Progeny array analysis to estimate outcrossing rates, inbreeding coefficients, and inbreeding depression among native, naturalized, and invasive populations of Mimulus guttatus (Phrymaceae)

The mating system of non-native plant populations plays a role in determining the colonizing success following introduction into locations outside of the native distribution. For plant species capable of mixed-mating, both selfing and outcrossing can be advantageous and promote the establishment, persistence, and spread of newly arrived populations. To investigate how mating systems may contribute to the invasion process we estimated mating system parameters in perennial populations of the model plant species, <i>Mimulus guttatus</i> from its native range (West coast USA), non-native populations that are established but have not become invasive (East coast USA, >50 years), and populations in invasive regions (UK >200 years). Studies that include mating system data across the continuum of the invasion process are rare, thus here we utilize molecular markers to estimate outcrossing rates (t), inbreeding coefficients (F), and inbreeding depression in native, naturalized, and invasive populations. Overall, we found support for the persistence of mixed-mating across populations, variability in the relationship between outcrossing rates and inbreeding depression across populations, and evidence for the bridgehead process, where non-native populations may be the sources for the further establishment or reinforcement of additional non-native populations. The methodology we deployed had its own assumptions and sampling design constraints, that contributed to the variation in the parameter estimates. All <i>M. guttatus</i> populations likely rely on selfing through both within clone, and within flower and plant mating in addition to vegetative propagation. The results underscore the importance of introduction history in determining the role of both sexual and asexual reproduction in the successful establishment of a plant species outside its native range.