Data from: Pulsed food resources, but not forest cover, determines lifetime reproductive success in a forest-dwelling rodent

1. The relative contributions of habitat and food availability on fitness may provide evidence for key habitat features needed to safeguard population persistence. However, defining habitat quality for a species can be a complex task, especially if knowledge on the relationship between individual performance and habitat quality is lacking. 2. Here, we determined the relative importance of availability of suitable forest habitat, body mass, and food from masting tree species on female lifetime reproductive success (LRS) of Siberian flying squirrels (Pteromys volans). 3. We calculated LRS of 500 female flying squirrels based on a 22 year-long longitudinal data set of two populations from western Finland. We assessed with generalised additive models the potential effects of availability of suitable habitat and cumulative lifetime availability of food from masting tree species on female LRS, longevity and fecundity. On a reduced dataset, we evaluated the importance of female winter body mass and conducted a piecewise path analysis to determine how variables were connected. 4. According to generalised additive models female longevity, fecundity and LRS were mainly determined by variation in cumulative lifetime availability of food from masting alder and birch. Instead, habitat and body mass had smaller role. The path analysis indicated that lifetime food availability had direct effect on longevity and fecundity, and these had equal effect on LRS at both study sites. 5. Our results on LRS shows that the occurrence of tree masting events during a flying squirrel female’s lifetime have profoundly larger effect on lifetime reproductive success than the cover of suitable forest habitat. Furthermore, this study emphasises the importance of both fecundity and longevity, and the indirect effects of food availability via those components, as determinants of lifetime fitness of female flying squirrels.

1. 生境与食物可获得性对适应度（fitness）的相对贡献，可为维持种群存续所需的关键生境特征提供理论依据。然而，为某一物种界定生境质量往往是一项复杂工作，尤其是在缺乏个体表现与生境质量之间关联认知的情况下。
2. 本研究针对西伯利亚飞鼠（*Pteromys volans*），探讨了适宜森林生境可获得性、体质量以及结实树种（masting）食物资源对雌性个体终生繁殖成功率（Lifetime Reproductive Success, LRS）的相对重要性。
3. 本研究基于芬兰西部两个种群长达22年的纵向数据集，计算了500只雌性飞鼠的终生繁殖成功率。我们采用广义加性模型（Generalized Additive Models, GAM），评估了适宜生境可获得性以及结实树种食物资源的终生累积可获得性，对雌性飞鼠终生繁殖成功率、寿命与繁殖力的潜在影响。此外，我们通过精简数据集评估了雌性冬季体质量的重要性，并开展分段路径分析以明确各变量间的关联路径。
4. 广义加性模型分析结果显示，雌性飞鼠的寿命、繁殖力以及终生繁殖成功率，主要由桤木与桦树这类结实树种的食物终生累积可获得性差异所决定；而生境与体质量的影响相对较小。路径分析表明，在两个研究样地中，终生食物可获得性均对寿命与繁殖力存在直接正向影响，而寿命与繁殖力对终生繁殖成功率的影响程度相当。
5. 本研究关于终生繁殖成功率的结果表明，雌性飞鼠存活期内发生的树种结实事件，对其终生繁殖成功率的影响远大于适宜森林生境的覆盖占比。此外，本研究强调，繁殖力与寿命二者，以及食物可获得性通过这两个组分产生的间接效应，均是决定雌性飞鼠终生适应度的关键因素。