The rate of evolution of postmating-prezygotic reproductive isolation inDrosophila

Abstract

21 22Reproductive isolation (RI) is an intrinsic aspect of species, as described in the Biological 23 Species Concept. For that reason, the identification of the precise traits and mechanisms 24 of RI, and the rates at which they evolve, is crucial to understanding how species 25 originate and persist. Nonetheless, precise measurements of the magnitude of 26 reproductive isolation are rare. Previous work has measured the rates of evolution of 27 prezygotic and postzygotic barriers to gene flow, yet no systematic analysis has carried 28 out the study of the rates of evolution of postmating-prezygotic (PMPZ) barriers. We 29 systematically measured the magnitude of two barriers to gene flow that act after mating 30 occurs but before zygotic fertilization and also measured a premating (female mating rate 31 in nonchoice experiments) and two postzygotic barriers (hybrid inviability and hybrid 32 sterility) for all pairwise crosses of species within the Drosophila melanogaster 33 subgroup. Our results indicate that PMPZ isolation evolves faster than hybrid inviability 34 but slower than premating isolation. We also describe seven new interspecific hybrids in 35 the group. Our findings open up a large repertoire of tools that will enable researchers to 36 manipulate hybrids and explore the genetic basis of interspecific differentiation, 37 reproductive isolation, and speciation.

Application of a dense genetic map for assessment of genomic responses to selection and inbreeding in Heliothis virescens.

“…As one example, only 57% of the An. gambiae genome went to fixation, as observed according to SNP markers, following 10 generations of inbreeding (Turissini et al, 2014). Observed differences between our H. virescens population and other insects could be species specific, but is more likely related to the proportion of the genome containing balanced lethal systems (Falconer & Mackay, 1996).…”

“…Indeed, our inbreeding coefficient F IT , as observed from our ddRAD-seq data, met theoretical expectations for all subsets of loci. Our H. virescens laboratory population was more amenable to inbreeding than other insect species (Munstermann, 1994;Rumball et al, 1994;Turissini et al, 2014;You et al, 2013), despite their relatively high levels of genomic diversity (Figure 1 288 several other insect species following experimental inbreeding attempts (Munstermann, 1994;Rumball et al, 1994;Turissini et al, 2014;You et al, 2013). As one example, only 57% of the An.…”

Fine scale mapping of genomic introgressions within theDrosophila yakubaclade

“…If D. melanogaster is the outgroup of the test, the most common direction of introgressions is D. yakuba into D. santomea ( yak- into- san ). All of our other analyses (see below) however indicate that introgression is more common in the yak-into-san direction indicating that D. melanogaster reads might not map well to the D. yakuba genome due to the increased divergence between D. melanogaster and D. yakuba (Ks~0.26 [72]; especially at regions less constrained by selection such as intergenic regions); the choice of outgroup is clearly relevant.…”

Genetic basis to hybrid inviability is more complex than hybrid male sterility in Caenorhabditis nematodes

“…Consequently, much research aims to understand the genetic architecture underlying intrinsic hybrid sterility and inviability. In many systems, hybrid sterility evolves before hybrid inviability (Wu 1992;Moyle et al 2004;Presgraves 2010;Turissini et al 2017). Among the open questions related to the genetic architecture of hybrid incompatibilities, one key issue is whether barriers that evolve earlier will correspondingly accumulate more underlying genetic incompatibilities per unit time to make them genetically more complex.…”