Heat stress but not inbreeding affects offensive sperm competitiveness in Callosobruchus maculatus
Article first published online: 24 JUL 2013
© 2013 The Authors. Ecology and Evolution published by John Wiley & Sons Ltd.
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Ecology and Evolution
Volume 3, Issue 9, pages 2859–2866, September 2013
How to Cite
Ecology and Evolution 2013; 3(9): 2859–2866
- Issue published online: 8 SEP 2013
- Article first published online: 24 JUL 2013
- Manuscript Accepted: 31 MAY 2013
- Manuscript Revised: 30 MAY 2013
- Manuscript Received: 7 MAY 2013
- Australian Research Council
- Ejaculate size;
- heat shock;
- sperm competition;
Environmental and genetic stress have well-known detrimental effects on ejaculate quality, but their concomitant effect on male fitness remains poorly understood. We used competitive fertilization assays to expose the effects of stress on offensive sperm competitive ability in the beetle Callosobruchus maculatus, a species where ejaculates make up more than 5% of male body mass. To examine the effects of environmental and genetic stress, males derived from outcrosses or sib matings were heat shocked at 50°C for 50 min during the pupal stage, while their siblings were maintained at a standard rearing temperature of 28°C. Heat-shocked males achieved only half the offensive paternity success of their siblings. While this population exhibited inbreeding depression in body size, sperm competitiveness was unaffected by inbreeding, nor did the effect of heat shock stress on sperm competitiveness depend on inbreeding status. In contrast, pupal emergence success was increased by 34% among heat-stressed individuals, regardless of their inbreeding status. Heat-shocked males' ejaculate size was 19% reduced, but they exhibited 25% increased mating duration in single mating trials. Our results highlight both the importance of stress in postcopulatory sexual selection, and the variability among stressors in affecting male fitness.