Journal
MOLECULAR ECOLOGY
Volume 31, Issue 8, Pages 2435-2452Publisher
WILEY
DOI: 10.1111/mec.16405
Keywords
copulation duration; fertilization outcome; mating order; microsatellite markers; paternity; sperm competition; sperm precedence
Funding
- Danish Council for Independent Research [4002--00328B]
- Erasmus+
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Sperm competition is a driving force for the development of traits that enhance fertilization success. This study focuses on the polyandrous spider Pisaura mirabilis and examines the effects of female polyandry, male mating order, and sexual selection intensity on sperm precedence patterns and paternity. The findings suggest that intense sperm competition can shift sperm precedence patterns and that longer copulations increase paternity shares, highlighting the importance of traits that prolong copulation duration under intense competition.
Sperm competition drives traits that enhance fertilization success. The amount of sperm transferred relative to competitors is key for attaining paternity. Female reproductive morphology and male mating order may also influence fertilization, however the outcome for sperm precedence under intense sperm competition remains poorly understood. In the polyandrous spider Pisaura mirabilis, males offer nuptial gifts which prolong copulation and increase sperm transfer, factors proposed to alter sperm precedence patterns under strong sperm competition. First, we assessed the degree of female polyandry by genotyping wild broods. A conservative analysis identified up to four sires, with a mean of two sires per brood, consistent with an optimal mating female rate. Then we asked whether intense sperm competition shifts sperm precedence patterns from first male priority, as expected from female morphology, to last male advantage. We varied sexual selection intensity experimentally and determined competitive fertilization outcome by genotyping broods. In double matings, one male monopolised paternity regardless of mating order. A mating order effect with first male priority was revealed when females were mated to four males, however this effect disappeared when females were mated to six males, probably due to increased sperm mixing. The proportion of males that successfully sired offspring drastically decreased with the number of competitors. Longer copulations translated into higher paternity shares independently of mating order, reinforcing the advantage of traits that prolong copulation duration under intense competition, such as the nuptial gift. Sperm competition intensity enhances the impact of competitive sexual traits and imposes multiple effects on paternity.
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