Resolving the life-history trade-off paradox: Measuring resource acquisition to reveal life-history trade-offs over different temporal scales

为了物种和种群的延续，个体必须繁殖。然而，生殖产出是有限制的，因为没有这些限制，个体就会有无限的后代。因此，进化生态学中的关键模型表明，繁殖的成本表现为生存概率的降低，从而降低了未来的繁殖产出。然而，尽管研究已经模拟了个体的生活史路径，但他们很少在野外发现这些权衡。虽然目前和未来的繁殖之间的权衡被广泛接受，但它继续逃避检测。我们认为造成这种情况的主要原因有两个：首先，当前与未来繁殖之间的权衡是由资源驱动的。这些通常是有限的，因此必须在当前和未来的生殖努力之间进行分配。由于大多数研究无法衡量每个人的实际资源价值，估计这些资源如何分配的努力受到阻碍。如果我们不知道一个人有多少资源，我们就无法理解这些资源是如何在生活史特征之间分配的。其次，众所周知，个体在将资源用于当前或未来的繁殖方面会表现出差异。但未来是什么时候？对于个体A来说，未来可能是下一个繁殖尝试，但对于个体B来说，未来可能是更晚的生活。然而，令人惊讶的是，研究未能模拟个体之间的这种差异。模拟表明，固定权衡的时间尺度将无法检测到发生在另一个时间尺度上的权衡，因此可能是掩盖权衡的主要驱动因素。我们的模型系统提供了整个南大洋四个地点信天翁繁殖和觅食行为的数据。从我们的研究系统中，我们有证据表明，个体觅食行为存在实质性变化，因此可以获得用于繁殖的资源。我们知道，一些个体在短时间内的繁殖成功率会有所不同，而另一些则会持续很长一段时间。因此，需要进行个人层面的分析，以衡量资源变化的影响及其对生殖的影响。我们将使用现有的关于繁殖行为的长期数据（60万次繁殖尝试；63年时间序列）和觅食（1305个个体；25年时间序列），再加上新收集的数据（150个个体），来研究个体在可用资源方面的差异，以及它们如何利用这些资源。我们预计资源获取对于分配给繁殖的资源数量至关重要，因此通过捕获这些措施，我们将能够发现当前和未来繁殖之间先前隐藏的权衡。我们期望个体将来会在不同的时间点为繁殖付出代价，并且通过对这些差异进行建模，我们将能够准确地检测到繁殖的权衡。随着时间的推移，环境会改变可用的资源，我们预测一些生命史策略将在选择中，因为它们使个体能够在不断变化的气候中最大限度地适应环境。通过模拟适应能力在未来气候条件下的变化，我们可以预测自然选择将如何作用于个体的生活史策略。

For species and populations to persist, individuals must reproduce. However, there are constraints on reproductive output, because without these, individuals would have limitless young. As such, pivotal models in evolutionary ecology demonstrate a cost to reproduction which manifests as a reduction in survival probability, and hence future reproductive output. However, although studies have modelled individual life-history pathways, they have rarely detected these trade-offs in the wild. Although the trade-off between current and future reproduction is widely accepted to exist, it continues to evade detection. We suggest there are two main reasons why this is the case:First, the trade-off between current versus future reproduction is driven by resources. These are generally limited so they must be divided between current and future reproductive effort. Attempts to estimate how these resources are allocated are hampered by the inability of most studies to measure actual resource values for each individual. If we don't know how many resources an individual has we can not understand how these are divided between life-history traits.Second, it is known that individuals can show differences in whether they use their resources for current or future reproduction. But when is the future? To individual A the future may be the next breeding attempt but to individual B the future may be much later in life. However, surprisingly studies fail to model such differences between individuals. Simulations have shown that fixing the temporal scale of trade-offs will fail to detect trade-offs that occur at another temporal scale and hence could be a major driver in masking trade-offs.Our model system provides data on the reproductive and foraging behaviour of albatrosses at four sites throughout the Southern Ocean. We have evidence from our study system of substantial variation in individual foraging behaviour, and hence the resources available for reproduction. We know that some individuals show variation in reproductive success over short time frames, and others over very long periods of their life. Hence, individual level analyses are required to measure the effects of changes in resources and consequences for reproduction. We will use existing long-term data on breeding behaviour (>100,000 breeding attempts; 63-year time series) and foraging (1305 individuals; 25-year time series), coupled with newly collected data (150 individuals), to examine how individuals vary in the resources they have available, and how they use them. We expect resource acquisition to be crucial to how many resources are allocated to reproduction, so that by capturing these measures, we will be able to detect previously hidden trade-offs between current and future reproduction. We expect that individuals will pay the cost of reproduction at different time points in the future, and that by allowing these differences to be modelled, we will be able to accurately detect reproductive trade-offs. The environment will change the resources available over time and we predict that some life-history strategies will be under selection as they enable individuals to maximise fitness in a changing climate. By modelling how fitness varies under future climate conditions we can predict how natural selection will act on individual life-history strategies.