School of Biological Sciences, University of Aberdeen, Aberdeen, UK.
Centre for Biodiversity Dynamics, NTNU, Trondheim, Norway.
J Anim Ecol. 2022 Sep;91(9):1781-1796. doi: 10.1111/1365-2656.13748. Epub 2022 Jul 17.
Among-individual and within-individual variation in expression of seasonal migration versus residence is widespread in nature and could substantially affect the dynamics of partially migratory metapopulations inhabiting seasonally and spatially structured environments. However, such variation has rarely been explicitly incorporated into metapopulation dynamic models for partially migratory systems. We, therefore, lack general frameworks that can identify how variable seasonal movements, and associated season- and location-specific vital rates, can control system persistence. We constructed a novel conceptual framework that captures full-annual-cycle dynamics and key dimensions of metapopulation structure for partially migratory species inhabiting seasonal environments. We conceptualize among-individual variation in seasonal migration as two variable vital rates: seasonal movement probability and associated movement survival probability. We conceptualize three levels of within-individual variation (i.e. plasticity), representing seasonal or annual variation in seasonal migration or lifelong fixed strategies. We formulate these concepts as a general matrix model, which is customizable for diverse life-histories and seasonal landscapes. To illustrate how variable seasonal migration can affect metapopulation growth rate, demographic structure and vital rate elasticities, we parameterize our general models for hypothetical short- and longer-lived species. Analyses illustrate that elasticities of seasonal movement probability and associated survival probability can sometimes equal or exceed those of vital rates typically understood to substantially influence metapopulation dynamics (i.e. seasonal survival probability or fecundity), that elasticities can vary non-linearly, and that metapopulation outcomes depend on the level of within-individual plasticity. We illustrate how our general framework can be applied to evaluate the consequences of variable and changing seasonal movement probability by parameterizing our models for a real partially migratory metapopulation of European shags Gulosus aristotelis assuming lifelong fixed strategies. Given observed conditions, metapopulation growth rate was most elastic to breeding season adult survival of the resident fraction in the dominant population. However, given doubled seasonal movement probability, variation in survival during movement would become the primary driver of metapopulation dynamics. Our general conceptual and matrix model frameworks, and illustrative analyses, thereby highlight complex ways in which structured variation in seasonal migration can influence dynamics of partially migratory metapopulations, and pave the way for diverse future theoretical and empirical advances.
个体间和个体内季节性迁徙与居留表达的变化在自然界中普遍存在，这可能会极大地影响季节性和空间结构环境中部分迁徙复合种群的动态。然而，这种变化在部分迁徙系统的复合种群动态模型中很少被明确纳入。因此，我们缺乏能够确定可变季节性运动以及相关的季节性和位置特定生命率如何控制系统持续的通用框架。我们构建了一个新的概念框架，该框架可以捕获季节性环境中部分迁徙物种的全年周期动态和复合种群结构的关键维度。我们将个体间季节性迁徙的变化视为两个可变生命率：季节性移动概率和相关的移动生存概率。我们将个体内的三种变化（即可塑性）概念化为季节性迁徙或终身固定策略的季节性或年度变化。我们将这些概念制定为一个通用矩阵模型，该模型可针对不同的生活史和季节性景观进行定制。为了说明可变季节性迁徙如何影响复合种群增长率、人口结构和生命率弹性，我们为假设的短寿命和长寿命物种参数化了我们的通用模型。分析表明，季节性移动概率和相关生存概率的弹性有时可以等于或超过通常对复合种群动态有重大影响的生命率（即季节性存活率或繁殖力）的弹性，弹性可以呈非线性变化，并且复合种群的结果取决于个体内可塑性的水平。我们通过参数化我们的模型来评估可变和不断变化的季节性移动概率的后果，说明了我们的通用框架如何应用于评估可变和不断变化的季节性移动概率的后果，假设终生固定策略，用于评估具有部分迁徙性的欧洲海雀 Gulosus aristotelis 的真实部分迁徙复合种群。在给定观察到的条件下，居留种群繁殖季节成年居留者的存活率对复合种群增长率的弹性最大。然而，在季节性移动概率加倍的情况下，移动过程中的生存变化将成为复合种群动态的主要驱动力。我们的通用概念和矩阵模型框架以及说明性分析，突出了季节性迁徙结构变化如何影响部分迁徙复合种群动态的复杂方式，并为未来的理论和经验进展铺平了道路。
