Using ImageJ to Quantify Hybrid Growth Rates and Reproductive Isolation in Mimulus

Author: Isabella FrancodaSilva

Field of Study: Science, Technology, Engineering, and/or Math

Faculty Mentors: James Sobel

Easel: 10

Timeslot: Midday

Abstract: Reproductive isolation is a key driver of speciation, yet the mechanisms underlying hybrid inviability remain poorly understood. In Mimulus (section Diplacus) – a recent, rapid radiation of perennial, woody shrubs found in California – hybrid offspring, produced from crosses between closely related taxa, exhibit differences in viability and growth, particularly in the early stages of development. Using ImageJ, we analyze post-germination growth rates in first-generation and second-generation hybrids to quantify how genetic incompatibilities impact seedling survivability. Growth rates in F2s suggest that DMIs (Dobzhansky-Muller Incompatibilities) accumulate over generations, ultimately leading to developmental failure in some hybrids. By measuring size differences and growth trajectories, this component of the study provides a quantitative approach to understanding postzygotic isolation and improves our knowledge of how genetic incompatibilities shape species fitness.