Mechanisms promoting speciation with gene flow in host-specialized haplodiploids

University Of Kentucky Research Foundation, Lexington KY

Investigators

Abstract

One of the longest running debates in evolutionary biology is whether new species can form while exchanging genes with one another. Gene exchange is thought to make species formation difficult because it mixes up genetic backgrounds. This mixing prevents the buildup of differences between species. Nevertheless, genetic data tell us that many species do exchange genes in nature. The goal of this project is to understand how some species can withstand gene exchange. To do so, this project focuses on a pair of pine-feeding insect species that are common pests in the eastern United States. These two species are adapted to different pine species and have exchanged genes throughout their history. By focusing on immature and adult life stages and both sexes, this project will produce a more complete picture of how adaptation to different environments produces new species. By filling gaps in our understanding of how new species arise, this work will deepen our understanding of the world around us. This knowledge will help us preserve biodiversity and combat pests. Additionally, the researchers will use their project to develop educational materials for teaching genetics and evolution to first-year Biology students. This project will also provide opportunities for dozens of students to participate in authentic scientific research. Such experiences can help us retain talented students in STEM disciplines. Evolutionary theory predicts that speciation with gene flow is difficult, yet empirical data indicate such divergence scenarios are common in nature. To reconcile these seemingly contradictory findings, the proposed work takes advantage of an experimentally tractable pair of pine sawfly species (Neodiprion lecontei and N. pinetum) that are adapted to different pines and have exceptional genomic resources, extensive complementary data, and a history of divergence with gene flow. First, larval diet manipulations of the focal species and their reciprocal male and female hybrids will be used to quantify reproductive isolation on all combinations of host plants and to evaluate the role of phenotypic plasticity in promoting speciation with gene flow. Second, larval transcriptomes of the two species and their reciprocal first-generation hybrids reared on both parental hosts will be used to uncover how divergent transcriptional responses to larval diet contribute to host adaptation and gene misexpression in hybrids. Third, quantitative trait locus mapping in second-generation hybrid males reared on both parental hosts will be used to describe the genetic architecture of host-dependent and host-independent hybrid viability, larval performance, and adult male morphology. Because this work provides intuitive examples of the complexity of phenotypic variation and mechanisms through which natural selection produces new species, data from the proposed work will be used to develop a case study and scientist spotlights for use in introductory Biology courses and to fuel student-driven research. 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.