Genetic differentiation in Spanish populations of Ceratitis capitata as revealed by abundant soluble protein analysis

Ceratitis capitata is one of the most important pest species in the tropica l and temperate regions of the world, however, genetic knowledge of this sp ecies is still very limited. In the present study, we have attempted for th e first time an analysis of the genetic variability in seven natural popula tions of C. capitata by means of abundant soluble proteins, combining high resolution techniques such as polyacrylamide gel electrophoresis and silver staining methods. A total of 66 polypeptides have been analyzed. The resul ts show the existence of a decreasing trend in the 'levels' of polymorphism from the southern areas to the northern that is correlated with the latitu de of the sampling areas, most probably due to the colonization process of the Iberian Peninsula. On the other hand, and with relation to the 'pattern ' of the variability, a geographic differentiation (not strictly latitudina l) is detected when an UPGMA clustering method was applied to the data. Mor eover, principal component anaysis has revealed that a part of this differe ntiation could be explained in relation with environmental factors such as annual rainfall and minimum temperature in winter months. This is suggestin g that selection (added to the historical process) could be playing an impo rtant role in the process of geographic differentiation, 'shaping' the patt ern of that variability. No host-related differentiation has been observed in these samples.