UMR 5023 LEHNA, Université de Lyon, Lyon1, CNRS, ENTPE, Villeurbanne, France.
CNRS, PSL Research University, EPHE, UM, SupAgro, IRD, INRA, UMR 5175 CEFE, Montpellier, France.
J Anim Ecol. 2019 Jan;88(1):164-177. doi: 10.1111/1365-2656.12906. Epub 2018 Oct 31.
Understanding the mechanisms that regulate the dynamics of spatially structured populations (SSP) is a critical challenge for ecologists and conservation managers. Internal population processes such as births and deaths occur at a local level, while external processes such as dispersal take place at an inter-population level. At both levels, density dependence is expected to play a critical role. At a patch scale, demographic traits (e.g., survival, breeding success) and the population growth rate can be influenced by density either negatively (e.g., competition effect) or positively (e.g., Allee effects). At the scale of an SSP, although positive density-dependent dispersal has been widely reported, an increasing number of studies have highlighted negative density-dependent dispersal. While many studies have investigated the effects of density on population growth or on dispersal, few have simultaneously examined density-dependent effects at the scale of both the local population and the entire SSP. In this study, we examine how density is related to demographic processes at both the pond level (survival and population growth) and the SSP level (between-pond dispersal) in a pond-breeding amphibian, the great crested newt (Triturus cristatus). The study was based on 20 years of individual capture-recapture (CR) data (from 1996 to 2015) gathered from an SSP made up of 12 experimental ponds ("patches"). We first used a CR multievent model to estimate both survival and dispersal rates in specific ponds as a function of distance between ponds. Then, using a second CR multievent model, we examined whether survival and recapture rates were influenced by population density in a pond. Lastly, we used state-space time series models to investigate whether density affected population growth in each pond. Our results found a positive density-dependent effect on survival and a negative density-dependent effect on departure. In addition, the findings indicate that population growth was negatively related to density in all 12 ponds. These results support the hypothesis that in SSPs, density may have multiple and contrasting effects on demographic parameters and growth rates within local populations as well as on dispersal. This study underlines the need to better understand how density dependence may influence potential trade-offs between life-history strategies and life-history stages.
了解调节空间结构种群（SSP）动态的机制是生态学家和保护管理者面临的一个关键挑战。内部种群过程，如出生和死亡，发生在局部水平，而外部过程，如扩散，发生在种群间水平。在这两个水平上，密度依赖预计都将发挥关键作用。在斑块尺度上，种群的特征（例如，存活率、繁殖成功率）和种群增长率可能受到密度的负（例如，竞争效应）或正（例如，阿利效应）影响。在 SSP 尺度上，尽管已广泛报道了正密度依赖的扩散，但越来越多的研究强调了负密度依赖的扩散。虽然许多研究已经调查了密度对种群增长或扩散的影响，但很少有研究同时在局部种群和整个 SSP 尺度上同时检验密度依赖的影响。在这项研究中，我们研究了密度如何与池塘水平（存活率和种群增长）和 SSP 水平（池塘间扩散）上的种群特征相关，以研究池塘繁殖的两栖动物——大冠蝾螈（Triturus cristatus）。该研究基于 20 年的个体捕获-再捕获（CR）数据（1996 年至 2015 年），这些数据来自由 12 个实验池塘组成的 SSP（“斑块”）。我们首先使用 CR 多事件模型来估计特定池塘中生存和扩散率与池塘间距离的关系。然后，使用第二个 CR 多事件模型，我们研究了在池塘中生存和再捕获率是否受到种群密度的影响。最后，我们使用状态空间时间序列模型来研究密度是否影响每个池塘的种群增长。我们的结果发现，生存具有正密度依赖性，而离开具有负密度依赖性。此外，研究结果表明，所有 12 个池塘的种群增长与密度呈负相关。这些结果支持了这样一种假设，即在 SSP 中，密度可能对局部种群中的种群特征和增长率以及扩散具有多种且相反的影响。本研究强调了需要更好地理解密度依赖性如何影响生活史策略和生活史阶段之间的潜在权衡。
