Speciation and social plasticity: signal-preference phenotypes in social and genetic hybrids

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This project investigates how social interactions produce variants in animal behavior, potentially leading to speciation. Besides the familiar pattern where new mutations lead to new traits, recent work indicates that social interactions may also expose existing genetic variation to selection much more broadly, facilitating divergence and speciation. The implications for whether and how natural animal populations adapt to new environments are of broad relevance and utility to society, and this work helps to elucidate the conditions under which adaptation to novel environments may be faster than currently anticipated. The project integrates research, mentorship, teaching, and community outreach to study plant-feeding insects that communicate with plant-borne vibrational signals, and the ways in which behavioral encounters between closely related species of these insects induce variation in their mating signals and mate preferences. The project involves a trans-Atlantic collaboration between senior and junior researchers; resource-development for researchers (making new software tools broadly and freely available); a pilot program for alternative-career training track in software development for PhD graduates; community outreach for families; and leveraging the host university's position as an urban-access university to broaden the participation of under-represented groups in science.Biologists can best conceptualize speciation when population divergence in ecological and reproductive traits is accomplished by changes in a single locus. But speciation often involves divergence in complex suites of polygenic traits, and it is not clear how linkage disequilibrium is established and sustained in these cases. This project will test the hypothesis that social plasticity can cause polygenic traits such as mating signals and mate preferences to co-diverge as if they were controlled by a single locus. This could prevent gene flow between diverging populations early in speciation and help build up linkage disequilibrium. This would extend the efficiency of the simplest known speciation scenario to cases involving divergence in polygenic traits. The project integrates both empirical and theoretical approaches. The empirical component of the proposal will use the Enchenopa binotata species complex of treehoppers. This group of plant-feeding insects offer a case study of signal-preference co-divergence that provides unusual resolution in the analysis of the causes and consequences of variation in signals and preferences. Experiments will contrast phenotypic variation in mating signals and mate preferences due to developing in conditions mimicking first contact between closely related species with that due to genetic hybridization. Support for the hypothesis requires that signals and preferences co-diverge due to social plasticity upon first contact between nascent species. The project will also assess geographic variation in the social plastic response to test the competing hypothesis of reinforcement on signal-preference plasticity. Theoretical work will generalize the empirical tests of the hypotheses.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.