Rescue of hybrid sterility in crosses between D. melanogaster and D. simulans

Abstract

The genetic analysis of reproductive isolation between species of Drosophila has now reached the resolution necessary to start answering one of the fundamental questions of evolution: what is the genetic basis of species differences? A.H. Sturtevant, one of the founders of Drosophila genetics, was fascinated by this question and thought he had found a way to analyse it when he realized that 'Drosophila melanogaster' was actually two species: D. melanogaster and D. simulans. By passing genes between these two species he hoped to investigate their genetic differences directly. No doubt he was disappointed to find that the D. melanogaster/D. simulans hybridization resulted only in unisexual sterile hybrids, a disappointment appreciated all the more by modern evolutionary biologists. Seventy-five years after Sturtevant's description of D. melanogaster/D. simulans hybrid sterility, we have discovered a strain of D. simulans that produces fertile female hybrids in crosses with D. melanogaster. Our discovery promises to bring the enormous resolution of D. melanogaster genetics to the study of reproductive isolation and species differences.

Drosophila melanogaster and D. simulans rescue strains produce fit offspring, despite divergent centromere-specific histone alleles

“…These mutations generally fall into two classes: those that restore the Hutter et al (1990), Sawamura et al (1993), Davis et al (1996), and presented in this paper. Refuses to be rescued, has low viability of females when In(1)AB, f-M1 is the father and has no sterility rescue.…”

“…The D. simulans strains C167.4, Tsimbazaza, S-17 vermilion, and Oxnard and the D. melanogaster strains In(1)AB, In(1)AB, f-M1/C(1)M4,y (a recombinant derivative of In(1)AB with males that carry the forked bristle, abbreviated as In (1)AB, f-M1 in this paper), Antigua, and Oregon-R are all described in Davis et al (1996). The D. simulans strain wild type is described in Johnson and Wu (1992).…”

“…Finally, the D. melanogaster strains Taï 255.1 and Melbourne and the D. simulans strain mhr were kindly provided by John Roote. Taï 255.1 is described in Lachaise et al (1986), Melbourne is described in Davis et al (1996), and mhr is described in Sawamura et al (1993).…”

“…Other strains rescue female viability; however, we limit our analysis to the lines Taï 255.1 (D. melanogaster), Melbourne (D. melanogaster), and mhr (D. simulans). In each of these strains, the rescue mutations are either unmapped (Taï 255.1 and Melbourne) or map to the region of chromosome 2 containing the cid gene (Lachaise et al, 1986;Sawamura et al, 1993;Davis et al, 1996;Carracedo et al, 2000). In two of the known lines where male viability is rescued (Hmr and Lhr), the mutations responsible have been mapped outside of the region containing cid and are excluded from this study (Watanabe, 1979;Hutter et al, 1990).…”

“…Initial studies of these species by Malik and Henikoff (2001) focused on strains that exhibit reproductive isolation in the form of both inviable and sterile hybrids, depending on the direction of the cross (see Table 1). However, several 'rescue strains' of each species exist that restore hybrid viability and female fertility when crossed in specific combinations, as shown in Table 1 (Lachaise et al, 1986;Hutter et al, 1990;Sawamura et al, 1993;Davis et al, 1996). In the majority of these strains, the genetic basis of hybrid rescue is very poorly understood (Hollocher, 1998;Hollocher et al, 2000).…”