicationsfor previous estimates of sexual selection in this group of
insectsbecause pre- and postmating sexual selection will be antagonisticdue
to limitations in male sperm production: males mating frequently(high mating
success) will on average transfer fewer sperm ineach mating and will hence
tend to fertilize fewer eggs permating (low fertilization success). |
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Keywords: | body size copulation duration cryptic female choice ejaculate size Gerris lateralis recovery period reproductive effort sexual selection sperm competition sperm precedence water striders |
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