EECB and Biology Department, University of Nevada, Reno, NV, 89557, USA.
EECB and Biology Department, University of Nevada, Reno, NV, 89557, USA.
Curr Opin Insect Sci. 2019 Apr;32:68-76. doi: 10.1016/j.cois.2018.11.008. Epub 2018 Nov 28.
Increases in data availability and geographic ranges of studies have allowed for more thorough tests of latitudinal gradients in trophic interactions, with numerous recent studies testing hypotheses that strength of interactions, herbivory, plant chemical defense, and dietary specialization all increase with decreasing latitude. We review the issues surrounding these latitudinal gradients, discuss some methodological challenges, and provide some caveats relevant to inferences from existing approaches. To examine some potential issues with studies on latitudinal gradients in dietary specialization, we simulate a latitudinal gradient of communities that increase in diversity and specialization towards the equator then test the power of different sampling designs for detecting the gradient. Based on this simple simulation, as well as apparent incongruities in the literature, we conclude that subtle differences in sampling design can be responsible for failure to detect existing gradients. Despite calls for rejecting some latitudinal gradient hypotheses, it is clear that a great deal of careful research remains to determine important correlates of the well-established latitudinal gradient in diversity. In particular, future studies should focus on replicated gradients, greater emphasis on continuous sampling, and use of taxonomic controls that allow for meaningful analyses across latitudes.
随着数据可用性和研究地理范围的增加，人们可以更彻底地检验营养相互作用的纬度梯度，许多最近的研究检验了这样的假设，即相互作用强度、食草作用、植物化学防御和饮食专业化都随着纬度的降低而增加。我们回顾了这些纬度梯度的问题，讨论了一些方法学挑战，并提供了一些与现有方法推断相关的注意事项。为了研究饮食专业化的纬度梯度上的一些潜在问题，我们模拟了一个沿着纬度梯度的群落，从多样性和专业化方面逐渐向赤道增加，然后测试了不同采样设计检测梯度的能力。基于这个简单的模拟，以及文献中的明显不一致，我们得出结论，采样设计的细微差异可能是导致未能检测到现有梯度的原因。尽管有人呼吁拒绝某些纬度梯度假说，但很明显，要确定多样性的既定纬度梯度的重要相关因素，仍需要大量仔细的研究。特别是，未来的研究应该关注复制的梯度，更加重视连续采样，并使用允许跨纬度进行有意义分析的分类控制。
