Edge shape, animal dispersal and habitat fragmentation.

栖息地破碎化是物种灭绝的最重要威胁之一，使其成为当代最重要的保护问题。人类的发展将自然栖息地分裂成一块块的小块——动物现在需要穿过危险的栖息地，从一个小块旅行到另一个小块。栖息地周围的边缘影响着动物迁徙的容易程度，而它们种群的稳定性取决于它们迁徙的容易程度。***到目前为止，保护生物学家一直认为，影响动物旅行的最重要的方面是边缘的长度——例如，如果一只动物在一片区域内移动，那么它遇到边缘的次数越多，就越有可能越过边缘。因此，边缘越曲折，动物迁徙的距离就越大。但在初步研究中，我发现一些动物也会对边缘的形状做出反应。这一点很重要，因为即使对于相同长度的边，也有许多不同形状的边。例如，边缘变化的一种方式是其弯曲度的空间尺度。因此，根据栖息地边缘的形状，动物的迁徙可能比我们之前认为的要多或少得多。而且，动物种群的稳定性可能比我们想象的要大得多，也可能要小得多。***我建议找出动物对边缘的反应机制，以及这种反应如何依赖于边缘形状的各个方面——a)边缘弯曲度的空间尺度，b)边缘硬度或宽度，c)边缘几何形状的特定形状。首先，我将使用计算机模拟来制定具体的预测。然后，我将用甲虫的实验室实验，草地田鼠的野外实验，以及野生骡鹿和麋鹿的运动数据来验证这些预测。实验室实验的重要性并不在于甲虫本身很重要，而是因为我可以控制系统并测试特定因素。草地田鼠的重要性在于，碎片化对它们的种群数量有很大的影响，而且在野外进行实验也很容易。鹿和麋鹿的重要性在于它们是自由生活的动物，我可以在没有任何操作的情况下进行研究——这是对边缘概念的终极测试。这一部分将与俄勒冈州的鹿和麋鹿长期研究合作，那里的生物学家已经追踪了许多个体多年。这样，我就可以从麋鹿和鹿的运动模式中获得详细的数据，以及数字化的栖息地地图。边缘形状的影响很重要，因为它们在食物链的上下都能感受到。这里有三个例子。首先，许多小型哺乳动物对边缘有反应，从而影响了许多以它们为食的捕食者。其次，一些传粉蜜蜂在觅食时避开边缘，从而影响了它们所传粉的开花植物。最后，许多鸟类在散布植物时对边缘有反应。我的研究结果将显示所有这些过程是如何受到边缘形状的影响的。* * * * *

Habitat fragmentation is one of the most important threats to species extinction, making it perhaps the most important contemporary conservation issue. Human development fragments natural habitats into patches - animals now need to cross dangerous habitat to travel from one patch to another. The kind of edge around habitat patches affects how easily animals do this and the stability of their populations hinges on how easily they can travel.***Conservation biologists till now have thought that the most important aspect of edges that affects animal travel is edge length - for example, if an animal is moving around inside of a patch, then the more often it encounters an edge, the more likely it is to cross the edge. Thus, the more tortuous the edges the greater the animal travel.***But in preliminary work I have discovered that some animals also respond to the shape of the edge. This is important because there are many different shapes of edges, even for the same edge length. For example, one way that edges vary is in the spatial scale of their tortuousity. Thus animal travel may be much greater or less than we previously thought, depending on the shapes of habitat edges. And, animals' population stability might be much greater or less than we thought. ***I propose to find out what mechanisms animals use respond to edges, and how does this response depend on various aspects of edge shape - by a) the spatial scale of edge tortuosity, b) edge hardness, or width and c) particular shapes of edge geometries. ***First, I will use computer simulations to develop specific predictions. Then I will test those predictions using lab experiments with beetles, field experiments with meadow voles, and movement data of wild mule deer and elk. The importance of the lab experiments is not that the beetles are themselves important, but because I can control the system and test specific factors. The importance of the meadow voles is that fragmentation has a great effect on their populations - and, because it is easy to carry out experiments in the wild. The importance of the deer and elk is that they are freely-living animals that I can study without any manipulations - the ultimate test of ideas about edges. This part will be a collaboration with a long-term study of deer and elk in Oregon, where biologists have tracked many individuals for many years. Thus I will have I have access to detailed data from movement patterns of elk and deer as well as digitized habitat maps.***Edge shape effects are important because they are felt both up and down the food chain. Here are three examples. First, many small mammals respond to edges, thus affecting the many predators that eat them. Second, some pollinating bee species avoid edges while foraging, thus affecting the flowering plants they are pollinating. Finally, many birds respond to edges while dispersing plants. Results from my research will show how all of these processes are affected by the shape of edges. *** **