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  • 1
    Electronic Resource
    Electronic Resource
    Patterns of Differentiation in Wiregrass (Aristida beyrichiana): Implications for Restoration Efforts (1998)
    Cambridge, MA, USA : Blackwell Science Inc
    Restoration ecology 6 (1998), S. 0 
    Details
    ISSN: 1526-100X
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Aristida beyrichiana (wiregrass) is increasingly being planted in restoration projects across the southeastern coastal plain, with little focus on genetic differences among populations across the region. Local and regional population differentiation for establishment and growth traits were examined in common garden and reciprocal transplant experiments. Seeds from up to 20 plants from each of seven populations were collected in northern and central Florida sites that encompassed gradients of soils, hydrology, and temperature. Reciprocal seed transplants using three of the common garden populations were conducted in two consecutive years. In the common garden, significant population differences were seen in seed weight, seedling emergence and survival, tiller height, number of tillers, the relationship between tiller number and tiller height, and flowering. Variation among maternal families was seen in tiller number and in the relationship between tiller number and tiller height. The reciprocal transplant study did not detect either local adaptation to sites of origin or consistent superiority of one source population or planting site in seedling establishment. These results suggest that the probability of seedling establishment is primarily dependent on environmental conditions rather than genetic differences. Genetic variation for traits related to fitness (e.g., tiller number) may be retained within populations because phenotypically plastic growth responses of seedlings to environmental variation buffer genetic variation against the action of selection. But despite the lack of evidence for genetic influences on initial establishment in wiregrass, our common garden study suggests genetic differences among populations. This result, when combined with previous results indicating local adaptation in later life stages of wiregrass, suggests that restoration efforts involving this species should use local seed sources from sites with similar soil and hydrological conditions.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1526-100X.1998.00627.x
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  • 2
    Electronic Resource
    Electronic Resource
    Restoration Biology: A Population Biology Perspective (1997)
    Oxford, UK : Blackwell Publishing Ltd
    Restoration ecology 5 (1997), S. 0 
    Details
    ISSN: 1526-100X
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: A major goal of population biologists involved in restoration work is to restore populations to a level that will allow them to persist over the long term within a dynamic landscape and include the ability to undergo adaptive evolutionary change. We discuss five research areas of particular importance to restoration biology that offer potentially unique opportunities to couple basic research with the practical needs of restorationists. The five research areas are: (1) the influence of numbers of individuals and genetic variation in the initial population on population colonization, establishment, growth, and evolutionary potential; (2) the role of local adaptation and life history traits in the success of restored populations; (3) the influence of the spatial arrangement of landscape elements on metapopulation dynamics and population processes such as migration; (4) the effects of genetic drift, gene flow, and selection on population persistence within an often accelerated, successional time frame; and (5) the influence of interspecific interactions on population dynamics and community development. We also provide a sample of practical problems faced by practitioners, each of which encompasses one or more of the research areas discussed, and that may be solved by addressing fundamental research questions.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1526-100X.1997.00542.x
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  • 3
    Electronic Resource
    Electronic Resource
    Centaurea solstitialis Invasion Success Is Influenced by Nassella pulchra Size (2005)
    Oxford, UK; Malden, USA : Blackwell Science Inc
    Restoration ecology 13 (2005), S. 0 
    Details
    ISSN: 1526-100X
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Replacement of perennial grasses with non-native annual grasses in California's Central Valley grasslands and foothills has increased deep soil water availability. Yellow starthistle (Centaurea solstitialis), a deep-rooted invasive thistle, can use this water to invade annual grasslands. Native perennial bunchgrasses, such as Purple needlegrass (Nassella pulchra), also use deep soil water, so there is an overlap in resource use between N. pulchra and C. solstitialis. Restoration of N. pulchra to annual grasslands could result in strong competitive interactions between N. pulchra and C. solstitialis, which may reduce survival, growth, and reproduction of the invader. The strength of this competitive interaction can increase as N. pulchra plants mature, increase in size, and develop more extensive root systems. We studied how the size of N. pulchra affected the success of C. solstitialis invasion over 2 years. We allowed C. solstitialis seed to fall naturally into plots containing N. pulchra plants. For each plot, we measured the number of C. solstitialis seedlings and mature plants, as well as C. solstitialis biomass and seedhead production. In both years of the study, C. solstitialis number, biomass, and seedhead production declined significantly as N. pulchra size increased. However, even C. solstitialis grown with the largest N. pulchra plants produced some seed, especially during the higher rainfall year. We conclude that restoration plantings with larger, established N. pulchra plants will be more resistant to invasion by C. solstitialis than young N. pulchra plantings, but site management must continue as long as a C. solstitialis seed source is present.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1526-100X.2005.00065.x
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  • 4
    Electronic Resource
    Electronic Resource
    Radial Dispersion of Neighbors and the Small-Scale Competitive Impact of Two Annual Grasses on a Native Perennial Grass (2004)
    Oxford, UK; Malden , USA : Blackwell Science Inc
    Restoration ecology 12 (2004), S. 0 
    Details
    ISSN: 1526-100X
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: In California's Mediterranean type grasslands, native perennial grasses such as Nassella pulchra are surrounded by introduced annual species and these annuals are thought to have displaced natives through much of their range. Amongst other invaders, two grasses Lolium multiflorum and Bromus hordeaceus, commonly dominate portions of the grassland with potential for N. pulchra restoration. We hypothesized that competitor species differences and small-scale gaps (150 cm2) could be important determinants of N. pulchra survival and performance on these sites. Lolium multiflorum and B. hordeaceus were planted in 20 cm diameter circular plots at a constant rate of 1 seed per cm2 surrounding newly transplanted N. pulchra plants. Nassella pulchra showed no significant effect of the species of competitor or from the distribution of the competitors. Both interspersion of patches of bare ground and separation of competitors into patches did not increase N. pulchra pre-dawn water potential, basal area change, number of seeds produced, or average weight of seeds. The presence of L. multiflorum was associated with a decrease in N. pulchra survival compared with plots with only B. hordeaceus. Plants with increases in basal area of less than 0.75 cm2 during the growing season had 74% mortality compared with no mortality in plants with more growth. However, initial N. pulchra plant size was not a good predictor of mortality. Limiting competition from annuals may increase survival of N. pulchra plantings, but 60% of the plants survived for at least 1 year, despite being transplanted into soil containing substantial annual grass seed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1061-2971.2004.00266.x
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  • 5
    Electronic Resource
    Electronic Resource
    Genetic Structure and Gene Flow in Elymus glaucus (blue wildrye): Implications for Native Grassland Restoration (1996)
    Oxford, UK : Blackwell Publishing Ltd
    Restoration ecology 4 (1996), S. 0 
    Details
    ISSN: 1526-100X
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Interest in using native grass species for restoration is increasing, yet little is known about the ecology and genetics of native grass populations or the spatial scales over which seed can be transferred and successfully grown. The purpose of this study was to investigate the genetic structure within and among populations of Elymus glaucus in order to make some preliminary recommendations for the transfer and use of this species in revegetation and restoration projects. Twenty populations from California, Oregon, and Washington were analyzed for allozyme genotype at 20 loci, and patterns of variation within and among populations were determined. Allozyme variation at the species level was high, with 80% of the loci polymorphic and an average expected heterozygosity (an index of genetic diversity) of 0.194. All but two of the populations showed some level of polymorphism. A high degree of population differentiation was found, with 54.9% of the variation at allozyme loci partitioned among populations (Fst= 0.549). A lesser degree of genetic differentiation among closely spaced subpopulations within one of the populations was also demonstrated (Fst= 0.124). Self-pollination and the patchy natural distribution of the species both likely contribute to the low level of gene flow (Nm= 0.205) that was estimated. Zones developed for the transfer of seed of commercial conifer species may be inappropriate for transfer of E. glaucus germplasm because conifer species are characterized by high levels of gene flow. Limited gene flow in E. glaucus can facilitate the divergence of populations over relatively small spatial scales. This genetic differentiation can be due to random genetic drift, localized selective pressures, or both. In order to minimize the chances of planting poorly adapted germplasm, seed of E. glaucus may need to be collected in close proximity to the proposed restoration site.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1526-100X.1996.tb00101.x
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  • 6
    Electronic Resource
    Electronic Resource
    The Mark of Zorro: Effects of the Exotic Annual Grass Vulpia myuros on California Native Perennial Grasses (2000)
    Boston, MA, USA : Blackwell Science Inc
    Restoration ecology 8 (2000), S. 0 
    Details
    ISSN: 1526-100X
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Native perennial grasses were once common in California prairies that are now dominated by annual grasses introduced from Europe. Competition from exotics may be a principal impediment to reestablishment of native perennial grasses. Introduced annual grasses, such as Vulpia myuros (zorro fescue), are often included with native perennial species in revegetation seed mixtures used in California. To examine the potential suppressive effect of this graminoid, we evaluated the growth and performance of a mixture of California native perennial grasses and resident weeds when grown with varying densities of V. myuros. The annual fescue exhibited a strongly plastic growth response to plant density, producing similar amounts of above-ground biomass at all seeding densities. Perennial grass seedling survival and above- ground biomass decreased and individuals became thinner (i.e., reduced weight-to-height ratio) with increasing V. myuros seeding density. V. myuros also significantly suppressed above-ground biomass and densities of weeds and had a more negative effect on weed densities than on native perennial grass densities. Biomass of native grasses and weeds was not differentially affected by increasing densities of V. myuros. Overall, because V. myuros significantly reduced the survival and performance of the mixture of native perennial grasses and this effect increased with increasing V. myuros density, we conclude that including this exotic annual in native seed mixtures is counterproductive to restoration efforts.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1526-100x.2000.80003.x
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  • 7
    Electronic Resource
    Electronic Resource
    “How Local Is Local?”—A Review of Practical and Conceptual Issues in the Genetics of Restoration (2005)
    Oxford, UK; Malden, USA : Blackwell Science Inc
    Restoration ecology 13 (2005), S. 0 
    Details
    ISSN: 1526-100X
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: In plant conservation, restoration (the augmentation or reestablishment of an extinct population or community) is a valuable tool to mitigate the loss of habitat. However, restoration efforts can result in the introduction of novel genes and genotypes into populations when plant materials used are not of local origin. This movement is potentially important because many plant species are subdivided into populations that are adapted to local environmental conditions. Here we focus on genetic concerns arising from ongoing restoration efforts, where often little is known about “How local is local?” (i.e., the geographic or environmental scale over which plant species are adapted). We review the major issues regarding gene flow and local adaptation in the restoration of natural plant populations. Finally, we offer some practical, commonsense guidelines for the consideration of genetic structure when restoring natural plant populations.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1526-100X.2005.00058.x
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  • 8
    Electronic Resource
    Electronic Resource
    Evidence of spatial genetic structure in a California bunchgrass population (1997)
    Springer
    Oecologia 112 (1997), S. 333-339 
    Details
    ISSN: 1432-1939
    Keywords: Key words Conservation ; Nassella(Stipa) pulchra ; Population genetics ; RAPD ; Spatial scale
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract We investigated the scale of genetic variation of purple needlegrass (Nassella pulchra), a species commonly used in California for grassland restoration. Common garden and field data revealed evidence of genetic differentiation between two intermixed microhabitats characterized by differences in soil depth and community composition. We assessed the genetic variation within a single population using randomly amplified polymorphic DNA (RAPD) data collected from clusters of five individuals in 40 locations. We found no evidence for genetic structure at the whole population level. At smaller spatial scales, however, we found strong evidence that genetic subdivision of the population occurs at the level of the maternal neighborhood. We suggest that the interaction between widespread pollen dispersal and restricted seed dispersal may be the primary factor generating these results; panmictic pollen dispersal will make detection of genetic patterning difficult at larger spatial scales while limited seed dispersal will generate local genetic structure. As a result, the detection of population genetic structure will depend on the spatial scale of analysis. Local selection gradients related to topography and soil depth are also likely to play a role in structuring local genetic variation. Since N. pulchra is widely used in California in grassland and woodland habitat restoration, we suggest that, as a general rule, care should be exercised in transferring germplasm for the purposes of conservation when little is known about the within-population genetic subdivision of a plant species.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004420050317
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  • 9
    Electronic Resource
    Electronic Resource
    Ecological genetics of Bromus tectorum (1991)
    Springer
    Oecologia 88 (1991), S. 77-83 
    Details
    ISSN: 1432-1939
    Keywords: Bromus tectorum ; Ecological genetics ; Genetic differentiation ; Heritability estimates ; Invading species
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary An understanding of how genetic differentiation and phenotypic plasticity may interact to promote the spread of an introduced species requires information on the hierarchical distribution of genetic variation within the species in its new range. For example, a lack of genetic variation within marginal populations of an introduced species may slow its rate of spread into new habitats. In a glasshouse study, we examined the phenotypic variation among populations, among families, within families, and the homogeneity of variances within families for morphological and life history characters of an alien, self-pollinating annual grass, Bromus tectorum. The populations of B. tectorum studied were collected from both large, central populations in steppe habitats and small, peripheral populations in forest sites along a broad temperature-moisture gradient in western North America. Most variation in average flowering time was due to differences among seed source populations; among family variation contributed less than 20% to the total variance for flowering time. Populations from arid steppe habitats were the earliest flowering while the population from the most mesic forest habitat was last to flower. In contrast, the within-family variance was a major contributor to the total variance for plant dry weight, seed number per plant, total seed weight, and individual seed weight. The amount of total variation explained by among-family differences ranged between 18% for average seed weight to 30% for total plant dry weight. There was no consistent difference in within-population genetic variability between large, central populations in steppe habitats and smaller, potentially more isolated populations in forest habitats. Significant heterogeneity in within-family variance in some of the source populations suggest that families differ in the capacity for phenotypic response to environmental variation. Considered independently from source population, there was no consistent trend linking a particular trait to increased heterogeneity of within-family variances
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00328406
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  • 10
    Electronic Resource
    Electronic Resource
    Competitive reversals and environment-dependent resource partitioning in Erodium (1985)
    Springer
    Oecologia 67 (1985), S. 430-434 
    Details
    ISSN: 1432-1939
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Effects of drought and varying plant density on the competitive coexistence of two winter annual Erodium species were studied using multiple regression analysis. Significant indications of resource partitioning were detected for interspecific mixtures under spring drought. Competitive superiority also was environment-dependent with E. botrys dominating with drought in autumn, while E. brachycarpum dominated with drought in spring. The results suggest that competitive coexistence in Erodium is promoted by processes both equilibrial (e.g., resource partitioning) and nonequilibrial (e.g. competitive reversals).
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00384951
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