Species that reproduce both through apomixis, the formation of asexual seeds, and sexually present complex questions around reproductive dynamics in mixed populations. Apomicts arise from sexual plants meaning that early populations that contain apomicts are mixed populations. The sexual cytotype exclusion principle theorizes that in these mixed populations sexual plants will bear the cost of hybridization. Sexuals are diploids while apomicts are polyploid and the hybrids that form between them are inviable. The cost is unidirectional because apomicts do not require external pollen for reproduction, but sexual mothers risk the chance of producing these inviable offspring if pollinated with apomictic pollen. Townsendia hookeri is an ideal system to explore these dynamics. T. hookeri is a rocky-mountain species that has both a triploid apomictic and diploid sexual form. Both forms occur in southern Wyoming and northern Colorado, but populations are always split and composed of one cytotype type or the other. Are the dynamics outlined in the sexual cytotype exclusion principle the key to explaining why we don’t find mixed populations? The answer to that depends on the strength of those reproductive interactions and therefore on their potential to increase the cost of co-occurrence. To begin to measure these forces, we collected achenes from an open pollinated garden composed of 16 apomicts and 19 sexuals. Achenes were collected and weighed prior to germination. Germination was tracked and growth was measured after 5 weeks. We are using a genotyping by sequencing protocol to designate offspring as either hybrids, the product of sexual outcrossing, or the product of facilitated selfing (mentor effect). A proximity score was assigned to each sexual plant in the array based on their relative proximity to other sexuals. Plants scored high when they were closer to other sexuals and lower when they were further from sexuals and more surrounded by apomicts. These scores will be evaluated on their ability to act as predictors for hybrid formation, achene weight, germination, and growth. We will also be examining the correlation between the traits measured and offspring type (hybrid, outcrossed, or selfed). This, in conjunction with the proximity scores, will determine the variation in the strength of reproductive interactions at a local scale.  This will provide insight into if these forces operate over small spatial scales or if at that scale spatial isolation is insignificant. From these results I will be able to determine the role of reproductive dynamics in mixed T. hookeri populations.