North American Dryopteris hybrid complex

Hybridization and polyploidy are common phenomena in ferns, and the genus Dryopteris is known to be one of the most freely-hybridizing fern genera.

[1] North American botanists recognized early that there were close relationships between many of the species of Dryopteris on the continent, and that these relationships reflected hybrid ancestry.

[2] The complex includes six sexual diploid parents (one of which, "D. semicristata", is hypothesized to be extinct[3]), six sexual allopolyploids, and numerous sterile hybrids at various ploidal levels.