Can asexuality confer a short term advantage? Investigating apparent biogeographic success in the apomictic triploid fern Myriopteris gracilis

Premise of the study: Although asexual taxa are generally seen as evolutionary dead ends, asexuality appears to provide a short-term benefit in some taxa, including a wider geographic distribution compared to sexual relatives. However, this may be an illusion created by multiple, morphologically cryptic, asexual lineages, each occupying a relatively small area. In this study we investigate the role of multiple lineages in the biogeography of Myriopteris gracilis Fée (Pteridaceae), a North American apomictic triploid fern species with a particularly large range. Methods: Rangewide asexuality was assessed by counting spores/sporangium in 606 M. gracilis specimens from across the species range, and lineage structure was assessed with both plastid DNA sequence and Genotyping By Sequencing (GBS) SNP datasets. Key Results: Spore counting of >600 specimens identified no sexual populations, establishing that M. gracilis is exclusively asexual. The plastid data estimated the crown age of...