Developmental Stability of Interspecies Hybrids among Drosophila Melanogaster, D. Simulans and D. Mauritiana (diptera: Drosophilidae)

Interspecies hybridization is expected to cause developmental instability (DI) as a consequence of outbreeding depression and genomic stress. The variability of fluctuating asymmetry (FA) of bilaterally symmetrical organs can accompany such stress conditions and change from parental individuals to hybrids. The aims of the present study were to estimate, under laboratory conditions, the degree of prezygotic reproductive isolation among three sibling Drosophila species, D. simulans, D. mauritiana and D. Melanogaster and to estimate the effects of interspecies hybridization on wing FA. The results show that D. mauritiana females are the most discriminating toward males from other species, whereas D. simulans females are the least discriminating and successfully give progeny of both sexes with both other species. D. melanogaster females give only female progeny with males of the other two species. Interspecies hybridization changes DI, but it is species-, sex-, and trait-specific. Our data support the heterozygosity hypothesis only in the case of the significant decrease of FA in wing width of female hybrids obtained from the D. simulans x D. melanogaster cross. Most of the obtained hybrids in our experiments show increases in FA due to disturbed coadaptive inter-allelic balances within the genome of each species, which is in favour of the coadaptation hypothesis.