Format: ORAL

Bertrand Black1, Michael Sundue2

1 Plant Biology Department, University of Vermont 2 Royal Botanical Gardens Edinburgh

Athyrium filix-femina (L.) Roth is a terrestrial fern that is widespread in forest regions across the Northern Hemisphere and South America. Despite its prevalence, its taxonomy in the Americas remains unresolved and the evolutionary relationships between taxa remain poorly understood. Uncertainty about whether to recognize a single widespread A. filix-femina or several endemic American species has persisted to the present day due to unclear morphological differences between regional varieties and a lack of a comprehensive study across its range. To address this uncertainty, we sampled herbarium specimens from four continents and employed an integrative methodology that combined molecular, morphological, and biogeographic data to examine evidence for speciation, hybridization, and cryptic diversity in this species complex. Our results indicate that there are at least five monophyletic lineages in North America with diagnosable morphology, habitat preferences, and discreet geographic ranges. In spite of many documented hybrids in Asia, we found no evidence for widespread hybridization or reticulation among North American species. In South America, we did not find clear species boundaries defined by morphology, geography or molecular evidence to recognize more than a single species. Allele phasing identified a single putative hybrid from Queretaro, Mexico of unknown origin. Research such as this enhances our capacity to recognize and document American floristic diversity that may be concealed in plain sight and highlights the value of utilizing integrative molecular methods to facilitate biologically accurate classification of plant species.