Establishing interspecific mosaic genome lines between Drosophila ananassae and Drosophila pallidosa by means of parthenogenesis

Abstract

Strong sexual isolation exists between the closely related species Drosophila ananassae and D. pallidosa, but there is no obvious post-mating isolation; both sexes of the hybrids and their descendants appear to be completely viable and fertile. Strains exhibiting parthenogenesis have been derived from wild populations of both species. We intercrossed such strains and established iso-female lines after the second generation of parthenogenesis. These lines are clones, carrying homozygous chromosomes that are interspecific recombinants. We established 266 such isogenic lines and determined their genetic constitution by using chromosomal and molecular markers. Strong pseudo-linkage was seen between loci on the left arm of chromosome 2 and on the right arm of chromosome 3; the frequency of inheriting the two chromosome regions from the same species was significantly larger than expected. One possible cause of pseudo-linkage is female meiotic bias, so that chromosomes of the same species origin tend to be distributed to the same gamete. But this possibility is ruled out; backcross analysis indicated that the two chromosome regions segregated independently in female hybrids. The remaining possibility is elimination of low-fitness flies carrying the two chromosome regions from different species. Thus, genetic incompatibility was detected in the species pair for which no hybrid breakdown had previously been indicated. The 'interspecific mosaic genome' lines reported here will be useful for future research to identify genes involved in speciation and phenotypic evolution.

Cytonuclear Genic Incompatibilities Cause Increased Mortality in Male F2 Hybrids of Nasonia giraulti and N. vitripennis

“…Selected markers close to hypothesized TRDL were finally tested for distorted segregation ratios in a second population with the same cytoplasm as the one in which the effect was initially observed. Segregation data were further explored for negative nuclearnuclear and nuclear-nuclear-cytoplasmic (i.e., between a cytoplasmic and two nuclear loci) genic interactions by testing for deviations between the expected and the observed frequency of recombinant and nonrecombinant genotypes between markers from different linkage groups (see also Gadau et al 1999;Sawamura et al 2006), assuming an independent assortment of markers on different chromosomes. The tests were performed with the help of a Perl script using the x 2 test for goodness of fit (d.f.…”

Genetic analysis of female mating recognition between Drosophila ananassae and Drosophila pallidosa: application of interspecific mosaic genome lines

“…The ana-Im, y and pal-Im, + strains had been established by isolating virgin females from the original strains, where Im stands for ''impaternate''. Females from interspecific mosaic genome lines constructed by crossing ana-Im, y females and pal-Br, + males were examined for the present analysis; Sawamura et al (2006) have established 266 lines and 239 of them were examined here (the others had been accidentally lost before the mating test). Males used for the mating experiments are from the iso-female lines, D. ananassae TBU209 and D. pallidosa TBU155, both of which were originally captured in Tongatapu, Tonga, by Fuyama, Takanashi (Matsuura), and Tobari in 1981(Tomimura et al 1993).…”

“…The genetic constitution of each interspecific mosaic genome line has been determined (Sawamura et al 2006). Eight molecular markers were used other than the visible marker y for XL (cytological position, 5D).…”

“…To do this, we used interspecific mosaic genome lines previously established by crossing D. ananassae and D. pallidosa strains with parthenogenetic potential (Sawamura et al 2006). Briefly, each line derives from a second-generation founder female parthenogenetically produced from the female hybrid.…”

Effect of chromosome arrangements on mate recognition system leading to behavioral isolation in Drosophila ananassae

“…Sexual isolation, maintained by strong mating preferences has been reported between the light and dark forms of D. ananassae in laboratory stocks (Futch 1966). These forms were found to be sibling species (D. ananassae and D. pallidosa) of the ananassae complex which show strong sexual isolation (Futch 1973;Doi et al 2001;Sawamura et al 2006;Vishalakshi and Singh 2006). In spite of their sympatric distribution, post-mating reproductive barriers such as hybrid sterility or hybrid inviability do not exist between them (Futch 1966;Bock and Wheeler 1972).…”