introduction - Pennsylvania Natural Heritage Program

What It Looks Like:Appalachian Gametophyte(Vittaria appalachiana)Pennsylvania DistributionFern species have two phases in their life cycle. The first phase to develop whena fern spore germinates is the gametophyte. From this typically small andinconspicuous tissue grows the sporophyte, the leafy fronds of the fern. TheAppalachian gametophyte is a unique fern species that has never been known todevelop a sporophyte phase. Populations consist of many small gametophytesand resemble a bed of moss rather than the typical upright, leafy fern form. Mostferns reproduce through the spores produced by the sporophyte and thegametophyte does not reproduce at all; the Appalachian gametophyte has theunusual capacity to produce vegetative propagules (Farrar 1998).Adapted from Parks 1989Where It Is Found:The fern lives in moist crevices of sandstonerocks, and is found exclusively in theAppalachian mountains. There are severalother species in the same family which arefound in the southeastern U.S, and only one ofthese species is known to produce asporophyte. Most species of this fern familyare found in tropical climates, and do producesporophytes (Farrar 1998).Photo: Dana Lee LingA Vittaria species in tropical Micronesia—sporophyte formIt is theorized that the Appalachian gametophyte once occupied a much larger range, 15-50 million years ago when the climate of thearea was tropical or subtropical, and had a typical fern life cycle including sporophyte and gametophyte phases. Upon the cooling ofthe climate with the Pleistocene-era glaciation, the species survived only in the highly sheltered environments of sandstonerockhouses, where temperatures very rarely reach freezing. Because in many other species of fern the sporophyte phase is moresensitive to cold temperatures than the gametophyte phase, it is theorized that the sporophyte phase of the Appalachian gametophytecould not survive in the cooler climates during and after glaciation, and thus the capacity of the fern to produce the sporophyte phasewas eventually lost. The fern is rare today because of its highly specialized habitat requirements, and because its form of vegetativereproduction gives it a very limited ability to disperse to new locations. Several populations are known from areas north of theglaciation line, thus some dispersal must have taken place, but genetic studies suggest that many populations have had no newindividuals immigrate for a very long time (Farrar 1998).Global Distribution:South-eastern North America.NatureServe. 2003. NatureServe Explorer:An online encyclopedia of life [web application].Version 1.8. NatureServe, Arlington, Virginia.http://www.natureserve.org/explorerConservation Status Ranks (Natureserve)G4: Vittaria appalachiana is abundant within its range. Much of its rock-shelter habitat is currently protected. This species is extremelyvulnerable, however, to any changes in its specialized habitat.S2: Imperiled in state because of rarity (6 to 20 occurrences or few remaining individuals or acres) or because of some factor(s)making it vulnerable to extirpation from the state. 51 51