Typha angustifolia L. and Typha ×glauca Godron have increased their ranges on the North American continent over the past 150 years, and the pollen record has potential to document this spread. In T. angustifolia, pollen disperses as a reticulate, monoporate monad, similar in appearance to the pollen of Sparganium eurycarpum Engelm. Typha angustifolia and Sparganium are generally not distinguished, and T. ×glauca is rarely shown on pollen diagrams. My study of pollen reference material shows that Typha monads and Sparganium can be separated using diameter and roundness at a known level of statistical confidence. Typha monads are on average significantly smaller in diameter (mean and standard deviation = 22.7 ± 2.6 µm) than Sparganium (25.3 ± 2.7 µm). The incidence of angularity is higher in T. angusti folia pollen grains, whereas Sparganium grains are more often rounded. The pollen signature of T. ×glauca consists of mostly monads, but can contain up to 30% dyads, and (or) 14% tetrads, and (or) 10% triads. I suggest that T. angusti folia and T. ×glauca can be identified as one category in the pollen record and, where their dates of arrival are known, this category may be used as a chronostratigraphic indicator.Key words: Typha, Sparganium, pollen, invasive species, wetlands.
Genetic structure in hybrids and progenitors provides insight into processes underlying an invasive cattail (Typha × glauca) hybrid zone