Abstract
Proteins involved in post-copulatory interactions between males and females are among the fastest evolving genes in many species, usually attributed to their involvement in reproductive conflict. As a result, these proteins are thought to often be involved in the formation of postmating-prezygotic incompatibilities between species. The Drosophila dunni subgroup consists of a dozen recently diverged species found across the Caribbean islands with varying levels of hybrid incompatibility. We performed experimental crosses between species in the dunni group and see some evidence of hybrid incompatibilities. We also find evidence of reduced survival following hybrid mating, likely due to postmating-prezygotic incompatibilities. We assessed rates of evolution between these species genomes and find evidence of rapid evolution and divergence of some reproductive proteins, specifically the seminal fluid proteins. This work suggests the rapid evolution of seminal fluid proteins may be associated with postmating-prezygotic isolation, which acts as a barrier for gene flow between even the most closely related species.
Highlights
We considered a cross to be conspecific if we mated within species and a cross to be heterospecific if we mated with the most closely related species where fertile hybrids were found in previous crosses
The Drosophila dunni group is a species group endemic to islands in the Caribbean, with each island inhabited by a different complement of species
This is facilitated by the extensive genetic tools available in the species group to identify the genetic basis of reproductive isolation, both prezygotic and postzygotic
Summary
Numerous groups of recently diverged species have been used to study speciation across multicellular taxa (COYNE AND ORR 1989; MCKINNON AND RUNDLE 2002; GLOR et al 2005; KITANO et al 2009; BREKKEAND GOOD by varying levels of divergence across genomes, incomplete isolation and differing forms of reinforcement (COYNE AND ORR 2004; ORR 2004; PRESGRAVES 2007; MATUTE et al 2010; MOYLE AND NAKAZATO2010; ORR et al 2013; PAYSEUR AND RIESEBERG 2016). ORR 1989; GOURBIÈRE AND MALLET 2010; PRESGRAVES 2010) These species groups can be used in QTL studies to identify loci which contribute to the reduced fitness of hybrids (HOWARD et al 2002; NOOR et al 2007; KITANO et al 2009), or to identify genes which may be involved in the early stages of speciation, such as those causing inviability or sterility in the heterogametic sex Several studies have highlighted that proteins transmitted in the seminal fluid to the female reproductive tract may drive isolation as a post-mating-prezygotic mating barrier for incompletely separated species, either caused by, or resulting in, reinforcement 2004; ANDRES et al 2008; GOURBIÈRE AND MALLET 2010; LARSON et al 2012; LARSON et al
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