Spatial and temporal differentiation in colonizing populations of Ceratitis capitata

Twoancestral 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.