In the Southern Appalachians: Preliminary Findings
Tom Goforth, Crow Dog Native Ferns and Gardens
Study Description
From South Carolina west to the Mississippi River and north to Southern Canada, there are 12 known fertile species in the Dryopteris genus: six diploid, five tetraploid, and one hexaploid. One diploid species, inferred in the genetic profile of the fertile tetraploids D. cristata and D. carthusiana, and of several sterile hybrids has never been found. Dryopteris species ranges vary by latitude and elevation and by regional geology and soil conditions. Some species occur together in common habitats providing opportunities for hybridization. Approximately 26 triploid to pentaploid sterile hybrids are documented in the aforementioned geographical range in North America. Heretofore, only one fertile hexaploid species, Dryopteris clintoniana, has been identified.
Most Dryopteris species in the eastern North America occur in the Northeast, Upper Midwest, and in the Appalachian Mountains as far south as the middle to higher elevations of the Carolinas. This study focuses on a Dryopteris population near the Blue Ridge Parkway in the Appalachian Mountains of North Carolina at approximately 5700 feet in elevation.
The research site was initially identified in 2006 as having probable hybrids that potentially involve Dryopteris intermedia, Dryopteris campyloptera, Dryopteris expansa, Dryopteris carthusiana, Dryopteris cristata, and the unknown diploid species mentioned above. The site is at the extreme southern range limit of D. campyloptera and near the southern range limit of D. intermedia, D. carthusiana and D. cristata. Dryopteris expansa has not been documented in the region. Research began in August 2007.
The goals of this research are to identify, describe and document Dryopteris hybrids in the study population, decipher parentage, ascertain polyploidy conditions of hybrids, synthesize a hybridization time line, examine the evolutionary choices and behavior of the ferns, and describe a full ecological profile of the communities.
The study area is located on a west facing forested slope on U.S. Park Service land along the Blue Ridge Parkway in Jackson County, North Carolina at approximately 5600 feet in elevation. The site has varied density tree canopy, very acidic and organically rich A horizon soil (Burton Series), and substrates of biotite granite gneiss and biotite schist. The site generally corresponds to a Red Spruce-Frazier Fir Forest (Herb Subtype to Birch Transition Herb Subtype) as described in Classification of the Natural Communities of North Carolina, Fourth Approximation (Schafale, 2002). The most abundant canopy species is Picea rubens with scattered Betula alleghaniesis, Betula papyrifera, Abies frazeri, Aesulus octandra, and Fagus grandifolia. Canopy cover varies from 60-90 %. The herb layer includes Dennstaedtia punctilobula, Athyrium asplenioides, Thelypteris noveboracensis, Huperzia lucidula, Aster divaricatus, and Rubus spp.
Sampling, Description, and Analysis
100 ferns were sampled in September, 2007 including field identified Dryopteris intermedia, D. campyloptera, and Dryopteris spp. with field identified hybrid characteristics. For each sample fern, one frond was collected and pressed. Morphological characteristics were measured in the field at collection times and in the lab from the pressed fronds. A database of 36 characters was established using MS Excel. Analysis and grouping of the ferns was completed using visual comparison, Excel sorting, and PC ORD ordination. Extensive literature searches and correspondence with other researchers is ongoing. Spore analysis and sorus characteristics will be added to the database in the summer/fall of 2008.
Preliminary Findings
Dryopteris campyloptera is a fertile tetraploid cross between D. expansa and D. intermedia. By many accounts, D. campyloptera is essentially indistinguishable from D. expansa except through DNA analysis. D. intermedia differs significantly from D. campyloptera at a glance. D. campyloptera's only easily discernable inheritance from D. intermedia is climatic range. Currently the southern range limit of D. expansa in eastern NA is the Upper Midwest US and southern Canada. D. campyloptera occurs from southern Canada south to the higher elevations (approximately above 5500 feet) of the Southern Appalachians in North Carolina. D. intermedia occurs with D. expansa and D.campyloptera in the north and extends to the south to lower and middle elevations of the Southern Appalachians. D. expansa is not documented in the Southern Appalachians, although several ferns in the study sample have characters consistent with some documented descriptions of D. expansa. But given the difficulty of morphologically distinguishing D. campyloptera from D. expansa, DNA analysis is needed to verify the existence of D. expansa at the study site.
The possible hexaploid, pictured below, is eglandular, and its basal pinna pair is morphologically similar to the basal pinna pair in D. intermedia.
