Florence S. Wagner

Polyploidy in Pteridophytes

Chromosome studies of pteridophytes had their major impetus in the work of Irene Manton (1) who was the first to show the far-reaching significance of Polyploidy in these plants. Her work was followed not only by numerous investigations by her own students at the University of Leeds but by researchers in many parts of the world, including especially India, Japan, New Zealand, Costa Rica, United States, Canada, Germany, Italy, and Hungary. Two major works have appeared in the past couple of years, namely the very thorough analysis of “Evolutionary Patterns and Processes in Ferns” by J.D. Lovis (2) and “A Cytotaxonomical Atlas of the Pteridophyta” by A Love, D. Love, and R.E.G. Pichi-Sermolli (3,4).

Cryptic Species, Species Delimitation, and Taxonomic Practice in the Homosporous Ferns

Biologists generally agree that species are to be delimited on the basis of genetic discontinuities. The two species concepts that depend on such discontinuities to delimit species are the biological and the evolutionary species concepts. A biological species is a group of interfertile populations that is reproductively isolated from other such groups and that occupies a specific niche in nature (following Mayr, 1982). An evolutionary species is a single lineage of ancestor-descendant populations that maintains its own identity from other such lineages, that fits into its own ecological niche, and that has a unique evolutionary history (Simpson, 1961; Grant, 1981; Wiley, 1981). It thus differs from the biological species concept in that it is equally applicable to both sexually and asexually reproducing organisms. Under both the biological and the evolutionary species concepts, genetic discontinuities between sister species are thought to arise stochastically following speciation. It is assumed that as time passes, the two diverge progressively in a suite of morphological, physiological, and ecological attributes. Although most botanists espouse an evolutionary species concept in their theoretical writings, in their classifications they often recognize only species that have distinctive structural characters by which the taxa can be identified. In so doing, they are employing the morphological species concept of their

Two Moonworts of the Rocky Mountains; Botrychium hesperium and a New Species Formerly Confused with It

The taxonomy of western North American botrychiums still needs much research. Interpretations of the past were based largely upon scanty and poorly prepared collections. For over 30 years only two B. matricariifolium-like moonworts have usually been accepted for this region-B. boreale subsp. obtusilobum (Rupr.) Clausen and B. matricariifolium subsp. hesperium Maxon and Clausen (Clausen, 1938). As to the former, we conclude that the western North American plant is not closely related to B. boreale, as will be discussed in a monograph of this genus currently in preparation. The correct name for taxon obtusilobum is B. pinnatum St. John (Fig. 1, a-g). Taxon hesperium also proves to be a distinct species, readily distinguished from B. matricariifolium A. Br. subsp. matricariifolium, which occurs in North America only east of the Great Plains (Fig. 2, h-n). With our recent opportunity to investigate large populations of these plants in the field in numerous localities, we are now confident of the distinctness of not only B. pinnatum and B. hesperium, but of a third element as well, which is described here for the first time. It is no surprise to discover a new species related to B. hesperium in western North America, where the rate of endemism among moonworts is the highest in the world. With some ten out of 14 of the described and undescribed species known only there, western North America is clearly the metropolis for this subgenus (Botrychium subg. Botrychium). Using primarily the sterile lamina as a basis, we

Complex Venation Patterns in the Leaves of Selaginella: Megaphyll-Like Leaves in Lycophytes

Venation patterns of the leaves of two lycophytes, Selagiella adunca and Selaginella schaffneri, do not fit the definition of microphylls as having a single, unbranched vein. Although S. adunca has a simple pattern, S. schaffneri has a complexity matching that of many megaphylls, with numerous branching veins. The veins of S. schaffneri undergo an average of 13 branchings (range, 8 to 21), and reticulation between veins is frequent. The discovery of this radical departure from the familiar microphylls of lycophytes indicates that complex venation patterns in leaves do not necessarily arise from fusion of whole branches. The microphyll may not be as structurally stable as formerly believed.

A new natural hybrid in the appalachian asplenium complex and its taxonomic significance

A new spleenwort hybrid, Asplenium pinnatifidum×trichomanes, from southern Illinois is nicely intermediate in morphology between the parents, and shows no pairing of its genomes: two sets of chromosomes from A.×pinnatifidum and one from A. trichomanes. Taxonomically the cross is significant for its bearing on the interpretation of the taxon A. stotleri Wherry, previously believed to have originated from the same parents. New studies of A. stotleri based upon materials from the now extinct type colony in West Virginia, and from a newly discovered extant colony in Arkansas, show clearly that this taxon is not the same as A. pinnatifidum×trichomanes. Comparisons with A.×bradleyi D. C. Eaton (the tetraploid of A. montanum×platyneuron) indicate that the taxon A. stotleri is similar in all respects except for its more rounded segments. Asplenium stotleri is therefore reinterpreted as a synonym of A.×bradleyi, of which it is regarded as a slightly differentiated local form.

Another Nothospecies in the Appalachian Asplenium Complex

Based on three endemic diploid spleenwort species-mountain spleenwort, Aspienium montarum Willd., ebony spleenwort, A. platyneuron (L.) B.S.P.; and walking fern, A. rhizophyllum L-a hybrid polyploid system of great complexity has developed, involving not only the interactions of these ferns but also more widespread taxa such as wall rue, A. ruta-muraria L.; forked spleenwort, A. septentrionale L.; and maidenhair spleenwort, A. trichomanes L. These hybrids are often of great interest because they combine widely different morphologies, producing striking intermediates. Recently Thomas N. Morgan of Carmel, New York, has turned up some unusual natural hybrids during his studies of the spleenworts in the Harpers Ferry region of Maryland and adjacent Virginia and West Virginia. Included is the very distinctive new one described here, which we attribute to the combination of A. platyneuron with A. ruta-muraria. Asplenium x morganii W. Wagner, nothosp. nov. Folia partim dimorpha, usque ad 10.5 cm alta; petiolus et pars proximalis rhachidis atrobrunneae; lamina bipinnata, anguste deltoidea, pinnis basalibus usque ad 1.7 cm longis; pinna terminalis pinnatifida, usque ad 0.9 cm longa; pinnae laterales et pinnulae stipitibus angustis usque ad 1.5-2.0 mm longis; apices pinnatifidi pinnarum usque ad 6 mm longi; sori 0.5-1.5 mm longi indusiis tenuibus denticulatis; chromosomatum numerus 3x = 108,