BIOSYSTEMATIC Christopher H . Haufier , 2 ANALYSIS OF Michael D . Windham 2 ' 3 and

The allotetraploid Cystopteris tennesseensis and its putative diploid progenitors, C. bulbifera and C. protrusa, constitute the C. tennesseensis complex. Although previous studies provided evidence of morphological, ecological, and chromosomal differences among the members of this complex, puzzling morphological variability precluded consistent identification and treatment of the taxa. The current study combined morphometric analyses with surveys of chromosomal, isozymic, and gametophytic features and supported past treatments of the complex as three separate species. The diploids shared no allozymes for the nine enzymes examined, and meiotic analyses of triploid hybrids with C. tennesseensis provided additional evidence that the diploid genomes are nonhomologous. Because C. tennesseensis has a relatively narrow range and contains isozymic profiles that are consistently additive of diploid patterns, we suggest that this allopolyploid is a relatively young species. Isozymic variation in the tetraploid parallels that observed in the diploids, implying that genetic variability was introduced through recurrent hybridization. Analyses of isozymic data and gametophytic features indicated that the diploids outcross frequently and thus may form hybrids readily when sympatric with the tetraploid. In part because of these characteristics, precise identification of species and hybrids in this complex is difficult and depends on evaluation of cryptic features. The cosmopolitan genus Cystopteris Bernh. has been called "perhaps the most formidable biosystematic problem in the ferns" (Lovis, 1977, p. 356). Although Cystopteris species are primarily north temperate and therefore readily accessible to pteridologists, complex patterns of morphological variation have thwarted satisfactory taxonomic treatments. The most recent monograph (Blasdell, 1963) recognized ten species in two subgenera. Subgenus Acystopteris includes the Asian species C. japonica and C. tenuisecta, which are so distinctive that some have placed them in a separate genus (Nakai, 1933; Pichi-Sermolli, 1977). Blasdell divided the remaining species (all in subg. Cystopteris) into two sections based on the pattern of vein termination in the leaves. Species having veins directed into teeth were placed in sect. Cystopteris, while those with veins directed into sinuses were assigned to sect. Emarginatae. Blasdell encountered variability for this vein termination character in some specimens and suggested that such anomalies could result from introgression. Lovis (1977), on the other hand, considered it more likely that venation features are not as stable in some species as in others and should not be used to define sections. Our observations suggested that Lovis was correct and, rather than organizing the North American Cystopteris species into morphologically based sections, we have chosen to concentrate on interactive species complexes involving allopolyploid species and their putative diploid progenitors. One I CHH is profoundly indebted to Alice and Rolla Tryon for providing the opportunity through a Gray Herbarium Postdoctoral Fellowship to delve deeply into the world of ferns and for passing on by example their infectious curiosity about these marvelous plants. This research was supported by the National Science Foundation. We thank Donald Burke, Cara Burres, Lori Hanson, Warren Hauk, Carol Kuhn, Robin Prentice, and Eric Rabe for technical assistance, David Barrington for drawing Figure 1, and the officers of the following herbaria for loans of specimens: COLO, DAO, GH, ILLS, IND, KANU, KE, KY, MICH, MIL, MO, NY, PAG, OAC, OS, SIU, TENN, UARK, US, VPI, VT, and WIS. We are especially thankful to Ralph Brooks and Ron McGregor of KANU for housing the many hundreds of specimens. Living specimens were generously supplied by D. M. Britton, R. E. Brooks, S. C. Churchill, J. J. Doyle, R. C. Moran, T. Reeves, D. E. Soltis, W. C. Taylor, C. K. Teale, and W. H. Wagner. 2 Department of Botany, University of Kansas, Lawrence, Kansas 66045, U.S.A. 3Present Address: Utah Museum of Natural History, University of Utah, Salt Lake City, Utah 84112, U.S.A. 4University of Hawaii, Hawaiian Evolutionary Biology Program, Honolulu, Hawaii 96822, U.S.A. ANN. MISSOURI BOT. GARD. 77: 314-329. 1990. This content downloaded from 129.237. 46.100 on Thu, 11 Sep 2014 14:45:22 PM All use subject to JSTOR Terms and Conditions Volume 77, Number 2 Haufler et al. 315 1990 Analysis of the Cystopteris tennesseensis