Dogmatic is problematic: Interpreting evidence for latitudinal gradients in herbivory and defense

It has long been believed that plant-animal interactions, including herbivory, are more intense toward the tropics. The more intense interactions in the tropics are thought to have selected for higher levels of defenses against herbivores. These ideas are fundamental to our understanding of global patterns in diversity, and for our understanding of plant-animal interactions. However, recent analyses have tended not to support the traditional hypothesis of higher herbivory and defenses at lower latitudes. Despite mounting empirical evidence, many ecologists have been slow to re-assess their beliefs. I show clear evidence for citation bias, with papers that support the traditional idea being cited over six times as often as papers that show higher herbivory at higher latitudes and over four times as often as papers showing higher defense at higher latitudes. I also highlight examples where interpretations that are counter to the available empirical evidence have been published in high profile journals. I suggest that providing rigorous empirical tests for ideas that have become widely established without appropriate testing should be a priority for ecologists. We need to make sure the objectivity of peer-reviewed science stands out from the mass of unchecked opinion available on the web.