Factors influencing the spatial patterns of vertebrate roadkill in South Africa: The Greater Mapungubwe Transfrontier Conservation Area as a case study

Few studies have investigated the factors that influence roadkill occurrence in developing countries. In 2013, we monitored a 100‐km section of the road (comprising the R572 and R521 regional highways and the D2662) that pass through the Greater Mapungubwe Transfrontier Conservation Area in South Africa, to assess the possible factors influencing roadkill. Over a period of 120 days, and across the three ecological seasons, we recorded 981 roadkills (rate = 0.08 roadkill/km/day) from four vertebrate taxonomic groups. We generated predictive models of roadkill from one combined data set that considered eight variables identified from the literature as potential correlates of roadkill. The model that included the distance of the fence from the road, habitat type adjacent to the road, and the presence of a hill in the road (i.e., elevation) or a bank on the side of the road best explained roadkill occurrence. More roadkill was predicted to occur in both open and dense mopane and dense mixed bushveld habitats, on a hill, when there was a bank on the side of the road, and as the distance between the road verge and a fence decreased. Our model provides some insight into the significant predictors of roadkill occurrence and is therefore a valuable tool in identifying sites of high‐potential roadkill frequency and formulating mitigation measures for reducing road mortalities.     

Modeling density dependence and climatic disturbances in caribou: a case study from the Bathurst Island complex, Canadian High Arctic

Peary caribou Rangifer tarandus pearyi is the northernmost subspecies of Rangifer in North America and endemic to the Canadian High Arctic. Because of severe population declines following years of unfavorable winter weather with ice coating on the ground or thicker snow cover, it is believed that density-independent disturbance events are the primary driver for Peary caribou population dynamics. However, it is unclear to what extent density dependence may affect population dynamics of this species. Here, we test for different levels of density dependence in a stochastic, single-stage population model, based on available empirical information for the Bathurst Island complex (BIC) population in the Canadian High Arctic. We compare predicted densities with observed densities during 1961–2001 under various assumptions of the strength of density dependence. On the basis of our model, we found that scenarios with no or very low density dependence led to population densities far above observed densities. For average observed disturbance regimes, a carrying capacity of 0.1 caribou km⁻² generated an average caribou density similar to that estimated for the BIC population over the past four decades. With our model we also tested the potential effects of climate change-related increases in the probability and severity of disturbance years, that is unusually poor winter conditions. On the basis of our simulation results, we found that, in particular, potential increases in disturbance severity (as opposed to disturbance frequency) may pose a considerable threat to the persistence of this species.     

A method for validating stochastic models of population viability: a case study of the mountain pygmy-possum (Burramys parvus)

1.  A method of validating stochastic models of population viability is proposed, based on assessing the mean and variance of the predicted population size.
2.  The method is illustrated with a model of the population dynamics of the mountain pygmy-possum ( Burramys parvus Broom 1895), based on annual census data collected from a single population in the Snowy Mountains of New South Wales, Australia between 1986 and 1997. The model incorporates density-dependence in survivorship and recruitment, and demographic and environmental stochasticity.
3.  The model appeared to make reasonable predictions for the three populations that were used for validation, provided the equilibrium population size was estimated accurately. This may require that differences in habitat quality between populations be taken into account.
4.  Following validation, the model was given new parameters using the additional data from the three populations, and the risk of population decline within the next 100 years was assessed. Although populations as small as 15 females are predicted to be relatively safe from extinction caused by stochastic processes, B. parvus appears vulnerable to loss of habitat and reductions in the population growth rate.
5.  The approach used in this paper is one of few attempts to validate a model of population viability using field data, and demonstrates that some aspects of stochastic population models can be tested.     

Current state and the future of the crested ibis (Nipponia nippon): A case study by population viability analysis

There is only one population of the crested ibis (Nipponia nippon) surviving in the wild, which has not exceeded 40 individuals since it was rediscovered in 1981. We used detailed data of the annual population size and natality collected by the Crested Ibis Conservation and Observation Station (CICOS) over the past 17years. We were able to obtain a more accurate census of age structure and mortality as all of the fledglings have been identified by leg bands in 1987. Consequently, we analyzed the current state of the crested ibis and predicted its future using Population Viability Analysis (PVA) with the help of the computer simulation model VORTEX (Version 7.2). The results indicated that the extinction probability of the crested ibis was 19.7% in 100years. Sensitivity analysis showed that the extinction probabilities were sensitive to catastrophes and environmental variation, and the long-term existence of the population was dependent on the carrying capacity of the habitat and inbreeding depression. Conservation efforts are critical for the survival of the crested ibis. The prior conservation project involves controlling hunting and predation, as well as improving the life level of these few remnant creatures.     

Molecular resolution of marine turtle stock composition in fishery bycatch: a case study in the Mediterranean

Based on an extensive sampling regime from both nesting populations and bycatch, frequency analyses of mitochondrial (mt) DNA control region haplotypes in the Mediterranean were used to assess the genetic structure and stock composition of the loggerhead sea turtle, Caretta caretta, in different marine fisheries. The analyses show the following. (i) In drifting longline fisheries working in Mediterranean pelagic habitats 53–55% of turtles caught originated from the Mediterranean stock; (ii) In bottom-trawl fisheries all turtle bycatch is derived from this regional stock; (iii) This regional stock contribution to fishery bycatch suggests that the population size of the Mediterranean loggerhead nesting population is significantly larger than previously thought. This is consistent with a recent holistic estimate based on the discovery of a large rookery in Libya. (iv) Present impact of fishery-related mortality on the Mediterranean nesting population is probably incompatible with its long-term conservation. Sea turtle conservation regulations are urgently needed for the Mediterranean fisheries. (v) The significant divergence of mtDNA haplotype frequencies of the Turkish loggerhead colonies define this nesting population as a particularly important management unit. Large immature and adult stages from this management unit seem to be harvested predominantly by Egyptian fisheries. (vi) Combined with other data, our findings suggest that all the nesting populations in the Mediterranean should be considered as management units sharing immature pelagic habitats throughout the Mediterranean (and possibly the eastern Atlantic), with distinct and more localized benthic feeding habitats in the eastern basin used by large immatures and adults. (vii) Between the strict oceanic pelagic and the benthic stages, immature turtles appear to live through an intermediate neritic stage, in which they switch between pelagic and benthic foods.     

Population assessment using multivariate time‐series analysis: A case study of rockfishes in Puget Sound

Estimating a population's growth rate and year‐to‐year variance is a key component of population viability analysis (PVA ). However, standard PVA methods require time series of counts obtained using consistent survey methods over many years. In addition, it can be difficult to separate observation and process variance, which is critical for PVA . Time‐series analysis performed with multivariate autoregressive state‐space (MARSS ) models is a flexible statistical framework that allows one to address many of these limitations. MARSS models allow one to combine surveys with different gears and across different sites for estimation of PVA parameters, and to implement replication, which reduces the variance‐separation problem and maximizes informational input for mean trend estimation. Even data that are fragmented with unknown error levels can be accommodated. We present a practical case study that illustrates MARSS analysis steps: data choice, model set‐up, model selection, and parameter estimation. Our case study is an analysis of the long‐term trends of rockfish in Puget Sound, Washington, based on citizen science scuba surveys, a fishery‐independent trawl survey, and recreational fishery surveys affected by bag‐limit reductions. The best‐supported models indicated that the recreational and trawl surveys tracked different, temporally independent assemblages that declined at similar rates (an average of ?3.8% to ?3.9% per year). The scuba survey tracked a separate increasing and temporally independent assemblage (an average of 4.1% per year). Three rockfishes (bocaccio, canary, and yelloweye) are listed in Puget Sound under the US Endangered Species Act (ESA ). These species are associated with deep water, which the recreational and trawl surveys sample better than the scuba survey. All three ESA ‐listed rockfishes declined as a proportion of recreational catch between the 1970s and 2010s, suggesting that they experienced similar or more severe reductions in abundance than the 3.8–3.9% per year declines that were estimated for rockfish populations sampled by the recreational and trawl surveys.     

Natural regeneration of forest related to the spatial structure of trees: A study of two forest communities in Western Carpathians,southern Poland

The existence of a relationship between the spatial pattern of trees and the distribution of young individuals beneath the canopy has been tested in the beech (Fagus sylvatica) and spruce (Picea abies) — fir (Abies alba) forests in the mountainous region, using two different methods. The first method was the analysis of spatial pattern of individuals, the second one was based on calculating sums of influences of all trees occurring within analysed plot on a given point on the forest floor. Results of spatial pattern analyses were surprisingly consistent: almost all mature trees and seedlings didplayed a random pattern of spatial arrangement. However, there is a clear, although statistically insignificant tendency towards uniformity of spatial pattern with increasing sizes of analysed trees. Results of comparing sums of influences on regularly distributed points with sums of influences on seedlings or saplings revealed no tendency in forest regeneration to concentrate in places, where the sums were smaller than the average for a plot. This, coupled with the dominance of random spatial pattern of trees, suggests, that viewed on a small spatial scale, influence of competition among forest trees on their spatial arrangement is obscured by other factors, which are not closely related to the distribution of individuals.     

Using broad-scale, community survey data to compare species conservation strategies across regions: A case study of the Koala in a set of adjacent 'catchments'

Summary   Managers of wildlife populations with a wide geographical range are understandably interested in the question of whether they can manage a broader population with a single conservation strategy (e.g. covering a set of adjacent management regions, referred to as 'catchments' in Australia) or whether separate strategies are required for individual catchments. We addressed this question using data from a statewide, community wildlife survey to quantify Koala ( Phascolarctos cinereus ) habitat relationships in the catchments of four adjacent Catchment Management Authorities or CMA (>10 000 km²) of New South Wales, Australia and then tested whether these habitat relationships were similar across catchments. Although the results were constrained by the coarse resolution of the community survey and environmental data, we were able to model broad-scale patterns of habitat use. Model explanatory power and cross-regional predictability was low, but consistent with Koala ecology. Two environmental variables emerged as having a strong relationship with Koala presence – mean elevation and percentage of fertile soils – the importance of which varied among catchments depending on land-use patterns. The results highlight the need for local wildlife management plans, not a single plan covering multiple catchments.     

世界古老果树榅桲在中国的归化及其种群动态——以湖南省褒忠山种群为例

外来植物归化因其对本地生态系统有潜在的入侵风险而受到生态学家的广泛关注。群落和种群结构反映植物的环境适应性、种群地位、稳定性和发展趋势,可为判定外来植物归化提供可靠依据。榅桲(Cydonia oblonga)为在全球广泛引种栽培达4000多年的古老果树,引入中国已有2500多年,但关于其野外逸生种群的生存状态未见报道。以目前中国唯一逸生地——湖南省褒忠山的榅桲种群为对象,在其所在群落物种组成和群落结构分析的基础上,采用时空替代法,运用静态生命表、生存曲线和时间序列预测模型对榅桲种群动态进行了定量分析。结果表明：(1)群落内共有维管束植物20科28属31种,其中木本植物16种,草本植物15种;区系以温带成分为主,占群落内非世界分布总属数的75%;(2)群落具有明显层次结构,可分灌木层和草本层,灌木层个体集中于0—1.5 m高度级,占总个体数的81.81%;(3)种群龄级结构呈近倒“J”型,存活曲线趋近于Deevey-Ⅱ型,具有稳定的更新潜力;(4)生存分析表明榅桲种群具有前期优势、中期减少、后期稳定的特点;时间序列预测表明该种群个体数量未来能够持续增长,但幼苗及小树个体基本保持稳定,其种...     

Role of a geodatabase to assess the distribution of plants of conservation interest in a large protected area: A case study for a major national park in Italy

We use a geodatabase to investigate the distribution patterns of an important subset of floristic reports recorded for the Parco Nazionale delle Foreste Casentinesi, Monte Falterona, Campigna in the northern Apennines, Italy. This database was analysed using spatial statistical techniques and a digital elevation model. Significant relationships between species presence, sampling effort and species richness were then analysed in relation to topographical variables and to an existing vegetation map. Report-based rarefaction techniques were used to compare areas having different numbers of species recorded. Overall, the analysis shows that some areas of the park are richer in species of conservation interest than others, and that these have been more intensely investigated. Meanwhile, for other areas, botanical knowledge is scarce or even absent. This has led to clustering and redundancy of floristic data in some areas. The study confirms that the existence of a complete and up-to-date geodatabase creates a valuable resource which enables information gaps to be bridged. Such gaps often exist in biological databases for rare and narrowly distributed species. The wider application of these analyses should also give useful indications of how the incidences of these species of conservation interest are associated with particular environmental variables.     

Measuring the effectiveness of regional conservation assessments at representing biodiversity surrogates at a local scale: A case study in Réunion Island (Indian Ocean)

In a context of scarce financial and human resources, the allocation of conservation efforts needs to be optimized. Our analysis attempts to draw conclusions on the integration of regional and local conservation assessments, specifically, with regard to the acquisition of fine‐scale data to complement the regional assessment. This study undertaken in Réunion Island (Indian Ocean) assessed how biodiversity surrogates targeted at a regional scale represented other biodiversity surrogates at a local scale. Biodiversity surrogates at both scales consisted of species, habitats and processes. Habitats and processes at regional scale were defined using a coarser scale of thematic resolution than at local scale. The surrogacy was tested in terms of incidental representation of local‐scale features in the regional assessments, and correlation of irreplaceability values between scales. Near‐minimum sets and irreplaceability values were generated using MARXAN software. Our results revealed that conservation targets for processes at local scale were never met incidentally, while threatened species and fragmented habitats were also usually under‐represented. More specifically, requiring only 12% of the local planning domain, the application of species as surrogates at regional scale was the least effective option at representing biodiversity features at local scale. In contrast, habitats at a coarse scale of thematic resolution achieved a significant proportion of conservation targets incidentally (67%) and their irreplaceability values were well correlated with the irreplaceability values of surrogates at local scale. The results highlighted that all three types of biodiversity surrogates are complementary for assessing overall biodiversity. Because of the cost of data acquisition, we recommended that the most efficient strategy to develop nested regional/local conservation plans is to apply habitats and processes at a coarse scale of thematic resolution at regional scale, and threatened species and degraded habitats at local scale, with their fine‐scale mapping limited to highly transformed areas.     

A rapid and cost-effective tool for managing habitats of the European Natura 2000 network: a case study in the Italian Alps

“Habitats” Directive 92/43/EEC is the pivotal European law for building a continental network of sites of community importance (SCIs) for nature conservation. Article 6 of such directive underlines the importance of biodiversity conservation through the realization of proper management plans. As a result, such plans are increasingly common. A management plan based on intensive field studies and monitoring activities requires time and financial resources, which are generally limited. The aim of this paper is to offer a rapid, cost-effective and scientifically based decision tool aimed to achieve GIS-based conservation strategies for habitats of EU interest within SCIs and, in general, within protected areas. As a case study, we considered species-rich Nardus grasslands (threatened by natural reconversion and intensive cattle grazing), and transition mires (threatened by pasturing and human disturbance) in a SCI in the Alps. Through a multi-criteria evaluation, we selected indicators and weights based upon our knowledge of the study area. As a result, we were able to: (a) quantify the level of existing threats, (b) suggest urgent conservation strategies, and (c) suggest future monitoring activities. Since the study area is representative of many protected areas in the Alps and the conservation topics under evaluation are frequent threats impacting habitats of EU interest, our decision model might be transferable to further areas given proper adaptation of weights to the intensity and the frequency of current threats.