Data from: Evolutionary time-series analysis reveals the signature of frequency-dependent selection on a female mating polymorphism

A major challenge in evolutionary biology is understanding how stochastic and deterministic factors interact and influence macroevolutionary dynamics in natural populations. One classical approach is to record frequency changes of heritable and visible genetic polymorphisms over multiple generations. Here, we combined this approach with a maximum likelihood–based population-genetic model with the aim of understanding and quantifying the evolutionary processes operating on a female mating polymorphism in the blue-tailed damselfly Ischnura elegans. Previous studies on this color-polymorphic species have suggested that males form a search image for females, which leads to excessive mating harassment of common female morphs. We analyzed a large temporally and spatially replicated data set of between-generation morph frequency changes in I. elegans. Morph frequencies were more stable than expected from genetic drift alone, suggesting the presence of selection toward a stable equilibrium that prevents local loss or fixation of morphs. This can be interpreted as the signature of negative frequency-dependent selection maintaining the phenotypic stasis and genetic diversity in these populations. Our novel analytical approach allows the estimation of the strength of frequency-dependent selection from the morph frequency fluctuations around their inferred long-term equilibria. This approach can be extended and applied to other polymorphic organisms for which time-series data across multiple generations are available.

进化生物学的核心挑战之一，在于阐释随机与确定性因素如何相互作用，并影响自然种群的宏观进化动力学。经典研究策略之一，便是记录多世代间可遗传且表型可见的遗传多态性的频率变化。本研究将该策略与基于最大似然法（maximum likelihood）的种群遗传模型相结合，旨在解析并量化蓝尾豆娘（Ischnura elegans）雌性交配多态性所经历的进化过程。针对这一色彩多态性物种的既往研究表明，雄性会对雌性形成搜索图像（search image），进而导致常见雌性形态遭遇过度的交配骚扰。我们分析了一套大规模时空重复数据集，涵盖蓝尾豆娘（I. elegans）各世代间的形态频率变化。研究发现，形态频率的稳定性显著高于仅由遗传漂变（genetic drift）所预期的水平，这表明存在指向稳定平衡的选择作用，可阻止种群内形态的局部丢失或固定。这一现象可被视为负频率依赖选择（negative frequency-dependent selection）的特征标记，该选择维持了这些种群的表型稳态与遗传多样性。我们提出的新型分析方法，可通过形态频率围绕其推断的长期平衡值的波动情况，估算频率依赖选择的作用强度。该方法可被拓展并应用于其他拥有多世代时间序列数据的多态性生物研究中。