The flowering phenology and pollen viability of Typha latifolia, Typha angustifolia, and Typha x glauca in northern lower Michigan: implications for hybridization and evolution.

Abstract

In this study, we recorded the flowering phenologies of three cattail taxa (Typha latifolia, T. angustifolia, and their hybrid, T. x glauca) at two sites in northern lower Michigan and assessed the viability of their pollen. These traits are fundamental to the potential for hybridization and gene flow among the three taxa, and have implications for the spread of T. angustifolia and T. x glauca (invasive plants in North America) into currently uncolonized areas. Additionally, greater understanding of the pollen viability and flowering phenology of T. x glauca may provide insight into its capacity for backcrossing with its parental sepcies and experiencing concomitant gene flow. All plants in this study were identified by their pollen morphology. These species assignments will be confirmed in the coming months by using random amplified polymorphic DNA (RAPD) markers. We found that there is substantial overlap (~1-2 weeks) in the flowering times of T. angustifolia, T. latifolia, and T. x glauca in northern lower Michigan. This indicates that hybridization can occur quite frequently in this region, and that there is no phenological barrier to backcrossing between T. x glauca and its parental species. Contrary to previous findings reported in the literature, we also found that T. x glauca plants can show great variation in the viability of their pollen. Although 14% of the putative T. x glauca in our study (N=50) produced pollen that contained less than 40% viable grains, 66% of the plants yielded pollen that was more than 80% viable. The range in viability found among T. angustifolia was very similar. These results suggest that T. x glauca may be more capable of backcrossing, experiencing gene flow, and possibly undergoing evolutionary change than is currently believed.