Assessing predation through time and space

捕食，一种生物杀死另一种生物以获取食物的行为，被认为会极大地影响物种的进化和多样性。鉴于现代生物多样性危机（每天有70个物种灭绝），我们必须更好地了解影响生命多样性的因素。然而，包括捕食在内的许多影响是难以估计的，特别是在海洋环境中，很难直接计算捕食行为。同样，对过去的直接观察是不可能的，但评估化石记录中的捕食行为将极大地扩展我们的知识。因此，我们需要一种不用直接观察就能估计捕食的方法。一种解决办法是利用被捕食的痕迹，比如猎物壳上的伤疤，来估计被捕食的情况。本研究有两个目的：第一，利用野外现代实验，检验用捕食痕迹估计捕食强度的有效性；第二，将从现代实验中学到的知识应用到化石记录中，以测试中古生代（3.8 - 2.9亿年）捕食的影响。这项研究的现代组成部分将包括在多个地点标记有壳的无脊椎动物。在每个地方，将有一个不包括捕食者的笼养区和一个未笼养区；这两个区域之间的死亡率差异归因于捕食。将这一死亡率与每个地点的各种掠食性痕迹的比率进行比较，以确定是否有任何痕迹成功地跟踪了死亡率。如果是这样，痕迹可以用来比较不同地点和时间的捕食强度。该研究的古生物学部分将使用有效的捕食痕迹来测试中古生代是否是一个捕食强度增加的时期，以及中古生代海洋无脊椎动物是否进化出新的形状和“盔甲”来应对捕食，通过比较痕迹活动和猎物形状的变化。中古生代生物与现代生物的关系并不密切，因此，如果中古生代和现代生物都受到相同因素的影响，这样的结果将更加普遍，从而对生物学和保护有更大的用处。

Predation, the act of an organism killing another for food, is believed to influence the evolution and diversity of species greatly. Given the modern biodiversity crisis (70 species per day go extinct), we must understand better those factors that influence life's diversity. However, many influences, including predation, are hard to estimate, especially in marine settings, where it is difficult to count acts of predation directly. Similarly, direct observations of the past are impossible, but assessing predation in the fossil record would greatly expand our knowledge. Thus, we need a means of estimating predation without direct observations. One solution is to use traces of predation, such as scars on prey shells, to estimate predation. This research has two goals: first, to test the validity of using predation traces as an estimate of predation intensity, using in-field modern experiments; and second, to apply what was learned from the modern experiments to the fossil record to test for the influence of predation during the Mid-Paleozoic (380-290 million years). The modern component of the research will involve marking shelled invertebrates at multiple localities. At each locality, there will be a caged zone excluding predators and an uncaged zone; the difference in deaths between the two zones is attributed to predation. This mortality rate will be compared to rates of various predatory traces at each locality to determine if any traces successfully track mortality. If so, traces can be used to compare predation intensity from place to place, and through time. The paleontological component of the study will use the valid predation traces to test if the Mid-Paleozoic was a time of increasing predation intensity, and if Mid-Paleozoic marine invertebrates evolved new shapes and "armor" in response to predation, by comparing changes through time in trace activity and prey shape. Mid-Paleozoic organisms were not closely related to modern organisms, so if Mid-Paleozoic and Recent organisms were both influenced by the same factors, such a result would be more general, and thus of greater use to biology and conservation.