Genetic data facilitate research into a widespread and invasive cattail (Typha × glauca) hybrid zone in North America

Genetic data can provide insights into the evolutionary ecology of hybrid zones and may be particularly important for investigating widespread and cryptic hybrids. In North America an expansive hybrid zone comprises the cattails Typha latifolia, T. angustifolia, and their hybrid T. × glauca. This hybrid is a problematic wetland invader that alters ecosystem functioning and reduces biodiversity. It is fertile and produces both backcrossed and advanced-generation hybrids, leading to morphological overlaps with parent species; therefore, genetic data are necessary for understanding the dynamics of this hybrid zone. In this review we summarize some of the ways in which genetic data have helped us to understand this hybrid zone, including the distributions of parent species and hybrids; symmetrical and asymmetrical hybrid crosses; the prevalence of different hybrid classes; hybrid fitness and hybrid breakdown; and gene flow and genetic diversity. We end by identifying some knowledge gaps and future research directions that can help us to further understand what may be the most widespread hybrid macrophyte in North America.