Gametophytic Plasticity among Four Species of Ferns with Contrasting Ecological Distributions

Abstract

The goals of this study were to test the hypothesis that plasticity of life history traits is greater among species with broad ecological distributions than among species with narrow ecological distributions and to determine whether homosporous filicalean fern gametophytes exhibit adaptively meaningful responses to soil substrates. Sporophyte populations of Asplenium platyneuron and Polystichum acrostichoides have broader ecological distributions and were therefore expected to exhibit a greater amount of gametophytic plasticity than either Asplenium rhizophyllum or Diplazium pycnocarpon. Changes in reproductive effort (i.e., gametangia mm-2) were investigated across the four following soil treatments, which represent major edaphic environments on which sporophyte populations of these species occur: stream bank, Pinus strobus canopy, oak forest ridge top, and soil from a lime-bearing rock outcrop. Our results failed to support the "ecological breadth" hypothesis. Three of the four species-A. rhizophyllum, D. pycnocarpon, and P. acrostichoides-exhibited similar amounts and directions of plasticity, with reproductive effort greatest in treatments that were unfavorable to growth; A. platyneuron exhibited the least amount of plasticity. Nevertheless, species-specific patterns in gametophytic size and reproductive effort reflected the distributions of their sporophytic counterparts. Plasticity of size-related reproductive effort may be common among homosporous filicalean fern gametophytes because of their short life spans and limited capacity for vegetative competition.

The reproductive biology of the invasive ferns Lygodium microphyllum and L. japonicum (Schizaeaceae): implications for invasive potential

“…The potential presence of an antheridiogen system may support increased gametophyte densities within an infestation since they have been shown to induce dark germination of spores (Weinberg and Voeller, 1969;Schneller et al, 1990;Haufler and Welling, 1994). The promotion of spore germination would lead to an increase in gametophyte densities, particularly of males (Greer and McCarthy, 1999).…”

“…Under stressful environmental conditions, gametophytes may have a shorter life span. Fern gametophytes that reach sexual maturity quickly would have the greatest chance to produce sporophytes before dying (Greer and McCarthy, 1999). Sexually mature gametophytes of L. microphyllum and L. japonicum were observed within 5 wk of germination.…”

Phenotypic plasticity and biomass allocation pattern in three Dryopteris (Dryopteridaceae) species on an experimental light-availability gradient

“…Odland et al 1990;Tuomisto and Poulsen 1996;Greer et al 1997;Wild and Gagnon 2005) or illumination conditions (e.g. Hill and Silander 2001;Hietz 2001;Proctor 2003;Reudink et al 2005;Saldañ a et al 2005) determine the distribution of fern sporophytes or gametophytes (Hill 1971;Li and Ong 1997;Greer and McCarthy 1999). Considerably less attention has been turned on life-history traits (Cousens et al 1988;Peck et al 1990;Guo et al 2003) and biotic interactions (Hamilton and Lloyd, 1991;Chiou and Farrar 1997;Greer and Curry 2004;Rü nk et al 2004).…”

Do fern gametophytes have the capacity for irradiance acclimation?

“…Gametophytic generation is essential in the fern life cycle, however, very little is known about its ecology and physiology (Greer et al 1999, Johnson et al 2000, Watkins et al 2007a. In fact, to the best of our knowledge this study is the first report to show the carotenoid and tocopherol composition of fern gametophytes.…”