Using simple species lists to monitor trends in animal populations: new methods and a comparison with independent data

There is an urgent need to develop simple and inexpensive methods for monitoring wildlife populations in resource-poor countries. List-based methods have been advocated as simple yet potentially useful biodiversity monitoring tools, and systems have recently been launched in a number of countries to collect species lists. We attempt to advance the use of systematic list-based monitoring by (1) suggesting improvements to the way in which list reporting rates are calculated; (2) assessing the extent to which degrading effort-corrected measures of abundance into simple species lists results in loss of information on population trends; (3) comparing long-term trends in list reporting rates with population trends from a wholly independent monitoring scheme. Daily species lists of birds were derived from regular trapping at a nature reserve in southern England. Most species showed a strong correlation across years between the proportion of lists on which they occurred, adjusted for list length (adjusted list reporting rate; ALRR), and an effort-corrected measure of abundance (captures per unit effort; CPUE). ALRR revealed almost as much about annual variation in abundance as CPUE for all but the most frequently captured species. Long-term (>20 years) trends in ALRRs at the nature reserve were positively correlated with UK national population trends recorded over the same period by an independent, labour-intensive monitoring scheme that counted birds at a large number of widely spread sites. Our results support previous claims that simple species lists could generate data useful for monitoring long-term population trends, particularly where such lists are collected systematically. However, further research on the efficiency of list reporting rates relative to more sophisticated methods is necessary, before list-based methods can be advocated for dedicated monitoring schemes in resource-poor regions.     

Applying complementary species vulnerability assessments to improve conservation strategies in the Galapagos Marine Reserve

Marine biodiversity can be protected by identifying vulnerable species and creating marine protected areas (MPAs) to ensure their survival. A wide variety of methods are employed by environmental managers to determine areas of conservation priority, however which methods should be applied is often a subject of debate for practitioners and scientists. We applied two species vulnerability assessments, the International Union for the Conservation of Nature (IUCN) red list of threatened species and FishBase’s intrinsic vulnerability assessment, to fish communities in three coastal habitats (mangrove, rocky and coral) on the island of San Cristobal, Galapagos. When using the IUCN red list of threatened species, rocky reefs hosted the greatest number of vulnerable species, however when applying the FishBase assessment of intrinsic vulnerability mangroves hosted the greatest abundance of ‘very-highly’ vulnerable species and coral ecosystems hosted the greatest abundance of ‘highly’ vulnerable species. The two methods showed little overlap in determining habitat types that host vulnerable species because they rely on different biological and ecological parameters. Since extensive data is required for IUCN red list assessments, we show that the intrinsic vulnerability assessment from FishBase can be used to complement the IUCN red list especially in data-poor areas. Intrinsic vulnerability assessments are based on less data-intensive methods than the IUCN red list, but nonetheless may bridge information gaps that can arise when using the IUCN red list alone. Vulnerability assessments based on intrinsic factors are not widely applied in marine spatial planning, but their inclusion as a tool for forming conservation strategies can be useful in preventing species loss.     

Population genetics and distribution data reveal conservation concerns to the sky island endemic <Emphasis Type="Italic">Pithecopus megacephalus</Emphasis> (Anura,Phyllomedusidae)

Pithecopus megacephalus is a reticulated monkey–frog species endemic to the highlands of the Espinhaço Mountain Range in southeastern Brazil, an important centre of endemism in South America. This species has a discontinuous distribution and is considered “data-deficient” by the IUCN Red List, raising concerns about its conservation. Understanding the historical dynamics and connectivity of P. megacephalus populations can provide guidelines for preservation of this species in the wild. To investigate the population dynamics of P. megacephalus, we obtained multilocus DNA data for 55 individuals from different locations along the species’ known distribution. Spatial population structure, genetic diversity and demographic parameters were evaluated using population genetic and phylogeographical tools. We also evaluated its extent of occurrence and area of occupancy to investigate extinction risk of this species. We found genetic structure along P. megacephalus’ spatial distribution in the South Espinhaço Mountain Range corresponding to three population groups: northern, central and southern. Our results could provide important data on geographic distribution and population dynamics for a Data Deficient species. Therefore, we suggest these population data, together with the species’ limited occurrence in sky island environments could be used for a more accurate classification of P. megacephalus in the IUCN list, and conservation strategies for the species should be planned accordingly.     

全球变化情景下的中国木本植物受威胁物种名录

生物多样性正面临快速丧失的风险, 气候和土地利用变化已成为生物多样性的主要威胁之一。受威胁物种名录是区域和全球生物多样性保护的重要基础数据, 也是保护区规划的基础。作为一个生物多样性大国, 中国已开展了高等植物受威胁状况的系统性评估, 建立了受威胁植物名录, 为植物多样性保护规划提供了支撑。但由于数据和方法限制, 现有受威胁植物名录制定时未定量考虑全球变化对植物分布的潜在影响, 因而可能低估物种的受威胁等级及未来生物多样性的丧失风险。本研究基于高精度的木本植物分布数据和物种分布模型, 评估了未来气候和土地利用变化对木本植物分布的潜在影响。基于每个物种适宜分布区大小的变化, 并依据IUCN红色名录评估指标A3c的阈值标准, 更新了木本植物的受威胁等级, 补充了未来中国潜在受威胁木本植物名录。结果显示: 综合不同的气候变化情景(RCP 2.6、RCP 6.0和RCP 8.5)和扩散情景(完全扩散、20 km/10年、不扩散), 约12.9%-40.5%的木本植物被评估为受威胁物种。该名录将为制定木本植物保护优先级、开展保护区规划、提升全球变化情景下的生物多样性保护成效提供基础数据, 也为其他类群制定全面的受威胁物种名录提供参考。     

Analytical evidence for scale-invariance in the shape of species abundance distributions

The distribution of species abundances within an ecological community provides a window into ecological processes and has important applications in conservation biology as an indicator of disturbance. Previous work indicates that species abundance distributions might be independent of the scales at which they are measured which has implications for data interpretation. Here we formulate an analytically tractable model for the species abundance distribution at different scales and discuss the biological relevance of its assumptions. Our model shows that as scale increases, the shape of the species abundance distribution converges to a particular shape given uniquely by the Jaccard index of spatial species turnover and by a parameter for the spatial correlation of abundances. Our model indicates that the shape of the species abundance distribution is taxon specific but does not depend on sample area, provided this area is large. We conclude that the species abundance distribution may indeed serve as an indicator of disturbances affecting species spatial turnover and that the assumption of conservation of energy in ecosystems, which is part of the Maximum Entropy approach, should be re-evaluated.     

Declining population trends of European mountain birds

Mountain areas often hold special species communities, and they are high on the list of conservation concern. Global warming and changes in human land use, such as grazing pressure and afforestation, have been suggested to be major threats for biodiversity in the mountain areas, affecting species abundance and causing distribution shifts towards mountaintops. Population shifts towards poles and mountaintops have been documented in several areas, indicating that climate change is one of the key drivers of species’ distribution changes. Despite the high conservation concern, relatively little is known about the population trends of species in mountain areas due to low accessibility and difficult working conditions. Thanks to the recent improvement of bird monitoring schemes around Europe, we can here report a first account of population trends of 44 bird species from four major European mountain regions: Fennoscandia, UK upland, south‐western (Iberia) and south‐central mountains (Alps), covering 12 countries. Overall, the mountain bird species declined significantly (?7%) during 2002–2014, which is similar to the declining rate in common birds in Europe during the same period. Mountain specialists showed a significant ?10% decline in population numbers. The slope for mountain generalists was also negative, but not significantly so. The slopes of specialists and generalists did not differ from each other. Fennoscandian and Iberian populations were on average declining, while in United Kingdom and Alps, trends were nonsignificant. Temperature change or migratory behaviour was not significantly associated with regional population trends of species. Alpine habitats are highly vulnerable to climate change, and this is certainly one of the main drivers of mountain bird population trends. However, observed declines can also be partly linked with local land use practices. More efforts should be undertaken to identify the causes of decline and to increase conservation efforts for these populations.     

Bias in the effect of habitat structure on pitfall traps: An experimental evaluation

Habitat structure has been implicated as a source of bias for pitfall-trap data but most evidence is observational or anecdotal. This study used an experimental approach to quantify biases due to habitat structure. In a randomized block design, I manipulated native grassland to create three types of habitat structure and measured pitfall-trap catches of grassland ants. Small patches of modified habitat were surrounded by otherwise unmodified grassland with the assumption that population density remained unaffected by the modification and that the effects observed were due to changes in trappability. I assessed magnitude, direction, predictability, and consistency of bias for the following types of data: population abundance for single species, relative abundance among species, species composition of assemblages, and species richness. The magnitude of the bias in population abundance was large for most species. However, since the direction of the bias varied predictably with habitat structure, pitfall-trap data can be used to judge differences in population abundance in some situations. The magnitude of the bias in relative abundance was less than for abundance. However, there was inconsistency in the direction and magnitude of bias among species. Thus, interpretation of relative abundance data in pitfall-trap studies may be compromised. Species richness and species composition were biased by habitat structure but were affected significantly only when the groundcover was very dense, suggesting a threshold effect of habitat structure. To help to interpret survey data, pitfall-trap studies should routinely measure attributes of habitat structure and incorporate an experimental component to characterize the bias.     

Modelling changes in species’ abundance in response to projected climate change

Aim Existing climate envelope models give an indication of broad scale shifts in distribution, but do not specifically provide information on likely future population changes useful for conservation prioritization and planning. We demonstrate how these techniques can be developed to model likely future changes in absolute density and population size as a result of climate change. Location Great Britain. Methods Generalized linear models were used to model breeding densities of two northerly‐ and two southerly‐distributed bird species as a function of climate and land use. Models were built using count data from extensive national bird monitoring data and incorporated detectability to estimate absolute abundance. Projections of likely future changes in the distribution and abundance of these species were made by applying these models to projections of future climate change under two emissions scenarios. Results Models described current spatial variation in abundance for three of the four species and produced modelled current estimates of national populations that were similar to previously published estimates for all species. Climate change was projected to result in national population declines in the two northerly‐distributed species, with declines for Eurasian curlew Numenius arquata projected to be particularly severe. Conversely, the abundances of the two southerly distributed species were projected to increase nationally. Projected maps of future abundance may be used to identify priority areas for the future conservation of each species. Main conclusions The analytical methods provide a framework to make projections of impacts of climate change on species abundance, rather than simply projected range changes. Outputs may be summarized at any spatial scale, providing information to inform future conservation planning at national, regional and local scales. Results suggest that as a consequence of climate change, northerly distributed bird species in Great Britain are likely to become an increasingly high conservation priority within the UK.     

A decision tool for listing species for protection on different geographic scales and administrative levels

An important task in conservation biology is to assess the spatial scale pertinent for species protection since some species may require protection throughout their distribution, others in only part of their range. Once this is done, species can be correctly identified for listing at different administrative levels (e.g. continental, national, and local). Here, we propose an objective method to list taxa at nested administrative levels based on three criteria (responsibility, rarity and vulnerability). We tested the method using quantitative data on the distribution, abundance and decline of orchids in France. The proposed method enables increased protection status in regions where species’ abundance and diversity are higher, gives priority to species for which an individual administrative unit has high responsibility and allows objective integration of species decline at different administrative levels. The method also enables the integration of locally rare species at their distribution limits and avoids repetition of species listing across second-level administrative units. The use of an objective method such as this could contribute to a standardised system of priority setting that integrates the geographic scale of rarity in relation to different administrative levels for protection.     

Discrepancies in occupancy and abundance approaches to identifying and protecting habitat for an at‐risk species

Predicting how environmental factors affect the distribution of species is a fundamental goal of conservation biology. Conservation biologists rely on species distribution and abundance models to identify key habitat characteristics for species. Occupancy modeling is frequently promoted as a practical alternative to use of abundance in identifying habitat quality. While occupancy and abundance are potentially governed by different limiting factors operating at different scales, few studies have directly compared predictive models for these approaches in the same system. We evaluated how much occupancy and abundance are driven by the same environmental factors for a species of conservation concern, the greater short‐horned lizard (Phrynosoma hernandesi). Occupancy was most strongly dictated by precipitation, temperature, and density of ant mounds. While these factors were also in the best‐supported predictive models for lizard abundance, the magnitude of the effects varied, with the sign of the effect changing for temperature and precipitation. These discrepancies show that while occupancy modeling can be an efficient approach for conservation planning, predictors of occupancy probability should not automatically be equated with predictors of population abundance. Understanding the differences in factors that control occupancy versus abundance can help us to identify habitat requirements and mitigate the loss of threatened species.     

Mixture models for estimating the size of a closed population when capture rates vary among individuals

We develop a parameterization of the beta-binomial mixture that provides sensible inferences about the size of a closed population when probabilities of capture or detection vary among individuals. Three classes of mixture models (beta-binomial, logistic-normal, and latent-class) are fitted to recaptures of snowshoe hares for estimating abundance and to counts of bird species for estimating species richness. In both sets of data, rates of detection appear to vary more among individuals (animals or species) than among sampling occasions or locations. The estimates of population size and species richness are sensitive to model-specific assumptions about the latent distribution of individual rates of detection. We demonstrate using simulation experiments that conventional diagnostics for assessing model adequacy, such as deviance, cannot be relied on for selecting classes of mixture models that produce valid inferences about population size. Prior knowledge about sources of individual heterogeneity in detection rates, if available, should be used to help select among classes of mixture models that are to be used for inference.     

台湾海峡小型浮游植物的物种多样性和分布特征

在整合两岸学者有关台湾海峡的浮游植物物种多样性研究的基础上, 作者提出了一份台湾海峡小型浮游植物物种名录, 共包含620种, 并按照其生态类群和赤潮种类进行了区分。同时以1984年5月至1985年2月在福建海岸带和台湾海峡共86个观测站四个季度月浮游植物的344份调查资料为基础, 来阐明物种分布的基本格局和丰度变化的时空趋势。结果表明: 此次调查所鉴定的299种浮游植物中硅藻门为199种, 其丰度占浮游植物丰度的99.25%, 对本海区浮游植物的分布起支配作用。浮游植物的种类数和丰度年高峰均在夏季。就平面分布而言, 海峡区的种类数多于近岸区, 与海水的温度和盐度成正相关关系; 而近岸区的丰度高于海峡区, Shannon-Wiener指数和均匀度则是海峡区高于近岸区。     

Revising the British Red Data List for birds: the biological basis of U.K. conservation priorities

The list of British Red Data birds (Batten et al. 1990) includes 117 species, 109 of which qualified on one or more quantitative criteria referring to rarity, localized distribution, population decline and international importance. A wealth of data on bird population levels and trends in the United Kingdom and Europe has recently become available, allowing refinement and improvement of the criteria for qualification. Here we propose that in assigning priorities for conservation action in the U.K. (Britain and Northern Ireland), three biological axes need to be considered: national threat (measured as rarity, localized distribution and population decline in the U.K.), international importance (the proportion of the European population in the U.K.) and international threat (European/global conservation status). Only the first two of these axes were considered by Batten et al. (1990). Each of these axes has been sub-divided into high, medium and low categories using quantitative thresholds, and from this we produce a national 'conservation cube' (three axes, each with three categories and thus 27 cells). Data permitting, every species in the U.K. can be allocated to one of these cells. We suggest that species high on either (or both) of the national or international threat axes be considered as species of high conservation priority (the red list) and that among the remainder those that rank at least medium on one of the axes be considered as of medium conservation priority (the amber list). All other species are of low conservation priority (the green list). We suggest that this three-axis model could be applicable to other taxa and countries.     

Inverse link between density and dispersal distance in butterflies: field evidence from six co-occurring species

A pertinent question in animal population ecology is the relationship between population abundance, density, and mobility. Two extreme ways to reach sufficient abundance for long-term persistence are to inhabit restricted locations at high densities, or large areas in low densities. The former case predicts low individual mobility, whereas the later predicts high one. This assumption is rarely tested using across-species comparisons, due to scarcity of data on both mobility and population sizes for multiple species. We used data on dispersal and local population densities of six butterfly species gained by mark-recapture, and data on their (relative) regional abundance obtained by walking transects in a landscape surrounding the mark-recapture sites. We correlated both local density and regional abundance against slopes of the inverse power function, appropriate for describing the shape of dispersal kernel. Local densities correlated negatively with the dispersal kernel slopes both when sexes were treated as independent data points and if treated together. For regional abundance, the correlation was also negative but only marginally significant. Our results corroborate the notion that a trade-off exists between living in dense populations and having poor dispersal, and vice versa. We link this observation to resource use by individual species, and distribution of such resources as host plants in the study landscape.     

Climate change likely to reduce orchid bee abundance even in climatic suitable sites

Studies have tested whether model predictions based on species’ occurrence can predict the spatial pattern of population abundance. The relationship between predicted environmental suitability and population abundance varies in shape, strength and predictive power. However, little attention has been paid to the congruence in predictions of different models fed with occurrence or abundance data, in particular when comparing metrics of climate change impact. Here, we used the ecological niche modeling fit with presence–absence and abundance data of orchid bees to predict the effect of climate change on species and assembly level distribution patterns. In addition, we assessed whether predictions of presence–absence models can be used as a proxy to abundance patterns. We obtained georeferenced abundance data of orchid bees (Hymenoptera: Apidae: Euglossina) in the Brazilian Atlantic Forest. Sampling method consisted in attracting male orchid bees to baits of at least five different aromatic compounds and collecting the individuals with entomological nets or bait traps. We limited abundance data to those obtained by similar standard sampling protocol to avoid bias in abundance estimation. We used boosted regression trees to model ecological niches and project them into six climate models and two Representative Concentration Pathways. We found that models based on species occurrences worked as a proxy for changes in population abundance when the output of the models were continuous; results were very different when outputs were discretized to binary predictions. We found an overall trend of diminishing abundance in the future, but a clear retention of climatically suitable sites too. Furthermore, geographic distance to gained climatic suitable areas can be very short, although it embraces great variation. Changes in species richness and turnover would be concentrated in western and southern Atlantic Forest. Our findings offer support to the ongoing debate of suitability–abundance models and can be used to support spatial conservation prioritization schemes and species triage in Atlantic Forest.     

The Saturniidae of Barro Colorado Island,Panama: A model taxon for studying the long‐term effects of climate change?

We have little knowledge of the response of invertebrate assemblages to climate change in tropical ecosystems, and few studies have compiled long‐term data on invertebrates from tropical rainforests. We provide an updated list of the 72 species of Saturniidae moths collected on Barro Colorado Island (BCI), Panama, during the period 1958‐2016. This list will serve as baseline data for assessing long‐term changes of saturniids on BCI in the future, as 81% of the species can be identified by their unique DNA Barcode Index Number, including four cryptic species not yet formally described. A local species pool of 60 + species breeding on BCI appears plausible, but more cryptic species may be discovered in the future. We use monitoring data obtained by light trapping to analyze recent population trends on BCI for saturniid species that were relatively common during 2009‐2016, a period representing >30 saturniid generations. The abundances of 11 species, of 14 tested, could be fitted to significant time‐series models. While the direction of change in abundance was uncertain for most species, two species showed a significant increase over time, and forecast models also suggested continuing increases for most species during 2017‐2018, as compared to the 2009 base year. Peaks in saturniid abundance were most conspicuous during El Niño and La Niña years. In addition to a species‐specific approach, we propose a reproducible functional classification based on five functional traits to analyze the responses of species sharing similar functional attributes in a fluctuating climate. Our results suggest that the abundances of larger body‐size species with good dispersal abilities may increase concomitantly with rising air temperature in the future, because short‐lived adults may allocate less time to increasing body temperature for flight, leaving more time available for searching for mating partners or suitable oviposition sites.     

Rarity and species/area relationships of vascular plants in deciduous woods, western Norway - applications to nature reserve selection

The Rabinowitz s model of rarity was applied to a vascular plant census list from 60 deciduous woods in western Norway By applying information from distribution maps and plant sociological literature from western Norway it was possible to obtain data on geographical distribution, habitat specificity, and maximum local population size at the regional-scale of western Norway This enabled a comparison between rarity at the local scale and rarity at the regional scale At the local scale rarity was primarily due to narrow geographic distribution At the regional scale, however, the most frequent form of rarity was due to restricted habitat specificity The species/area relationship and the SLOSS effect for the rare species at the regional scale are compared with patterns involving the total species list It is shown that a single large wood supports fewer regional-scale rare species than do combinations of two small woods of equal area The species/area relationship for species with small population sizes at the regional scale has a different slope from the species/area relationship for all species Area is a better predictor of regional-scale rarity than is the number of common species     

Pheromone production, male abundance, body size, and the evolution of elaborate antennae in moths

The males of some species of moths possess elaborate feathery antennae. It is widely assumed that these striking morphological features have evolved through selection for males with greater sensitivity to the female sex pheromone, which is typically released in minute quantities. Accordingly, females of species in which males have elaborate (i.e., pectinate, bipectinate, or quadripectinate) antennae should produce the smallest quantities of pheromone. Alternatively, antennal morphology may be associated with the chemical properties of the pheromone components, with elaborate antennae being associated with pheromones that diffuse more quickly (i.e., have lower molecular weights). Finally, antennal morphology may reflect population structure, with low population abundance selecting for higher sensitivity and hence more elaborate antennae. We conducted a phylogenetic comparative analysis to test these explanations using pheromone chemical data and trapping data for 152 moth species. Elaborate antennae are associated with larger body size (longer forewing length), which suggests a biological cost that smaller moth species cannot bear. Body size is also positively correlated with pheromone titre and negatively correlated with population abundance (estimated by male abundance). Removing the effects of body size revealed no association between the shape of antennae and either pheromone titre, male abundance, or mean molecular weight of the pheromone components. However, among species with elaborate antennae, longer antennae were typically associated with lower male abundances and pheromone compounds with lower molecular weight, suggesting that male distribution and a more rapidly diffusing female sex pheromone may influence the size but not the general shape of male antennae.     

Springtail communities (Collembola) of Eastern European broad-leaf forests

The fauna and communities of Collembola in Eastern European broad-leaf forests are analyzed. A list of species and dominants, the local diversity and abundance, the range of life forms, and vertical distribution are described. Special attention is paid to the problems of dynamics and representativeness of ecological samplings. The population density of springtails is relatively low in broad-leaf forests; the local species richness is similar to that in coniferous forests and averages 25–30 species. In spite of some differences, the springtail populations of broad-leaf and coniferous forests can be assigned to the same type of community, namely that of Eastern European forests.     

两种珍稀植物群落物种多度分布的核方法研究

首次提出物种多度分布的非参数核密度估计方法,介绍了此方法的构造和主要性质。珍稀濒危植物观光木群落和长苞铁杉群落的乔木层、灌木层、所有木本植物物种多度分布实例拟合结果表明,核方法能很好地描述群落物种多度分布。非参数核估计方法是群落物种多度分布模拟的一种有效方法,它丰富了物种多度分布拟合方法,为珍稀濒危植物的管理与保护提供了理论参考。