ECOLOGY AND GENETICS OF FLORAL & MATING SYSTEM EVOLUTION
NSF Evolutionary Processes (2018-2022)
NSF Evolutionary Processes (2010-2014)
NSF Dissertation Improvement Grant (1999-2001)
The evolutionary shift from outcrossing to self-fertilization is one of the most common transitions in the diversification of flowering plants. Although ecological factors have been considered important to the selection of selfing at least as early as Darwin, much of contemporary research has considered the importance of genetic factors, such as inbreeding depression, in directing plant mating system evolution. I have examined how ecological context (community and population-level factors) and plant-pollinator interactions influence natural selection on mating system traits.
Our work has focused on Clarkia xantiana, a species with remarkable population differentiation in mating system across its restricted geographic range. Our initial work on pollination ecology in this system has shown that community context can influence the dynamics of plant-pollinator interactions (Geber & Moeller 2006). The presence of pollinator-sharing congeners can facilitate outcross reproduction in C. xantiana, particularly when populations are very small (Moeller 2004, 2005). This type of effect may stabilize population dynamics and facilitate population expansion and colonization of new sites.
To examine the role of these ecological factors in mating system evolution, I have used large-scale field experiments, manipulating ecological factors (population size, community context) to test the hypothesis that self-fertilization evolves as a form of reproductive assurance in environments where pollinators and/or mates limit the potential for outcrossing. This work has shown that natural selection favors mating system traits that promote selfing when populations are reduced in size and where the diversity of pollinator-sharing plant species is low (Moeller and Geber 2005).
We have also taken a biogeographic approach to investigate the relationship between mating system differentiation and pollinator communities. Geographic surveys of bee pollinator communities have shown a striking correspondence between the distribution of specialist pollinators and genetic differentiation in mating system traits (Moeller 2006). Together, these different approaches have indicated that reproductive assurance may play an important role in directing mating system evolution in Clarkia.Most recently, we examined selection on floral traits through both female and male fitness using paternity analyses of an experimental population. Our results show evidence of disruptive selection on floral traits, where intermediate phenotypes suffer low male fitness — intermediate phenotypes were less successful at achieving male fitness through selfing and outcross siring success (Briscoe Runquist et al. 2017). These results suggest that predominantly outcrossing and selfing mating strategies (at the extremes of the phenotypic distribution) are favored over mixed mating strategies.
Related Publications: Clarkia
Briscoe Runquist, R.D., M.A. Geber, M. Pickett-Leonard†, & D.A. Moeller. 2017. Mating system evolution under strong pollen limitation: Evidence of disruptive selection through male and female fitness in Clarkia xantiana. American Naturalist 189:549-563.
Briscoe Runquist, R.D. & D.A. Moeller. 2014. Floral and mating system divergence in secondary sympatry: testing an alternative hypothesis to reinforcement in Clarkia. Annals of Botany 100:1916-1921
Briscoe Runquist, R.D. & D.A. Moeller. 2013. Resource reallocation does not influence estimates of pollen limitation or reproductive assurance in Clarkia xantiana ssp. parviflora (Onagraceae). American Journal of Botany 100:1916-1921.
Moeller, D.A., M.A. Geber, V.M. Eckhart, & P. Tiffin. 2012. Reduced pollinator service and elevated pollen limitation at the geographic range limit of an annual plant. Ecology 93:1036-1048.
Moeller, D.A. 2006. Geographic structure of pollinator communities, reproductive assurance, and the evolution of self-pollination. Ecology 87: 1510-1522.
Moeller, D.A. & M.A. Geber. 2005. Ecological context of the evolution of self-pollination in Clarkia xantiana: population size, plant communities, and reproductive assurance. Evolution 59: 786-799.
Moeller, D.A. 2005. Pollinator community structure and sources of spatial variation in plant-pollinator interactions in Clarkia xantiana ssp. xantiana. Oecologia 142: 28-37.
Moeller, D.A. 2004. Facilitative interactions among plants via shared pollinators. Ecology 85: 3289-3301.
Related Publications: Review & Synthesis
Moeller, D.A., R.D. Briscoe Runquist, A.M. Moe, M.A. Geber, C. Goodwillie, P.-O. Cheptou, C.G. Eckert, E. Elle, M.O. Johnston, S. Kalisz, R.H. Ree, R.D. Sargent, M. Vallejo-Marin, & A.A. Winn. 2017. Global biogeography of mating system variation in seed plants. Ecology Letters 20:375-384.
Winn, A.A., E. Elle, S. Kalisz, P.-O. Cheptou, C.G. Eckert, C. Goodwillie, M.O. Johnston, D.A. Moeller, R.H. Ree, R.D. Sargent, & M. Vallejo-Marin. 2011. Analysis of inbreeding depression in mixed mating plants provides evidence for selective interference and stable mixed mating. Evolution 65:3339-3359.
Goodwillie, C., R. Sargent, C.G Eckert, E. Elle, M.A. Geber, M.O. Johnston, S. Kalisz, D.A. Moeller, R.H. Ree, M. Vallejo-Marin, & A. Winn. 2010. Correlated evolution of mating system and floral display traits in flowering plants and its implications for the distribution of mating system variation. New Phytologist 185: 311-321.
Eckert, C.G., S. Kalisz, M.A. Geber , R. Sargent, E. Elle, P.-O. Cheptou, C. Goodwillie, M.O. Johnston, J.K. Kelly, D.A. Moeller, E. Porcher, R.H. Ree, M. Vallejo-Marin, & A. Winn. 2010. Plant mating systems in a changing world. Trends in Ecology & Evolution 25: 35-43.
Johnston, M.O., E. Porcher, P.-O. Cheptou, C.G. Eckert, E. Elle, M.A. Geber, S. Kalisz, J.K. Kelly, D.A. Moeller, M. Vallejo-Marin, & A. Winn. 2009. Correlations among fertility components can maintain mixed mating in plants. American Naturalist 173: 1-11.