Cystopteris hybrid complex

The fern genus Cystopteris is one that widely hybridizes internally.

North American Cystopteris Hybrids

The diploid parent species within the genus include:

C. bulbifera
C. "hemifragilis" (an undiscovered or extinct diploid)
C. protrusa
C. reevesiana

The hybrid species include:

C. fragilis (C. "hemifragilis" X C. reevesiana; allotetraploid)
C. laurentiana (C. bulbifera X C. fragilis; allohexaploid)
C. tennesseensis (C. bulbifera X C. protrusa; allotetraploid)
C. tenuis (C. "hemifragilis" X C. protrusa; allotetraploid)
C. utahensis (C. reevesiana X C. bulbifera; allotetraploid)

Non-species hybrids include:

Cystopteris Xillinoensis (C. bulbifera X C. tenuis; allotriploid)
Cystopteris Xwagneri (C. tennesseensis X C. tenuis; allo-allotetraploid)
Cystopteris fragilis X Cystopteris tenuis (allo-allotetraploid)

References

Lellinger, David B. A Field Manual of the Ferns & Fern-Allies of the United States & Canada. Smithsonian Institution, Washington, DC. 1985.