Behavioral Ecology Advance Access originally published online on July 17, 2007
Behavioral Ecology 2007 18(5):958-966; doi:10.1093/beheco/arm067
| ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
Sexual conflict over copula timing: a mathematical model and a test in the yellow dung fly
Zoologisches Museum, Universität Zürich, Winterthurerstrasse 190, CH-8057 Zürich, Switzerland
Address correspondence to W.U. Blanckenhorn. E-mail: wolf.blanckenhorn{at}zm.uzh.ch.
 |
Abstract |
|---|
Sexual conflict over mating occurrence, timing, or duration is common in animals. This explains conspicuous female mate rejection behavior in many species, often involving shaking, fighting, and occasional forced copulations. We present a simple model that generates predictions about whether and when copulation occurs in such conflict situations and how much female rejection behavior should be observed. Predictions depend on 2 underlying parameters affecting female resistance and male persistence. We supply 2 qualitative tests of the model using the yellow dung fly Scathophaga stercoraria (Diptera: Scathophagidae). We manipulated adult age, body size (large and small), and adult food availability (low and high), independently in males and females, staging replicate pairings of all treatment combinations. In agreement with predictions of our model, shaking duration first increased to a maximum at intermediate age, when the average female copulated, and then decreased again. Contrary to expectation, body size did not affect copulation timing, female resistance, or male persistence. As predicted, adult food limitation delayed sexual maturity and hence prolonged female resistance, resulting in later copulations after more shaking. However, although food limitation equally delayed the increase in male persistence with age, copulation also occurred later after more shaking, opposite to the model prediction. We conclude that shaking is driven primarily by female age and male responses to it. Although female shaking can initially successfully deter males in S. stercoraria, this behavior is subtle and has apparently shifted function from an effective means of mate choice to a signal of nonreceptivity, though its importance in nature remains unclear.
Key words: body size, copulation duration, food limitation, Scathophaga stercoraria, Scatophaga, sexual conflict, sexual selection.
Received 18 June 2007; revised 18 June 2007; accepted 18 June 2007.