Data from: Parallelism isn't perfect: could disease and flooding drive a life history anomaly in Trinidadian guppies?

Nonparallel evolution, where independent populations occupy similar environments but show phenotypic differences, can uncover previously ignored selective factors. We investigated a nonparallelism in the life-history strategy of a Trinidadian guppy population, a system famous for parallel adaptation to differences in predation risk. We tested the hypothesis that high mortality drives an observed fast life-history pattern (i.e., earlier maturation and more frequent reproductive events) that is atypical for a low-predation environment. Using mark-recapture techniques, we compared neighboring low-predation populations, finding significantly higher mortality rates in the population with atypical life-history traits. Mortality was elevated during the wet season, when flooding was common. Moreover, individuals from the anomalous population were more likely to transition from healthy to infected disease states. Our results stand out against previous patterns observed in this system, indicating that higher mortality caused by disease and flooding may have selected for a faster life history. Thus, we highlight that even in systems famous for parallel adaptation, variation in selective pressures can result in nonparallel phenotypic evolution.

非平行演化 (Nonparallel evolution) 指独立种群栖息于相似环境却呈现表型差异，该过程可揭示此前被忽视的选择因子。我们以特立尼达孔雀鱼种群为研究对象，该研究体系因针对捕食风险差异的平行适应性演化而闻名，本次研究聚焦其生活史策略中的非平行性现象。我们验证了如下假说：高死亡率推动了在低捕食压力环境下显得非典型的快速生活史模式（即发育提前且繁殖频次更高）。我们借助标记重捕技术 (mark-recapture techniques) 对邻近的低捕食压力种群开展对比分析，发现携带非典型生活史特征的种群死亡率显著更高。死亡率在洪水频发的雨季显著升高。此外，该异常种群的个体更易从健康状态转向感染疾病状态。本研究结果与该体系此前观测到的既有规律形成鲜明反差，表明由疾病与洪水引发的高死亡率可能对快速生活史产生了选择作用。据此我们强调，即便在以平行适应性演化为标志性特征的类群中，选择压力的变异仍可导致非平行的表型演化。