Gemmiferous Fern Gametophytes—vittariaceae

Abstract

Approximately 10 % of all fern species reproduce vegetatively in the gametophytic stage by means of gemmae. Gametophyte morphologies in these species depart radically from the commonly figured heart‐shaped type and expand considerably the opportunities for physiological and morphological studies utilizing fern gametophytes. Original observations on four species of vittarioid ferns are presented and compared with earlier observations on gametophytes of this family. Vittarioid gametophytes grow from a discontinuous marginal meristem which results in a much branched thallus of indeterminant growth. Aerial branches of the gametophytes terminate in gemma production, which proceeds by a regular and predictable sequence of events. The sequence may differ considerably among species but is remarkably constant within species. Archegonia are produced on short ventral branches, and antheridia are produced primarily on germinating gemmae. Ananthacorus angustifolius is the only known member of the Vittariaceae which does not produce gemmae and is considered to represent the primitive condition. In this species antheridia are scattered over the thallus, suggesting that a change in the mode of control of antheridium production may have evolved in the family along with gemma production.

Sexual conflict and the alternation of haploid and diploid generations

“…This may be an indirect consequence of sporophytes being more effective than gametophytes as colonizers of new space. About 10% of pteridophyte species, however, have gametophytes that reproduce vegetatively via gemmae (Farrar 1974). In these taxa, maternal gametophytes are faced with a question of how much to invest in asexual versus sexual reproduction.…”

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

“…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.…”

“…Fée 1852aFée , 1852bBenedict 1907;Shaffer-Fehre 1996). Little is known about the gametophytes of the Vittariaceae but those of the few species that have been investigated (actually 18 species; 12 New World; 6 Old World) are ribbon-shaped and perennial (gametophytes of most fern species are heart-shaped and short-lived) and all, except one species, bear filamentous gemmae (also rare in ferns) with which they can propagate themselves asexually (Atkinson & Stokey 1964;Nayar & Kaur 1969, 1971Farrar 1974Farrar , 1985Emigh & Farrar 1977;Sheffield & Farrar 1988). The morphology and ecology of the gametophytes of Vittariaceae are discussed in more detail later in this paper.…”

Phylogenetic Placement of Rheopteris and the Polyphyly of Monogramma (Pteridaceae s.l.): Evidence from rbcL Sequence Data

“…Vittarioid gametophytes, on the other hand, are indeterminate and ribbon-like. They can be exceptionally long-lived (years) and can also reproduce asexually via propagules called gemmae (Atkinson and Stokey 1964;Farrar 1974Farrar , 1985. In addition, Adiantum and vittarioids occupy two dramatically different niches.…”