A Study of Spatial Features of Clones in a Population of Bracken Fern, Pteridium Aquilinum (Dennstaedtiaceae)

Abstract

Allozymes were used to study the spatial attributes of clones (genets) comprising a population of Pteridium aquilinum (L.) Kuhn var. latiusculum (Desv.) Underw. ex Heller (bracken fern) in the Appalachian Mountains of Virginia. Ramets (individual leaves) were sampled at intervals of 165 m (or less in some cases) and genotyped for six polymorphic isozyme loci to produce a map depicting the spatial patterning of genets. Forty-five distinct genotypes were detected, 14 of which were sampled more than once, five of these more than four times. Genotype proportions at all loci except Pgm-1 conformed to Hardy-Weinberg expectations. Estimation of allele frequencies in the population used a "round-robin" approach that removed any upward bias for rare alleles that distinguish genets. Based on these allele frequencies, the probability that each genotype could arise independently and be sampled was calculated. Some genotypes represented by widely separated ramets had very low probabilities of re-encounter, documenting fragmentation of widespread genets. Coarse-scale mapping indicated a population consisting of many small genets and a few very large ones (up to 1,015 m across). The larger genets tended to be irregular in shape, fragmented, and overlapping. Fine scale mapping of individual fronds in spatially discrete patches of ramets revealed extensive intergrowth of genets, indicating that P. aquilinum exhibits a "guerrilla-type" clonal morphology.

The relative importance of sexual reproduction versus clonal spread in an aridland bunchgrass

“…Hardy-Weinberg equilibrium was assumed (see Results) in the calculation of ISSR allele frequencies used in estimating H e . The probability of occurrence of a multilocus ISSR genotype (assuming no genetic linkage) was determined following Parks and Werth (1993) and Montalvo et al (1997).…”

“…Allozymes (reviewed in Ellstrand and Roose 1987; see also Parks and Werth 1993;Montalvo et al 1997;Mayes et al 1998;Pappert et al 2000), anonymous DNA markers (Hsiao and Rieseberg 1994;Stewart and Porter 1995;Stiller and Denton 1995;Steinger et al 1996;Olfelt et al 1998;Suzuki et al 1999;Corradini et al 2002) and a combination of both methods (Waycott 1995;Ayres and Ryan 1997;Esselman et al 1999;Ge and Sun 1999) have been effectively used in studies of clonal plant populations. Molecular methods are also valuable tools for identifying levels of genetic variation within and among plant populations, providing information that can be used to infer their reproductive systems and demographic histories.…”

Intra-clonal variation and a similarity threshold for identification of clones: application to Salix exigua using AFLP molecular markers

“…They found a mean value of 0.17 for all 21 species. In other studies Pornon et al (2000) found a PD of 0.16 to 0.18 in Rhododendron, while Suyama et al (2000) found 0.43 for dwarf bamboo and Parks and Werth (1993) calculated a value of 0.51 for bracken fern. In this study we calculated a PD value of 0.22.…”

Comparison of phenotypic and genetic clone delineation in quaking aspen, Populus tremuloides

“…Fig. 6) Trees encounter of a specific genotype by sexual reproduction in a random mating population was calculated as P se = 1-(1 -P gen ) N , where N is the number of distinct genets (Parks and Werth 1993). The area covered by each genet (n C 11) was measured in Adobe Reader version XI based on the plot maps.…”

“…In order to assess the accuracy of genetic clonal identification, genotype probability was calculated as P gen = ( Q p i )2 h , where p i is the frequency of each allele in the multi-locus genotype, and h is the number of heterozygous loci, which gives the probability of two ramets that belong to different genets having the same genotype by chance (Parks and Werth 1993;Sydes and Peakall 1998). In addition, the probability of a second Leaf length ratio LR Leaf length from the leaf base to the widest part of the leaf divided by leaf length from the widest part of the leaf to the leaf tip (suppl.…”