Asplenium hybrids
Introduction 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 (''Asplenium montanum''), ebony spleenwort (''Asplenium platyneuron''), and American walking fern (''Asplenium rhizophyllum''). Their chromosome complements are abbreviated "MM", "PP" and "RR", respectively. Three possible sterile diploid hybrids can form from their hybridization:*''A. montanum × platyneuron'' (MP) has been collected on very rare occasions.*''A. montanum × rhizophyllum'' (MR) is theorized to exist, but has never been collected.*''A. platyneuron × rhizophyllum'' (PR) is known as Scott's spleenwort (''Asplenium × ebenoides'') and is relatively common.In addition, ''A. platyneuron'' and ''A. rhizophyllum'', which have a more extensive range, hybridize with other spleenwort species outside the Appalachian complex.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 nameScientific nameParentsChromosomesNotes/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, AlabamaSince 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 nameScientific nameParentsChromosomesPloidyNotes/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 dolomiticum'' × ''A. lepidum'' var. ''haussknechtii'')*''Asplenium azoricum''  (''A. anceps'' × ? )*''Asplenium × biscayneanum'' (''Asplenium dentatum'' × ''A. verecundum'')*''Asplenium × curtissii'' (''Asplenium abscissum'' × ''A. verecundum'')*''Asplenium majoricum'' (''A. fontanum'' × ''A. petrarchae'')*''Asplenium reuteri'' (''Asplenium lepidum'' × ''A. trichomanes'')