HIGH-DENSITY POPULATIONS OF DIAMONDBACK MOTH HAVE BROADER HOST-PLANT DIETS

Although ecological specialists exploit a relatively limited resource base, it is unclear whether specialization limits local population den sity. Here, we focus on the relationship between diet specialization a nd local population density of a phytophagous insect, the diamondback moth, Plutella xylostella L. (Lepidoptera: Plutellidae). We compared k ey life history traits and food plant use among five pairs of high-and low-density populations from widely separate geographical areas. Moth s from populations that persist at high densities were more generalize d in food plant use than moths from low-density populations. In partic ular, the oviposition preference and larval performance of moths from some high-density populations were less variable across a suite of foo d plants, suggesting that moths from high-density populations had a br oader diet. In addition, low-density populations were less similar to each other, exhibiting opposing preferences for particular plant speci es. Hence diet breadth may explain some of the persistent differences in the population density of diamondback moths in the field, consisten t with the idea that ecological specialization may be generally associ ated with population density.