Differential investment and size-related mating strategies facilitate extreme size variation in contesting male spiders
Differential investment and size-related mating strategies facilitate extreme size variation in contesting male spiders
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DOI：
10.1016/j.anbehav.2014.12.027
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发表时间：
2015-03
期刊：
影响因子：
2.5
通讯作者：
Rainer Neumann;J. Schneider
中科院分区：
文献类型：
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作者：
Rainer Neumann;J. Schneider
亮点在矮小雄性物种中，雄性体型的选择仍然是个谜。我们分析了成年体型10倍的竞争雄性的适合度。与体型相关的雄性交配策略产生了相同的适合度回报。雄性根据竞争和雌性价值灵活地调整交配投资。不同的投资可能会促进SSD的大小变化和维持。雄性身体大小的性别选择变异通常与其他生殖策略有关，这些策略可能会在依赖于频率的选择下持续存在，或者是由于劣势个体“充分利用糟糕的工作”而产生的。蜘蛛属NePhila以雌性巨人症和雄性侏儒症而闻名，是研究雄性大小选择和仍然神秘的性大小二型性(SSD)的已建立的模式系统。尽管有广泛的证据表明雄性在竞争中具有巨大的优势，但人们对一些NePhila物种中存在的雄性之间巨大的体型差异关注较少。由于现有的变异与不同表型之间的强烈偏向适应回报相矛盾，因此需要详细研究与不同体型相关的适应结果及其相关的交配策略。我们使用非洲金丝蜘蛛NePhila senegalensis来测试大小相关的替代交配策略是否会在大小不匹配的雄性竞争一只雌性的情况下产生相同的繁殖成功。我们的结果证实，不同大小的雄性实现了相似的父子关系，并揭示了相互竞争的策略之间复杂的相互关系，这些相互影响。雄性结合自身竞争能力、精子竞争强度和雌性生殖价值进行相应的交配投资调整。与体型相关的交配策略与行为灵活性相结合，可能因此通过平衡适应回报来促进雄性体型差异的维持，并举例说明选择性背景的变化如何消除主要的大型体型好处。我们认为，灵活的适应性反应可能对稳定SSD做出重大贡献。
HighlightsSelection on male body size in species with dwarf males is still enigmatic.We analyse fitness in competing males with a 10-fold range in adult body sizes.Size-related male mating strategies yielded equivalent fitness returns.Males flexibly adjusted mating investment to competition and female value.Differential investment may promote size variation and maintenance of SSD.Sexually selected variation in male body size is often associated with alternative reproductive strategies that may persist under frequency-dependent selection or result from ‘making the best of a bad job’in inferior individuals. The spider genus Nephila is well known for female gigantism and male dwarfism, serving as an established model system to investigate selection on male size and the still enigmatic sexual size dimorphism (SSD). Less attention has been paid to the enormous size variation among males that exists in some Nephila species despite broad evidence for large male advantages in contest competition. As the existing variation contradicts strongly biased fitness returns among different phenotypes, detailed investigations of fitness consequences related to different body sizes and their associated mating strategies are required. We used the African golden-silk spider Nephila senegalensis to test whether size-dependent alternative mating strategies yield equivalent reproductive success in dyads of size-mismatched males competing for a single female. Our results confirm that differently sized males achieve similar paternity and reveal complex interrelations between competing strategies, which mutually influence each other. Males integrate their own competitive ability, the intensity of sperm competition and female reproductive value to adjust their mating investment accordingly. Size-related mating strategies, combined with behavioural flexibility, may thus promote the maintenance of male size variation by balancing fitness returns and exemplify how changes in selective context can dissolve the principal large-size benefits. We suggest that flexible adaptive responses may significantly contribute to stabilizing SSD.