The Lady Slipper newsletter of the Kentucky Native Plant Society has been published since the Society’s founding in 1986. We occasionally feature an article from a past issue. This year’s Fall Meeting will include a hike at Pine Creek Barrens Nature Preserve in Bullitt county. This article, from the fall of 2014, is about a rare species of fern, the slender lip fern, Myriopteris gracilis, found only in Kentucky in Bullitt county. The location of this fern is along Cedar Creek, in similar habitat to Pine Creek Barrens, and is about a mile away as the crow flies. This article first appeared in the fall of 2014, Vol. 29, No. 3. If you would like to see other past issues, visit the Lady Slipper Archives, where all issues from Vol. 1, No. 1, February 1986 to Vol. 39, 2024, can be found.

The Slender Lip Fern in Kentucky

by James Beck

A single low dolomite ledge near Cedar Creek in Bullitt County harbors one of the most unique plant populations in Kentucky. At a distance this might appear to be a population of the hairy lip fern, Myriopteris lanosa (Michx.) Grusz & Windham, a species known from >20 Kentucky counties. Most will probably know M. lanosa as Cheilanthes lanosa (Michx.) D.C. Eaton, a species recently transferred (along with most North and Central American species of Cheilanthes) to Myriopteris (Grusz and Windham 2013). However, closer inspection will reveal that these Bullitt Co. ferns have smaller, nearly beadlike ultimate segments that are densely hairy underneath, keying clearly to the slender lip fern, Myriopteris gracilis Fée (Cheilanthes feeii T. Moore), in either Jones (2005) or Cranfill (1980).

As the only known M. gracilis locality in the state, this small population would warrant considerable attention. Further investigation would reveal, however, that it is also one of three highly disjunct populations of this species in the eastern United States. The slender lip fern is widespread in the western and central U.S., common on calcareous rock outcrops from British Columbia south to northern Mexico, from southern California east to the Ozark Plateau and the upper Midwest’s “Driftless Zone” (Windham and Rabe 1993). The Bullitt Co. population, discovered by Clyde Reed in the early 1950s, represents a ca. 200 km disjunction from the nearest populations in southern Illinois (Reed 1952). The other two eastern disjunct populations are in southwestern Virgina (Wieboldt and Bentley 1982) and Durham Co., NC (Rothfels et al.

2012). These Kentucky, Virginia, and North Carolina populations add to what is already a remarkably large geographic range, a surprising level of geographic success considering that M. gracilis is exclusively asexual. The slender lip fern undergoes a modified meiosis that produces unreduced spores, which germinate and produce free-living unreduced gametophytes that then develop into adult sporophytes through mitosis. Because they bypass both recombination and the fusion of gametes, asexual species like M. gracilis are essentially genetically “frozen” line-ages, with minimal opportunity to create new genetic variation. Sex and recombination are traditionally thought of as necessary for maintaining the variation needed for adaptation, and asexual species are generally considered incapable of long-term evolutionary success. However, M. gracilis is one of a number of asexual species that occupy wider ranges than their sexual relatives. Although these big ranges could perhaps indicate success over shorter evolutionary time scales, they could simply be biogeographic illusions. As a polyploid (triploid), M. gracilis could have been derived from a sexual ancestor repeatedly over time. As a result, its broad dis-tribution could represent a single, successful lineage or a composite of several geographically smaller lineages formed at different times.

This research question is the focus of my graduate student David Wickell’s M.S. thesis at Wichita State University, and we have spent the 2013 and 2014 field seasons collecting M. gracilis across its wide range. That is what brought me to Cedar Creek this July – the chance to visit the disjunct Kentucky population and add it to our growing genetic dataset. On the long drive east from Wichita I prepared myself for disappointment, however. Although Reed noted that plants were “quite frequent” in his original publication, by 1980 Ray Cranfill noted only “three or four adult individuals.” These plants were presumably the ones observed and photographed by Richard Cassell and the Kentucky State Nature Preserves Commission’s Deborah White in 1994, although subsequent visits failed to relocate this population. On my visit I had the good fortune of working with KSNPC’s Tara Littlefield, and within 10 minutes she led me right to the plants! The population was healthy and sporulating but still quite small (nine adult individuals), and thorough searches of numerous nearby ledges failed to locate additional plants. Photos, geographic coordinates, and habitat notes were taken, along with a tiny amount of leaf material from one plant. DNA extracted from this material will be analyzed along with 94 samples from 20 states collected by myself, my student David, and several collaborators. From each plant we will obtain a kind of genomic “fingerprint,” and the relative genomic distinctiveness of each plant will allow us to determine how many lineages are found across M. gracilis‘ range. The logic is straightforward; individuals from the same lineage are asexual clones of one another and should be essentially genetically identical. On the other hand, individuals from different lineages should exhibit considerably higher levels of genomic distinctiveness. Data from our 95-individual dataset should clearly distinguish between the two alternatives discussed earlier: that of a single successful asexual lineage, or that of many restricted, less successful lineages. The status of the KY and VA (also visited in July) populations will be particular interest. Do these two populations represent the same asexual lineage, suggesting a sort of “stepping” stone colonization? Or do they belong to different lineages, suggesting that M. gracilis was once more widespread and diverse in eastern North America?

Whatever secrets M. gracilis holds, the opportunity to visit a truly unique piece of the Kentucky flora was one this native Kentuckian will remember. Special thanks go to the KSNPC for permission to conduct sampling, to Tara Littlefield (KSNPC) for showing me the site, and to Richard Cassell, Ray Cranfill, Ron Jones, and Deborah White for insightful correspondences

Cranfill, R. 1980. Ferns and Fern Allies of Kentucky. Kentucky State Nature Preserves Commis-sion Scientific and Technical Series, no. 1. 284 pgs.

Grusz, A.L., and M.D. Windham. 2013. Toward a monophyletic Cheilanthes: the resurrection and recircumscription of Myriopteris (Pteridaceae). PhytoKeys 32: 49-64.

Jones, R.L. 2005. Plant Life of Kentucky. The University Press of Kentucky. 834 pgs.

Reed, C.F. 1952. Notes on the ferns of Kentucky, III. Cheilanthes feei on Silurian limestone in Kentucky. American Fern Journal 42: 53-56.

Rothfels, C.J., E.M. Sigel, and M.D. Windham. 2012. Cheilanthes feei T. Moore (Pteridaceae) and Dryopteris erythrosora (D.C. Eaton) Kunze (Dryopteridaceae) new for the flora of North Carolina. American Fern Journal 102: 184-186.

Wieboldt, T.F., and S. Bentley. 1982. Cheilanthes feei new to Virginia. American Fern Journal 72: 76-78.