Organism abundance is a critical parameter in ecology, but its estimation is often challenging. Approaches utilizing eDNA to indirectly estimate abundance have recently generated substantial interest. However, preliminary correlations observed between eDNA concentration and abundance in nature are typically moderate in strength with significant unexplained variation. Here, we apply a novel approach to integrate allometric scaling coefficients into models of eDNA concentration and organism abundance. We hypothesize that eDNA particle production scales nonlinearly with mass, with scaling coefficients < 1. Wild populations often exhibit substantial variation in individual body size distributions; we therefore predict that the distribution of mass across individuals within a population will influence population-level eDNA production rates. To test our hypothesis, we collected standardized body size distribution and mark–recapture abundance data using whole-lake experiments involving nine populations of brook trout. We correlated eDNA concentration with three metrics of abundance: density (individuals/ha), biomass (kg/ha) and allometrically scaled mass (ASM) (∑(individual mass^0.73)/ha). Density and biomass were both significantly positively correlated with eDNA concentration (adj. r² = 0.59 and 0.63, respectively), but ASM exhibited improved model fit (adj. r² = 0.78). We also demonstrate how estimates of ASM derived from eDNA samples in "unknown" systems can be converted to biomass or density estimates with additional size-structure data. Future experiments should empirically validate allometric scaling coefficients for eDNA production, particularly where substantial intraspecific size distribution variation exists. Incorporating allometric scaling may improve predictive models to the extent that eDNA concentration may become a reliable indicator of abundance in nature.

中文翻译：

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异速生长缩放加强了自然界中 eDNA 粒子浓度与生物体丰度之间的关系

生物体丰度是生态学中的一个关键参数，但其估计通常具有挑战性。利用 eDNA 间接估计丰度的方法最近引起了极大的兴趣。然而，在自然界中观察到的 eDNA 浓度和丰度之间的初步相关性通常是中等强度，具有显着无法解释的变化。在这里，我们应用一种新方法将异速生长缩放系数整合到 eDNA 浓度和生物体丰度模型中。我们假设 eDNA 粒子的产生与质量呈非线性关系，比例系数 < 1。野生种群通常在个体体型分布上表现出很大的变化；因此，我们预测群体内个体的质量分布将影响群体水平的 eDNA 生产率。为了验证我们的假设，我们使用涉及九个鳟鱼种群的全湖实验收集了标准化的体型分布和标记-重新捕获丰度数据。我们将 eDNA 浓度与三个丰度指标相关联：密度（个体/公顷）、生物量（公斤/公顷）和异速缩放质量（ASM）（∑（个体质量）^0.73 )/公顷)。密度和生物量均与 eDNA 浓度显着正相关（ 分别调整r ² = 0.59 和 0.63），但 ASM 表现出改进的模型拟合（调整r ²  = 0.78）。我们还展示了如何将来自“未知”系统中的 eDNA 样本的 ASM 估计值转换为具有额外尺寸结构数据的生物量或密度估计值。未来的实验应该凭经验验证 eDNA 生产的异速生长缩放系数，特别是在存在大量种内大小分布变化的情况下。结合异速生长缩放可以改进预测模型，使 eDNA 浓度可能成为自然界丰度的可靠指标。