BACKGROUND & AIMS:
:The thermal performance curve (TPC) illustrates the dependence on body- and therefore environmental- temperature of many fitness-related aspects of ectotherm ecology and biology including foraging, growth, predator avoidance, and reproduction. The typical thermal performance curve model is linear in its parameters despite the well-known, strong, non-linearity of the response of performance to temperature. In addition, it is usual to consider a single model based on few individuals as descriptive of a species-level response to temperature. To overcome these issues, we used generalized additive mixed modeling (GAMM) to estimate thermal performance curves for 73 individual hatchling Natrix natrix grass snakes from seven clutches, taking advantage of the structure of GAMM to demonstrate that almost 16% of the deviance in thermal performance curves is attributed to inter-individual variation, while only 1.3% is attributable to variation amongst clutches. GAMM allows precise estimation of curve characteristics, which we used to test hypotheses on tradeoffs thought to constrain the thermal performance curve: hotter is better, the specialist-generalist trade off, and resource allocation/acquisition. We observed a negative relationship between maximum performance and performance breadth, indicating a specialist-generalist tradeoff, and a positive relationship between thermal optimum and maximum performance, suggesting "hotter is better". There was a significant difference among matrilines in the relationship between Area Under the Curve and maximum performance - relationship that is an indicator of evenness in acquisition or allocation of resources. As we used unfed hatchlings, the observed matriline effect indicates divergent breeding strategies among mothers, with some mothers provisioning eggs unequally resulting in some offspring being better than others, while other mothers provisioned the eggs more evenly, resulting in even performance throughout the clutch. This observation is reminiscent of bet-hedging strategies, and implies the possibility for intra-clutch variability in the TPCs to buffer N. natrix against unpredictable environmental variability.
背景与目标:
: 热性能曲线 (TPC) 说明了外热学生态学和生物学的许多与健身相关的方面 (包括觅食,生长,避免捕食者和繁殖) 对身体温度以及因此对环境温度的依赖性。尽管性能对温度的响应具有众所周知的强非线性,但典型的热性能曲线模型在其参数上是线性的。此外,通常考虑基于少数个体的单个模型来描述物种水平对温度的响应。为了克服这些问题,我们使用广义加性混合模型 (GAMM) 来估计来自七个离合器的73个个体孵化Natrix natrix草蛇的热性能曲线,利用GAMM的结构来证明几乎16% 的热性能曲线偏差归因于个体间的变化,而只有1.3% 可归因于离合器之间的变化。GAMM允许对曲线特性进行精确估计,我们用来检验被认为会限制热性能曲线的折衷假设: 更热更好,专家-多面手的权衡以及资源分配/获取。我们观察到最大性能与性能广度之间存在负相关关系,表明专家与多面手之间存在权衡,而热最佳性能与最大性能之间存在正相关关系,表明 “更热更好”。母系之间的曲线下面积与最大绩效关系之间的关系存在显着差异,最大绩效关系是资源获取或分配均匀性的指标。当我们使用未喂食的幼体时,观察到的母系效应表明母亲之间的繁殖策略有所不同,有些母亲分配卵子不平等,导致某些后代比其他后代更好,而其他母亲则更均匀地分配卵子,从而在整个离合器中表现均匀。这一观察结果让人想起押注对冲策略,并暗示了TPCs中离合器内变化的可能性,以缓冲N. natrix免受不可预测的环境变化。