Metapopulation dynamics and climate change in a model system: the silver-spotted skipper

栖息地丧失和气候变化共同构成了对生物多样性的巨大威胁，因为物种面临着在人类主导的景观中改变其分布的艰巨任务，在这些景观中，合适的栖息地只是以前更广泛的植被类型的分散碎片。需要新的方法来理解和准确预测物种对这些环境变化驱动因素的反应，当它们共同作用时。复杂的是，气候变化本身通过改变适宜的“小气候”的可用性，改变了栖息地的质量和数量。例如，我们的研究物种，银斑跳蝶，到达了它在英国的欧洲分布的凉爽的北部边缘。因此，在20世纪80年代早期，它曾经局限于异常炎热的小气候（朝南山坡上的短草），但最近随着气候变暖，它已经占领了较冷的栖息地（较高的草地，东、西、北山坡）。过去太冷的栖息地现在对物种来说是可以进入的；尽管一些朝南的草原可能已经开始变得过于炎热和干燥，昆虫无法生存。东、西、北三面山坡的适宜性不断提高，使得热适宜的草地面积大幅增加，从而使银斑跳鹬开始扩大分布范围。然而，情况是复杂的，因为气候条件的年复一年的变化不断地改变着每一块剩余的钙质草地的适宜性（取决于坡度、坡向和植被）。根据每年的天气条件，大跳蝶的栖息地是一个不断变化的马赛克，因此很难为保护管理者提供明确的指导方针，以使该物种得以生存并扩大其分布范围。随着气候的变化，气候和栖息地之间的相互作用可能会使许多稀有物种的保护规划和栖息地管理过程复杂化，这些物种现在仅限于现代景观中的局部栖息地。迄今为止，气候和生境景观尺度分布之间的反馈回路尚未被纳入任何科学建模框架，但这是在对物种对气候变化的反应作出可信和可测试的预测之前所需要的。我们将开发一种新的方法，利用人口模型，将气候驱动的栖息地可用性随时间的变化纳入其中。这些模型将利用1982年至2001年期间英国银斑跳蝶的分布、栖息地和种群规模的大规模数据来开发。然后，这些模型将用于预测2001年后的变化，我们将根据2002年至2010年期间关于船长栖息地和分布变化的新信息来测试我们的预测。该项目将使我们能够测试我们预测物种分布变化的准确性，因为它们对气候变化的反应，以及气候、栖息地及其相互作用在解释物种扩展其分布速度方面的重要性。这一步骤对于确定保护行动是否能够减轻气候变化对生物多样性的影响，以及在使保护适应气候变化的过程中哪些行动最有效至关重要。我们将把我们开发的软件提供给其他科学家、政策制定者和保护从业者，使我们的方法能够应用于保护许多其他面临与银斑船长同样问题的稀有物种。

Habitat loss and climate change together represent a great threat to biodiversity because species face the difficult task of shifting their distributions across human-dominated landscapes in which suitable habitats are present only as scattered fragments of formerly more widespread types of vegetation. New approaches are needed to understand and predict accurately the responses of species to these environmental drivers of change when they act in combination. The complication is that climate change itself alters habitat quality and quantity, by changing the availability of suitable 'microclimates'. For example, our study species, the silver-spotted skipper butterfly, reaches the cool northern edge of its European distribution in England. As such, it used to be restricted to exceptionally hot microclimates (short grass on South-facing hillsides) in the early 1980s, but has recently colonised cooler habitats (taller grassland, and East, West, and North-facing hillsides) as the climate has warmed. Habitats that used to be too cool are now accessible to the species; although some south-facing grassland may have started to become too hot and dry for the insect. Increasing suitability of East, West, and North-facing hillsides has resulted in a major increase in the amount of grassland that is thermally acceptable, allowing the silver-spotted skipper to start to expand its distribution. However, the situation is complicated because year-to-year variation in climatic conditions constantly alters the suitability of each remaining area of calcareous grassland (depending on the slope, aspect and vegetation). The habitat available to the skipper is a shifting mosaic depending on the weather conditions each year, making it difficult to provide clear guidelines for conservation managers to allow the species to survive and extend its distribution. As the climate changes, this interaction between climate and habitat is likely to complicate the process of conservation planning and habitat management for the many rare species that are now restricted to localised areas of habitat in modern landscapes. To date, the feedback loop between climate and the landscape-scale distribution of habitat has not been incorporated in any scientific modelling framework, but this is required before believable and testable projections of species responses to climate change can be made. We will develop a new approach using a population model that incorporates variation over time in climate-driven habitat availability. These models will be developed using large-scale data on the British distribution, habitat and population sizes of the silver-spotted skipper butterfly for the period 1982 to 2001. The models will then be used to predict post-2001 changes, and we will test our projections against new information on changes in habitat and distribution for the skipper between 2002 and 2010. The project will allow us to test how accurately we can predict changes in species distributions as they respond to climate change, and the importance of climate, habitat and their interactions in explaining the rates at which species extend their distributions. This step is vital to determine whether conservation actions can alleviate the effects of climate change on biodiversity, and which actions are most efficient in this process of adapting conservation to climate change. We will make the software that we develop available to other scientists, policy-makers and conservation practitioners, allowing our approach to be applied to the conservation of the many other rare species facing the same problems as the silver-spotted skipper.