Takashina Nao, Fiksen Øyvind
Biodiversity and Biocomplexity Unit Okinawa Institute of Science and Technology Graduate University Okinawa Japan.
Department of Biological Sciences University of Bergen Bergen Norway.
Ecol Evol. 2020 Apr 16;10(10):4241-4250. doi: 10.1002/ece3.6192. eCollection 2020 May.
Intra-cohort cannibalism is an example of a size-mediated priority effect. If early life stages cannibalize slightly smaller individuals, then parents face a trade-off between breeding at the best time for larval growth or development and predation risk from offspring born earlier. This game-theoretic situation among parents may drive adaptive reproductive phenology toward earlier breeding. However, it is not straightforward to quantify how cannibalism affects seasonal egg fitness or to distinguish emergent breeding phenology from alternative adaptive drivers. Here, we devise an age-structured game-theoretic mathematical model to find evolutionary stable breeding phenologies. We predict how size-dependent cannibalism acting on eggs, larvae, or both changes emergent breeding phenology and find that breeding under inter-cohort cannibalism occurs earlier than the optimal match to environmental conditions. We show that emergent breeding phenology patterns at the level of the population are sensitive to the ontogeny of cannibalism, that is, which life stage is subject to cannibalism. This suggests that the nature of cannibalism among early life stages is a potential driver of the diversity of reproductive phenologies seen across taxa and may be a contributing factor in situations where breeding occurs earlier than expected from environmental conditions.
同群体内的自相残杀是大小介导的优先效应的一个例子。如果生命早期阶段的个体捕食稍小的个体，那么亲代就面临着在幼虫生长或发育的最佳时间进行繁殖与来自较早出生后代的捕食风险之间的权衡。亲代之间这种博弈论情境可能会驱使适应性繁殖物候朝着更早繁殖的方向发展。然而，要量化自相残杀如何影响季节性卵的适合度，或者将出现的繁殖物候与其他适应性驱动因素区分开来并非易事。在此，我们设计了一个年龄结构的博弈论数学模型来寻找进化稳定的繁殖物候。我们预测作用于卵、幼虫或两者的大小依赖性自相残杀如何改变出现的繁殖物候，并发现同群体间自相残杀情况下的繁殖比与环境条件的最佳匹配时间更早。我们表明，种群水平上出现的繁殖物候模式对自相残杀的个体发育敏感，也就是说，哪个生命阶段会遭受自相残杀。这表明生命早期阶段自相残杀的性质是不同分类群中所见繁殖物候多样性的一个潜在驱动因素，并且可能是繁殖时间比根据环境条件预期更早的情况下的一个促成因素。
