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

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. pteridoides is similar to other inbreeding species.