Haldane's rule and other aspects of reproductive isolation observed in theAnastrepha fraterculus complex (Diptera : Tephritidae)

Some aspects of reproductive isolation between allopatric populations of tw o closely related species of the Anastrepha fraterculus complex (A. fraterc ulus sp. 1 and sp. 2) were evaluated in laboratory conditions. Most of the crosses were fertile in each species as well as between sp. 2 females and s p. 1 males. In the reciprocal cross only 41.7% of the matings yielded viabl e progeny. Egg hatching occurred at similar rates within the two species, b ut was significantly lower in the crosses between the species. Adult emerge nce did not differ significantly among crosses. The sex ratio of adult prog eny within each species, as well as in the hybrid progeny derived from sp. 1 females crossed to sp. 2 males, did not differ from the expected 1:1 rati o. However, in the crosses between sp. 2 females to sp. 1 males, a signific ant deviation in the sex ratio in favor of females was observed, according to the Haldane's rule. The results reinforce previous data which indicated that A. fraterculus sp. 1 and A. fraterculus sp. 2 are distinct biological entities.