POLYMORPHIC INTRON SEQUENCES DETECTED WITHIN AND BETWEEN POPULATIONS OF THE ORIENTAL FRUIT-FLY (DIPTERA, TEPHRITIDAE)

Introns are fast evolving and apparently selectively neutral sequences that can be suitable for analyzing population structure within a spec ies as well as for reconstructing relationships among closely related species. We have used the polymerase chain reaction (PCR) and exon-pri med intron-crossing (EPIC) primers to amplify the intron sequences of an actin gene from individuals representing 2 different laboratory and 3 different wild Bactrocera dorsalis Hendel (Diptera: Tephritidae) po pulations. By direct sequencing we identified 3 alleles that exist in differ ent frequencies in these populations. Using this sequence infor mation we designed a diagnostic restriction digest protocol to identif y the alleles present in any given individual. In this way the frequen cies of homozygous and heterozygous individuals can also be determined rapidly without the need for direct sequencing. In the 3 wild populat ions (Kauai, Molokai, and Thailand) we have surveyed, allele 1 is foun d at varying frequencies in ail 3 samples; allele 2 is found only in t he 2 Hawaiian populations (Kauai and Molokai) and allele 3 is found on ly in the Thai population. Wright's F-st values were estimated between the 2 Hawaiian populations as well as between each of the Hawaiian an d the Thai samples. Heterozygosity values range from zero for the 2 la boratory populations to 0.14 for Kauai population.