Abstract
Zoophytophagous predators can substitute zoophagy for phytophagy to complete their development and reproduction. In such predators, variation in feeding behaviour is observed both across and within populations. This may be caused by genetic variation in diet specialization, some genotypes specializing on plant resources, whereas others rely mostly on prey to meet their energy and nutriment requirements. We tested the hypothesis that genotypes specialize either on prey or plant resources in the zoophytophagous mullein bug Campylomma verbasci. In the laboratory, we reared 11 isogroup lines of the mullein bug and recorded feeding behaviour on two diets. The first diet was composed of two-spotted spider mites and leaves, and in the second we added pollen, a high-quality vegetal resource. Overall differences in zoophagy among isogroup lines remained consistent regardless of the presence or absence of pollen. While some lines were insensitive to changes in trophic resource composition others switched from prey to pollen feeding when the pollen was available, revealing a negative genetic correlation between the probabilities of feeding on both resources. A significant line by diet interaction in the proportion of time spent feeding on prey in presence or absence of pollen indicated a genetic basis for diet preference. In absence of the preferred resource, nymphs act as generalists, but exhibited individual diet specialisation when facing the choice between high-quality animal and vegetal resources. Results suggest that zoophytophagous predators can exhibit genetic variation in diet preference, which can generate important ecological and economic differences in natural or agricultural systems.
Highlights
Zoophytophagous species can feed on either prey or plant resources to complete their development and reproduce [1, 2]. These species can be classified on a continuum ranging between phytozoophagy and zoophytophagous based on their overall feeding habits [1]
We tested for the effect of plant resource availability on feeding behaviour and on the propensity to feed on animal resources using 11 isogroup lines of the zoophytophagous mullein bug
Mullein bug nymphs were supplied with green peach aphids Myzus persicae (Sulzer) (Hemiptera: Aphididae), two-spotted spider mites Tetranychus urticae (Koch) (Acarina: Tetranychidae) and pollen
Summary
Zoophytophagous species can feed on either prey or plant resources to complete their development and reproduce [1, 2]. Some isogroup lines were clearly more zoophagous than others These results suggest the existence of potential diet specialization and of different foraging strategies in that species: some lines may consistently feed on animal resources and be considered zoophytophagous, whereas others may consume essentially vegetal resources and be considered phytozoophagous. We tested for the effect of plant resource (pollen) availability on feeding behaviour and on the propensity to feed on animal resources (spider mites) using 11 isogroup lines of the zoophytophagous mullein bug. Our hypothesis was that genetic differences in diet specialization towards either a zoophytophagous or a phytozoophagous strategy affect the ability to switch from prey to plant resources in response to pollen availability. We expect a negative correlation between the propensity to feed on either prey or pollen, and that the availability of pollen leads phytozoophagous lines to adopt diets with a low proportion of prey in contrast to the zoophytophagous lines
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