Rapid Evolution of Postzygotic Reproductive Isolation in Stalk-Eyed Flies

Abstract

We test the relative rates of evolution of pre- and postzygotic reproductive isolation using eight populations of the sexually dimorphic stalk-eyed flies Cyrtodiopsis dalmanni and C. whitei. Flies from these populations exhibit few morphological differences yet experience strong sexual selection on male eyestalks. To measure reproductive isolation we housed one male and three female flies from within and between these populations in replicate cages and then recorded mating behavior, sperm transfer, progeny production, and hybrid fertility. Using a phylogeny based on partial sequences of two mitochondrial genes, we found that premating isolation, postmating isolation prior to hybrid eclosion, and female hybrid sterility evolve gradually with respect to mitochondrial DNA sequence divergence. In contrast, male hybrid sterility evolves much more rapidly-at least twice as fast as any other form of reproductive isolation. Hybrid sterility, therefore, obeys Haldane's rule. Although some brood sex ratios were female biased, average brood sex ratio did not covary with genetic distance, as would be expected if hybrid inviability obeyed Haldane's rule. The likelihood that forces including sexual selection and intra- and intergenomic conflict may have contributed to these patterns is discussed.

Genetic divergence does not predict change in ornament expression among populations of stalk‐eyed flies

“…Evidence in support of cryptic Cyrtodiopsis dalmanni species has recently been obtained by a series of cross‐population mating studies, which indicate that most of the populations used in this study exhibit some form of reproductive isolation (Christianson et al . 2005).…”

Existence of a pattern of reproductive character displacement inHomobasidiomycotabut not inAscomycota

“…83–110). Positive correlations between reproductive isolation and genetic distance, commonly taken as a surrogate for time, have in fact been reported among several allopatric taxa, such as insects (Coyne & Orr, 1989; Presgraves, 2002; Christianson et al. , 2005), frogs (Sasa et al.…”

Rapid Evolution of Asymmetric Reproductive Incompatibilities in Stalk‐eyed Flies

“…The hatching success when these two populations are crossed is less than half that of either parental population. Previous work has shown that hybrid males produced by either possible reciprocal pairing of these populations are also sterile (Christianson et al ), indicating that both hybrid sterility and inviability evolve rapidly.…”

“…To investigate noncompetitive gametic isolation, we selected four allopatric populations of T. dalmanni (synonymized with Cyrtodiopsis; Meier and Baker ) that interbreed but exhibit varying degrees of RI (Christianson et al ). These populations descend from flies that were collected by hand net near streams from two sites in peninsular Malaysia (Ulu Gombak and Cameron Highlands) and two sites in Sumatra (Bukit Lawang and Soraya) in 1999 or 2000 (Swallow et al ) and are abbreviated G, C, L, and S, respectively.…”

“…In a previous study, Christianson et al () found that postzygotic RI, in the form of male hybrid sterility, could be detected in any T. dalmanni population cross that resulted in offspring. They also reported that progeny production decreased in crosses involving flies from different populations as a function of genetic distance but could not determine if this was due to gametic or postzygotic (i.e., embryonic inviability) effects.…”