Gene Namkoong is Pioneer Research Geneticist USDA Forest Service, Southeastern Forest Experiment Station Genetics Department, North Carolina State University, Raleigh, North Carolina, USA. This article is adapted from a slightly longer paper presented at the Ninth World Forestry Congress in Mexico City, 1 to 10 July 1985.
One of the greatest challenges awaiting foresters in the future - especially those working in tropical forests in developing countries - is genetics. It is in the tropical forests that most of the world's animal and plant species are located. Many of these species, at present, are virtually unknown. As knowledge of the resources contained in these forests increases and as the emerging field of biotechnology opens new possibilities for management and development, foresters will be presented with a wide new set of questions - scientific, economic, ethical and ecological. The first part of this article deals with these questions in general terms; the second examines, in detail, some of the concrete implications they might have for forest management.
The well-being and productivity of forests are dependent on the structure and dynamics of their genetic foundation. Their inherent capacities for growth and development are under strong genetic control and can be improved through breeding. The focus of this article, however, is not on breeding techniques but on the deeper question of how to maintain or generate useful genetic variation for the continued evolution, improvement and adaptation of forests to human and environmental demands. Methods for selective breeding and genetic manipulation of trees will be ad dressed, but the main concern will be the quantity and pattern of genetic diversity needed to inhibit the dangers arising from uniformly susceptible stands. We are seeking ways to ensure the diversity needed both for immediate benefits and for future generations - for new economic goals; for adaptability to changing sites and climates; and for survival within the ever-evolving living community of pathogens, pests, competitors and mutualists.
An immediate danger in the present situation is that the genetic resources of most crop species are being threatened by a severe reduction.
For these issues, we need to look beyond the trees we use for today's breeding to the past populations that gave rise to them and to the populations we will have to construct for future forests. We must consider populations that are at present of peripheral interest but that may contain variation that will be useful under other conditions in the future. We must also consider some species that may have little present commercial value but may have future value either in themselves or as sources of genes for use with other species. The conservation of genetic resources is a complex task, in which problems and solutions vary according to the immediacy of commercial use and the amount of knowledge about and manageability of the species involved.
CONTROLLED POLLINATION OF A PINE TREE tree-breeding becomes more deliberate
It is apparent that issues affecting forest genetic resources are not qualitatively different from those affecting agricultural genetic resources. The problems differ in detail and emphasis, but the array of conservation and management issues is similar for many species. The identification and conservation of new species is as much a concern for medicinal and agricultural species as it is for forest tree species. Ecogeographic surveys of wheat are as new as provenance studies of tropical pines, and the evaluation and enhancement of maize varieties are similar in design to testing radiate pine. It is therefore appropriate for us to consider forest genetic resource issues within the context of general plant genetic resources, and to clarify management objectives where more than one species and more than one objective may be involved in any operational decision. In addition to discussing management objectives, this article will describe genetic management for three types of species: (1) those of current commercial significance; (2) those of clear potential value; and (3) those of unknown value given present technology. Problems of investing in more intensive and complete programmes are considered, a basis for deciding on programme investments is proposed, and mechanisms to support gene conservation and management are suggested.
Decisions about conservation of species or ecosystems depend on value judgements. We must therefore ask who benefits from conservation efforts and establish the measures by which values will be judged by the people on whose behalf we operate. For commercial species, the interests of local growers and users are not necessarily the same as those of large industries, even if they are in the same country. Furthermore, people other than those directly affected by our broad definition of commercial use (see below) derive benefit from, and therefore are concerned about, commercial and non-commercial species and the land they occupy. In addition, there are future generations of people whose welfare depends on how well we manage the genetic resource.
FOUR-YEAR-OLD TREES IN ARACRUZ, BRAZIL at harvest, an impressive 45 m3/ha/yr
One critical factor affecting all available alternatives is under-investment in genetic conservation and management programmes. The International Board for Plant Genetic Resources estimates that worldwide expenditures on all forms of genetic conservation and development for all animal and plant crops total US$50 million per year. While the danger of genetically ameliorable famine increases annually, worldwide investment has not grown in the last five years. Hence, in addition to describing the management options that are available, we must consider the values placed on genetic resources. Who benefits? Who invests in programmes affecting those resources? How can a conservation management programme be supported?
This total reliance on market forces to determine investment priorities implies that political or ethical concerns for future generations are secondary.
It is clearly possible to ensure the continued evolution and availability of plant and animal populations. However, it is also clear that only very meagre funding is available for any but the most important commercial species in industrialized forestry. Even the execution of such projects as an ecogeographic survey of world wheat genetic resources, which would require funding of $10 million each year for several years, is by no means certain. If only the major commercial food and fibre species are considered, investments of an order of magnitude much greater than the present level would be needed to conserve and develop the genetic resource base adequately. While such funding is not large in relation to the international trade in agricultural and forestry products, there is an obvious gap between needs and investment. That gap has not been reduced in recent years.
The situation is not qualitatively different between forestry and agronomic crops. It is particularly obvious in forestry that investments in genetic resource development come primarily from industrialized country sources, while the needs for that development exist over a much broader area. The dangers inherent in this situation are that the overall global good may not be best served if development is restricted to the interests of a small segment of the public. While it is not necessarily true that the wider public interest is not well served by industrial development, it is also not necessarily true that it is. It is essential to allocate costs fairly, to decide who pays for programmes, and to determine who is to benefit from gene resource management.
I am assuming that a just solution to this central problem would lead to reasonable but much higher investment in genetic management. The interests expressed by agri-businesses, by governments and by United Nations agencies - FAO most notably - indicate that there is a recognition of the need for investment and development. The disagreement is over means. The immediate dangers in the present situation are that the genetic resources of most crop species are being threatened by a severe reduction, that potential progress from breeding is foregone, and that the genetic and ecological vulnerability of our food and fibre crops is increasing.
One of the features of the current global economy is the unequal distribution of resources and of the benefits to be derived from them. Even within nations, the interests of rural agriculturists or wood-users differ from those of urban consumers or timber merchants. Many genetic resources lie in remote areas or in isolated, scattered populations which may have to be extracted and tested elsewhere. While the present value of at least some of those populations may be due to past policies and practices, including protection of the populations, it also seems clear that modern genetic technologies can more rapidly develop their potential and expand their utility and benefits.
Developmental technology itself, however, can be considered to be yet another resource which is not uniformly distributed, either within or between nations. Technological centres are commonly concentrated in urban areas, supported by industries or central governments, and staffed by professionals educated in these same technological centres. There are substantive reasons for these concentrations, but the results are often unfortunate. Maldistribution of technological capability leads to a concentration of technical efforts on species and for products of immediate commercial value to those who support those centres.
Another potential problem is the dependence of powerless future generations on the genetic endowment left by previous generations. The materials we leave and the technology we develop are our endowment to future generations. This endowment can be diminished or enhanced. Management objectives, even by government agencies, seldom explicitly consider future wishes. Obviously, industrial concerns must heavily discount future values, since only present investors can voice preferences. In fact, the perspective of present investors is often the only one in economic analysis of alternatives by government or private industry. This total reliance on market forces to determine investment priorities implies that political or ethical concerns for future generations are secondary.
How can the people of Amazonia justly bear the costs of maintaining, or not otherwise using, natural areas?
Capitalists might argue that only the free market can ensure such fairness, while socialists would argue otherwise. In any case, neither could argue that the only objective should be industrial profit. Free-market motivation may arguably result in economic fairness, but it does not necessarily represent justice. Management objectives are properly set by political and ethical considerations, only one of which is industrial profit.
Investments in developing and managing the genetic resources are now made largely by industrial interests, either directly or indirectly through support for government policies and technologies. I emphasize that this is not a condemnation of the maldistribution of power, but an observation that there are inequalities in the distribution of genetic technologies, resources and power which affect management plans. If we accept that it is feasible to consider various levels of genetic management to ensure the productivity of future forests, the main question to consider is how to generate the investments needed to do so with some sense of justice.
Given the assumption that current industrial investment in genetic management is that which can be justified by expected financial returns under present conditions, far greater investment needs nevertheless do exist and greater inducements for investment by industries and governments must be sought. Since private industrial interests cannot be expected to invest in programmes that provide few returns, there is considerable debate over how the necessary exchange of genetic resources should be managed. A focal point for the debate is the concept of genetic resources as the "common heritage" of all people.
A libertarian view might consider the genetic heritage something available to everyone - and thus to anyone with the means to develop it. Investors therefore use technological and other resources to develop a varietal product of higher value or lower cost for sale to potential buyers. By such means as patent rights, the initial investment can be protected and the investor can obtain returns for those efforts. Furthermore, by this view, all people eventually benefit as the profits from the better varieties trickle down to society in general. People lucky enough to possess gene resources of unrealized potential value in their own countries benefit by private development of that potential, possibly by the sale of improved varieties back to their own people.
An egalitarian view of genetic resources would see them as a "common heritage" from which all people have a claim to any benefits derived. By this view, the fact that one nation may have a particularly valuable genetic population while another may have the testing facilities and analytical capabilities for developing a new variety gives neither of them exclusive rights of ownership or profit. The unequal distribution of resources is viewed as the result of a kind of natural global lottery. A proper function of governments is to support the coordination of resource use for maximum total benefit, while allowing each to receive profit from his or her investment.
The conflict between these two views inhibits what I believe to be a justifiable need for larger investments in gene management. Industrialized nations, together with forest and agribusiness industries, are the primary sources of investment capital, and they largely subscribe to the "libertarian" view. The Third World nations, which house many of the genetic resources, largely subscribe to the egalitarian view. In this situation, private investors are reluctant to capitalize long-term development programmes without at least some assurance of varietal protection while developing countries seek programme support for the development of their own research and training facilities. Meanwhile, some agricultural seed companies and industrial cooperatives such as CAMCORE (Central America and Mexico Coniferous Resources Cooperative) are beginning breeding and conservation efforts on an international scale. Other agencies, like the Commonwealth Forestry Institute and the Danish International Development Agency, have had international conservation and breeding programmes funded by governments for philanthropic reasons. As more private and governmental agencies enter the arena, conflicting objectives may preclude efficiencies in cooperation and mutual support. Indeed, the role of international assistance agencies is not clear, given the multiple objectives of genetic management programmes.
We cannot rely upon gene transfer as a usable technique any time soon.
When the objective of management is simple and unequivocal, such as financial profit, and the subject is merely a single agency or investor, determining optimal investments and programmes is relatively easy. However, when the subjects who can be harmed or benefited by genetic management do not share the same political and economic status, may not even be in the same generation, and may have a multitude of different needs, programme evaluations will be quite different. Whereas the costs of ecological destabilization may be viewed mainly as an externality to a timber investor, a local community dependent on the land for other products may view it as an "internal risk" - as may the global community, which may be hurt indirectly. Private investments made for the benefit of future generations risk that future generations may or may not want certain forest products as at present defined. Public bodies, however, may wish to reduce such risks greatly by making certain assumptions about the anticipated needs of future generations.
Various systems of public subsidies can probably achieve gene management objectives, but not without substantial problems. There are problems in achieving public awareness of the significance of the issues involved, and problems in adjudicating the responsibilities of the interested parties. While most parties may agree on the desirability of sharing costs and benefits, it is not clear how to do that. How, for example, can we best bear the costs of conservation programmes in this generation while future generations reap the benefits? How can the people of Amazonia justly bear the costs of maintaining, or not otherwise using, natural areas - a policy that may benefit the global environment and future generations, but not themselves? How can the gene-rich but technology-poor developing nations trade with the gene-poor but technology and capital-rich industrialized nations? Can the philanthropies of certain groups support programmes that may profit private entities such as seed companies but not the general public? How can national programmes of foreign aid equitably allocate funds among programmes or evaluate benefits among government agencies, private investors and other governments? Finally, how should subsidies be derived in the first place, and which segments of the affected people should be expected to bear the costs?
I believe that justice for future generations of people requires protection of evolutionary potential, and I believe such protection is feasible (Namkoong, 1982). This goal can be accomplished in a programme of genetic conservation (Namkoong, 1984a) that includes directional selective breeding in at least one and preferably in multiple populations. It would also include conservation in multiple populations when direct management intervention is not feasible. For species with high market value, private investment may sometimes be sufficient for the development of commercially valuable varieties and for the protection of the interests of all affected people. Obviously, for species or varieties at the edges of commercial utility, and for those without known commercial benefits, private investment cannot be expected. The values to be derived from the genetic management of species with little or no commercial value are generally of such long-term and diffuse global value that the general global public is the prime beneficiary. In that case, international agencies such as the International Union for the Conservation of Nature and Natural Resources and the Nature Conservancy may be needed to invest in such programmes. In one sense, these organizations would be subsidizing the later development of more immediate and exploitable commercial values. This is similar to the functions of state and federal agricultural research stations in the United States, which support the development of breeding populations which they or others may use for commercial variety development. For the vast majority of less directly useful species, however, public and non-governmental investments will be required. If some commercial products are eventually realized, payment of royalties to these organizations would seem proper.
LABORATORY TESTING INDOORS the outdoor laboratory is the forest
Perhaps the greatest conflicts are associated with commercial or near-commercial species that require some research and development. Developing nations may resist the notion of granting Plant Breeder Rights (PBRs) and protecting the privileges of developers, but they lack the capital and technological capacity to develop varieties on their own. I suggest that since the varietal developments that may occur in an industrial country are not likely to be useful in a Third World country, PBRs can be granted without harm to developing countries. However, since the materials used for varietal development are affected by the people in the nations of origin and by the ecosystems that supported their evolution, some royalty is owed to the nations of origin. To this extent, royalties on profits and fees for use of such materials might appropriately be deposited in a trust agency for the development of technologies deemed useful for gene management by the people in those nations. A special United Nations-FAO fund might be created and supplemented by governmental and non-governmental agencies for the development of local options in the use of the genetic resource and for the long-term development of the resource itself. These could then be integral parts of a larger gene management programme and would fit into an effective system for ensuring genetic diversity.
The issues involved are complex, and the difficulties in fine-tuning any broad programme proposal are substantial. Nevertheless, there seems to be substantial room for agreement on a global policy toward the development of the genetic resource.
We have the opportunity to make much progress while protecting the interests of the powerless in present and future generations. Can we afford to do less than to seek just agreements?
In this article the term "commercial" is not meant to distinguish between capitalist and socialist economies or between market and peasant exchange values. Its function is rather to indicate the status of various species as resources that return direct value on some form of investment. Value may come from the sale of a highly manufactured forest product or from direct consumption of fuel. The concept encompasses values that may be measured differently by different managers. In the analyses that are envisioned, indirect effects of forestry practices on soil, water or socioeconomic consequences are not considered as commercial returns.
The commercial objective of breeding is to produce a genotype or set of genotypes that will return an economic yield sufficiently higher or more assured than the current level of yield to satisfy management's definitions of "good". This definition is solely in terms of the manager's organization, and the interests of outsiders and of the resource itself may be ignored. The "manager" involved can be a private owner or a stockholder in a private corporation, or just as easily a peasant in a developing nation. The only requirement of this manager is the investment of personal time, effort or capital with the expectation of some economic return.
In general, commercial breeding can be expected to reduce drastically the effective population size.
Breeding theory The typical forest tree-breeding operation includes a finite number of selections (from 10 to 300) made from a population that usually contains more than a few thousand individuals. General yield improvements are thought to be caused by many different genetic "loci", or by genes within a chromosome. Each locus may have several "allelic" variants of a given gene. Increases in, for example, the quantitative yield of wood from a species are thought to be a consequence of an accumulation of alleles positively affecting this characteristic; such alleles can occur at many different loci. In forest trees, where clear estimates of single gene effects are difficult to obtain, it may most generally be necessary to treat inheritance as a quantitative phenomenon. In any case, the assumption is usually made, and often borne out, that careful selection results in heritable improvement in the next generation. Hence, the focus of research in tree-breeding has been on obtaining precise estimates of the breeding quality of potential parents and on developing several aids to selection. In the initial generation, several source populations are often screened and the best of these used as the initial population.
In subsequent generations, the breeding population is effectively closed. Even if the initial selections were numerous, it is naive to assume that the effective population size will remain large. In general, commercial breeding can be expected to reduce drastically the effective population size. In spite of the best intentions to maintain a large base population, a corporate tree breeder may find that the immediate gain achievable by using, for example, the 5 best rather than the 10 to 20 best parents outweighs the long-term risks of loss of genetic variance. This is true for simple recurrent selection programmes as well as for any hybrid recurrent: selection programmes.
STUDYING GERMINATION IN PERU making bigger, better arid faster- growing trees
Reduced population sizes, in addition to inbreeding depression, cause a loss of genetic variability and a consequent loss of the ability to respond to shifts in selection objectives. These are related to shifts in economic or management objectives or to changing requirements for ecological adaptability. Reduced effective population sizes also reduce the ability of populations to respond cumulatively to reiterated selection pressure, or to reverse selection. The problem seems less acute than when applying new selection to an entirely independent trait. The loss of genetic variation also precludes selecting for qualitative trait genes if they were lost from the breeding population, and precludes the possibilities of selecting for new environmental response functions or resistances if that variability is lost (Dudley, 1977).
EUCALYPT RESEARCH IN AUSTRALIA long, painstaking efforts are needed
One answer to reduced breeding population size is maintaining a hierarchy of relatively large, less highly selected populations (Kannenberg, 1984). For agronomic crop plants, this approach requires large pools of unimproved varieties and source collections and perhaps one or two large populations that are partially tested and selected for some levels of adaptability. From these more or less enhanced populations, breeders can develop commercial varieties. These processes, however, are often difficult, expensive, and time-consuming (Stuber, 1978), and in forest trees they may only involve one base level of selected populations (Namkoong et al., 1971). However, owing to the nature of tree-breeding operations, such base populations would be useless unless substantially improved and, if substantially improved, might better be bred selectively in multiple populations for useful diversity (Namkoong, 1984c).
Breeding in multiple populations for genetic diversity is also potentially useful for traits where the adaptability of individual trees is not infinite and there is a range of economic or environmental variability (Namkoong et al., 1980). When breeding base populations for immediate commercial use, it is theoretically more cost-effective to improve yield or value in different populations that are adapted to different environments. By applying simple breeding procedures within each, an adaptable array of foundation populations can be developed as easily as a single large hierarchical base population, and the resulting array is more readily incorporated into advanced varieties. Such an array can also serve as part of a gene conservation programme, since intraspecies diversity can be maintained and may often be enhanced (Namkoong, 1984a).
Almost all of the commercial angiosperms and the firs, the larches, the cedars and most pines of North America fall into this category of moderate neglect.
Either of the above methods permits use of advanced biotechnology, including cloning and gene transfer. Tissue cultures or other clonal material can be generated as easily in population arrays as in single breeding populations. Thus, cloning does not directly affect the gene management programme. It is merely a special way of using the end-products of the programme.
Similarly, controlled gene transfer need not alter gene conservation programmes, though it would certainly alter the breeding programmes themselves. At the moment, there are many obstacles to the use of gene transfer, but it is theoretically possible to transfer an operational gene from one organism to another. It is also theoretically possible to alter such genes if enough is known about them. Eventually, after a long period of rather tedious experimentation, gene exchanges may become feasible.
However, problems remain in the use of this technology since we must still know far more than we do now about specific genes and the alleles we wish to transfer. Genes capable of causing qualitative changes must be structured simply enough to be transferable and to be able to operate in the host genotype with the desired effect. Therefore, as in traditional breeding with single gene traits, we are limited to those few genes about which we can develop some clear idea of qualitative effects. Since gene exchanges allow otherwise impossible transfers and potential alterations, it will undoubtedly expand our vision of what it is possible for single genotypes to do; it will also be of direct commercial value; and it will teach us about inheritance. At this time, however, it can be viewed only as an intriguing supplement to traditional breeding methods of gene management (Sederoff et al., 1985). Certainly, we cannot rely upon direct gene transfer as a usable technique for gene conservation any time soon.
Managing breeding populations Obviously, all breeding methods require greater investments than those needed to manage an unimproved forest. A breeding programme can involve elaborate testing, estimation and breeding for different kinds of gene effects for several different commercial objectives in several different geographical areas. However, it is also possible to scale operations down to very simple systems that produce some genetic gain in the short run - within one or a few generations. In a breeding programme with no testing and no base populations other than the commercial one, genetic variation is lost rapidly and only additive gene effects for, for example, general average growth in one kind of environment can be exploited. In elaborate breeding systems, far more flexibility is created, and information is generated to improve future gains, without loss of genetic variation. Various levels of compromise exist between these two extremes. Each agency thus requires a decision-making strategy for each species concerned. When only one species is involved, the allocations involve choices of the number of populations to develop, their size, range of adaptability, etc.
We must exercise caution when extrapolating from present conditions to any assumptions that the present population structures are optimal, equilibrium states.
Agencies could organize affordable long-term development programmes for the various subpopulations and consider the collection of breeding populations a meta-breed with the objective of ensuring the overall utility and improvement of the species (Namkoong et al., 1980). However, for multiple species programmes, an allocation of effort among them must be determined. For commercial needs, it is unlikely that all species would be of equal importance, and for biological potential it is unlikely that all species would be equally likely to generate gains. Therefore, to maximize commercial profit with finite resources, particular sets of traits in particular sets of environments for a limited array of species could be programmed. For example, Ohba (1984) proposes to subdivide Japan into zones with different sets of priority selection criteria that dictate the intensity of breeding to be followed.
Assuming that some method of allocation is chosen, each agency is likely to derive a list of species, each with a different assigned priority. Many agencies will probably arrive at a highly skewed distribution of effort with one species developed intensively in many multiple populations and all the rest relegated to the simplest level possible. Even if several species are given some attention by several different agencies, it is likely, even considering those species at present commercially useful, that many of them will not be bred intensively by any one agency. These species may therefore never be developed as a collection of populations in a cohesive meta-breed. Almost all of the commercial angiosperms and the firs, the larches, the cedars and most pines of North America fall into this category of moderate neglect. For such species, interagency efforts may be required to conserve and develop populations in low-intensity programmes to enhance their potential use for future generations.
While some commercial species can be expected to be well developed, either within government or private organizations or by efforts such as the International Union of Forestry Research Organizations working parties, many commercially useful species will not. Future users of forests will likely find that opportunities for enhancement were lost, and that the genetic resource was eroded to some extent. In North America, Europe and East Asia, the main problem is expected to be the lack of enhancement programmes, while elsewhere both conservation and enhancement programmes are underfunded.
The design of future forests would be better informed and would likely lead to more stable forest ecosystems with populations more broadly adaptable to variable environments.
Unfortunately, there is no general forum in which to discuss a global strategy to identify species that can be safely neglected. Hence, there are no rational choices being made for an optimum programme of research and development except the present, narrowly contained economic criteria. Recommendations of the Panel of Experts on Forest Gene Resources, an FAO statutory body meeting every three to four years, include lists of priorities by region, species and operation; this is a useful first step in identifying global priorities for action.
There are generally good biological and economic reasons for the primary commercial species to occupy our immediate interest and for us to devote major efforts to improving species that are already economically and ecologically well adapted. Nevertheless, as product requirements and the physical and biotic environments of forests change, it is not unreasonable to expect that the list of commercially important species will change. In the United States, for example, a small change in wood prices, or in the location of commercial forestry sites, or in planting techniques, could make some species of Alnus, Prunus or Quercus much more likely candidates for commercial development. The need for reserve or substitute species and varieties as a safety net is obvious. This need becomes more critical as the genetic base of the primary varieties narrows. There are, of course, abundant examples in forestry around the Pacific Basin and from North America and Europe where native species are displaced by other commercial species, populations or provenances.
Testing has been extensive for some species, and trials will undoubtedly continue to be established. The objective of most of these past trials has been to replace whole populations or species with others that better meet present-day needs. They are, however, similar to tests designed to evaluate specific traits of populations for possible back-crossing or gene transfer of given traits into established varieties or populations. These trials often have two principal objectives: (1) discerning and sampling the distribution of genetic variation; and (2) analysing and discriminating useful differences between genes, individuals or populations. These two objectives are discussed below.
Genetic variation The first objective is to understand the present distribution of genetic variation produced by the combination of natural forces and human activities. Fundamental questions need to be answered about the structure of species, the ways in which different genes and gene combinations may be common in some areas and rare in others, and the extent to which such patterns are related to the species' survival strategy. A few species such as Pinus resinosa contain relatively little genetic variability; samples from adjacent trees or from different ends of the distribution of the population are alike (Fowler and Lester, 1970). Most tree species, however, seem to contain high levels of genetic variability, of which the proportions located within stands are great - at least in relation to most other plant species (Hamrick, 1983). However, it also seems that there are finely tuned heritable adaptations to environmental gradients even in species such as Pseudotsuga menziesii (Campbell, 1979) which generally do not display much discernible variation between stands (Yeh, 1981). The lack of high genetic variability among stands therefore does not necessarily indicate the absence of genes that confer special adaptations. Furthermore, there is substantial evidence of significant levels of differentiation among conifers in Europe (Muhs, 1981) and in Japan (Sakai et al. 1974).
Only very meagre funding is available for any but the most important commercial species in industrialized forestry.
One of the problems we have in studying the existing levels and patterns of allelic distributions is that we can sample populations only within a very narrow slice of time. While the changes in forest gene patterns that influence adaptability may take many years and several generations to equilibrate, studies of gene variations have generally been limited to one or two decades and often to samples from one or two years. Longer patterns of generational changes in stand structure are easy to miss with limited sampling. Thus, the pattern of allele dispersal sampled in eastern North American forests, for example, may reflect only the dispersal conditions extant at the time of stand establishment; they may reflect the socio-economic milieu of the 1930s and 1940s more than any biological steady-state condition. Humans may strongly influence the genetic structure of forest trees directly by selection effects and indirectly by changing pollen and seed dispersal and seedling densities. Thus, as detailed elsewhere (Namkoong, 1984b; 1985), the genetic dynamics of our forest species may be undergoing substantial changes, and it is not at all clear that even the temperate conifer species are at present in a steady state. For example, in Pinus taeda (Roberds and Conkle. 1984) and Pinus sylvestris (Tigerstedt, 1984), the populations are not in equilibrium. Similarly in southern pine beetle (Dendroctonus frontalis Zimmermann), the populations are not at a stable equilibrium (Namkoong et al., 1979). Furthermore, if tree species are in a state of transition, so too are associated species as well as their pest and pathogen populations (Namkoong, 1983). It is especially important for us to recognize that states of disequilibrium may have been caused by human impacts on the genetic structure of interacting species. As a result, we must exercise caution when extrapolating from present conditions to any assumptions that the present population structures are optimal, equilibrium states.
For tropical species, with more complex and restricted reproductive modes (Stern and Roche, 1974) and more complex stand structures (Ashton. 1976; Bawa, 1976), ecological and genetic structural complexity may be important for species adaptability and continued evolution. Forest populations may have evolved in the tropics with fine, stable subdivisions of populations. Temperate forests, while not stable, may be adapted to wide variations on population size and distribution. In the tropics, however, multiple small populations appear to be the normal structural mode for tree species, perhaps buffering species against pathogen epidemics.
A problem in using such species is our nearly total ignorance of their genetic structure. In the absence of knowledge of the coevolution of competitors, pests and pathogens, it is necessary to save a greater diversity than may be ultimately needed until such variations as may be redundant can be safely eliminated. Thus, the first objective of provenance trials is the study of natural population structures.
Useful populations The second objective of provenance trials is to identify populations for use. It does not necessarily conflict with the first objective - understanding the distribution of genetic variation - but it is oriented toward practical breeding decisions about initial gain and immediate gene conservation. Assuming that we know what traits or genes are desirable, the direct problem is to estimate the probability that a resampling will achieve sufficient additional gain to be worth the attempt to find such better populations. We must feel not only that such populations exist but also that the tests are designed to locate and sample better populations in a timely manner. If there is little evidence of large population differences, little benefit will result from new population samples (Namkoong. 1978). Similarly, even if differences do exist but are random with respect to any measurable feature of the environment, we will have little chance of directing a population search with a reasonable probability of achieving additional gain. Furthermore, any expected gain from population reselection may not equal the gain achievable by ordinary breeding with previously established breeding populations. However, until the distribution of alleles for all traits of potential value is known, we cannot know the costs of forgone opportunities to incorporate particular traits or levels of trait performances.
Hence, the search for populations useful as sources of genes for producing subsets of desired traits is directed toward finding genetic variation. The design and analysis of such tests require no new statistical theory: multiple regression techniques can be extended to multivariate analysis (Namkoong, 1967). For these purposes, several regression variables can be identified as causal variables or variables useful for identifying the location or identity of populations. The analysis of association between a dependent response variate, such as growth, and independent variables, such as'' altitude of origin, is then carried out with several response variates as I well as with the correlated relationships among the variates. It can ' then be determined whether variations are other than random, and the size and utility of those variations can be estimated for any single trait or combination. In this way, we can determine the usefulness either of any previously sampled population or of unsampled but potentially usable populations.
Advances in the design and analysis of such tests have made the achievement of these objectives attainable in moderate-sized plantings. However, for pests and pathogens, which can evolve relatively rapidly, estimates of types and effects of resistance have to be made within the context of their population and their evolutionary dynamics. Testing and estimation procedures for them differ from those for responses to physical environmental variables. Testing is directed to discerning genetic variations in forms of resistance or reaction phenomena. Dynamic analysis is then required to predict the effects of introducing resistance types into a forest ecosystem.
Similar testing procedures are, needed to conserve and develop agronomic species and varieties not currently in commercial use. Often, little is known of the present or natural distribution of traits or alleles, of the location of potentially useful populations, or of especially useful trait expressions. Therefore, studies of wild relatives of crop plants are directed to understanding the evolution of the crops and to finding sources of genes for introduction into commercial varieties. The ecogeographic studies of noncommercial varieties are directed primarily to finding genes that may be useful in established varieties and in new breeding populations. For many of these crop species, with their short breeding cycles and long histories of breeding, concern has focused on preservation. Once endangered sources of germ-plasm are secured, geneticists trust that the testing and enhancement stages of selection can be carried out at some leisure. The organization of such programmes is not well defined or fixed (Kannenberg, 1984), and the difficulties of breeding and back-crossing are not trivial (Frey et al., 1984). Nevertheless, I believe that success will be achieved. Thus, while specific breeding techniques and the organization of breeding populations may differ (Namkoong, 1984c), the problems in testing tree and agronomic crop species are similar for species or varieties not currently in commercial use.
Two kinds of programmes, are needed to realize the potential value inherent in preserved secondary populations: testing, and development. Testing is generally required to judge inherent capabilities; the testing efforts needed are those outlined above for provenance testing. The developmental or enhancement efforts are those outlined for the creation of hierarchical or multiple populations.
TROPICAL RAIN FOREST AT A CROSSROADS can a wealth of species be saved?
The source materials for testing and development must be some ex situ or in situ sample of the available gene pool. As a minimum, such a sample must be large enough to have a reasonable chance of saving the useful genes. Even with the best sampling efforts, however, this minimum may miss many alleles if they are present only in small quantities at the time and in the place where the sampling is done. That is why it is so vital to determine patterns and structures of variation. To reflect the structural diversity which may exist in populations, samples are needed from different areas, stands and individuals. While difficult, such programmes are feasible.
The vast majority of forest plant species have little recognized current or future commercial value, or no function that is not otherwise served by other species. They may be useful only for some elements of ecosystem stability, or they may be considered to be potentially useful, but only for unforeseen future possibilities. For such species there exists no effective concept of "improvement" for human use. Hence, merely ensuring the continued existence of a sample of such populations or species may be the only management objective. The sample should have some minimum number and a reasonable distribution.
There are at least two reasons, however, for considering somewhat more intensive management than that which is implied only by the need to conserve such species. The first is the direct utility of such populations for the study and understanding of essentially natural population processes. The second is the possibility of uncovering uses at present unknown, such as medicines or insecticides. Since our understanding of the evolution of forest ecosystems, and even of the most valuable commercial species, is so tenuous, there is clear advantage to maintaining at least a sample of the evolutionary system. For species in some rough state of equilibrium, it is important to know if their genetic and ecological features are simple or complex, if viability selection factors or mating habits and fecundity interact to conserve or dissipate genetic variation. If species are not in a stable equilibrium, their ability to return to an original equilibrium or to shift to new equilibria or limit cycles, or to go extinct, is an important consideration.
We would like to know also what features of evolution have conspired to create such stable or unstable behaviour. By learning about the possible behaviour of systems, we can inform ourselves of the possible ways in which the commercial species and forests in general can function. The design of future forests would undoubtedly be better informed and would likely lead to more stable forest ecosystems with populations more broadly adaptable to variable environments. There are, of course, the further benefits inherent in simply understanding how the world really operates, whether this leads to increased human utilization of forests or not.
Other contributions of non-commercial species to ecosystem functioning and stability cannot be lightly dismissed. While highly complex and interdependent webs of association may often be fragile and easily degenerated with high extinction rates of component species (May, 1973), the existence of fragility does not imply that species or systems should be allowed to die. Rather, for our own benefit, we must recognize that the various functions of non-commercial species include the long-term productivity of all other parts of the ecosystem.
The management options for these populations are more restricted than for commercial species and stands. Some form of in situ conservation seems best, even though it may be neither the most secure nor the least costly option. Since species values are likely to be associated with community functions, conservation is perhaps most easily assured by area management as in reserves, parks or natural areas. The requirements of population size and multiple population dispersal remain the same, and since little direct control of each species in any one area can be expected, some redundancy is needed in size of individual populations and in numbers of populations. For species in which population size is a driving factor in evolution, the multiple populations should be of variable sizes. For species that respond to know environmental variables, including the coevolution of other species, sampling from the range of those variables is an efficient method for capturing significant genetic variability.
For many species, however, even such recommendations are futile, since so little is known of the species distribution or even of their existence. For these, targeted sampling in centres of diversity such as outlined by Pires (1978) may be the only realistic hope of their conservation. Obviously, where known centres of diversity exist within a species, those would be prime targets for sampling. Supplementary sampling from more extreme populations is desirable (Namkoong, 1980). Similarly, we should not rely exclusively on natural reserves in centres of origin or diversity, but should also reserve areas of more extreme habitat for the various biotypes to ensure sampling the genetic diversity of the contained species. There is, in fact, reason to believe that there is a substantial degree of independence between measures of bio logical diversity and the adaptive variations that exist within species. While certain types of species interaction may tend to increase intraspecific genetic variation (Leonard, 1984; Futuyama, 1983), other types may reduce it. Thus, in order to conserve the viability of an ecosystem and to ensure the availability of genetic variation, the dynamics of species evolution will require multiple population sampling.
Whether we consider a species and its associates to be of commercial value or not, we know that genetic and ecological variations are not likely to be in an evolutionarily static state. While some may have impoverished gene pools, and some may contain all genetic variations within single large populations, most must be considered to be in some transient evolutionary state. Whether they have been stable in the recent past or not, human activities have probably at least changed many of their equilibrium. For managers of genetic resources, the goal is not to conserve a static state but to contain a dynamic system, even though our understanding of its dynamics is very meagre.
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