Data from: Spatial variation in the relationship between performance and metabolic rate in wild juvenile Atlantic salmon

1. Maintenance metabolic rate (MR, the energy cost of self-maintenance) is linked to behavioural traits and fitness and varies substantially within populations. Despite having received much attention, the causes and consequences of this variation remain obscure. 2. Theoretically, such within-population variation in fitness-related traits can be maintained by environmental heterogeneity in selection patterns, but for MR this has rarely been tested in nature. 3. Here, we experimentally test if the relationship between MR and performance can vary spatially by assessing survival, growth rate and movement of Atlantic salmon (Salmo salar L.) juveniles from 10 family groups differing in MR (measured as egg metabolism) that were stocked in parallel across 10 tributaries of a single watershed. 4. The relationship between MR and relative survival and growth rate varied significantly among tributaries. Specifically, the effect of MR ranged from negative to positive for relative survival, whereas it was negative for growth rate. The association between MR and movement was positive and did not vary significantly among tributaries. 5. These results are consistent with a fitness cost of traits associated with behavioural dominance that varies across relatively small spatial scales (within a single watershed). More generally our results support the hypothesis that spatial heterogeneity in environmental conditions contributes to maintain within-population variation in fitness-related traits, such as MR.

1. 维持代谢率（Maintenance metabolic rate，MR，即个体自我维持的能量消耗）与行为性状及适合度紧密相关，且在种群内部存在显著差异。尽管该领域已受到广泛关注，但此类变异的成因与后果仍不明确。
2. 理论上，这类与适合度相关的性状的种群内变异，可通过选择模式的环境异质性得以维持，但针对MR的此类实证检验在自然环境中仍极为罕见。
3. 本研究通过实验检验MR与个体表现之间的关联是否存在空间异质性：我们将10个具有不同MR（以卵代谢水平衡量）家系组的大西洋鲑（Atlantic salmon, Salmo salar L.）幼体，平行放养于同一流域的10条支流中，并对其存活率、生长速率与移动能力进行评估。
4. MR与相对存活率、生长速率之间的关联在不同支流间存在显著差异。具体而言，MR对相对存活率的影响范围从负向延伸至正向，而对生长速率的影响则均为负向；MR与移动能力间呈正向关联，且在各支流间无显著差异。
5. 上述结果与“与行为优势度相关的性状存在适合度代价，且该代价在较小空间尺度（同一流域内）存在差异”的假说一致。总体而言，本研究结果支持“环境条件的空间异质性有助于维持与适合度相关的性状（如MR）的种群内变异”这一假说。