Data from: A critical assessment of estimating census population size from genetic population size (or vice versa) in three fishes

Technological and methodological advances have facilitated the use of genetic data to infer census population size (Nc) in natural populations, particularly where traditional mark-and-recapture is challenging. The effective number of breeders (Nb) describes how many adults effectively contribute to a cohort and is often correlated with Nc. Predicting Nc from Nb or vice-versa in species with overlapping generations has important implications for conservation by permitting (i) estimation of the more difficult to quantify variable and (ii) inferences of Nb/Nc relationships in related species lacking data. We quantitatively synthesized Nb/Nc relationships in three salmonid fishes where sufficient data has recently accumulated. Mixed-effects models were analyzed in which each variable was included as a dependent variable or predictor term (Nb from Nc and vice versa). Species-dependent Nb/Nc slope estimates were significantly positive in two of three species; variation in species slopes were likely due to varying life histories and reinforce caution when inferring Nb/Nc from taxonomically-related species. Models provided maximum probable estimates for Nb and Nc for two species. However, study, population, and year effects explained substantial amounts of variation (39-57%). Consequently, prediction intervals were wide and included or were close to zero for all population sizes and species; model predictive utility was limited. Cost-benefit trade-offs when estimating Nb and/or Nc were also discussed using a real-world system example. Our findings based on salmonids suggest that no short-cuts currently exist when estimating population size; researchers should focus on quantifying the variable of interest or be aware of caveats when inferring the desired variable because of cost or logistics. We caution that the salmonid species examined share life-history traits that may obscure relationships between Nb and Nc. Sufficient data on other taxa were unavailable; additional research examining Nb/Nc relationships in species with potentially relevant life-history trait differences (e.g. differing survival curves) are needed.

技术与方法学的进步推动了遗传数据在自然种群普查种群数量（census population size, Nc）推断中的应用，尤其适用于传统标记重捕法难以开展的场景。有效繁殖种群数量（effective number of breeders, Nb）指的是实际对同生群有繁殖贡献的成年个体数，且通常与Nc存在相关性。在存在世代重叠的物种中，通过Nb推断Nc，或反之，对物种保护具有重要意义：这既可以（i）估算难以直接量化的种群参数，又能够（ii）在缺乏相关数据的近缘物种中推断Nb与Nc的关系。本研究针对近期积累了足够数据的3种鲑科鱼类（salmonid fishes），对Nb与Nc的关系进行了定量综合分析。本研究采用混合效应模型（mixed-effects models）进行分析，将两个变量分别作为因变量或预测因子建模（即通过Nc推断Nb，或反之）。在3个物种中，有2个物种的Nb/Nc斜率估计值呈显著正相关；物种间斜率的差异可能源于不同的生活史特征，这也提醒我们，在从近缘类群推断Nb与Nc的关系时需谨慎。模型为其中2个物种提供了Nb与Nc的最大概似估计值。但研究、种群及年份效应解释了39%~57%的变异量。因此，所有种群规模与物种的预测区间（prediction intervals）均较宽，且区间包含或接近0，模型的预测效用有限。本研究还结合一个真实研究系统案例，探讨了估算Nb与/或Nc时的成本效益权衡（cost-benefit trade-offs）。基于鲑科鱼类的研究结果表明，当前估算种群规模尚无捷径可循；研究者应直接量化目标参数，或在因成本或实操限制而需要推断目标参数时，充分意识到其存在的局限性。本研究提醒，本次研究所涉及的鲑科鱼类具有相似的生活史特征，这可能会掩盖Nb与Nc之间的真实关联。目前尚无其他类群的足够数据；未来需针对生活史特征存在潜在关键差异（例如不同的存活曲线（survival curves））的物种，开展Nb与Nc关系的相关研究。