Zubillaga María, Skewes Oscar, Soto Nicolás, Rabinovich Jorge E, Colchero Fernando
Centro de Estudios Parasitológicos y de Vectores (CEPAVE, CONICET- CCT- La Plata, UNLP), Universidad Nacional de La Plata, La Plata, Argentina.
Departamento de Ciencias Pecuarias, Universidad de Concepción, Chillán, Chile.
PLoS One. 2014 Dec 16;9(12):e115307. doi: 10.1371/journal.pone.0115307. eCollection 2014.
Understanding the mechanisms that drive population dynamics is fundamental for management of wild populations. The guanaco (Lama guanicoe) is one of two wild camelid species in South America. We evaluated the effects of density dependence and weather variables on population regulation based on a time series of 36 years of population sampling of guanacos in Tierra del Fuego, Chile. The population density varied between 2.7 and 30.7 guanaco/km2, with an apparent monotonic growth during the first 25 years; however, in the last 10 years the population has shown large fluctuations, suggesting that it might have reached its carrying capacity. We used a Bayesian state-space framework and model selection to determine the effect of density and environmental variables on guanaco population dynamics. Our results show that the population is under density dependent regulation and that it is currently fluctuating around an average carrying capacity of 45,000 guanacos. We also found a significant positive effect of previous winter temperature while sheep density has a strong negative effect on the guanaco population growth. We conclude that there are significant density dependent processes and that climate as well as competition with domestic species have important effects determining the population size of guanacos, with important implications for management and conservation.
了解驱动种群动态的机制是野生种群管理的基础。原驼（骆马属）是南美洲两种野生骆驼科动物之一。我们基于对智利火地岛原驼36年种群抽样的时间序列，评估了密度依赖性和天气变量对种群调节的影响。种群密度在每平方公里2.7至30.7头原驼之间变化，在前25年呈现明显的单调增长；然而，在过去10年中，种群出现了大幅波动，表明它可能已达到其承载能力。我们使用贝叶斯状态空间框架和模型选择来确定密度和环境变量对原驼种群动态的影响。我们的结果表明，种群受到密度依赖性调节，目前正围绕平均45000头原驼的承载能力波动。我们还发现前一个冬季温度有显著的正向影响，而绵羊密度对原驼种群增长有强烈的负向影响。我们得出结论，存在显著的密度依赖性过程，气候以及与家养物种的竞争对决定原驼种群数量有重要影响，这对管理和保护具有重要意义。
