Inbreeding and homozygosity in the fern, Ceratopteris pteridoides (Hooker) Hieronymus (Parkeriaceae)

Abstract

Ceratopteris pteridoides is an inbreeding species. Intralocus homozygosity is deduced from the almost total absence of genetic load (recessive deleterious and lethal genes) in sporophytes from natural populations, and from gametangial sequences which indicate intragametophytic selfing. This mating system and the profound capacity of the species for vegetative reproduction, coupled with the small size and geographical isolation of many populations, strongly support the hypothesis of individual homozygosity. However, polymorphism is exhibited both within and between populations in specific, genetically mediated, gametophytic characteristics. The population genetic structure of C. pUridoidcs is similar to other inbreeding species.

Characterization and genetic analysis of antheridiogen-insensitive mutants in the fern Ceratopteris

“…and C. thalictroides (L.) Brongn. have documented substantial variations in the response of different strains to both population dependent and supplemented antheridiogen (Lloyd C(r IVarne, 1978;Warne & Lloyd, 1981;Klekowski, 1970;Schedlbauer & Klekowski, 1972;Schedlbauer, 1974). Similar types of variable responses have been reported for other fern taxa, including Sudleria (Blechnaceae) (Holbrook-Walker gL Lloyd,197 1 ), Bommeria (Polypodiaceae) (Haufler & Gastony, 1978), Blechnum spicant (L.) J.…”

Genetic load and soft selection in ferns

“…Some species have a measurable genetic load of lethal and deleterious mutations whereas other species are essentially free of such mutations (Warne and Lloyd, 1981) in inbreeding tests. Although the causes of genetic load in homosporous ferns are not clear (mutational, heterotic, other), given that load occurs, it is possible to show how the life cycle influences the level of load.…”

Mutational Load in Clonal Plants: A Study of Two Fern Species

“…Because of these two attributes (free-living gametophytes and intragametophytic selfing), the ferns are very useful organisms in genetic load studies (Klekowski, 1979). Many different fern species have been investigated for genetic load (Klekowski, 1970(Klekowski, , 1973Ganders, 1972;Verma and Kapur, 1972;Holbrook-Walker and Lloyd, 1973;Lloyd, 1974aLloyd, , 1974bLloyd, , 1974cLloyd and Gregg, 1975;Saus and Lloyd, 1976;Lloyd and Warne, 1978;Cousens, 1979;Khare and Kaur, 1979;Masuyarna, 1979;Schneller, 1979;Warne and Lloyd, 1981). Load levels vary greatly between species, the highest load levels documented occur in Osmunda regalis with an average of 2.39 recessive sporophytic lethals per zygote (Klekowski, 1982b) to a low of .006 recessive sporophytic lethals per zygote in Ceratopteris pteridoides (calculated from Warne and Lloyd, 1981).…”