The peculiar life cycles of ferns, as exemplified by cheilanthoid genera, create abundant opportunities for the rapid formation of new taxa as a result of polyploidy and apogamy. Chromosome doubling and conversion from sexual reproduction to apogamy allow otherwise sterile taxa to regain fertility and also impose genetic barriers between hybrids and parental taxa. This "instantaneous evolution" gives rise to species, such as Pellaea lyngholmii, that initially comprise a single individual (the ultimate genetic bottleneck). Such taxa are of significant conservation concern because they represent a vital source of future biodiversity. They may remain rare and geographically restricted for long periods of time and are thus prone to annihilation from development, grazing, and other human-mediated perturbations of the environment. Given appropriate conservation efforts, many such derivative taxa successfully become widely dispersed and relatively abundant, to the extent that they can replace their diploid progenitors. For example, Pellaea glabella ssp. glabella, the common eastern North American tetraploid apomict, apparently was derived through autopolyploidy from the diploid sexual ssp. missouriensis, which presently is known from only five stations in eastern and central Missouri. At each of these five localities, ssp. missouriensis occurs scattered within populations of the more abundant ssp. glabella. From a conservation standpoint, the gradual extinction of a sexual progenitor also results in the loss of genetic information for the species, as the apomictic derivative retains only the subset of genotypic data present in the two individual parental plants. The genetic bottlenecks concomitant with rapid taxon formation and gradual extinction are natural processes. However, they should not be overlooked when evaluating the conservation implications of changing management practices on natural habitats.

Key words: apomixis, cheilanthoid ferns, conservation, polyploidy, population genetics