Microsatellite analysis of medfly bioinfestations in California

The Mediterranean fruit fly, Ceratitis capitata, is a destructive agricultu ral pest with a long history of invasion success. This pest has been affect ing different regions of the United States for the past 30 years, but a num ber of studies of medfly bioinfestations has focused on the situation in Ca lifornia. Although some progress has been made in terms of establishing the origin of infestations, the overall status of this pest in this area remai ns controversial. Specifically, do flies captured over the years represent independent infestations or the persistence of a resident population? We pr esent an effort to answer this question based on the use of multilocus geno typing. Ten microsatellite loci were used to analyse 109 medflies captured in several infestations within California between 1992 and 1998. Using thes e same markers, 242 medflies from regions of the world having 'established' populations of this pest including Hawaii, Guatemala, El Salvador, Ecuador , Brazil, Argentina and Peru, were also analysed. Although phylogenetic ana lysis, AMOVA analysis, the IMMANC assignment test and GENECLASS exclusion t est analysis suggest that some of the medflies captured in California are d erived from independent invasion events, analysis of specimens from the Los Angeles basin provides support for the hypothesis that an endemic populati on, probably derived from Guatemala, has been established.