The evolution of omnivory in heteropteran insects
Although omnivory is common and widespread across many animal taxa, the evolutionary origin of omnivory, the selective forces that promote or constrain omnivory, and the morphological, physiological, and behavioral hurdles that animals have to overcome to become omnivores have not been studied. The goal of this paper is to stimulate the development of ideas concerning the evolution of omnivory. We focus on the terrestrial lineages of the insect order Heteroptera and use published life history data and recent phylogenies to test two hypotheses concerning the evolutionary origin of feeding on both plants and prey: (1) that the propensity to feed on seeds and pollen is correlated with the evolution of omnivory, and (2) that broad host range (polyphagy) is correlated with the evolution of omnivory. In order to test these hypotheses, we mapped the plant part consumed and host plant range of insect species in two heteropteran suborders onto their respective phylogenies and used phylogenetically independent contrasts to test for correlations of these traits with omnivory. We found evidence that seed and pollen feeding and broad host ranges are correlated with the evolution of omnivory within both ancestrally herbivorous and ancestrally predaceous lineages of terrestrial heteropterans.