Herbivory by the cabbage seed weevil (Ceutorhynchus assimilis) in natural populations of brassica oleracea
Moyes CL., Raybould AF.
Glucosinolate profiles vary among populations of wild cabbage (Brassica oleracea) on the Dorset coast. As part of a study of the role of herbivory in the origin and maintenance of this polymorphism we investigated the interaction between wild cabbage plants and the cabbage seed weevil (Ceutorhynchus assimilis). In 1995 and 1996, there was variation among cabbage populations in the proportion of seed pods infested with weevil larvae, and in both years the number of viable seed was significantly reduced in infested pods. In addition to being consumed by the larvae, seed were lost to infection by fungal pathogens. The proportion of pods attacked by fungi varied among populations and the number of seed lost to fungal infection was higher in weevil-infested pods. A further factor was parasitism of the weevil by a chalcid parasitoid which reduced seed consumption by the weevil. The proportion of parasitised weevils was consistent among populations in 1995 but varied significantly among populations in 1996. The effects of the weevil are discussed in relation to the distribution of secondary defense compounds in the wild cabbage populations of Dorset.