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Behavioral isolation in grasshoppers

Ngan Nguyen @unsplash

Background

Questions

Implications

Team

How does the extent of gene flow help inferring the genes maintaining behavioral isolation?

The ‘omics’ era reveals an increasing number of species that are practically indistinguishable in morphology, ecology or even in genetics, despite being reproductively isolated from one another in sympatry. While such species complexes present an example of a taxonomic conundrum for systematists, they are prized as valuable study systems for evolutionary biologists because the behavioral traits that maintain species boundaries can directly be observed. Here, we study one of such systems, sympatric grasshopper species of the genus Chorthippus that have radiated under pervasive gene flow. This offers opportunities for identifying the genes underlying behavioral isolation and speciation.

Using a comparative phylogeographic approach, experimental crosses, population genomics, and behavioral assays, we aim to answer:

 

  1. Did species diverge in allopatric glacial refugia, facilitating the evolution of behavioral isolation?

  2. Is there a genetic association between cues and preference of behavioral isolation, which facilitates the maintenance of species boundaries in the face of gene flow?

  3. Did gene flow play a role in generating hybrid species that are reproductively isolated from their parentals?

This research program will not only offer new insights on how gene flow interacts with sexual selection during species formation, but it will provide a transferable multi-disciplinary approach for evolutionary studies in organisms characterized by large genomes that remain challenging to study.

Ricardo Pereira (SMNS), Dörte Neumeister (LMU), Diana González (LMU), Sarah Gaugel (SMNS), Tunca Deniz Yazici (LMU), Holger Schielzeth (Uni Jena), Richard Bailey (Lodz University) 

Fig. 1. The grasshopper Chorthippus jutlandica is hypothesized to be a species of hybrid origin. The Chorthippus species C. biguttulus and C. brunneus have highly divergent male song (top row) and coupled female preference, resulting in complete reproductive isolation in a broad range of sympatry between these species. The species C. jutlandica is characterized by a different male song (not represented). To produce that unique song, males of C. jutlandica make the same leg movements as experimental hybrids between C. biguttulus and C. brunneus, raising the hypothesis that C. jutlandica is a species of hybrid origin.

Fig. 1. The grasshopper Chorthippus jutlandica is hypothesized to be a species of hybrid origin. The Chorthippus species C. biguttulus and C. brunneus have highly divergent male song (top row) and coupled female preference, resulting in complete reproductive isolation in a broad range of sympatry between these species. The species C. jutlandica is characterized by a different male song (not represented). To produce that unique song, males of C. jutlandica make the same leg movements as experimental hybrids between C. biguttulus and C. brunneus, raising the hypothesis that C. jutlandica is a species of hybrid origin.

Fig. 2. Testing for genetic association between male signaling and female preference. In principle, hybridization can break the association between male signaling and female preference, leading to the collapse of species, including of Chorthippus species. We test if physical linkage between genes underlying male signaling (blue) and female preference (red) can maintain this association in spite of hybridization, using experimental hybrids between C. biguttulus and C. brunneus.

Fig. 2. Testing for genetic association between male signaling and female preference. In principle, hybridization can break the association between male signaling and female preference, leading to the collapse of species, including of Chorthippus species. We test if physical linkage between genes underlying male signaling (blue) and female preference (red) can maintain this association in spite of hybridization, using experimental hybrids between C. biguttulus and C. brunneus.

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