Dimensionless Life Histories and Effective Population Size

The effective size ( N _e ) of a population can be estimated from demographic information. We evaluated a recent model, showing that N _e depends strongly on the relationship between age at reproductive maturity ( M ) and average adult lifespan ( A ). N _e converges on half the number of potentially reproducing adults ( N/2 ) as M decreases relative to A , but it increases linearly as M increases for a given value of A . Therefore, convergence of N _e on N/2 is more likely in organisms with a short sexual maturation period scaled to adult lifespan. To assess the generality of this convergence we asked whether most organisms are characterized by this requisite relationship between M and A . The dimensionless number M/A is approximately invariant within taxa, but it is markedly different across taxa. Previous work focused on birds and mammals, taxa with unusually small M/A (0.4 and 0.75). Other animal taxa take longer than most birds and mammals to reach maturity for a given reproductive lifespan, so they are characterized by larger M/A (e.g., fish, 2.0). In theory, these taxon-specific life histories strongly influence N _e . We conclude that N _e is expected to approach N/2 , provided that M/A is (unusually) small, and that N _e / N among poikilotherms may often exceed that of mammals and especially birds.     

Effective Population Size and Lifetime Reproductive Success

The mean and variance of lifetime reproductive success, E_LRS and V_LRS, influence the ratio of effective to census population size, N_e/N_c. Because the complete data needed to calculate E_LRS and V_LRS are seldom available, we provide alternatives for estimating N_e/N_c from incomplete data. These estimates should be useful to conservation biologists trying to compute the effective size of a censused population. An analytical approach makes assumptions regarding the process influencing offspring survival. We provide a method for examining the validity of those assumptions and show that particular violations can result in either over- or underestimates. When the assumptions are violated or when more data are available, we suggest estimating N_e/N_c using computer simulations of models based on individuals. We examine how such simulations can be used to estimate N_e/N_c using an individual-based model for Lesser Snow Geese ( Anser caerulescens ). We demonstrate that such estimates can be biased unless the simulations are based on complete cohorts and samples of known age. We show that because the estimate of N_e/N_c depends on the stage of the reproductive cycle used as a point of reference in the model, the census population size N_c must be based on the same stage to provide unbiased estimates of N_e.     

Supportive Breeding and Variance Effective Population Size

The practice of supporting weak, wild populations through release of individuals bred in captivity is becoming an increasingly important conservation measure. A frequently recommended form of such breeding-release activity refers to supportive breeding: a fraction of the target population is brought into captivity for reproduction, and the resulting progeny are released to mix with the wild segment of the population. We derived an expression for the variance effective size of a population managed through supportive breeding and discuss its relationship to previously published equations that are based on the assumption of random mating. We show that the effect of supportive breeding may be quite different on the inbreeding and the variance effective sizes. Whereas supportive breeding always results in a reduction of the inbreeding effective number, the variance effective number may either decrease, increase, or remain unchanged. We discuss these observations in relation to conservation management and suggest some general guidelines for supportive breeding situations. Our recommendations include making a distinction between inbreeding and variance effective numbers; taking particular care when dealing with organisms with high reproductive potential; assuring that the amount of drift be no larger than it would be without supportive breeding; and focusing primarily on the variance effective size of a population-that is, on the effective number directly related to the rate of loss of gene diversity.     

Effective Population Size in Winter-Run Chinook Salmon

Winter-run chinook salmon from the Sacramento River, California, is federally listed as endangered. Since 1989 there has been aprogram to augment the natural population by capturing adults, artificially spawning them, raising tine young and releasing the smolt. Here we estimate the effective population size of these captive-raised fish, the natural run, and the combination of both groups over the three-year period from 1991 to 1993. We find that the most appropriate estimate of the effective population size of the captive-raised progeny is a variance estimate of effective population size standardized so that the number of released smolts returning to spawn was the same as the number of spawners used to produce the smolts originally. We have generated 10,000 random samples to simulate returns from these released progeny. The estimates of the effective population sizes in 1991, 1992, and 1993 were only 7.02, 19.07, and 7.74, respectively. We then determined limits on the effective population size of the natural run based on 0.1 and 0.333 of the run-size estimates. Using estimates of the captive proportion of the run, the minimum estimates of the effective population size of the overall run for the three years were 21.9, 127.3, and 39.0, and the maximum estimates were 61.6, 401.0, and 108.7. It does not appear that the hatchery program has reduced the overall effective population size. The run sizes in each year are extremely low, however, and it is possible that fish will be lost from this run in one of the years in the immediate future, making reestablishment of a healthy run even more difficult.     

Effective Population Size in Red-Cockaded Woodpeckers: Population and Model Differences

Loss of genetic variability in isolated populations is an important issue for conservation biology. Most studies involve only a single population of a given species and a single method of estimating rate of loss. Here we present analyses for three different Red-cockaded Woodpecker ( Picoides borealis ) populations from different geographic regions. We compare two different models for estimating the expected rate of loss of genetic variability, and test their sensitivity to model parameters. We found that the simpler model (Reed et al. 1988) consistently estimated a greater rate of loss of genetic variability from a population than did the Emigh and Pollak (1979) model. The ratio of effective population size (which describes the expected rate of loss of genetic variability) to breeder population size varied widely among Red-cockaded Woodpecker populations due to geographic variation in demography. For this species, estimates of effective size were extremely sensitive to survival parameters, but not to the probability of breeding or reproductive success. Sensitivity was sufficient that error in estimating survival rates in the field could easily mask true population differences in effective size. Our results indicate that accurate and precise demographic data are prerequisites to determining effective population size for this species using genetic models, and that a single estimate of rate of loss of genetic variability is not valid across populations.     

Interdisciplinary Guidelines for Developing Effective Koala Conservation Policy

Abstract: Adequacy of the ongoing koala policy process and whether it can conserve koalas is currently in dispute. To address this issue, interdisciplinary guidelines are available to improve koala policy and management and to find consensus. These guidelines focus attention on five policy elements. The first three are rational, political, and moral perspectives on koala policy; the fourth the standpoint of a participant, and the fifth is knowledge integration for practical action. We discuss and illustrate these elements with koala case material. Rationality in policy is addressed through problem orientation, which requires participants to clarify goals, identify problems, and create alternatives in an iterative way. We examined the political dynamics—value clashes—in decision processes. A decision process ideally clarifies and secures common interests. We provide standards for each decision function, such as reliability, comprehensiveness, timeliness. Morality rests on basic premises that are used to justify policy positions. Clarification of the participant's standpoint addresses differing personalities, epistemologies, disciplines, and organizational and parochial biases. Integrating knowledge for practical policy action requires a conceptual framework that is up to the demands of the task. Together the five policy elements make up a logically comprehensive set of interrelated concepts for koala policy development, implementation, and appraisal. Many opportunities exist to use these guidelines skillfully in on-the-ground koala conservation efforts to improve koala policy outcomes.     

我国城市污水处理的有效措施

我国水环境污染和水资源短缺,促进了污水处理厂的建设,而污水处理工艺在很大程度上决定了污水处理厂的投资、基建费用、用地和运行管理费用。文章介绍了我国有污水处理厂的工艺、投资和运行费用。结合我国的基本国情,提出了建立经济有效的处理工艺的措施。     

Reorienting Systematic Conservation Assessment for Effective Conservation Planning

Abstract: Systematic conservation assessment (an information‐gathering and prioritization process used to select the spatial foci of conservation initiatives) is often considered vital to conservation‐planning efforts, yet published assessments have rarely resulted in conservation action. Conservation assessments may lead more directly to effective conservation action if they are reoriented to inform conservation decisions. Toward this goal, we evaluated the relative priority for conservation of 7 sites proposed for the first forest reserves in the Union of the Comoros, an area with high levels of endemism and rapidly changing land uses in the western Indian Ocean. Through the analysis of 30 indicator variables measured at forest sites and nearby villages, we assessed 3 prioritization criteria at each site: conservation value, threat to loss of biological diversity from human activity, and feasibility of reserve establishment. Our results indicated 2 sites, Yiméré and Hassera‐Ndrengé, were priorities for conservation action. Our approach also informed the development of an implementation strategy and enabled an evaluation of previously unexplored relations among prioritization criteria. Our experience suggests that steps taken to ensure the closer involvement of practitioners, include a broader range of social data, encourage stakeholder participation, and consider the feasibility of conservation action can improve the relevance of assessments for conservation planning, strengthen the scientific basis for conservation decisions, and result in a more realistic evaluation of conservation alternatives.     

Estimating the Effective Population Size of Conserved Populations

Accurate estimation of effective population size is important in attempts to conserve small populations of animals or plants. We review the genetic and ecological methods that have been used to estimate effective population size in the past and suggest that, while genetic methods may often be appropriate for the estimation of N _e, and its monitoring, ecological methods have the advantage of providing data that can help predict the effect of a changed environment on N _e. Estimation of N _e, is particularly complex in populations with overlapping generations, and we summarize previous empirical estimates of N _e that used ecological methods in such populations. Since it is often difficult to assess what parameters and assumptions have been used in previous calculations, we suggest a method that provides a good estimate of N _e, makes clear what assumptions are involved, and yet requires a minimum of information. The method is used to analyze data from 14 studies. In 36% (5) of these studies, our estimate is in excellent agreement with the original, and yet we use significantly less information, in 21% (3) the original estimate is markedly lower, in 43% (6) it is markedly higher. Reasons for the discrepancies are suggested. Two of the underestimates involve a failure in the original to account for a long maturation time, and four of life overestimates involve problems in the original with the correction for overlapping generations.     

Relationship of Effective to Census Size in Fluctuating Populations

Abstract: The effective size of a population (    N _e   ) rather than the census size (    N ) determines its rate of genetic drift. Knowing the ratio of effective to census size, N _e  /   N , is useful for estimating the effective size of a population from census data and for examining how different ecological factors influence effective size. Two different multigenerational ratios have been used in the literature based on either the arithmetic mean or the harmonic mean in the denominator. We clarify the interpretation and meaning of these ratios. The arithmetic mean N _e  /   N ratio compares the total number of real individuals to the long-term effective size of the population. The harmonic mean N _e  /   N ratio summarizes variation in the N _e  /   N ratio for each generation. In addition, we show that the ratio of the harmonic mean population size to the arithmetic mean population size provides a useful measure of how much fluctuation in size reduced the effective size of a population. We discuss applications of these ratios and emphasize how to use the harmonic mean N _e  /   N ratio to estimate the effective size of a population over a period of time for which census counts have been collected.     

Effective antibacterial and antioxidant properties of methanolic extract of Laurus nobilis seed oil

This study was carried out to determine the in vitro antimicrobial and antioxidant activities of the essential oil, seed oil, and methanolic extract of seed oil obtained from Laurus nobilis L. (Lauraceae). The methanolic extract of seed oil exhibited more effective antibacterial activity comparing to essential oil and seed oil, GC-MS analyses of the essential oil resulted in the identification of 25 compounds. 1.8-Cineol (44.72%), a-Terpinyl acetate (12.95%), Sabinene (12.82%) were the main components. The fatty acid composition was characterized with the high content of linoleic acid (40.79%) and lauric acid (38.08%). The 50% (IC50) inhibition activity of the essential oil on the free radical DPPH was determined as 94.655 mg ml(-1), whereas IC50 value of methanolic extract of seed oil was found unstable. In the case of the linoleic acid system, oxidation of linoleic acid was inhibited by essential oil and methanolic extract of seed oil, which showed 64.28 and 88.76% inhibition, respectively. The inhibition value of the methanolic extract of seed oil was quite close to the synthetic antioxidant BHT, 92.46% inhibition.     

Understanding and Estimating Effective Population Size for Practical Application in Marine Species Management

Abstract: Effective population size (N_e) determines the strength of genetic drift in a population and has long been recognized as an important parameter for evaluating conservation status and threats to genetic health of populations. Specifically, an estimate of N_e is crucial to management because it integrates genetic effects with the life history of the species, allowing for predictions of a population's current and future viability. Nevertheless, compared with ecological and demographic parameters, N_e has had limited influence on species management, beyond its application in very small populations. Recent developments have substantially improved N_e estimation; however, some obstacles remain for the practical application of N_e estimates. For example, the need to define the spatial and temporal scale of measurement makes the concept complex and sometimes difficult to interpret. We reviewed approaches to estimation of N_e over both long‐term and contemporary time frames, clarifying their interpretations with respect to local populations and the global metapopulation. We describe multiple experimental factors affecting robustness of contemporary N_e estimates and suggest that different sampling designs can be combined to compare largely independent measures of N_e for improved confidence in the result. Large populations with moderate gene flow pose the greatest challenges to robust estimation of contemporary N_e and require careful consideration of sampling and analysis to minimize estimator bias. We emphasize the practical utility of estimating N_e by highlighting its relevance to the adaptive potential of a population and describing applications in management of marine populations, where the focus is not always on critically endangered populations. Two cases discussed include the mechanisms generating N_e estimates many orders of magnitude lower than census N in harvested marine fishes and the predicted reduction in N_e from hatchery‐based population supplementation.     

Crafting Effective Solutions to the Large Carnivore Conservation Problem

How problems are defined and redefined largely dictates how they will (or if they can) be solved, especially complex problems such as the challenge of conserving large carnivores in North America. We describe a practical and comprehensive method for analyzing problems within specific human and ecological contexts and for inventing, evaluating, and selecting solutions. We conducted a problem definition exercise for the large carnivore conservation problem and arrived at five key variables that must be addressed in order to protect these threatened species: cultural history, valuation, ecology, management systems, and the policy process. Our analysis maps the broad dimensions of the problem and identifies areas to be targeted by any successful solution strategy. The method we present and our proposed initial definition of the carnivore conservation problem can serve as a springboard for further analysis and policy making at specific sites and at appropriate scales for on-the-ground solutions to this and other natural resource problems.     

Conservation and Aid: Designing More Effective Investments in Natural Resource Governance Reform

Abstract:  Biodiversity conservation outcomes are closely related to the rules and institutions governing resource use. Creating local incentives for conservation through more secure resource tenure is central to conservation outcomes on private and communal lands, where the preponderance of biodiversity occurs. Conservation efforts in sub-Saharan Africa are therefore centrally concerned with governance dynamics and institutional reform processes, such as the decentralization of property rights, and how best to achieve such reforms. Traditional mechanisms for financing conservation efforts in Africa rely heavily on funds channeled through multilateral and bilateral aid agencies. The history of development aid highlights a range of constraints these aid agencies face in terms of working toward more effective resource governance arrangements and promoting reforms. Government aid agencies possess incentives for promoting large-scale and short-term projects that maximize expenditure volumes and tend to define issues in technical rather than political terms. The history of development aid suggests that these and other characteristics of aid agencies impedes their ability to influence governance reform processes and that aid funding may discourage the adoption of reforms. Greater emphasis in African conservation financing needs to be placed on flexible, small-scale investments aligned to local interests and constituencies that prioritize innovation, learning, and experimentation. Additionally, more research is required that explores the linkages between conservation funding, donor decision-making processes, and governance reforms.