Matzke Magdalena, Toft Søren, Bechsgaard Jesper, Pold Vilstrup Astrid, Uhl Gabriele, Künzel Sven, Tuni Cristina, Bilde Trine
Department of Biology, Ludwig Maximilian University of Munich, Planegg-Martinsried, Germany.
Department of Biology, Aarhus University, Aarhus C, Denmark.
Mol Ecol. 2022 Apr;31(8):2435-2452. doi: 10.1111/mec.16405. Epub 2022 Mar 3.
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.
精子竞争促使生物形成能提高受精成功率的性状。相对于竞争对手而言，精子的输送量是获得父权的关键。雌性的生殖形态和雄性的交配顺序也可能影响受精，然而在激烈的精子竞争中精子优先的结果仍知之甚少。在多配性的奇异盗蛛中，雄性会提供婚飞礼物，这会延长交配时间并增加精子输送量，这些因素被认为会改变在激烈精子竞争下的精子优先模式。首先，我们通过对野生窝进行基因分型来评估雌性的多配程度。一项保守分析确定最多有四个父本，每个窝平均有两个父本，这与最佳交配雌性率一致。然后我们研究了激烈的精子竞争是否会使精子优先模式从雌性形态预期的第一只雄性优先转变为最后一只雄性占优。我们通过实验改变性选择强度，并通过对窝进行基因分型来确定竞争性受精结果。在双重交配中，无论交配顺序如何，一只雄性垄断了父权。当雌性与四只雄性交配时，显示出第一只雄性优先的交配顺序效应，然而当雌性与六只雄性交配时，这种效应消失了，可能是由于精子混合增加。成功成为父本的雄性比例随着竞争对手数量的增加而急剧下降。交配时间越长，无论交配顺序如何，父权份额越高，这强化了在激烈竞争下延长交配持续时间的性状（如婚飞礼物）的优势。精子竞争强度增强了竞争性性状的影响，并对父权产生多种影响。
