Population structure, genetic diversity, and clone formation in Quercus chrysolepis (Fagaceae)

Abstract

Stands of canyon live oak (Quercus chrysolepis, Fagaceae) are maintained for fuelwood, fire management, recreation, and as habitat for wildlife. Information about the link between the oak's reproductive ecology and its extent of genetic diversity is important in developing land management policies that will maintain the long-term viability of populations. Basal sprouting is the primary means of reproduction following fire or cutting, and stands frequently include groups of visibly connected trees in a clustered distribution that suggests cloning. We determined the extent to which clusters of trees were clonal and defined the spatial pattern and diversity of genotypes for six populations across nearly the entire east-west extent of the San Bernardino Mountains in southern California. We mapped over 100 trees at each of five sites and genotyped each tree for allozymes at seven polymorphic loci. We identified clones using these multilocus genotypes and detected an average of 34.4 ± 7.3 (SD) clones per site, most of which had unique genotypes. In general, clustered trees belong to single clones and most clones consist of few trees (mean = 3.4 ± 0.6 trees per clone). However, clone size increased significantly with increased individual heterozygosity, suggesting that selection may favor highly heterozygous clones. Clonal diversity and evenness were high relative to reports for most other clonal species; an average of 97% of clones had distinct genotypes, and Simpson's index of diversity averaged 0.95 ± 0.02. Population genetic analyses of 319 clones from six sites revealed high genetic diversity within sites (mean HS = 0.443). Only a small proportion of the total genetic diversity was explained by variation among sites (mean GST = 0.018), which is consistent with high gene flow among sites (Nm = 9.5). We found no significant substructure among plots within sites, and fixation indices within sites were generally small, suggesting that either little inbreeding occurs, and/or few inbred progeny survive. However, spatial autocorrelation analysis of clones indicated fine-scale genetic structure at distances under 4 m, possibly due to limited seed dispersal. Our data suggest that guidelines for seed collection of canyon live oak for use in restoration can be specified in a manner similar to that recommended for conifer species within the region studied.

Ecological and genetic effects of cutting in an Alnus trabeculosa Hand.-Mazz. (Betulaceae) population

“…Previously reported ranges of individuals or clumps of ramets include 2-4 m in Fagus japonica (Kitamura et al, 1992), 4 m in Quercus chrysolepis (Montalvo et al, 1997), 8 m in Fagus grandifolia (Jones and Raynal, 1987), and areas of 50 m 2 in Thujopsis dolabrata (Hashimoto et al, 1999) and up to 43 ha in Populus tremuloides (Kemperman and Barnes, 1976). Thus, the A. trabeculosa range found in this study was similar to those of F. japonica and Q. chrysolepis.…”

Genetic neighbourhood of clone structures in eelgrass meadows quantified by spatial autocorrelation of microsatellite markers

“…marina clones show spatial fragmentation (clone structure (b) Figure 2 and Table 1). Spatially separated groups of trees with identical genotype also indicated such a structure to be present in Quercus chrysolepsis (Montalvo et al, 1997). In the latter study, it was probably responsible for values of coancestry too high to be explained solely by limited dispersal.…”

“…Our values from the analysis including all samples range from 0.028 to 0.161 for the 2 m interval (Table 1). For the same distance, autocorrelation values from Louisiana iris hybrid populations showed a range of E0-0.2 (Burke et al, 2000) and for populations of canyon life oak E0.38-0.42 and 0.25 excluding multiple samples per genet (Montalvo et al, 1997). For the marine environment, Coyer has reported significant coancestry values of 0.060-0.092 for Z. noltii (Jim Coyer, unpublished data) at the 2 m scale and JL Olsen reported significant coancestry of 0.25 for Ascophyllum sp on a scale of 40 cm-1 m (Jeanine L Olsen, unpublished data).…”

“…First, in a study of allozyme polymorphism in a stand of Quercus chrysolepsis, Montalvo et al (1997) found that compared to an analysis including all possible joins (clonal structure (a) Table 1), significant positive autocorrelation of coancestry over the shortest distance class (2 m) decreased after excluding joins between clone mates (clonal structure (c) Table 1). Since absolute values were still substantially higher than expected for full and halfsib progeny, they assumed that a large amount of the genetic structure, which occurs over short distances, is due to clonal growth and might have been caused by scoring errors and/or somatic mutations.…”

Fine-Scale Genetically Based Differentiation of Life-History Traits in the Perennial Shrub Lupinus Arboreus

“…Outcrossed, insect-pollinated plants are predicted to have moderate to high gene flow (Loveless and Hamrick 1984; but see Hogbin et al 1998). Montalvo et al (1997) found that canyon live oak similarly lacked genetic subdivision and showed high levels of gene flow between populations more distantly separated than ours. In our system, seeds from Bayshore, the Dunes, and Mussel Point are likely to be genetically similar because of very low F ST -values.…”