Asplenium hybrids
The fern genus Asplenium is well known for its hybridization capacity, especially in temperate zones.
Appalachian ''Asplenium'' hybrid complex
The Appalachian hybrid complex in Asplenium is a polyploid complex composed of 3 diploid species, 3 allotetraploid species formed by hybridisation and chromosome doubling from the former, and assorted diploid, triploid and tetraploid hybrids between the 6 species.The three diploid parent species are mountain spleenwort, ebony spleenwort, and American walking fern. Their chromosome complements are abbreviated "MM", "PP" and "RR", respectively. Three possible sterile diploid hybrids can form from their hybridization:
- A. montanum × platyneuron has been collected on very rare occasions.
- A. montanum × rhizophyllum is theorized to exist, but has never been collected.
- A. platyneuron × rhizophyllum is known as Scott's spleenwort and is relatively common.
At some point in the past, each of the sterile diploid hybrids experienced a chromosome doubling event that made them fertile allotetraploids; allozyme analysis shows that this happened on several independent occasions for A. montanum × platyneuron and A. montanum × rhizophyllum. These doubling events gave rise to the following tetraploids:
| Common name | Scientific name | Parents | Chromosomes | Notes/Distribution |
| Bradley's spleenwort | Asplenium bradleyi | A. montanum × platyneuron | MMPP | The Appalachians, Ozarks, and Ouachita Mountains. |
| Lobed spleenwort | Asplenium pinnatifidum | A. montanum × rhizophyllum | MMRR | The Appalachians and the Shawnee Hills. |
| Tutwiler's spleenwort | Asplenium tutwilerae | A. platyneuron × rhizophyllum | PPRR | Havana Glen, Alabama |
Since these allotetraploids are fertile, they are capable of crossing with each other and with the three diploid species to form the following sterile triploid and tetraploid hybrids, most of which are quite rare and occur sporadically where their parents' ranges overlap:
| Common name | Scientific name | Parents | Chromosomes | Ploidy | Notes/Distribution |
| Wherry's spleenwort | Asplenium × wherryi | A. bradleyi × montanum | MMP | triploid | |
| A. bradleyi × platyneuron | MPP | triploid | Believed to have been collected once at an early date in Pennsylvania; the site is now destroyed. Also reported from Sequatchie County, Tennessee. | ||
| Graves' spleenwort | Asplenium × gravesii | A. bradleyi × pinnatifidum | MMPR | tetraploid | |
| Trudell's spleenwort | Asplenium × trudellii | A. pinnatifidum × montanum | MMR | triploid | The Appalachians and the Shawnee Hills. |
| Kentucky spleenwort | Asplenium × kentuckiense | A. pinnatifidum × platyneuron | MPR | triploid | |
| A. tutwilerae × pinnatifidum | MPRR | tetraploid | Created in culture. | ||
| Boydston's spleenwort | Asplenium × boydstoniae | A. tutwilerae × platyneuron | PPR | triploid | Havana Glen, Alabama |
| A. tutwilerae × rhizophyllum | PRR | triploid | Created accidentally in culture. |
New Zealand hybrids
19 hybrids within the genus have been described from New Zealand, but have not been given binomials.Other hybrid species
- Asplenium afghanicum
- Asplenium azoricum
- Asplenium × biscayneanum
- Asplenium × curtissii
- Asplenium majoricum
- Asplenium reuteri