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Sceptridium dissectum, the most variable North American grapefern species, demonstrates variation in degree of blade dissection, blade color, pinnule shape, and pinnule margins. Historically, various morphologies have been included within S. dissectum. For example, Clausen's monograph recognized five infraspecific taxa in S. dissectum, of which only the morphologies of variety dissectum and obliquum are currently retained. However, the taxonomic status of the two varieties has been debated. We used ISSR (Inter-Simple Sequence Repeat) markers to assess the genetic distinctness of S. dissectum var. dissectum and var. obliquum in 17 Ohio populations. Five ISSR primers generated 69 reproducible loci. In UPGMA analyses and AMOVA, S. dissectum var. dissectum individuals did not cluster separately from var. obliquum individuals, nor did individuals from the same population cluster together. ISSR markers revealed levels of population genetic structure in S. dissectum similar to levels detected by previous isozyme investigations. Our results concur with recent treatments of S. dissectum that do not formally recognize infraspecific taxa, and may bring into question current species circumscriptions in Sceptridium. We illustrate the use of ISSR markers for examining taxonomic boundaries in Sceptridium.
The spores of Diphasiastrum sitchense germinate in the dark on a nutrient medium containing inorganic nutrients and glucose. Dark-grown prothalli develop into white, carrot-shaped gametophytes with a tapering base, constricted neck, and gametangial cap. The antheridia are large and sunken, and the archegonia have long necks with numerous neck canal cells. The tapering base has a zone of radially elongated cells that is comparable to the inner mycorrhizal zone of Diphasiastrum gametophytes from nature. Although possessing few derived sporophytic characters, D. sitchense has a typical carrot-shaped, Diphasiastrum gametophyte.
The gametophyte development of Lomagramma sorbifolia (Willd.) Ching has been studied. Spore germination is of the polar and Vittaria-type. Prothallial development is either of the Adiantum-type, or more rarely of the Drynaria-type. This Adiantum-type is unusual among most of the other genera of the lomariopsidoid ferns. The Drynaria-type of gametophyte development is more characteristic of the lomariopsidoid ferns. Older prothalli are cordate and naked throughout. Early development seems to be somewhat plastic and perhaps of limited usefulness as a character for systematic purposes.
While working on the taxonomy of Ctenitis (Tectariaceae) from Brazil we detected two species that needed to have combinations in that genus: Ctenitis abyssi (Sehnem) Salino & Morais comb. nov. and Ctenitis laetevirens (Rosenst.) Salino & Morais comb. nov. The first species is similar to Ctenitis nigrovenia (H. Christ) Copel., but differs mainly by the short-creeping stem and ctenitoid hairs on the segment margins. Ctenitis laetevirens is related to C. submarginalis (Langsd. & Fisch) Ching, but differs by having pinnae long-petiolulate, ctenitoid hairs absent on the segment margins, the abaxial side of costae, costule and veins, and by having exindusiate sori.
The typically lithophilic Polypodium appalachianum was discovered as a canopy epiphyte 35 to 40 m above ground on a horizontal branch of a champion-size Liriodendron tulipifera in the Great Smoky Mountains National Park. Occurring along with this first documentation of P. appalachianum from the tree canopy was an assemblage of normally terrestrial mosses, an unusual assortment of collembola (springtails), and a flightless proturan insect species previously known only from soil and litter. The distinctive features of this canopy habitat may duplicate some ecological conditions usually found only at ground level, establishing the opportunity for translocating an entire community and providing biologists with new insights on the origin of some epiphytes.