Introduction to Native Plant Specifications
There are three primary questions that need answering when specifying native plants for restoration programs and for open spaces.
- Species – How to choose which species will satisfy a specific goal or purpose?
- Genetics – How to obtain suitable genetics for the chosen species?
- Form – How to choose the most appropriate size or form; often a cost-benefit evaluation?
Few publically-available documents describe how to adequately perform the above activities. Instead, individuals and organizations tend to rely on professionals and pseudo-professionals for advice, with very mixed results. In general, seeking answers from websites is the least reliable option.
This document provides a conceptual framework for answering the above questions that should help with assessing advice procured through various means.
Download a PDF of this document here.
Native Species Selection
Aside from decorating a backyard landscape, choosing native plants for nearly any other purpose is a scientific process rooted in both the ‘reference site’ and ‘plant community’ concepts. In its simplest form, observation and documentation of the target or project site allows the professional to assign a label or category, such as ‘Dry Oak – mixed hardwood forest’ or ‘’Red-cedar – prickly pear shale shrubland’ or any of 100s more. From this starting point, a nearby site with the same or very similar characteristics is evaluated to determine both the species composition and proportions. The idea is that, “if these plants are working well over there, in very similar conditions, then they should work well over here.”
Biodiversity is rarely something that can be purchased and planted. In most common natural conditions, regardless of habitat type, research shows that typically 8-12 species comprise 80% of all species present. This range increases to 15-18 to capture 90% of all species present. So, usually, plant lists should typically include only 8-12, maybe 15, different plant species and ideally reflect the relative proportions found in natural settings.
‘Restoration’ efforts that really aren’t focused on restoration per-se but instead have different goals are exceptions to this approach. For example, in heavily degraded or post-agricultural sites where most, if not all, native plant seed sources have been eradicated, the land owner might choose an objective of re-introducing several dozens of different species into a dedicated ‘nursery’ area to act as a seed source for surrounding areas. Another is agro-forestry, where plant lists are built using species that provide near and mid-term cash crops.
Plant lists should always list the full botanical names. Common names are easily misunderstood and abused by the nursery trade. Specifying ‘bluestem’ is a reference to more than 26 different species. Even specifying ‘little bluestem’ is a reference to 6 different species, none of which are replacements for the other.
Schizachyrium scoparium (little bluestem) is an over-specified native plant, often used in inappropriate situations, that actually doesn’t exist! Instead, there are three distinct and different species and each grows in different habitats and have different growth habits:
The proper way to request the ubiquitous ‘little bluestem’ is to list Schizachyrium scoparium var. scoparium. High-quality native plant nurseries know the difference and their plant labelling system should reflect the actual species in the container. You’ll at least be asking for, and hopefully getting, the plant that you actually want.
Use the USDA Plants Database (click the link) to lookup the proper names for the species that you want.
Three important notes on looking up correct plant names:
- Botanical names aren’t always what you think they are or what the nursery trade regularly uses. For example, Aster novae-angliae (New England aster) is now Symphyotrichum novae-angliae.
- Botanical names change frequently. Taxonomists, for example, can’t make up their mind if chokeberries are of Aronia or Photinia genus, and they have flipped back and forth over the years.
- The USDA site sometimes lags behind the taxonomists’ name changes. For the most current and up-to-date botanical names, check the Integrated Taxonomic Information System (ITIS) where you can read the latest accepted botanical name and all of the preceding names for a particular species. Click this link to view the nearly 50 defunct species now all considered to be variants of the generic Schizachyrium scoparium.
Specifying Native Plant Genetics
This seemingly complex topic really isn’t. The countless number of papers and research programs looking into plant genetics all point to one simple reality: genes matter and using local seed sources is safer than using foreign ones. See Appendix A for a list of papers related to this subject.
At one end of the genetic spectrum we have Equisteum hyemale var. affine (scouring rush), for which genetic studies suggest that this is effectively the same plant growing everywhere around the world from Alaska to Florida to Ukraine. At the other end, we have Trillium erectum (red trillium), for which each population is considered genetically distinct and unique to that population. The implication is that you can plant scouring rush anywhere you like from any source and be accurate and appropriate in doing so. However, buying red trillium and planting it anywhere other from where it originated is probably a futile, and certainly an inappropriate, exercise.
Most native plants demonstrate genetic uniqueness to a set of site conditions nearer to red trillium than scouring rush. For example, Asclepias tuberosa (butterfly milkweed) appears to exhibit noticeable and important genetic differences every 50 miles or so, which reflects the various changes in soils, hydrology, and other relevant factors when you travel 50 miles in any direction.
The problem with using distance as a measure of genetic appropriateness has very severe limitations, however. There can be a dozen or more different combinations of soil, hydrology, and other factors within a small geographic area. Take Bucks County PA, for example, which has 5 very different ecological zones (click this link) ranging from dry upland areas, to ancient volcanic diabase areas, to coastal plain areas. These areas are amazingly different from each other in terms of their soil, hydrology, and other factors, which is what makes Bucks County such a botanically-rich area. And the types of plants that grow in each zone are quite different from each other. A specification stating that all plants must be native to within 50 miles of Philadelphia, for example, is almost meaningless as that would include all of Bucks County and several other counties from Maryland, Virginia, Delaware, and New Jersey. Specifying native plants doesn’t work this way. Instead, we need a land classification system that identifies areas of relative same-ness irrespective of where they are located geographically.
The value of using a land classification system is that it focuses on similar site characteristics and is a proxy for the ‘reference site’ conceptual construct and it provides a standardized means of communication between researchers, producers, and consumers of native plants. Here are two examples of how this is used:
- A plant species that grows in a shale barren near State College, PA should be genetically similar and suitable for use in a shale barren in the Green Ridge in Maryland, given their relative proximity and nearly identical habitat characteristics
- A plant species that grows well in the dense, wet clay of the upper Piedmont is genetically distinct and better attuned to growing in dense, wet clay than genes from the same species growing on a sand dune near Lake Erie.
A brilliant and forward-thinking employee of the Environmental Protection Agency (EPA) foresaw the need for such a land classification system. James Omernik published “Ecoregions: A Framework for Managing Ecosystems” in 1987 that is rapidly becoming the industry standard for land classification and specifying native plants. Click this link for a list of ecoregion publications by Omernik and the EPA staff.
Omernik’s EcoRegion land classification system is widely available for public use as a GIS layer. A quick link to an EcoRegion lookup tool can be found here (click the link).
The image below shows 6 the different EcoRegions within 20 miles of Manhattan. The New York City municipal nursery grows ecoregion-specific plants for use on projects throughout the city. ArcheWild grows ecoregion-specific plants for customers ranging from Boston to Cleveland to Roanoke to Asheville.
Open the lookup tool, enter your address, adjust the transparency level of the ecoregion layer, and then scroll in to see the ecoregion code for your project site. This ecoregion code is your preferred ecoregion for specifying and sourcing genetics for your plant list. ‘EcoRegion 064a’ (Level IV) denotes the upper Piedmont area. Simply specifying ‘EcoRegion 064’ (Level III) allows for anywhere within the Piedmont.
Some native plant nurseries collect their own seed and track seed provenance, but most do not. Even for those that do, proactively growing and stocking a single species from many different ecoregions is uncommon. For example, ArcheWild grows over 20 different Schizachyrium scoparium var. scoparium crops, each from a different ecoregion to service our broad customer base for this popular restoration species, but we might only grow Campanulastrum americanum from just 3 ecoregions. It’s impractical, if not impossible, for a single nursery to grow all native species from all ecoregions. This is why the ‘contract grow’ arrangement is so quickly dominating the restoration-grade native plant industry. For example, if the US Forest Service wants to use red spruce to restore a portion of Spruce Knob, WV, they collect the seed themselves and have it ‘contract grown’ by a nursery that will track ecoregion and accession codes for each seed lot, thereby guaranteeing the genetic suitability of their plants to their project sites.
So when specifying native plants for your project, the minimum requirement is listing the ecoregion but can also include the accession code if your nursery supplier is equipped to track crops by seed lot.
Click here for an article covering Native Plant Labeling Standards.
Click here for another case study for specifying a grass species for use near Lake Erie.
Choosing a Native Plant Form
Do you buy bareroot, plugs, tubelings, band pots, containers, or B&B? 18” tall or 6’ tall. The choices and combinations can seem daunting. Often the choice is determined dimply by budgetary restrictions but the rule-of-thumb that one should buy the least expensive plant so that you can plant more plants is rarely the most efficacious approach.
The least expensive plants are often small bareroot, which are easy to plant but have terrible survival rates compared to other product forms. Usually, buying tree tubelings or band pots are up to 3X the cost of bareroot but can have a 10-20x survival rate. So which is the better option?
Similarly, buying a 6’ tall containerized tree is easily 3X the cost of a 1-2’ tall tree. But the shorter tree must be caged or tubed and/or is subject to deer browse, which is why the 6’ tree is normally preferred over the shorter, less-expensive tree.
Conversely, many projects still request gallons, quarts, or even deep plugs for herbaceous species when starter plugs are 80% less expensive to buy and to plant and often have higher survival rates than their larger forms due to lower desiccation risk. In one trial conducted by Izel Plants, an online native plant broker, showed that there were no discernable performance differences between small starter plugs that can cost as little as $0.50 and quarts that can cost up to $5.00, all in an unirrigated setting, and that within a few months the small plugs had achieved exactly the same size as the larger starting form.
Click here to see an article on small starter plugs.
So the new rule-of-thumb is that one should specify the smallest ‘containerized’ form that can be purchased except in the case of trees and shrubs where the terminal buds should be above the deer browse line. Small starter plugs are the most cost-effective form for herbaceous species and tubelings are the most cost-efficient tree/shrub form. Specify 6’ trees and shrubs in unprotected settings.
Native Plant Specification Writing Summary
Use the below checklist to see if your plant specifications are meeting the new industry standards:
- Specify the full botanical name; use USDA Plants Database as your everyday guide
- Specify the EcoRegion genetic source; use the EPA ecoregion Level III or Level IV codes
- Specify the seed lot from which your plants should be grown, using an accession code
- Require that the full botanical name, ecoregion source, and accession codes are on plant tags
- Specify the smallest containerized (plug flat) option available, or specify 5-6’ tall trees/shrubs
- Validate your plant list by referencing plant community documentation or a trusted ecologist
Sample Native Plant Specification
Appendix A – Plant Genetics Papers
Regardless what you might hear from plant marketers and landscape designers, genes do matter for lots of reasons. Below is a selection of papers cited in a nice piece of work titled, “‘‘How Local Is Local?’’—A Review of Practical and Conceptual Issues in the Genetics of Restoration,” by McKay, Christian, Harrison, and Rice. The first paragraph of their summary section reads,
“A major genetic concern of restoration practitioners is, ‘‘How local is local?’’ Practitioners have a tendency to assume that local adaptation is almost ubiquitous at most spatial scales. Ecological genetics studies generally support the idea that local adaptation, especially across larger geographic or climatic gradients, is the norm. There are also many scientific studies indicating that local adaptation can occur (to varying degrees) at small spatial scales. However, there is also evidence that gene flow, seed banks and, perhaps most importantly, temporal fluctuations in selection can reduce the probability of highly localized ecotypes.”
Note the reference to EcoRegions in the underlined text above.
Antonovics, J., and A. D. Bradshaw. 1970. Evolution in closely adjacent plant populations. VII. Clinal patterns at a mine boundary. Heredity 25:349–362.
Arntz, A. M., and L. F. Delph. 2001. Pattern and process: evidence for the evolution of photosynthetic traits in natural populations. Oecologia 127:455–467.
Avise, J. C. 1998. The history and purview of phylogeography: a personal reflection. Molecular Ecology 7:371–379.
Barton, N. H., and G. M. Hewitt. 1989. Adaptation, speciation and hybrid zones. Nature 341:497–503.
Beerli, P., and J. Felsenstein. 2001. Maximum likelihood estimation of a migration matrix and effective population sizes in n subpopulations by using a coalescent approach. Proceedings of the National Academy of Sciences U.S.A. 98:4563–4568.
Bradshaw, A. D. 1984. Ecological significance of genetic variation between populations. Pages 213–228 in R. J. S. Dirzo, editor. Perspectives on plants population ecology. Sinauer Associates, Inc., Sunderland, Massachusetts.
Brenzel, K. N. 2001. Western garden book. 7th edition. Sunset Publishing, Menlo Park, California.
Britten, H. 1996. Meta-analyses of the association between multilocus heterozygosity and fitness. Evolution 50:2158–2164.
Brown, J. M., J. H. Leebens-Mack, J. N. Thompson, O. Pellmyr, and R. G. Harrison. 1997. Phylogeography and host association in a pollinating seed parasite Greye politella (Lepidoptera: Prodoxidae). Molecular Ecology 6:215–224.
Buck, J. M., R. S. Adams, J. Cone, M. T. Conkle, W. J. Libby, C. J. Eden, and M. J. Knight. 1970. California tree seed zones. U.S. Forest Service, San Francisco, California.
Byers, D. L., and D. M. Waller. 1999. Do plant populations purge their genetic load? Effects of population size and mating history on inbreeding depression. Annual Review of Ecology and Systematics 30:479–513.
California Department of Parks and Recreation. 1994. Statement of Policy II.4 Preservation of vegetative entities. Sacramento, CA.
Calsbeek, R., J. N. Thompson, and J. E. Richardson. 2003. Patterns of molecular evolution and diversification in a biodiversity hotspot: the California Floristic Province. Molecular Ecology 12: 1021–1029.
Cheverud, J., E. Routman, and C. Jaquish. 1994. Quantitative and molecular genetic variation in captive cotton-top tamarins (Saguinus oedipus). Conservation Biology 8:95–105.
Clausen, J., and W. M. Hiesey. 1958. Experimental studies on the nature of species. IV. Genetic structure of ecological races. Carnegie Institution of Washington Publication 615, Washington, D.C.
Coyne, J. A., and H. A. Orr. 2004. Speciation. Sinauer Associates, Inc., Sunderland, Massachusetts.
Crespi, B. J. 2000. The evolution of maladaptation. Heredity 84:623–629.
Cruden, R. W. 1977. Pollen-ovule ratios: a conservative indicator of breeding systems in plants. Evolution 31:32–46.
David, P. 1998. Heterozygosity-fitness correlations: new perspectives on old problems. Heredity 80:531–537.
Davis, M. B., and R. G. Shaw. 2001. Range shifts and adaptive responses to quaternary climate change. Science 292:673–679.
Devlin, B., and N. C. Ellstrand. 1990. The development and application of a refined method for estimating gene flow from angiosperm paternity analysis. Evolution 44:248–259.
Dobson, A. P., A. D. Bradshaw, and A. J. M. Baker. 1997. Hopes for the future: restoration ecology and conservation biology. Science 277: 515–522.
Edmands, S. 1999. Heterosis and outbreeding depression in interpopulation crosses spanning a wide range of divergence. Evolution 53: 1757–1768.
Edmands, S., and C. C. Timmerman. 2003. Modeling factors affecting the severity of outbreeding depression. Conservation Biology 17:883–892.
Ellstrand, N. C., B. Devlin, and D. L. Marshall. 1989. Gene flow by pollen into small populations: data from experimental and natural stands of wild radish. Proceedings of the National Academy of Sciences U.S.A. 86:9044–9047.
Endler, J. A. 1986. Natural selection in the wild. Monographs in Population Biology 21. Princeton University Press, Princeton, New Jersey.
Eriksson, G., S. Andersson, V. Eiche, J. Ifver, and A. Persson. 1980. Severity index and transfer effects on survival and volume production of Pinus sylvestris in northern Sweden. Studia Forestalia Suecica 156:1–32.
Fenster, C. B., and L. F. Galloway. 2000. Population differentiation in an annual legume: genetic architecture. Evolution 54:1157–1172.
Fenster, C. B., L. F. Galloway, and L. Chao. 1997. Epistasis and its consequences for the evolution of natural populations. Trends in Ecology and Evolution 12:282–286.
Geber, M. A., and L. R. Griffen. 2003. Inheritance and natural selection on functional traits. International Journal of Plant Science 164:S21–S42.
Gullberg, U., R. Yazdani, D. Rudin, and N. Ryman. 1985. Allozyme variation in Scots pine (Pinus sylvestris L.) in Sweden. Silvae Genetica 34:193–201.
Hamrick, J. L., andM. J.W. Godt. 1996. Conservation genetics of endemic plant species. Pages 287–291 in J. C. Avise and J. L. Hamrick, editors.
Conservation genetics: case histories from nature. Chapman and Hall, New York.
Hedrick, P. W. 1999. Perspective: highly variable loci and their interpretation in evolution and conservation. Evolution 53:313–318.
Hedrick, P. W., and S. T. Kalinowski. 2000. Inbreeding depression in conservation biology. Annual Review of Ecology and Systematics 30: 139–162.
Hickman, J. C., editor. 1993. The Jepson Manual. University of California Press, Berkeley.
Hobbs, R. J., and D. A. Norton. 1996. Towards a conceptual framework for restoration ecology. Restoration Ecology 4:93–110.
Hufford, K. M., and S. J. Mazer. 2003. Plant ecotypes: genetic differentiation in the age of ecological restoration. Trends in Ecology and Evolution 18:147–155.
Hurme, P. 1999. Genetic basis of adaptation: bud-set date and frost hardiness variation in Scots pine. Acta Univ. Oul. A339. University Oulu Press, Oulu, Finland.
Husband, B. C., and H. A. Sabara. 2004. Reproductive isolation between autotetraploids and their diploid progenitors in fireweed, Chamerion angustifolium (Onagraceae). New Phytologist 161: 703–713.
Johansen, B., and R. von Bothmer. 1994. Pollen size in Hordeum L. correlation between size, ploidy level, and breeding system. Sexual Plant Reproduction 7:259–263.
Jones, T. A. 2003. The restoration gene pool concept: beyond the native versus non-native debate. Restoration Ecology 7:42–50.
Keller, M., J. Kollmann, and P. J. Edwards. 2000. Genetic introgression from distant provenances reduces fitness in local weed populations. Journal of Applied Ecology 37:647–659.
King, R. B., and R. Lawson. 1995. Color-pattern variation in Lake Erie water snakes: the role of gene flow. Evolution 49:885–896.
Knapp, E. E., and K. J. Rice. 1994. Starting from seed: genetic issues in using native grasses for restoration. Restoration and Management Notes 12:40–45.
Knapp, E. E., and K. J. Rice. 1998. Comparisons of isozymes and quantitative traits for evaluating patterns of genetic variation in purple needlegrass (Nassella pulchra). Conservation Biology 12:1031–1041.
Kruckeberg, A. R. 1986. An essay: the stimulus of unusual geologies for plant speciation. Systematic Botany 11:455–463.
Lande, R., and S. Shannon. 1996. The role of genetic variation in adaptation and population persistence in a changing environment. Evolution 50:434–437.
Lenormand, T. 2002. Gene flow and the limits to natural selection. Trends in Ecology and Evolution 17:183–189.
Lesica, P., and F. W. Allendorf. 1999. Ecological genetics and the restoration of plant communities: mix or match? Restoration Ecology 7: 42–50.
Linhart, Y. B., and M. C. Grant. 1996. Evolutionary significance of local genetic differentiation in plants. Annual Review of Ecology and Systematics 27:237–277.
Lynch, M. 1996. A quantitative-genetic perspective on conservation issues. Pages 471–499 in J. C. Avise and J. L. Hamrick, editors. Conservation genetics: case histories from nature. Chapman and Hall, New York.
Mazer, S. J., and G. LeBuhn. 1999. Genetic variation in life-history traits: heritability estimates within and genetic differentiation among populations. Pages 85–170 in T. O. Vuorisalo and P. K. Mutikainen, editors. Life history evolution in plants. Kluwer Academic Publishers, Dordrecht, The Netherlands.
McKay, J. K., J. G. Bishop, J.-Z. Lin, A. Sala, J. H. Richards, and T. Mitchell-Olds. 2001. Local adaptation across a climatic gradient despite small effective population size in the rare Sapphire Rockcress. Proceedings of the Royal Society London B 268:1715–1721.
McKay, J. K., and R. G. Latta. 2002. Adaptive population divergence: markers, QTL and traits. Trends in Ecology and Evolution 17:285–291.
Mikola, J. 1982. Bud-set phenology as an indicator of climatic adaptation of Scots pine in Finland. Silva Fennica 16:178–184.
Montalvo, A. M., and N. C. Ellstrand. 2000. Transplantation of the subshrub Lotus scoparius: testing the home-site advantage hypothesis. Conservation Biology 14:1034–1045.
Montalvo, A. M., S. L. Williams, K. J. Rice, S. L. Buchmann, C. Cory, S. N. Handel, G. P. Nabhan, R. Primack, and R. H. Robichaux. 1997. Restoration biology: a population biology perspective. Restoration Ecology 5:277–290.
National Park Service. 1993. Western Region Directive #WR-094 and guidelines for revegetation in disturbed areas. San Francisco, CA.
Neigel, J. E. 1997. A comparison of alternative strategies for estimating gene flow from genetic markers. Annual Review of Ecology and Systematics 28:105–128.
Newman, D., and D. Pilson. 1997. Increased probability of extinction due to decreased genetic effective population size: experimental populations of Clarkia pulchella. Evolution 51:354–362.
Parker, K. M., R. J. Sheffer, and P. W. Hedrick. 1999. Molecular variation and evolutionarily significant units in the endangered gila topminnow. Conservation Biology 13:108–116.
Petit, C., F. Bretagnolle, and F. Felber. 1999. Evolutionary consequences of diploid-polyploid hybrid zones in wild species. Trends in Ecology and Evolution 14:306–311.
Petit, C., H. Freville, A. Mignot, B. Colas, M. Riba, E. Imbert, S. Hurtrez- Bousses, M. Virevaire, and I. Olivieri. 2001. Gene flow and local adaptation in two endemic plant species. Biological Conservation 100:21–34.
Ralls, K., and J. Ballou. 1983. Extinction lessons from zoos. Pages 164– 184 in C. M. Shonewald-Cox, S. M. Chambers, B. MacBryde, and L. Thomas, editors. Genetics and Conservation. Benjamin/Cummings, Menlo Park, California.
Ramsey, J., and D. W. Schemske. 1998. Pathways, mechanisms and rates of polyploidy formation in flowering plants. Annual Review of Ecology and Systematics 29:4676–4501.
Randall, W. K. 1996. Forest tree seed zones for western Oregon. Oregon Department of Forestry, Salem, Oregon.
Randall, W. K., and P. Berrang. 2002. Washington tree seed transfer zones. Washington Department of Natural Resources, Olympia, Washington, D.C.
Rannala, B., and J. L. Mountain. 1997. Detecting immigration using multi-locus genotypes. Proceedings of the National Academy of Sciences U.S.A. 94:9197–9201.
Raven, P. H. 2002. Science, sustainability, and the human prospect. Science 297:954–958.
Rice, K. J., and N. C. Emery. 2003. Managing microevolution: restoration in the face of global change. Frontiers in Ecology and the Environment 9:469–478.
Riddle, B. R., D. J. Hafner, L. F. Alexander, and J. R. Jaeger. 2000. Cryptic vicariance in the historical assembly of a Baja California Peninsular Desert biota. Proceedings of the National Academy of Sciences U.S.A. 97:14438–14443.
Rodriguez-Robles, J., D. F. DeNardo, and R. Staub. 1999. Phylogeography of the California mountain kingsnake, Lampropelits zonata (Colubridae). Molecular Ecology 8:1923–1934.
Saccheri, I., M. Kuussaari, M. Kankare, P. Vikman, W. Fortelius, and I. Hanski. 1998. Inbreeding and extinction in a butterfly metapopulation. Nature 392:491–494.
Savolainen, O., and P. Hedrick. 1995. Heterozygosity and fitness: no association in Scots pine. Genetics 140:755–766.
Schneider, C. J., T. B. Smith, B. Larison, and C. Moritz. 1999. A test of alternative models of diversification in tropical rainforests: ecological gradients vs. rainforest refugia. Proceedings of the National Academy of Sciences U.S.A. 96:13869–13873.
Slatkin, M. 1985. Gene flow in natural populations. Annual Review of Ecology and Systematics 16:393–430.
Soltis, D. E., P. S. Soltis, T. G. Collier, and M. L. Edgerton. 1991. Chloroplast DNA variation within and among genera of the Heuchera group (Saxifrigaceae): evidence for chloroplast transfer and paraphyly. American Journal of Botany 78:1091–1111.
Stebbins, G. L. 1950. Variation and evolution in plants. Columbia University Press, New York.
Stebbins, G. L. 1952. Aridity as a stimulus to plant evolution. American Naturalist 86:33–44.
Storfer, A. 1996. Quantitative genetics: a promising approach for the assessment of genetic variation in endangered species. Trends in Ecology and Evolution 11:343–348.
Storfer, A. 1999. Gene flow and endangered species translocations: a topic revisited. Biological Conservation 87:173–180.
Templeton, A. R. 1986. Coadaptation and outbreeding depression. Pages 105–116 in M. Soule, editor. Conservation biology: the science of scarcity and diversity. Sinauer Associates, Inc., Sunderland, Massachusetts.
Turelli, M., and L. R. Ginzburg. 1983. Should individual fitness increase with heterozygosity? Genetics 104:191–209.
USDA Forest Service. 1994. Use of native vegetative materials on National Forests. US Forest Service Pacific Southwest Region. San Francisco, CA.
Vitousek, P. M., H. A. Mooney, J. Lubchenco, and J. M. Melillo. 1997. Human domination of Earth’s ecosystems. Science 277: 494–499.
Vrijenhoek, R. C. 1994. Genetic diversity and fitness in small populations. Pages 37–53 in V. Loeschcke, J. Tomiuk, and S. K. Jain, editors. Conservation genetics. Birkhauser, Basel, Switzerland.
Waldman, P., and S. Andersson. 1998. Comparison of quantitative genetic variation and allozyme diversity within and between populations of Scabiosa canescens and S columbaria. Heredity 81:79–86.
Whitlock, M. C., P. C. Phillips, F. B.-G. Moore, and S. J. Tonsor. 1995. Multiple fitness peaks and epistasis. Annual Review of Ecology and Systematics 26:601–629.
Williams, D. G., R. N. Mack, and R. A. Black. 1995. Ecophysiology of introduced Pennisetum setaceum on Hawaii: the role of phenotypic plasticity. Ecology 76:1569–1580.
Wright, S. 1951. The genetical structure of populations. Annals of Eugenics 15:323–354.
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