Dispersal and depensation in low density culled mink populations

了解种群的生态动态范围的边缘，人口可能是不完整的，在低密度是至关重要的，我们了解如何范围扩展可以随之而来的，以及入侵物种如何传播。根据定义，受保护物种的密度低于预期。因此，了解导致低密度种群表现不佳的过程是保护和管理的基础。虽然有丰富的理论预测其对物种的传播和持久性的影响，经验研究depensation是稀缺的，由于固有的困难，在非常低的密度研究人口。然而，在一系列入侵物种中发现了Allee效应。然而，引人注目的是，尽管依赖过程定义了入侵物种的早期人口传播，但直到最近，建模研究才开始考虑在已建立的入侵物种管理中的依赖。该应用程序的目的是改善理论与实践之间的联系，并在这样做的过程中提高生态学的理解，并测试其作为入侵物种管理的有效工具的潜力。我们的研究计划是一个合作保护项目的组成部分，该项目已经从10,000平方公里的土地上清除了入侵的美国水貂。鉴于保护项目区周围是不受控制的水貂种群，它暴露于从其周边的重新入侵的过程中没有什么不同的初始入侵和物种在一个新的范围内传播。这是一个独特的机会，在一个大的空间尺度上，在一个自然环境中，通常无法进入调查，使人们有可能，第一次，以获得经验的理解，在低密度的过程中运行的移民和人口模式的预测。通过结合作为保护项目的一部分捕获的所有水貂的遗传和年龄信息，我们可以重建家谱，并随后测量水貂在环境中传播的程度。我们将对自2010年1月以来捕获的所有水貂进行此操作，并将这些数据与水貂种群饱和时捕获的365只水貂的信息结合联合收割机。因此，我们将有信息的扩散模式，从该地区要么饱和（控制前），部分耗尽（筏部署的第一年）或严重耗尽同种（随后）。我们将通过比较从（扩大）项目区周边迁入的低密度水貂种群的扩散和繁殖模式与饱和种群的模式，确定水貂的传播何时可能受到无法在极低密度下找到配偶的影响。我们还将考虑未交配的雌性水貂是否处于发情期，一段时间后可能会患贫血症，这是否会导致雌性水貂死亡率升高。我们还将确定是否观察到分散水貂往往定居在生产领域可能会导致紧急depensation描述为“范围钉扎”，即孤立的殖民地未能蔓延，因为人口损失由于移民是不被移民补偿。我们还将使用我们的数据来测试旨在最大限度地提高依赖性的管理选项的有效性。有人建议，一个潜在的控制策略，一些入侵物种可能是抑制人口丰度接近范围边界的高峰。这可能会增加入侵钉扎的可能性，通过减少来自前线后面高密度种群的个体流动。如果有效，这种管理可能具有成本效益，因为需要努力在广阔的控制区域中检测低密度的个体。我们的项目是独一无二的，它将生态理论与社区合作的入侵物种的实际管理相结合。

Understanding the ecological dynamics of populations at range margins where populations may be patchy and at low density is fundamental for our understanding of how range expansion can ensue and how invasive species spread. Species of conservation concern are by definition found at lower than expected densities. Therefore understanding processes causing low density populations to perform poorly is fundamental to conservation and management. While there is a rich body of theory predicting its impact on species spread and persistence, empirical studies of depensation are scarce owing to the inherent difficulty in studying populations at very low density. Allee effects however have been detected in a range of invasive species. Strikingly however, even though depensatory processes define the early demographic spread of invasive species, it is only very recently that modelling studies have started considering depensation in the management of established invasive species. The aim of this application is to improve the link between theory and practice and, in doing so improve both ecological understanding of depensation and test its potential as an effective tool for invasive species management. Our program of research is integral to a cooperative conservation project that has already removed invasive American mink from 10,000km2. Given the conservation project area is surrounded by uncontrolled mink populations, it is exposed to re-invasion from its periphery in a process not dissimilar to the initial invasion and to the spread of species in a new range. This represents a unique opportunity to test predictions on patterns of immigration and demography over a large spatial scale in a natural setting normally inaccessible to investigation, making it possible, for the first time, to gain an empirical understanding of processes operating at low density. By combining genetic and age information from all mink caught as part of the conservation project, we can reconstruct genealogies, and subsequently measure the extent to which mink spread through the environment. We will do this for all mink caught since January 2010 and combine these data with information already obtained from 365 mink caught when the mink population was at saturation. Thus we will have information on dispersal patterns from area that were either saturated (pre-control), partially depleted (first year of raft deployment) or severely depleted of conspecifics (subsequently). We will establish when the spread of mink may be affected by the inability to locate mates at very low density by comparing patterns of dispersal and reproduction in low density mink populations immigrating from the periphery of the (expanding) project area with patterns from saturated populations. We will also consider whether the fact that un-mated females mink remain in heat and after some time may suffer from anemia contribute to heightened mortality of females. We will also determine whether the observation that dispersing mink tend to settle in productive areas could lead to emergent depensation described as "range pinning", whereby isolated colonies fail to spread because population loss due to emigration is not be compensated for by immigration. We will also use our data to test the effectiveness of management options that aim to maximise depensation. It has been suggested that a potential control strategy for some invasive species may be to suppress peaks in population abundance close to range borders. This could increase the likelihood of invasion pinning by reducing the flow of individuals from higher density populations behind the front. If effective, such management might be cost effective given the effort required to detect individuals at low density in vast controlled areas. Our project is unique in combining ecological theory with practical management of an invasive species in partnership with communities.