Watanox Sahashi Outcrossing Rates

1 Some studies employed Gst Ranges of Fst and Nm are shown only for studies that calculated population pairwise values. 2 For these species one or more pairwise values of Fst were 0, thus calculations of Nm were not possible the reported mean and maximum extent of the range of Nm do not include information from those pairs of populations. A mixed-mating system is one wherein neither outcrossing nor inbreeding predominates (e.g., see Lande and Schemske, 1985). Although rare compared to the...

Conventional alternation of generations

The phenomena of apogamy and apospory, although easily induced and in some taxa the norm, have little impact on alternation of generations in the vast majority of lycophytes and ferns. The life cycle shown in Figure 2.2 shows the structures more conventionally concerned with alternation of generations in bracken fern, and which we can use as the basis of a consideration of the process in non-apogamous lycophytes and ferns. The reason for choosing bracken is that we know more about this fern...

Evolution of the nuclear genome of ferns and lycophytes

BARKER, LOREN H. Analyses of gene expression and function, genetic networks, population polymorphisms, and genome organization at the whole genome level have enabled research on previously intractable questions (reviewed in Wolfe and Li, 2003). Among plant lineages, genomic approaches have been most widely applied in the angiosperms, where significant resources have been developed. Angiosperm studies utilizing genome scale analyses have made several important...

Gametophyte ecology

FARRAR, CYNTHIA DASSLER, JAMES E. WATKINS, JR., AND CHANDA SKELTON Seed plant ecologists would find incredulous a proposal to study the ecology of a species that did not include critical examination of all aspects of recruitment in the field, relying instead on laboratory studies of seed germination, seedling growth and mortality, etc. Yet students of fern and lycophyte ecology are limited to data on gametophyte growth and reproduction collected almost exclusively from laboratory...

Obligate apogamy

Dryopteris affinis ssp. affinis needs no prompting to generate sporophytes apogamously, but we know that their induction is stimulated by auxins and gibberellins (Menendez et al., 2006). In common with many other apogamous species, this taxon is widely distributed and very successful. Bommeria pedata, for example, has a considerably more extensive distribution than most of its sexually reproducing congeners (Gastony and Haufler, 1976). It is usually held that the reason for this success is that...

Induction of chloroplast movement

When part of a long protonemal cell (Yatsuhashi et al., 1985) or a two-dimensional gametophyte (Kagawa and Wada, 1994) was irradiated with a red or blue light microbeam (either slit, spot, or rectangular in shape, from a few micrometers to 10 or 15 m in diameter) at a weak fluence rate (e.g., 1 W m-2), chloroplasts outside the beam moved towards the light irradiated area. When the fluence rate of blue light was increased above 10 W m-2, chloroplasts moved away from the beam. Red light does not...

Spore release and dispersal

Discuss The Spore Dispersal Ferns

Once spores have been formed, it stands to reason that they can only effect the next stage in the alternation process if they are released, dispersed, and alight somewhere conducive to germination and gametophyte growth. This presents a huge challenge for propagules that lack vectors which target such sites (cf. flowering plants with insect pollinators). There is scant evidence for productive interactions between animal vectors and fern spores, but very little study of this seems to have been...

Evolution of roots

Nothing is known about the evolutionary origin of roots. Recent molecular genetics shows that angiosperm RAMs and SAMs are controlled by similar mechanisms to maintain stem cell populations, suggesting that roots may be derived from a developmental program associated with the SAM (references cited in Friedman et al., 2004), but genetic data are lacking for fern and lyco-phyte roots. Roots are similarly endogenous in ferns and lycophytes, regardless of whether they branch endogenously (ferns) or...

Restoration

The role of natural disturbances at multiple scales has been important for fern and lycophyte regeneration processes and in maintenance of fern and lycophyte diversity Arens and Baracaldo, 1998 Page, 2002 . Ferns can also dominate degraded sites and impose barriers for tree regeneration by competing for soil moisture, nutrients, and light George and Bazzaz, 1999 Ashton et al., 2001 Slocum et al., 2004 . Slocum et al. 2004 found that clearing fern thickets caused rapid recruitment of woody...

Three evolutionary radiations ofhomosporous leptosporangiate ferns

Paleobotanical studies reveal a pattern of leptosporangiate evolution in which there have been three major pulses of evolutionary radiation Rothwell, 1987 . Diversity among the Paleozoic fossils is summarized by Stewart and Rothwell 1993 , whereas the Mesozoic and Cenozoic records of ferns recently have been compiled by Skog 2001 and Collinson 2001 respectively. Pulses of filicalean evolution were first recognized by Lovis 1977 , who concluded correctly that the species richness of filicaleans...