Southwell Colin, Emmerson Louise
Australian Antarctic Division Department of the Environment and Energy Kingston Tas. Australia.
Ecol Evol. 2020 Feb 20;10(5):2339-2351. doi: 10.1002/ece3.6037. eCollection 2020 Mar.
Density-dependent regulation is an important process in spatio-temporal population dynamics because it can alter the effects of synchronizing processes operating over large spatial scales. Most frequently, populations are regulated by density dependence when higher density leads to reduced individual fitness and population growth, but inverse density dependence can also occur when small populations are subject to higher extinction risks. We investigate whether density-dependent regulation influences population growth for the Antarctic breeding Adélie penguin . Understanding the prevalence and nature of density dependence for this species is important because it is considered a sentinel species reflecting the impacts of fisheries and environmental change over large spatial scales in the Southern Ocean, but the presence of density dependence could introduce uncertainty in this role. Using data on population growth and indices of resource availability for seven regional Adélie penguin populations located along the East Antarctic coastline, we find compelling evidence that population growth is constrained at some locations by the amount of breeding habitat available to individuals. Locations with low breeding habitat availability had reduced population growth rates, higher overall occupancy rates, and higher occupancy of steeper slopes that are sparsely occupied or avoided at other locations. Our results are consistent with evolutionary models of avian breeding habitat selection where individuals search for high-quality nest sites to maximize fitness returns and subsequently occupy poorer habitat as population density increases. Alternate explanations invoking competition for food were not supported by the available evidence, but strong conclusions on food-related density dependence were constrained by the paucity of food availability data over the large spatial scales of this region. Our study highlights the importance of incorporating nonconstant conditions of species-environment relationships into predictive models of species distributions and population dynamics, and provides guidance for improved monitoring of fisheries and climate change impacts in the Southern Ocean.
密度依赖调节是时空种群动态中的一个重要过程，因为它可以改变在大空间尺度上起作用的同步过程的影响。最常见的情况是，当较高的密度导致个体适合度和种群增长降低时，种群受到密度依赖的调节，但当小种群面临更高的灭绝风险时，也会出现反向密度依赖。我们研究密度依赖调节是否会影响南极繁殖的阿德利企鹅的种群增长。了解该物种密度依赖的普遍性和性质很重要，因为它被视为一个哨兵物种，反映了南大洋大空间尺度上渔业和环境变化的影响，但密度依赖的存在可能会给这一角色带来不确定性。利用沿东南极海岸线分布的七个区域阿德利企鹅种群的种群增长数据和资源可利用性指数，我们发现了令人信服的证据，表明在某些地点，种群增长受到个体可利用的繁殖栖息地数量的限制。繁殖栖息地可利用性低的地点，种群增长率降低，总体占用率较高，并且在其他地点很少被占用或被避开的陡坡上的占用率更高。我们的结果与鸟类繁殖栖息地选择的进化模型一致，即个体寻找高质量的巢穴地点以最大化适合度回报，随后随着种群密度的增加而占据较差的栖息地。关于食物竞争的其他解释没有得到现有证据的支持，但由于该区域大空间尺度上食物可利用性数据的匮乏，关于与食物相关的密度依赖的有力结论受到了限制。我们的研究强调了将物种与环境关系的非恒定条件纳入物种分布和种群动态预测模型的重要性，并为改进对南大洋渔业和气候变化影响的监测提供了指导。
