Problems in the Identity and Origin of the Appalachian Vittaria Gametophyte, a Sporophyteless Fern of the Eastern United States

Abstract

Populations of a fern gametophyte presumed to be of the genus Vittaria occur commonly in the uplands of the southeastern United States. The gametophytes occur on non‐calcareous rock outcrops of various composition in areas which provide continuous moisture and protection from temperature extremes. Gametophytes in these habitats are robust and long lived, frequently forming the dominant vegetation in areas covering several square feet. Reproduction is exclusively vegetative by production of gemmae. Although sex organs are present in most populations, viable sporophytes are never produced. The gametophytes have previously been considered most likely to be V. lineata, which occurs in Florida, but morphological and physiological comparisons do not support that conclusion. Significant differences between Appalachian and Florida gametophytes occur in growth form, growth rate, cold hardiness, sporophyte production, and patterns of gemma production. The distribution of the Appalachian gametophytes correlates with old, unglaciated land masses suggesting antiquity rather than recent introduction. Present evidence favors the interpretation that the Appalachian Vittaria gametophytes either belong to a tropical American species from which they have long been separated, or that they represent a distinct species of which the sporophyte no longer exists.

Retrotransposon Sequence Variation in Four Asexual Plant Species

“…Among the taxa examined in our study, the strongest evidence for ancient asexuality is in Vittaria appalachiana, where patterns of geographical distribution and genetic diversity indicate an age of at least 10 million years (Farrar 1967(Farrar , 1978(Farrar , 1990. A study of allozyme diversity in Vittaria showed V. appalachiana to have no recent origin from or close relation to sexual Vittaria species (Farrar 1985(Farrar , 1990.…”

Considerations for a revision of the fern family Vittariaceae for Flora Malesiana

“…To date, all independent gametophytes to which species names have been assigned (not an easy task -see Farrar (1978) and below) are members of three families; the Hymenophyllaceae, Grammitidaceae and the Vittariaceae, but it is not yet clear whether gametophytic independence is characteristic of these families or of only certain genera or species within them. Currently, independent gametophytes are known: in nine species of the Hymenophyllaceae in four genera (Hymenophyllum, Mecodium, Trichomanes, and Callistopteris); in the Grammitidaceae one species in one genus (Grammitis, Xiphopteris or Micropolypodium, depending on one's view-point); and in the Vittariaceae two species in one genus (Vittaria).…”

“…The reasons for believing this are three-fold: First, all the gametophytes of Vittariaceae for which at least some published morphological data is available (18 species representing the genera Ananthacorus, Anetium, Hecistopteris, Vittaria, Radiovittaria, Haplopteris, Antrophyum, Polytaenium, Scoliosorus, and Vaginularia;see Goebel 1888see Goebel , 1896Britton & Taylor 1902;Troll 1932;Stokey 1951;Atkinson & Stokey 1964;Farrar 1974Farrar , 1978and Crane 1997) are ribbon-shaped with multiple marginal meristems that frequently dichotomize (gametophytes of most fern species are heart-shaped, unless old or damaged, with a single recessed apical notch meristem). These features are consistent with a creeping, branching, mat or weftforming habit and a perennial existence.…”

“…Second, gametophytes of all but one of the 18 species known (the exception being Ananthacorus angustifolius (Sw.) Underw. & Maxon) also produce gemmae by which they can propagate themselves asexually (Goebel 1888 and1896;Troll 1932;Britton & Taylor 1902;Hughes 1971;Emigh & Farrar 1977;Farrar 1974Farrar & 1978Sheffield & Farrar 1988;Crane 1997). Reproduction by gemmae enables the gametophyte generation of any species to maintain a presence (and a particular genotype) in a new area, beyond that currently tolerated by the sporophyte generation, even if the original colonizing gametophyte does eventually die.…”

Distribution patterns of ferns and lycophytes in the Coastal Region of the state of Rio Grande do Sul, Brazil

“…In northeastern United States, gametophytes of the genus Vittaria Sm. can become established in certain environments, form extensive populations through asexual reproduction by apogamy and persist during prolonged frost while the sporophytes do not survive, dying at the beginning of their development (Farrar 1978). These reports were also corroborated by Sato & Sakai (1980) for many Asiatic species, where the gametophytic phase can resist temperatures below -40°C, while their sporophytes do not survive in temperatures below 0°C.…”