Genetic and behavioral variability in the ovary-feeding Nitidulid Brachypterolus pulicarius collected from Dalmatian and yellow toadflax

Abstract

Braychypteroluspulicarius is an ovary-feeding beetle in the family Nitidulidae. The species is found on Dalmatian and yellow toadflax, two non-native, invasive weeds. The beetle is native to Eurasia and is considered an important natural enemy and biological control agent for toadflax. Because B. pulicarius is found, at varying densities, on both yellow toadflax and Dalmatian toadflax, questions have been raised about the potential existence of host races in the species. Amplified fragment length polymorphism (AFLP) molecular genetic techniques are commonly used in studies of population genetics. Because it is a relatively easy and reliable method that does not require previous knowledge about the beetles’ genome, the AFLP technique was utilized to examine the patterns of variability of populations ofB. pulicarius. Patterns of observed variability that corresponded with commonality of host plant could serve as evidence for host races in B. pulicarius. Insects were collected from both yellow and Dalmatian toadflax at a total of 12 locations in the northwestern US, British Columbia, and Europe. Volatile collections were made from host plants to characterize their chemical emissions and to look for species-specific plant differences. Behavioral assays were attempted to determine if beetles showed a preference for the species of host plant from which they were collected. Volatile collections revealed variability in volatile production within and between host plant species. Behavioral trials were highly variable and preference results were not obtained. AFLP analyses revealed variation that did not correspond to host plant commonality. Overall, the study revealed the dynamic nature and a high level of uncertainty surrounding the fundamental knowledge of this biological system. No evidence was found for host race existence in B. pulicarius. Alternative explanations for the observed variabilities are discussed.