Total cover and cover quality: predicted and actual effects on a predator's foraging success
Total cover and cover quality: predicted and actual effects on a predator's foraging success
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总覆盖率和覆盖质量：对捕食者觅食成功的预测和实际影响
DOI：
10.3354/meps227001
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发表时间：
2002
影响因子：
2.5
通讯作者：
A. Bartholomew
中科院分区：
文献类型：
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作者：
A. Bartholomew
我测试的重要性，总覆盖和覆盖质量的大型底heteroclitus鱼在坦克的觅食能力。总覆盖测量为所有单个结构的组合面积，视为阴影。我将总覆盖面积除以水箱底部面积，得到Ct/At，这是一个衡量给定区域内可供猎物躲藏的结构总量的指数。覆盖质量的测量方法为每个个体结构的宽度除以个体猎物生物的宽度（Cw/Pw）。该指数测量了猎物生物体隐藏在个体结构后面时的可见度。这两个复杂性指数都是无量纲的，可能适用于任何生境类型和生境规模。我预测猎物的存活率应该随着Ct/At的增加而呈双曲线增加，因为增加栖息地内结构的数量会增加被检测到的栖息地的数量，但回报会减少。过去的实验表明，增加Ct/At确实增加了猎物的存活率，但这种关系的形式尚不清楚。我还预测，猎物的生存率应增加双曲线与增加Cw/Pw。我通过模拟一个被捕食的生物体躲在一个平面结构后面，被捕食者从所有潜在的角度观察来预测这一点。在这个简单的模拟中，“从视野中隐藏的猎物的平均数量”随着Cw/Pw的增加呈双曲线增加，渐近线为0.5。我做了两个实验来验证这些想法。在第一种方法中，我在处理之间保持Ct/At恒定，并改变个体结构的宽度相对于虾猎物Paleomonetes spp的宽度。在第二个实验中，我保持处理之间的结构间空间宽度几乎恒定，并改变Ct/At。第二个实验的猎物是移动的端足类动物。我使用对数线性模型对两个实验的生存率和治疗是独立的这一假设进行了检验。我发现，在Cw/Pw实验中，不同处理之间的存活率没有显著差异，而在Ct/At实验中，不同处理之间的存活率有显著差异。Ct/At与猎物存活率呈双曲线关系。最后，利用Ct/At实验结果和以往的研究结果，建立了大F生存曲面的模型回归方程。heteroclitus喂养端足类的各种水平的Ct/At和Sp/Pr（结构间空间大小/捕食者宽度）。该方程具有高度显著性，与数据拟合良好。在此回归中，端足类动物存活率随Ct/At的增加呈双曲线增加，随Sp/Pr的增加呈S形下降。
I tested the importance of both total cover and cover quality to the foraging ability of large Fundulus heteroclitus fish in tanks. Total cover was measured as the combined areas of all the indi- vidual structures, viewed as shadows. I divided total cover by the bottom area of the tank to form Ct/At, an index that measures the total amount of structure available in a given area for prey to hide behind. Cover quality was measured as the width of each individual structure divided by the width of the indi- vidual prey organism (Cw/Pw). This index measures how visible a prey organism is when hiding be- hind an individual structure. Both of these complexity indices are dimensionless and potentially ap- plicable to any habitat type and habitat scale. I predicted that prey survivorship should increase hyperbolically with increasing Ct/At, because increasing the amount of structure within a habitat in- creases the amount of the habitat blocked off from detection, but with diminishing returns. Past ex- periments demonstrated that increased Ct/At does increase prey survivorship, but the shape of the re- lationship was unclear. I also predicted that prey survivorship should increase hyperbolically with increasing Cw/Pw. I predicted this by simulating a prey organism hiding behind a flat structure being viewed by a predator from all potential angles. In this simple simulation, the 'average amount of the prey hidden from view' increased hyperbolically with increasing Cw/Pw to an asymptote of 0.5. I per- formed 2 experiments to test these ideas. In the first, I kept Ct/At constant between treatments and var- ied the width of the individual structures relative to the width of shrimp prey Paleomonetes spp. In the second experiment, I kept the inter-structural space widths nearly constant between treatments and varied Ct/At. The prey for the second experiment were mobile amphipods. I tested the hypothesis that survivorship and treatment were independent using log-linear models for both experiments. I found that there was no significant difference in survivorship between treatments for the Cw/Pw experiment, and there was a significant difference in survivorship between treatments for the Ct/At experiment. The relationship between Ct/At and prey survivorship appeared to increase hyperbolically, as pre- dicted. Finally, I used the results of the Ct/At experiment, and results from a past study, to form a mod- eled regression equation of the survivorship surface for large F. heteroclitus feeding on amphipods for various levels of Ct/At and Sp/Pr (inter-structural space size/predator width). This equation was highly significant, and fit the data well. In this regression, amphipod survivorship increased hyperbolically with increasing Ct/At, and decreased sigmoidally with increasing Sp/Pr.