Reuland Charel, Culbert Brett M, Fernlund Isaksson Erika, Kahrl Ariel F, Devigili Alessandro, Fitzpatrick John L
Department of Zoology, Stockholm University, Svante Arrhenius väg 18B, Stockholm, Sweden.
Department of Integrative Biology, University of Guelph, Guelph, Canada.
Behav Ecol. 2020 Nov 28;32(1):168-177. doi: 10.1093/beheco/araa118. eCollection 2021 Jan-Feb.
Higher social status is expected to result in fitness benefits as it secures access to potential mates. In promiscuous species, male reproductive success is also determined by an individual's ability to compete for fertilization after mating by producing high-quality ejaculates. However, the complex relationship between a male's investment in social status and ejaculates remains unclear. Here, we examine how male social status influences ejaculate quality under a range of social contexts in the pygmy halfbeak , a small, group-living, internally fertilizing freshwater fish. We show that male social status influences ejaculate traits, both in the presence and absence of females. Dominant males produced faster swimming and more viable sperm, two key determinants of ejaculate quality, but only under conditions with frequent male-male behavioral interactions. When male-male interactions were experimentally reduced through the addition of a refuge, differences in ejaculate traits of dominant and subordinate males disappeared. Furthermore, dominant males were in a better condition, growing faster, and possessing larger livers, highlighting a possible condition dependence of competitive traits. Contrary to expectations, female presence or absence did not affect sperm swimming speed or testes mass. Together, these results suggest a positive relationship between social status and ejaculate quality in halfbeaks and highlight that the strength of behavioral interactions between males is a key driver of social-status-dependent differences in ejaculate traits.
较高的社会地位有望带来健康益处，因为它能确保获得潜在配偶。在混交物种中，雄性的繁殖成功还取决于个体在交配后通过产生高质量精液来竞争受精的能力。然而，雄性在社会地位上的投入与精液之间的复杂关系仍不明确。在此，我们研究了在侏儒半颌鱼（一种小型、群居、体内受精的淡水鱼）的一系列社会背景下，雄性社会地位如何影响精液质量。我们发现，无论有无雌性在场，雄性社会地位都会影响精液特征。占主导地位的雄性产生的精子游动速度更快且更具活力，这是精液质量的两个关键决定因素，但仅在雄性之间频繁发生行为互动的条件下如此。当通过添加避难所实验性地减少雄性之间的互动时，占主导地位和从属地位的雄性在精液特征上的差异消失了。此外,占主导地位的雄性状况更好，生长更快，肝脏更大，这凸显了竞争特征可能对条件的依赖性。与预期相反，雌性的在场与否并不影响精子的游动速度或睾丸质量。总之，这些结果表明半颌鱼的社会地位与精液质量之间存在正相关关系，并强调雄性之间行为互动的强度是精液特征中社会地位依赖性差异的关键驱动因素。
