Abstract

Specialization onto different host plants has been hypothesized to be a major driver of diversification in insects, and traits controlling olfaction have been shown to play a fundamental role in host preferences. A diverse set of olfactory genes control olfactory traits in insects, and it remains unclear whether specialization onto different hosts is likely to involve a nonrandom subset of these genes. Here, we test the role of olfactory genes in a novel case of specialization in Drosophila orena. We report the first population‐level sample of D. orena on the West African island of Bioko, since its initial collection in Cameroon in 1975, and use field experiments and behavioral assays to show that D. orena has evolved a strong preference for waterberry (Syzygium staudtii). We then show that a nonrandom subset of genes controlling olfaction‐–those controlling odorant‐binding and chemosensory proteins–‐have an enriched signature of positive selection relative to the rest of the D. orena genome. By comparing signatures of positive selection on olfactory genes between D. orena and its sister species, D. erecta we show that odorant‐binding and chemosensory have evidence of positive selection in both species; however, overlap in the specific genes with evidence of selection in these two classes is not greater than expected by chance. Finally, we use quantitative complementation tests to confirm a role for seven olfactory loci in D. orena’s preference for waterberry fruit. Together, our results suggest that D. orena and D. erecta have specialized onto different host plants through convergent evolution at the level of olfactory gene family, but not at specific olfactory genes.

Highlights

  • Local adaptation is a fundamental evolutionary process that can drive phenotypic and genetic diversification and can be responsible for the origin of new traits and species (Darwin 1859; Schluter 2000; Rundle and Nosil 2005; Nosil 2012; Shafer and Wolf 2013)

  • Our results show that D. orena found on the island of Bioko have evolved a strong preference for waterberry fruits over other suitable substrates

  • This finding adds to the growing body of work that describes the natural history and evolution of the nine species within the melanogaster species subgroup (Lee and Watanabe 1987; David et al 2007; Dworkin and Jones 2009; Linz et al 2013; Yassin et al 2016)

Read more

Summary

Introduction

Local adaptation is a fundamental evolutionary process that can drive phenotypic and genetic diversification and can be responsible for the origin of new traits and species (Darwin 1859; Schluter 2000; Rundle and Nosil 2005; Nosil 2012; Shafer and Wolf 2013). The evolution of behavioral traits can result in individuals preferentially seeking out certain environments, and in plant-associated insects, preferences tend to be controlled by traits used to detect chemical cues generated by their preferred host plants (Tilmon 2008). Understanding how these traits evolve during host specialization is important for understanding potential trade-offs encountered during specialization into a given ecological niche (Thompson 1988; Shoval et al 2012; Anderson et al 2013; Schick et al 2015)

Methods
Results
Conclusion
Full Text
Published version (Free)

Talk to us

Join us for a 30 min session where you can share your feedback and ask us any queries you have

Schedule a call