Density dependence in an age-structured population of great tits: identifying the critical age classes
Density dependence in an age-structured population of great tits: identifying the critical age classes
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DOI：
10.1002/ecy.1442
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发表时间：
2016-09-01
期刊：
影响因子：
4.8
通讯作者：
Saether, Bernt-Erik
中科院分区：
文献类型：
--
作者：
Gamelon, Marlene;Grotan, Vidar;Saether, Bernt-Erik
经典的密度依赖分析方法假设种群中的所有个体对密度依赖的响应和贡献是相等的。然而，在年龄结构的种群中，不同年龄的个体对种群规模变化的反应可能不同，以及它们如何对影响整个种群增长率的密度依赖做出贡献。在这里，我们应用关键年龄组的概念，即，一个特定的标量函数，它描述了一个或多个年龄组的组合如何对人口增长率产生负面影响，以研究总密度对人口增长率的依赖性如何取决于特定年龄组的人口规模。在一个38年的数据集的年龄结构的大山雀（山雀）人口，我们发现，年龄组，包括最年轻的繁殖女性，是关键的年龄组的密度调节。这些年龄组对应于新的育种者，试图采取一个领域，并有最强的竞争力对其他育种女性的影响。它们强烈影响种群增长率，并降低所有繁殖雌性的招募和存活率。我们还表明，根据他们的年龄段，女性可能会有不同的反应不同的密度。特别是，繁殖雌性的数量的负面影响更强的补充率的最年轻的繁殖雌性。这些发现质疑了经典的假设，即人口中的所有个体都可以被视为对密度调节有同等的贡献，并且个体数量的影响与年龄无关。我们的研究结果提高了我们对自然种群密度调节的理解。
Classical approaches for the analyses of density dependence assume that all the individuals in a population equally respond and equally contribute to density dependence. However, in age-structured populations, individuals of different ages may differ in their responses to changes in population size and how they contribute to density dependence affecting the growth rate of the whole population. Here we apply the concept of critical age classes, i.e., a specific scalar function that describes how one or a combination of several age classes affect the demographic rates negatively, in order to examine how total density dependence acting on the population growth rate depends on the age-specific population sizes. In a 38-yr dataset of an age-structured great tit (Parus major) population, we find that the age classes, including the youngest breeding females, were the critical age classes for density regulation. These age classes correspond to new breeders that attempt to take a territory and that have the strongest competitive effect on other breeding females. They strongly affected population growth rate and reduced recruitment and survival rates of all breeding females. We also show that depending on their age class, females may differently respond to varying density. In particular, the negative effect of the number of breeding females was stronger on recruitment rate of the youngest breeding females. These findings question the classical assumptions that all the individuals of a population can be treated as having an equal contribution to density regulation and that the effect of the number of individuals is age independent. Our results improve our understanding of density regulation in natural populations.