Theory predicts that intra-genomic conflicts may play a central role in the evolution of hybrid sterility and inviability, but empirical examples are lacking. My research program leverages the natural diversity of reproductive barriers in Mimulus to understand the evolutionary drivers and genetic underpinnings of reproductive isolation, and to examine how important these barriers are at preventing introgression in nature. One of the most common barriers in plants is hybrid seed inviability, which is theorized to evolve as a byproduct of conflict between maternal and paternal interests in resource allocation to developing offspring. I recently uncovered a cryptic species complex- M. decorus- within the M. guttatus species complex that are largely reproductively isolated by hybrid seed inviability. Using genomics, development, field work, common garden experiments, and crossing surveys, I test whether parental conflict is driving the rapid evolution of hybrid seed inviability in this group and explore whether conflict-driven evolution can leave parallel developmental and genetic signatures. Lastly, I will discuss current and ongoing works to understand the importance of reproductive barriers in nature using both experimental evolution, and natural contact zones.