USE OF SHORT TANDEM REPEATS FOR THE ANALYSIS OF GENETIC-VARIABILITY IN SYMPATRIC POPULATIONS OF ANOPHELES-GAMBIAE AND ANOPHELES ARABIENSIS

Anopheles gambiae and An. arabiensis were analysed at 30 short tandem repeat (STR) loci originally developed for use in An. gambiae. All spe cimens were collected from the same village in Kilifi district, coasta l Kenya. All 30 loci were amplified in the An. gambiae specimens, wher eas 25 out of 30 loci (83.3%) were successfully amplified in the An. a rabiensis specimens. Both species had similar levels of polymorphism f or the Loci that were amplified (93.3% for An. gambiae and 92% for An. arabiensis). Median F-ST and R-ST values between the two species were 0.249 and 0.197, respectively, corresponding to Nm values of 0.75 and 0.51, respectively, and suggesting limited interchange of genes betwe en these species. These, together with the relatively high Nei unbiase d genetic distance (0.202) between the two sibling species, are consis tent with the occurrence of sympatric species with limited gene flow. F-ST/R-ST values for individual loci varied greatly (F-ST range 0.00-0 .87; R-ST range 0.00-0.73), indicating that the loci differ in their a bility to measure levels of differentiation between these two species. Location of loci within paracentric inversions seems to be,an importa nt factor affecting levels of differentiation measured by the differen t loci.