Genetic aspects of the worldwide colonization process of Ceratitis capitata

Multilocus enzyme electrophoresis data from 26 polymorphic loci (124 allele s) were used to analyze the genetic aspects of the worldwide colonization o f Ceratitis capitata (medfly), Eighty-two samples of 17 populations were co llected from six regions throughout the species range: Africa, extra-Medite rranean islands (Madeira and Gran Canaria), Mediterranean region, Latin Ame rica (Guatemala), Pacific (Hawaii), and Australia, The variability paramete rs (H, P, A) reveal that the geographical dispersal of medfly from its ance stral source area (East Africa) is associated with a great reduction in var iability. The pattern of decreasing variability occurs at two regional leve ls: in the African-Mediterranean region where the differentiation is gradua l, and in the Latin American-Pacific region where some ancestral variabilit y is still present as a consequence of recent colonization. The UPGMA phylo genetic tree, derived from Nei's genetic distances, shows the presence of i ntraspecific differentiative processes affecting mainly the two island popu lations, Reunion and Hawaii, The population genetic changes observed in the species range are consistent with both the chronology and the historical c ircuitous course of the medfly colonization process.