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 species as well as for reconstructing relationships among closely related species. We have used the polymerase chain reaction (PCR) and exon-primed 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) populations. By direct sequencing we identified 3 alleles that exist in differ ent frequencies in these populations. Using this sequence information we designed a diagnostic restriction digest protocol to identify the alleles present in any given individual. In this way the frequencies of homozygous and heterozygous individuals can also be determined rapidly without the need for direct sequencing. In the 3 wild populations (Kauai, Molokai, and Thailand) we have surveyed, allele 1 is found at varying frequencies in ail 3 samples; allele 2 is found only in the 2 Hawaiian populations (Kauai and Molokai) and allele 3 is found only in the Thai population. Wright's F-st values were estimated between the 2 Hawaiian populations as well as between each of the Hawaiian and the Thai samples. Heterozygosity values range from zero for the 2 laboratory populations to 0.14 for Kauai population.