PRJNA665237
Revealing the evolutionary history of a reticulate polyploid complex of Isoetes in northwestern North America
Polyploidy and hybridization are known to be important processes in the evolution of seedless vascular plants. Compared to spermatophytes (seed plants), ferns and lycophytes have fewer reproductive barriers which encourage the formation of reticulate species complexes. As such, there is a large body of research on reticulation in these groups, but much of this work focuses on homosporous ferns. Far fewer studies pay attention to these dynamics in heterosporous lycophytes, known to hybridize and produce high level polyploids. One such group is the aquatic lycophyte genus Isoetes, which has long been a recalcitrant clade for systematists. Extreme morphological conservation, recent radiations, many ploidy levels, and frequent hybridization have challenged traditional approaches (i.e., morphometrics and single-gene sequencing) to reveal the complicated evolutionary history of Isoetes. Next-generation sequencing approaches such as restriction site associated DNA sequencing (RADseq) have helped illuminate relationships in reticulate complexes and seem promising for difficult groups such as Isoetes. Here, we leverage these sequencing approaches in combination with plastome, cytological and reproductive data to investigate the evolutionary relationships of a reticulate species complex of Isoetes from northwestern North America.