Random amplified polymorphic DNA (RAPD) analysis and multilocus enzyme electrophoresis (MLEE) were used to assess genetic variability in six wild populations and in five laboratory strains of Ceratitis capitata. The RAPD technique reveals larger amounts of genetic variation than the conventional MLEE, and can improve discrimination within and between populations and strains.In our experimental conditions, RAPD analysis with four different primers produces 174

Two ancestral populations (Kenya and Reunion), two Mediterranean (Procida and Sardinia) and one new American population (Guatemala) of Ceratitis capitata were examined by electrophoresis for genetic variability at 27 enzyme loci. Two ordination approaches (principal component analysis and a tree representation) and F-statistical analysis have been used to distinguish the various patterns of genetic variations and to infer the underline causes and their relative contribution to the total variation. Three main patterns of variation emerge from the data: geographical, annual and seasonal differentiation. A main part of intraspecific variability involves the differentiation of central (Kenya and Reunion) versus peripheral populations (the Meditterranean and the American populations). The analysis suggests that the genetic structure of these populations is correlated with the historical events of their colonization. The affinity of the Guatemalan population with the Kenyan one could be the result of a recent founding of this population from the source area (Africa). More ancient historical events of colonization characterize the two Mediterranean populations. Seasonal variation has been found in the Procida population and chiefly involves the Mpi locus. In the same population the genetic variation across years has a minimum in 1986 due to the release of sterile T-101 males.

A concerted effort is under way to analyze, at the genetic, biochemical, and molecular level, the Adh gene system in the medfly Ceratitis capitata, an important agricultural pest. The isoelectric focusing (IEF) pattern of alcohol dehydrogenase (ADH) of the medfly demonstrates the presence of two well-differentiated, genetically independent dimeric proteins, called ADH-1 and ADH-2. These proteins do not exhibit interlocus heterodimeric isozymes, and the genes are not controlled coordinately during development, Adh1 and Adh2 being expressed mainly in muscle or in fat body and ovary, respectively. From the intensity of the IEF isozyme patterns, primary alcohols are judged to be better substrates than secondary alcohols, in contrast with Drosophila melanogaster ADH, and ethanol is probably the most efficient substrate for both sets of isozymes. The isoelectric points of ADH-1 (pI = 5.4) and ADH-2 (pI = 8.6) are different from D. melanogaster ADH (pI = 7.6), but the medfly ADH-1 has a native molecular weight (approx. 58 kD) close to that of D. melanogaster. A population survey of samples both from laboratory strains and from wild geographically different populations showed that the Adh1 locus is more polymorphic than Adh2. The most variable populations are from Africa, the supposed source area of the species. Further, a case of selection at the Adh1 locus under laboratory conditions is reported. The hypothesis of Adh gene duplication and the degree of similarity between medfly and Drosophila ADH are also discussed.

Genetic variation at 25 enzyme loci (64 alleles) has been considered in the attempt of an intra-species analysis of Ceratitis capitata. Twenty-seven hortologous loci (122 alleles) were selected to elucidate the relationships among Ceratitis capitata, Ceratitis rosa, Trirhithrum coffeae and Capparimya savastonoi of the Trypetinae subfamily. Two ordination approaches have been used for electrophoretic data: Principal Component Analysis (PCA) and cluster analysis through a tree representation. At the species level, for C. capitata ordination by means of PCA enabled the geographic and seasonal intraspecific differentiation to be recognized. At higher levels of taxonomy, when applied to species and genera, PCA has been used as an alternative to cluster analysis. Nei distance and UPGMA procedure have been used in both levels of systematic ordination. For species-genera level, genetic distances have been calculated using also Rogers, Cavalli and Edwards methods (UPGMA and Wagner procedure). The cophenetic correlation, and other measures, have been examined as measures of goodness of fit. All the trees give the same topology. C. savastanoi samples present the greatest range of distance. C. capitata appears closer to T. coffeae than to C. rosa. The disagreement between electrophroretic trees and the existing conventional systematic is discussed. Electrophoretic keys for distinguishing the immature stages of Trypetinae are proposed.

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