Multiple-year optimization of conservation effort and monitoring effort for a fluctuating population

We consider optimal conservation strategies for an endangered population. We assume that juvenile survival is affected by unpredictable environmental fluctuation and can be improved by costly conservation effort. The initial population size is not accurately known at the time that the conservation effort level is chosen, but the uncertainty of its estimate can be reduced by a costly monitoring effort. In a previous paper, we analysed the optimal management strategy that minimizes a weighted sum of extinction probability and economic costs when only a single year is considered. Here we examine the case in which the conservation period lasts for several years by dynamic programming with incompletely observed process states. We study the optimal levels of the conservation and the monitoring efforts, and their dependence on the length of the conservation period and other parameters. The main conclusions are: (1) The optimal conservation effort in the first year depends on the accuracy of the information on the population size in the first year, but is almost independent of the accuracy of the information in later years. (2) When the risk of population extinction is small, the optimal conservation effort increases with the uncertainty of the population size. In contrast when the population is endangered, the optimal conservation effort decreases with the uncertainty of the population size. (3) The optimal conservation and monitoring efforts both increase with the length of the conservation period, provided that the population is relatively safe. However, if the population is endangered, both types of effort become smaller when the conservation period increases.     

Conservation management for the past, present and future

Conservation managers are in the unenviable position of trying to conserve and restore biodiversity, without having a definitive timeframe to restore it to. Currently, managers around the world focus on various timeframes from recent to historical, but without a definitive target, countless conservation problems arise. Managers need to determine what constitutes a native species, which species to reintroduce, whether selective breeding should be implemented to resurrect supposedly extinct organisms, targets on population levels, whether assisted migration should be employed when climate change alters the environmental envelope of a species surrounded by human-altered landscapes, and how to manage for stochasticity and evolutionary processes. Without having definitive goals to target, these issues are difficult/impossible to address. It is only by discussing these important issues that some consensus will be attained that allow us to stop responding to crises and start predicting the future of biodiversity and plan and respond accordingly.     

Assessment of risk,extinction, and threats to Himalayan yew in Pakistan

Himalayan yew (Taxus wallichiana) is in high demand due to the presence of taxol in its bark, needles, and seeds. This metabolite is used for the treatment of breast and ovarian cancer. In addition, Himalayan yew wood is used to prepare slabs (Tabai), coffins (Taabut), for graveyards. Due to illegal cutting of plant parts and other anthropogenic pressures, Himalayan yew is endangered, and threatened with extinction, in Himalaya. This species grows slowly and regenerates poorly, primarily due to low production and delayed germination (1.5–2 years) of its seeds. The study being reported here was conducted to assess the factors (natural and anthropogenic) threatening this species. Nine valleys (Miandam, Kalam, Shinko, Beha, Lalku, Shahgram, Bishigram, Gurnai, and Daral) in the Swat district of Khyber Pakhtunkhwa (KP), Pakistan, have stands of Himalayan yew that were selected for the study. Before the survey was conducted, five informal discussions were carried out to identify people to be interviewed. A survey was conducted with 225 key informants in these valleys concerning the threats associated with this species. Nineteen percent of the respondents felt that the main problem was lack of awareness, while 17% indicated over-harvesting (peeling bark, lopping branches, etc.), and 13% thought it was slow growth. Other reasons for Himalayan yew decline included various anthropogenic pressures, such as: overgrazing, 15%; agriculture, 11%; roof construction, 9%; fuelwood, 7%; decoration, 5%; medicinal use, 3%; and other, 1% (e.g., utility poles, as blades in water turbine because of its hard nature). The results of this study suggest that there is an immediate need to protect T. wallichiana by increasing awareness of its importance and the threats from over-grazing; cuttings (peeling bark, lopping branches, etc.); and other damaging, anthropogenic activities. Biotechnological tools, such as vegetative propagation and in-vitro regeneration, could be practiced in nurseries and laboratories to produce large numbers of healthy, juvenile plants. In addition to in-situ and ex-situ conservation and management, there is a need for local community involvement in the large-scale reforestation efforts.     

Conservation of freshwater fish resources of India: new approaches, assessment and challenges

The freshwater resources of India are currently experiencing an alarming decline in fish biodiversity due to several factors and as a result, a sizeable portion of fresh water fishes have been categorized as threatened. This emphasizes an immediate need for initiating research and actions for alternative management techniques to protect these aquatic systems. One such option that has potential to protect freshwater ecosystem from numerous threats is the creation of freshwater aquatic sanctuary (FAS) within protected area network. Though similar conservation practices are well established in the terrestrial and marine ecosystem, however, the work on freshwater systems has been very slow and negligible. In the present communication we conceptualized the need and approach for developing FAS within the protected area network based on our observations in the water bodies of the selected wildlife sanctuaries in Northern India as well as success stories of some other countries. In this study we assessed the fish diversity in the selected protected areas of Northern India. The assessment indicated that these sanctuaries harbor 28.26–31.13% of freshwater fishes, which are threatened in other areas. Apart from Indian Major Carps, Tor putitora, Chitala chitala, Pangasius pangasius, Clupisoma gerua, Ailia coila, Aorichthys aor, Wallago attu, Rhinomugil corsula, Ompok pabda, Ombok pabo etc. were the important species encountered in the protected waters. The various issues related to FAS including objectives, approach, potential tools, implementation and management are discussed towards saving endangered fish germplasm resources. Approaches, tools and modus operandi proposed in this communication could be utilized by other developing countries in the region.     

Habitat selection and population regulation in temporally fluctuating environments

Understanding and predicting the distribution of organisms in heterogeneous environments lies at the heart of ecology, and the theory of density-dependent habitat selection (DDHS) provides ecologists with an inferential framework linking evolution and population dynamics. Current theory does not allow for temporal variation in habitat quality, a serious limitation when confronted with real ecological systems. We develop both a stochastic equivalent of the ideal free distribution to study how spatial patterns of habitat use depend on the magnitude and spatial correlation of environmental stochasticity and also a stochastic habitat selection rule. The emerging patterns are confronted with deterministic predictions based on isodar analysis, an established empirical approach to the analysis of habitat selection patterns. Our simulations highlight some consistent patterns of habitat use, indicating that it is possible to make inferences about the habitat selection process based on observed patterns of habitat use. However, isodar analysis gives results that are contingent on the magnitude and spatial correlation of environmental stochasticity. Hence, DDHS is better revealed by a measure of habitat selectivity than by empirical isodars. The detection of DDHS is but a small component of isodar theory, which remains an important conceptual framework for linking evolutionary strategies in behavior and population dynamics.     

Optimal Dynamic Allocation of Conservation Funding Among Priority Regions

The optimal allocation of conservation resources between biodiverse conservation regions has generally been calculated using stochastic dynamic programming, or using myopic heuristics. These solutions are hard to interpret and may not be optimal. To overcome these two limitations, this paper approaches the optimal conservation resource allocation problem using optimal control theory. A solution using Pontryagin’s maximum principle provides novel insight into the general properties of efficient conservation resource allocation strategies, and allows more extensive testing of the performance of myopic heuristics. We confirmed that a proposed heuristic (minimize short-term loss) yields near-optimal results in complex allocation situations, and found that a qualitative allocation feature observed in previous analyses (bang-bang allocation) is a general property of the optimal allocation strategy.     

Multitasking and the evolution of optimal clutch size in fluctuating environments

Adaptive studies of avian clutch size variation across environmental gradients have resulted in what has become known as the fecundity gradient paradox, the observation that clutch size typically decreases with increasing breeding season length along latitudinal gradients, but increases with increasing breeding season length along elevational gradients. These puzzling findings challenge the common belief that organisms should reduce their clutch size in favor of additional nesting attempts as the length of the breeding season increases, an approach typically described as a bet‐hedging strategy. Here, we propose an alternative hypothesis—the multitasking hypothesis—and show that laying smaller clutches represents a multitasking strategy of switching between breeding and recovery from breeding. Both our individual‐based and analytical models demonstrate that a small clutch size strategy is favored during shorter breeding seasons because less time and energy are wasted under the severe time constraints associated with breeding multiply within a season. Our model also shows that a within‐generation bet‐hedging strategy is not favored by natural selection, even under a high risk of predation and in long breeding seasons. Thus, saving time—wasting less time as a result of an inability to complete a breeding cycle at the end of breeding season—is likely to be the primary benefit favoring the evolution of small avian clutch sizes during short breeding seasons. We also synthesize the seasonality hypothesis (pronounced seasonality leads to larger clutch size) and clutch size‐dependent predation hypothesis (larger clutch size causes higher predation risks) within our multitasking hypothesis to develop an integrative model to help resolve the paradox of contrasting patterns of clutch size along elevational and latitudinal gradients. Ultimately, our models provide a new perspective for understanding life‐history evolution under fluctuating environments.     

Coalescent process with fluctuating population size and its effective size

We consider a Wright-Fisher model whose population size is a finite Markov chain. We introduce a sequence of two-dimensional discrete time Markov chains whose components describe the coalescent process and the fluctuation of population size. For the limiting process of the sequence of Markov chains, the relationship of the expectation of coalescence time to the harmonic and the arithmetic means of population sizes is shown, and the Laplace transform of the distribution of coalescence time is calculated. We define the coalescence effective population size (cEPS) by the expectation of coalescence time. We show that cEPS is strictly larger (resp. smaller) than the harmonic (resp. arithmetic) mean. As the population size fluctuates more quickly (resp. slowly), cEPS is closer to the harmonic (resp. arithmetic) mean. For the case of a two-valued Markov chain, we show the explicit expression of cEPS and its dependency on the sample size.     

Effective size of density‐dependent populations in fluctuating environments

Reliable estimates of effective population size are of central importance in population genetics and evolutionary biology. For populations that fluctuate in size, harmonic mean population size is commonly used as a proxy for (multi‐) generational effective size. This assumes no effects of density dependence on the ratio between effective and actual population size, which limits its potential application. Here, we introduce density dependence on vital rates in a demographic model of variance effective size. We derive an expression for the ratio in a density‐regulated population in a fluctuating environment. We show by simulations that yearly genetic drift is accurately predicted by our model, and not proportional to as assumed by the harmonic mean model, where N is the total population size of mature individuals. We find a negative relationship between and N. For a given N, the ratio depends on variance in reproductive success and the degree of resource limitation acting on the population growth rate. Finally, our model indicate that environmental stochasticity may affect not only through fluctuations in N, but also for a given N at a given time. Our results show that estimates of effective population size must include effects of density dependence and environmental stochasticity.     

Effects of parental survival on clutch size decisions in fluctuating environments

Whereas in constant environments parental survival has no effect on optimal clutch size in the absence of trade-offs between juvenile and parental survival, the situation is drastically different in fluctuating environments. We consider a model in which, with respect to reproduction, parents and offspring are equivalent at the start of the next breeding season. When generations are non-overlapping, the clutch size maximizing geometric mean surviving number of offspring is optimal among all pure clutch size strategies. We prove that, as parental survival increases relative to that of the offspring, the optimal clutch size converges to the arithmetic mean maximizing clutch size (the so-called ‘Lack clutch size’). We also give a numerical procedure for calculating optimal mixed strategies and we show that, as environmental variance increases and/or parental survival decreases, mixed rather than pure strategies become optimal. Furthermore, we explain how to estimate fitness from empirical data under the assumptions of our model. This revised version was published online in July 2006 with corrections to the Cover Date.     

基于红外相机技术对亚洲象个体识别和种群数量的评估

以云南西双版纳国家级自然保护区尚勇子保护区内亚洲象种群为研究对象,通过自动红外照相技术,估算了该地区亚洲象的最小种群数量。本研究于2016年1月,在研究区域内共布设了27个相机位点,野外安放时间为4个月。调查期间,每台相机的有效捕获日为9-52d不等（均值为24d）,红外相机有效捕获日621d,拍摄到亚洲象照片共1944张。通过红外相机照片开展个体识别,最终估算出尚勇保护区内亚洲象的最小种群数量为69头（其中成年象38头,亚成象15头,幼象16头）。拍到7头活动于中国-老挝边境区域的跨境象群。本文探讨利用红外相机拍摄的亚洲象照片进行个体识别的方法,指出与常规调查方法相比较的优势和不足,作为快速、实时有效的种群评估方法的价值。研究结果丰富了保护区内亚洲象种群数据库,为研究、制定和开展亚洲象保护行动提供重要支撑。     

Extinction of populations by inbreeding depression under stochastic environments

Inbreeding depression may induce rapid extinction due to positive feedbacks between inbreeding depression and reduction of population size, which is often referred to as extinction vortex by inbreeding depression. The present analysis has demonstrated that the extinction vortex is likely to happen with realistic parameter values of genomic mutation rate of lethals or semilethals, equilibrium population size, intrinsic rate of natural increase, and rate of population decline caused by nongenetic extrinsic factors. Simulation models incorporating stochastic fluctuations of population size further indicated that extinction by inbreeding depression is facilitated by environmental fluctuations in population size. The results suggest that there is a positive interaction between genetic stochasticity and environmental stochasticity for extinction of populations by inbreeding depression. Received: May 10, 1999 / Accepted: November 5, 1999     

The Effect of Wildlife Conservation on Local Perceptions of Risk and Behavioral Response

In this study, we examine the effect of Tarangire National Park (TNP) on local perceptions of risk and how these perceptions may influence behavioral responses. Data were collected during 2004–2005 through household surveys and participatory risk mapping (PRM) in eight villages east of TNP. By identifying and rank-ordering respondents’ perceived risks, PRM enhances understanding of the nature and variation of risks faced within a population by distinguishing between the incidence and severity of subjective risk perceptions. Results indicate that proximity to the park has a strong effect on the type and severity of perceived risks. Within villages close to the park, however, behavioral response to perceived risks varies considerably. This study contributes to an appreciation of how behavioral response to environmental and socioeconomic factors is mediated by human perception.

Conservation Biogeography: assessment and prospect

There is general agreement among scientists that biodiversity is under assault on a global basis and that species are being lost at a greatly enhanced rate. This article examines the role played by biogeographical science in the emergence of conservation guidance and makes the case for the recognition of Conservation Biogeography as a key subfield of conservation biology delimited as: the application of biogeographical principles, theories, and analyses, being those concerned with the distributional dynamics of taxa individually and collectively, to problems concerning the conservation of biodiversity. Conservation biogeography thus encompasses both a substantial body of theory and analysis, and some of the most prominent planning frameworks used in conservation. Considerable advances in conservation guidelines have been made over the last few decades by applying biogeographical methods and principles. Herein we provide a critical review focussed on the sensitivity to assumptions inherent in the applications we examine. In particular, we focus on four inter‐related factors: (i) scale dependency (both spatial and temporal); (ii) inadequacies in taxonomic and distributional data (the so‐called Linnean and Wallacean shortfalls); (iii) effects of model structure and parameterisation; and (iv) inadequacies of theory. These generic problems are illustrated by reference to studies ranging from the application of historical biogeography, through island biogeography, and complementarity analyses to bioclimatic envelope modelling. There is a great deal of uncertainty inherent in predictive analyses in conservation biogeography and this area in particular presents considerable challenges. Protected area planning frameworks and their resulting map outputs are amongst the most powerful and influential applications within conservation biogeography, and at the global scale are characterised by the production, by a small number of prominent NGOs, of bespoke schemes, which serve both to mobilise funds and channel efforts in a highly targeted fashion. We provide a simple typology of protected area planning frameworks, with particular reference to the global scale, and provide a brief critique of some of their strengths and weaknesses. Finally, we discuss the importance, especially at regional scales, of developing more responsive analyses and models that integrate pattern (the compositionalist approach) and processes (the functionalist approach) such as range collapse and climate change, again noting the sensitivity of outcomes to starting assumptions. We make the case for the greater engagement of the biogeographical community in a programme of evaluation and refinement of all such schemes to test their robustness and their sensitivity to alternative conservation priorities and goals.     

Plasticity of size and growth in fluctuating thermal environments: comparing reaction norms and performance curves

Ectothermic animals exhibit two distinct kinds of plasticityin response to temperature: Thermal performance curves (TPCs),in which an individual's performance (e.g., growth rate) variesin response to current temperature; and developmental reactionnorms (DRNs), in which the trait value (e.g., adult body sizeor development time) of a genotype varies in response to developmentaltemperatures experienced over some time period during development.Here we explore patterns of genetic variation and selectionon TPCs and DRNs for insects in fluctuating thermal environments.First, we describe two statistical methods for partitioningtotal genetic variation into variation for overall size or performanceand variation in plasticity, and apply these methods to availabledatasets on DRNs and TPCs for insect growth and size. Our resultsindicate that for the datasets we considered, genetic variationin plasticity represents a larger proportion of the total geneticvariation in TPCs compared to DRNs, for the available datasets.Simulations suggest that estimates of the genetic variationin plasticity are strongly affected by the number and rangeof temperatures considered, and by the degree of nonlinearityin the TPC or DRN. Second, we review a recent analysis of fieldselection studies which indicates that directional selectionfavoring increased overall size is common in many systems—thatbigger is frequently fitter. Third, we use a recent theoreticalmodel to examine how selection on thermal performance curvesrelates to environmental temperatures during selection. Themodel predicts that if selection acts primarily on adult sizeor development time, then selection on thermal performance curvesfor larval growth or development rates is directly related tothe frequency distribution of temperatures experienced duringlarval development. Using data on caterpillar temperatures inthe field, we show that the strength of directional selectionon growth rate is predicted to be greater at the modal (mostfrequent) temperatures, not at the mean temperature or at temperaturesat which growth rate is maximized. Our results illustrate someof the differences in genetic architecture and patterns of selectionbetween thermal performance curves and developmental reactionnorms.     

Optimal conservation strategy in fluctuating environments with species interactions: resource-enhancement of the native species versus extermination of the alien species

Alien species are often a major threat to native species. We consider optimal conservation strategies for a population whose viability is affected both by an alien species (such as a competitor, a predator, or a pathogen) and by random fluctuations of the environment (e.g. precipitation, temperature). We assume that the survivorship of the native population can be improved by providing resources such as food and shelter, and also by an extermination effort that decreases the abundance of the alien species. These efforts decrease the extinction probability of the native population, but they are accompanied by economic costs. We search for the optimal strategy that minimizes the weighted sum of the extinction probability and the economic costs over a single year. We derive conditions under which investment should be made in both resource-enhancement and extermination, and examine how the optimal effort levels change with parameters. When the optimal strategy includes both types of efforts, the optimal extermination effort level turns out to be independent of the density and economic value of the native species, or the variance of the environmental fluctuation. Furthermore, the optimal resource-enhancement effort is then independent of the density of the alien species. However, the parameter dependencies greatly change if one of the efforts becomes zero. We also examine the situation in which the impact of the alien species is uncertain. The optimal extermination effort increases with the uncertainty of this impact except when the cost of extermination is very high.     

Filling the gap to avoid extinction: Conservation status of Brazilian species of Epidendrum L. (Orchidaceae)

Orchidaceae has the largest percentage of threatened genera and species in relation to other plant families. One of the largest neotropical genus in this family is Epidendrum, represented in Brazil by 130 species. In this study, we assessed the conservation status of 63 Brazilian endemic species of Epidendrum. We characterized the extinction risk following the International Union for Conservation of Nature (IUCN) assessment guide, using criterion B. We considered species with a minimum number of four samples with confirmed occurrence localities and we measured the decline in quality or absolute reduction in the geographical distribution area of the species due to vegetation suppression (conditions bi, bii and biii of criterion B) in the last 35 years, using data available in MAPBIOMAS. A total of 2,754 records belonging to 37 assessed species were gathered, other 24 species were classified as Data Deficient (DD), and two were not assessed. Among the assessed species, 10 were categorized as Endangered (EN), six as Vulnerable (VU), 10 as Near Threatened (NT) and 11 as Least Concern (LC). The results reveal that epiphytic species of the Atlantic Forest were more frequently assessed in some degree of threat (55%). E. strobilicaule Hágsater & Benelli had the largest reduction of distribution area in the last 35 years to the classes of human use that include economical activities, while E. paniculosum Barb.Rodr. showed the smallest reduction. The main threats of the last 35 years for the analyzed species were conversion of land to pastures, urbanization, and the conversion of land to a mosaic of agriculture and pasture. This study provides important information about the conservation status of Brazilian endemic species of Epidendrum, helping to fill an expressive gap of non-assessed species.     

A new method for calculating Risk Tolerance in the assessment of threatened flora

This paper reports on a proposed method for evaluating threat categories for regional flora, based mainly on phytogeographical data. The method involves the creation of current distribution maps, analysis of threat factors and use of the RAMAS Red List software to facilitate rapid and objective classification of taxa in accordance with 2001 IUCN criteria. In order to ensure a more objective approach by the assessor and reduce the range of uncertainty, an index was created for calculating Risk Tolerance (RT) that enabled adjustment of the results obtained and thus supplemented the software used. For trial purposes, the proposed model was applied to Spanish gypsophilous flora currently protected under Spanish regional legislation. When classified using the new model, the taxa in question were placed in very different categories, ranging from least concern (LC) to endangered (EN), indicating the need to redefine both their current legal status and recommended management measures. Use of this method will enable scientists to optimise available information on the geographical distribution of endangered taxa, and help governments both to optimise their financial investment in conservation and to define their priorities. The authors endorse the use of IUCN categories in legal protection texts, and advocate as essential a greater degree of coordination between scientists and governments.     

Predicaments of endangered huemul deer, Hippocamelus bisulcus, in Argentina: a review

A total of 350–600 huemul (Hippocamelus bisulcus) remain as fragmented groups along 1,850 km of Argentine Andes. Their conservation depends on accurate knowledge of the species' requirements and the factors preventing their recovery. The Regional Delegation for Patagonian National Parks (RDP) erroneously alleged that huemul status is satisfactory, and current in situ efforts are sufficient to guarantee recovery. Therefore, conservation centers are regarded unnecessary and the associated risks too high, especially because previous attempts with manipulations have failed. No data support these claims, instead many subpopulations have disappeared recently even in national parks (NP) which hold <0.01 huemul/km². Causes preventing recovery or recolonization are unknown. Current pressures on huemul subpopulations include increased economic activities and alien species. Normal ranges for many biological parameters or population performance of huemul are unknown. Focus is on habitat studies using presence as surrogate for what should be studied on survival and reproduction. Factors important to small-sized populations or preventing recovery remain unstudied. RDPs insistence on indirect methodology prevents implementation of other potentially more promising research approaches. The lack of consensus regarding the necessity and feasibility of a conservation center prevented its establishment and related census flights in unprotected sites. RDP currently forecloses aerial census and capturing and thus prospects for a huemul conservation center, and the proposition of establishing such a center was neither discussed nor incorporated into the national recovery plan. Helicopter captures have been used successfully on deer in huemul habitat. Captures and translocation of huemul occurred since 1830; several zoos kept them successfully up to 10 years, and natural tameness facilitated husbandry. Recently, Chile successfully caught and transported huemul by helicopter to stock a private center. Unknowns can be addressed easily on semicaptive deer; other questions can be studied through reintroductions, employing adaptive management. RDP places faith in NP providing viable subpopulations. However, it remains doubtful whether some 220 huemul living in >22,000 km² of parks can guarantee species survival. For Argentine cervids, absence of studies and management plans due to lack of funds is typical. Considering the actual situation and future perspectives, it appears doubtful that recovery will be achieved based on strategies similar to those employed in the past.