Genetic variability and gene flow in geographical populations of Ceratitis capitata (Wied.) (medfly).

TwoAfrican populations of Ceratitis capitata (Kenya and Reunion IsL) and two Mediterranean
ones (Sardinia and Procida IsI.) have been studied for genetic variability at 25 foci by electro-
phoresis. Wright's F5 Slatkin's Nm gene flow estimator, Nei's distance (D) together with measures
of variability such as 1-1, P, A have been used to compare the population from Kenya with the other
three. Parameters using gene frequencies (F51, D, Nm) indicate the presence of substantial
geographic heterogeneity, largely attributable to genetic drift and correlated with dispersion of the
medfly from its source area (Subsaharan Africa) to the periphery. The Kenyan population has high
genetic variability (assessed by H, P and A), as might be expected given its native status. Significant
gene flow estimates between Kenya and the derived Mediterranean populations supports the
hypothesis of recent colonization. Part of the geographic heterogeneity is related to the presence of
fixed alleles in the more differentiated Reunion population although it maintains the genetic
attributes of the ancestral population. Selection or other forces may have played an important role
in the differentiation of this population.