Preference-performance hypothesis and host oviposition selection of Diabrotica speciosa: aboveground female avoids belowground conspecific larvae in maize

Abstract

According to the theory of optimal foraging and preference–performance hypothesis, herbivores usually select plant hosts that benefit themselves or their offspring. We investigated the hypothesis that gravid females of the cucurbit beetle Diabrotica speciosa use volatiles derived from non-infested maize plants and herbivore-infested plants under attack by their conspecific immatures and adults in selecting a host for oviposition. The response of D. speciosa females to volatiles was quantified for the following treatments: (i) non-infested plants; (ii) plants infested by larvae (root-infested); (iii) plants infested by adults (leaf-infested); and (iv) plants infested by larvae and adults (leaf + root-infested). We also assessed if females were able to identify conditions of competition and host adequacy for offspring by means of chemical cues emitted by these plants. The results indicated that the presence of D. speciosa conspecifics on maize plants triggered the emission of volatiles, which influenced host selection for oviposition. Gravid females avoided both plants infested by larvae and plants infested by larvae and adults. Leaf-infested plants did not affect the host-selection behavior of females. Weight gain was higher in larvae kept on non-infested and leaf-infested plants than on root-infested or root + leaf-infested plants, indicating that female preference is related to its offspring performance.