The Architectures and Underpinnings of Adaptive Evolution and Reproductive Isolation

University Of Wisconsin-Madison, Madison WI

Investigators

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Abstract

1 Summary: Architectures and Underpinnings of Adaptive Evolution and Reproductive Isolation 2 This research program informs foundational yet unresolved questions at the interface between genomic 3 diversity and evolutionary process. It focuses on two research themes: (1) Connecting Genomic Diversity 4 to Adaptive Evolution, and (2) Genetic Windows Into Early and Late Stage Reproductive Isolation. 5 This research fuses ambitious but cost-effective Drosophila experiments with novel approaches to the 6 analysis of large data sets. D. melanogaster offers key advantages for this work. The global expansion of this 7 species has given rise to adaptive trait differences, and early stage reproductive isolation, between populations 8 that diverged in the last ~13,000 years. The experimental efficiency of Drosophila, along with its compact and 9 well-annotated genome, and its wealth of genetic resources and transgenic tools, combine to allow these 10 evolutionary phenomena to be studied in ways that might not be practical in any other animal system. 11 This research will focus on Connecting Genomic Diversity to Adaptive Evolution in two major respects. 12 Following up on recent studies of the genetic architecture of adaptive trait evolution which showed that 13 causative variants consistently remain polymorphic, the proposed research will develop and apply population 14 genomic resources for performing genotype-phenotype association testing to identify underlying genes and 15 candidate variants within previously identified trait-associated genomic regions. Secondly, this research will 16 investigate how molecular regulatory traits provide a bridge between genomes and adaptive changes. Diverse 17 regulatory traits at chromatin, RNA, and protein levels will be assayed from the brains of flies from tropical and 18 temperate origins, and analyzed via an improved evolutionary framework. For the first time, the types of 19 regulatory traits that most frequently show the influence of adaptive evolution will be revealed. 20 The proposed work will also leverage this system to look through Genetic Windows Into Early and Late 21 Stage Reproductive Isolation. Research will build upon recent evidence of hybrid breakdown in male fertility 22 among the offspring of crosses between African and European D. melanogaster populations. By genetically 23 mapping incompatibilities using a novel framework, illuminating their biology, and identifying and testing 24 potential causative genes, this research will offer a very rare genetic perspective on the very earliest stages of 25 reproductive isolation. In contrast, D. melanogaster and D. simulans are commonly viewed as fully isolated 26 species. And yet, new population genetic results reject a simple isolation history for these taxa. Research will 27 test whether ancient genetic structure or else recent or ancient introgression best explains these observations. 28 Collectively, this research is highly consequential for fundamental evolutionary genetics. It also holds 29 substantial health relevance in terms of understanding how evolution is likely to proceed in biomedically 30 important insects such as disease vectors, and by informing the genetics human trait variation and infertility.