# The genetics and genomics of reinforcement

> **NIH NIH R35** · HARVARD UNIVERSITY · 2022 · $422,500

## Abstract

Project Summary
Natural selection and gene flow are important during species formation, and yet there is still
much to be learned about how these forces shape the evolution of mutations that cause
reproductive isolation. The overall vision for the proposed research program is to use functional
genetic and genomic investigations to determine when and how selection and gene flow
contributed to divergence during speciation. This research investigates reinforcement, which is
the evolution of reproductive isolation in response to selection to decrease costly hybridization.
Reinforcement can be a critical step during the speciation process, and yet there is little known
about this process at the molecular level. The mutations causing reinforcement have not been
identified for any organism, and the effect that reinforcement has on patterns of genetic variation
throughout the genome has not been previously investigated. Three major goals of the
proposed research are to 1. identify the mutations causing reinforcement; 2. infer the
evolutionary history of the mutations underlying reinforcement; and 3. determine the extent of
and gene flow during reinforcement. Mutations causing reinforcement will be identified using
genetic association mapping near candidate genes and transgenic functional validation. Once
the causal mutations are identified, population genetic analyses quantifying and describing
variation surrounding the causal mutations will be used to infer how the mutations evolved
through time. Specifically, this research will examine target genomic regions for evidence of
selection, and determine if the causal mutations were from standing genetic variation or arose
under selection. Finally, this research will use innovative comparative genomic analyses to
quantify introgression across geographic space, throughout time, and along the genome of two
species involved in the reinforcement. This research will be accomplished in the wildflower
Phlox drummondii, arguably the best-studied case of reinforcement. Previous work provides a
clear ecological and evolutionary understanding of how and why reinforcement occurred. Field
experiments have confirmed that reinforcement caused divergence in flower color and two
candidate genes causing this divergence have been identified. This system offers a unique
opportunity to identify the mutations causing reinforcement and the signature of variation this
process leaves across the genome. Understanding selection and gene flow during the evolution
of functional genetic variants is critical to determining how all organisms, including humans,
adapt to changing environments. This work is transformative because it develops a novel
genomic framework for understanding selection and gene flow during reinforcement.

## Key facts

- **NIH application ID:** 10471383
- **Project number:** 5R35GM142742-02
- **Recipient organization:** HARVARD UNIVERSITY
- **Principal Investigator:** Robin Hopkins
- **Activity code:** R35 (R01, R21, SBIR, etc.)
- **Funding institute:** NIH
- **Fiscal year:** 2022
- **Award amount:** $422,500
- **Award type:** 5
- **Project period:** 2021-08-18 → 2026-06-30

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/10471383

## Citation

> US National Institutes of Health, RePORTER application 10471383, The genetics and genomics of reinforcement (5R35GM142742-02). Retrieved via AI Analytics 2026-05-23 from https://api.ai-analytics.org/grant/nih/10471383. Licensed CC0.

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