Use Of Surrogate Species Research Articles

Using metabolomic profiling to inform use of surrogate species in ecological risk assessment practices

The U.S. EPA frequently uses avian or fish toxicity data to set protective standards for amphibians in ecological risk assessments. However, this approach does not always adequately represent aquatic-dwelling and terrestrial-phase amphibian exposure data. For instance, it is accepted that early life stage tests for fish are typically sensitive enough to protect larval amphibians, however, metamorphosis from tadpole to a terrestrial-phase adult relies on endocrine cues that are less prevalent in fish but essential for amphibian life stage transitions. These differences suggest that more robust approaches are needed to adequately elucidate the impacts of pesticide exposure in amphibians across critical life stages. Therefore, in the current study, methodology is presented that can be applied to link the perturbations in the metabolomic response of larval zebrafish (Danio rerio), a surrogate species frequently used in ecotoxicological studies, to those of African clawed frog (Xenopus laevis) tadpoles following exposure to three high-use pesticides, bifenthrin, chlorothalonil, or trifluralin. Generally, D. rerio exhibited greater metabolic perturbations in both number and magnitude across the pesticide exposures as opposed to X. laevis. This suggests that screening ecological risk assessment surrogate toxicity data would sufficiently protect amphibians at the single life stage studied but care needs to be taken to understand the suite of metabolic requirements of each developing species. Ultimately, methodology presented, and data gathered herein will help inform the applicability of metabolomic profiling in establishing the risk pesticide exposure poses to amphibians and potentially other non-target species.

Assessing the use of surrogate species for a more cost-effective traceability of geographic origin using elemental fingerprints of bivalve shells

Illegal, unreported and unregulated (IUU) fishing is a major threat to marine ecosystems and their living resources. IUU fishing promotes fraudulent mislabeling of seafood, which can pose serious risks to consumers’ health if specimens being traded originate from contaminated areas. The development and optimization of reliable tools to confirm the geographic origin of seafood is therefore of utmost importance under these scenarios. These tools are usually based in reference models of a given species that allows to trace the geographic origin of conspecifics. However, to date, the accuracy of such reference models requires the sampling of specimens of the species being surveyed, an issue that may impair the generalized use of this approach by authorities under real-case scenarios. A potential way to overcome this constraint is to apply a model built for a given species (working as surrogate) to trace the geographic origin of another one. The present study evaluated the effect of species-specific and spatial variability associated with the elemental fingerprints (EF) of shells of three commercially important bivalve species (Cerastoderma edule, Ruditapes decussatus and R. philippinarum) from five different locations over the northwestern and western Iberian coast and tested if a reference model based on one of this species could be used to reliably trace the geographic origin of specimens from the two other species. The EF of shells of the three species were significantly different within each location, as well as among different locations within each species. The reference models of the three species presented high cross-validation accuracy (ranging from 95.3% to 99.3%). The tests to infer if these models could reliably trace the geographic origin of samples from another species presented an overall accuracy ranging between 50% and 82.3%. Based on these results, and other requirements that a surrogate species must fulfil, it is possible to conclude that the three species hold the potential to be used as surrogates of each other, although C. edule is the one that better fulfills the requirements of a surrogate species. The optimization proposed in this study improves the cost-efficiency of using EF of bivalve shells as a tool to trace and confirm the geographic origin of bivalves, while also allowing to deliver a prompter reply to authorities.

Cross-taxon relationships in Mediterranean urban ecosystem: A case study from the city of Trieste

Urbanization directly and indirectly impacts biodiversity to the extent that it is considered one of the main causes of biotic homogenization and extinction. However, urban green areas can act as reservoir of biodiversity, and knowledge regarding species distribution in such contexts is crucial to define appropriate conservation and management strategies. Since inventories of species are generally time-consuming and costly, a commonly used approach consists in the use of surrogate species. However, studies investigating the effectiveness of surrogate species in urban environments still seem to be under-represented. In this research, we investigated the biodiversity of ants, plants, and carabid beetles in six different green areas within the urban area of the city of Trieste. The role of vascular plants as a potential surrogate for the diversity of ants and carabid beetles has been tested, investigating the influence of the environmental variables (dead wood, litter, anthropic disturbance, bare soil, bedrocks and rocks) on these relationships. Patterns of species richness and complementarity were compared among the sampled sites and their correlations were tested with Mantel tests and Co-Correspondence Analysis (Co-CA). Results pointed out that even disturbed and isolated sites within the urbanised matrix can sustain a high diversity of species of ants, carabids and plants, while in the semi-natural sites intermediate diversity levels were found. Plants were found to correlate directly with the diversity of ants; on the contrary, carabid species composition resulted only indirectly influenced by vascular plants, confirming the key role of abiotic variables in determining carabid diversity. Co-CA showed a clear distinction between forested and semi-natural environments and more open and disturbed environments. Furthermore, the Co-CA highlighted that the considered environmental variables (particularly dead wood, anthropic disturbance, rocks and litter) can significantly influence the distribution of analyzed taxa. Our results highlight the important role of urban green areas within the urban matrix as source of biodiversity and, furthermore, once more, support the role of vascular plants as meaningful surrogate for the diversity of ants and carabids.

Toxicity of pesticides in lizards.

Many threats exist to reptile populations, environmental pollutants being one of them. Lizards and other reptiles are usually not taken into consideration in environmental risk assessments, with the use of surrogate species for their estimates. Unfortunately, not all pesticides have the same effects in the reptile species and on these surrogates, birds and mammals, some being more toxic in lizards. This difference brings the need to evaluate their toxicity in lizards to safeguard its protection. Studies in the last decades involving contaminants' toxicity in lizard species have increased, thus we proposed to gather these information in this comprehensive review. Through searches in databases about the toxicity of pesticides in lizards, 16 scientific articles were found. Most studies investigated locomotor performance, histopathology, oxidative stress, neurotoxicology, and genetic damage from diverse pesticides with different modes of action. Progress has been made to acquire data on lizard ecotoxicology and more research is needed to cover more variables, such as studies in the embryologic stage and different pesticides.

Use of surrogate species to cost-effectively prioritize conservation actions.

Conservation efforts often focus on umbrella species whose distributions overlap with many other flora and fauna. However, because biodiversity is affected by different threats that are spatially variable, focusing only on the geographic range overlap of species may not be sufficient in allocating the necessary actions needed to efficiently abate threats. We developed a problem‐based method for prioritizing conservation actions for umbrella species that maximizes the total number of flora and fauna benefiting from management while considering threats, actions, and costs. We tested our new method by assessing the performance of the Australian federal government's umbrella prioritization list, which identifies 73 umbrella species as priorities for conservation attention. Our results show that the federal government priority list benefits only 6% of all Australia's threatened terrestrial species. This could be increased to benefit nearly half (or 46%) of all threatened terrestrial species for the same budget of AU$550 million/year if more suitable umbrella species were chosen. This results in a 7‐fold increase in management efficiency. We believe nations around the world can markedly improve the selection of prioritized umbrella species for conservation action with this transparent, quantitative, and objective prioritization approach.

Scavenger removal of bird carcasses at simulated wind turbines: Does carcass type matter?

AbstractWind energy development can negatively impact bird populations due to bird–turbine collisions. To accurately estimate bird mortality at wind farms, the number of dead birds found under turbines is commonly corrected for carcass removal by scavengers, which is quantified by measuring persistence of experimental carcasses through time. These studies often use domestic birds as surrogates because carcasses of wild birds (e.g., raptors) are difficult to obtain. We assessed scavenger removal of carcasses from five bird species at simulated turbines to determine whether domestic surrogates are scavenged at a different rate than raptors, species of interest for wind turbine mortality. The percentage of carcasses scavenged during 14‐d rounds ranged from 34.6% for American kestrels (Falco sparverius) to 65.4% for chickens (Gallus gallus), and the percentage of carcasses completely removed ranged from 13.5% for red‐tailed hawks (Buteo jamaicensis) to 67.3% for northern bobwhites (Colinus virginianus). Carcass type (i.e., species) was the only predictor included in the best‐fit logistic regression model of complete carcass removal, and a survival analysis indicated carcass type influenced elapsed time to scavenging events. Our results suggest the use of surrogate species to quantify carcass removal at wind turbines could lead to inaccurate mortality estimates.

Indicators of Diptera diversity in wet grassland habitats are influenced by environmental variability, scale of observation, and habitat type

In low intensity agri-ecosystems such as wet grassland habitats, the inclusion of invertebrates in conservation assessments and monitoring is usually limited to charismatic groups such as bees or butterflies. However, wet grasslands support a wide range of inveterate groups, some of which may exhibit limited movement not generally represented by more mobile groups such as those typically examined. The use of surrogate species which exemplify broader invertebrate diversity has been suggested as a possible means of including these overlooked invertebrates (such as Diptera) in conservation planning within these habitats. Based on collections made by Malaise trap, we utilized two families of Diptera (Sciomyzidae and Syrphidae) as indicators of a wider range of dipteran diversity (nine Diptera families identified to parataxonomic unit level [PUs]) in wet grassland habitats. We examined the role of environmental variability, spatial scale, and habitat type on patterns of cross-taxon congruence for all three assemblages. Both environmental correlation and community congruence were significantly stronger among assemblages when examined at low spatial scales, highlighting the need to examine dipteran groups at scales untypical of current agri-environmental assessments; namely field and farm level. Furthermore, when wet grasslands were differentiated into two habitat categories (sedge and rush dominated grasslands), the significance of the community congruence increased markedly. This correlation was particularly strong between Sciomyzidae and PUs which demonstrated similar differentiation based on habitat type, implying that assemblages which exhibit comparable ecological partitioning are more likely to be useful surrogates of one another. Correlations between richness, abundance and Shannon’s diversity were highly variable among groups, suggesting compositional analysis as the most appropriate examination of dipteran diversity for surrogacy studies. The results indicate that cross-assemblage congruence of Diptera is influenced by similarity of response to environmental variability, scale of observation, and examination of assemblages differentiated into appropriate habitat categories. The results illustrate the need to investigate invertebrate biodiversity surrogates at scales appropriate to the indicator groups and examine congruence among assemblages within specific habitat categories. Such an approach has the potential to maximise gamma diversity in areas where wet grasslands are under threat of intensification or abandonment.

Surrogate species versus landscape metric: does presence of a raptor species explains diversity of multiple taxa more than patch area?

Prioritizing conservation areas is a central theme in conservation biology. The use of surrogate species and landscape metrics to identify areas with high conservation value is common. However, few studies have examined the relative efficacy of these two surrogates. In this study, we compared the efficacy of the presence/absence (PA) of a top predator (Eastern Marsh Harrier, Circus spilonotus) and wetland patch area on species richness, total abundance, and community composition of birds, plants, and small mammals, but species richness and community composition only for plants, in a fragmented wetland landscape. Although harrier PA was an effective indicator of the distribution of birds, it had no significant efficacy on the distributions of plants and small mammals. Patch area was more effective indicator of the distributions of plants and small mammals. These results suggest that surrogate species can be more effective indicators than landscape surrogates when there are ecological linkages between surrogate species and the focal taxa (e.g., similarity of habitat requirements between surrogate species and focal taxa or hetero-specific attraction). On the other hand, landscape surrogates would be useful when ecological knowledge about the relationships is limited.

Multiple factors and thresholds explaining fish species distributions in lowland streams

Appropriate restoration and conservation measures require a good understanding of the factors limiting the distribution of species, the presence of steep changes in the distribution along environmental gradients and the effect of environmental interactions on species distribution. We used 12 environmental variables describing connectivity, hydrology, climate and stream morphology, to model the distributions of 17 fish species from 2005 Swedish stream sites that were sampled between 2000 and 2011. Modeling was performed using boosted regression trees and random forest, two machine learning techniques to assess the relationship between species distributions and their environment. Temperature, width and connectivity (minimum distance to lake or the sea and water discharge), were the most important variables explaining changes in species distribution at large spatial scales. Response curves of fitted occurrence probabilities along predictors often showed abrupt changes, however, clear threshold effects were difficult to detect. Our results show also differences across species and even in the outcomes of the two algorithms, implying that a simultaneous assessment of multiple species may provide a better signal of ecosystem change than the use of surrogate species.

A Hierarchical Community Occurrence Model for North Carolina Stream Fish

AbstractThe southeastern USA is home to one of the richest—and most imperiled and threatened—freshwater fish assemblages in North America. For many of these rare and threatened species, conservation efforts are often limited by a lack of data. Drawing on a unique and extensive data set spanning over 20 years, we modeled occurrence probabilities of 126 stream fish species sampled throughout North Carolina, many of which occur more broadly in the southeastern USA. Specifically, we developed species‐specific occurrence probabilities from hierarchical Bayesian multispecies models that were based on common land use and land cover covariates. We also used index of biotic integrity tolerance classifications as a second level in the model hierarchy; we identify this level as informative for our work, but it is flexible for future model applications. Based on the partial‐pooling property of the models, we were able to generate occurrence probabilities for many imperiled and data‐poor species in addition to highlighting a considerable amount of occurrence heterogeneity that supports species‐specific investigations whenever possible. Our results provide critical species‐level information on many threatened and imperiled species as well as information that may assist with re‐evaluation of existing management strategies, such as the use of surrogate species. Finally, we highlight the use of a relatively simple hierarchical model that can easily be generalized for similar situations in which conventional models fail to provide reliable estimates for data‐poor groups.Received January 13, 2014; accepted May 5, 2014

Do laboratory species protect endangered species? Interspecies variation in responses to 17β-estradiol, a model endocrine active compound.

Although the effects of estrogens on model laboratory species are well documented, their utility as surrogates for other species, including those listed as endangered, are less clear. Traditionally, conservation policies are evaluated based on model organism responses but are intended to protect all species in an environment. We tested the hypothesis that the endangered Rio Grande silvery minnow (Hybognathus amarus) is more vulnerable to endocrine disruption-as assessed through its larval predator-escape performance, survival, juvenile sex ratios, and whole-body vitellogenin concentration-than the commonly used toxicological model species fathead minnow (Pimephales promelas) and the bluegill sunfish (Lepomis macrochirus). Fish were exposed concurrently for 21 days to the model endocrine active compound (EAC) 17ß-estradiol (E2) at 10 ng E2/L and 30 ng E2/L in a flow-through system using reconstituted water that simulated the physicochemical conditions of the Middle Rio Grande in New Mexico, USA. No significant differences were observed between the fathead and silvery minnow in larval predator-escape response or juvenile sex ratio. Rio Grande silvery minnow survival decreased significantly at day 14 compared with the other two species; by day 21, both cyprinid species (silvery minnow and fathead minnow) exhibited a significant decrease in survival compared with bluegill sunfish, a member of the family Centrarchidae. Male Rio Grande silvery minnow showed a significant increase in whole-body vitellogenin concentration in the 10 ng/L treatment, whereas fathead minnow and bluegill sunfish showed no significant increases in vitellogenin concentrations across treatments. Our study showed response differences to estrogen exposures between the two cyprinid species and further divergence in responses between the families Cyprinidae and Centrarchidae. These results suggest that commonly used laboratory model organisms may be less sensitive to EACs than the endangered Rio Grande silvery minnow. However, this study supports the continued use of surrogate species for the beneficial implementation of water-quality regulations for the protection of threatened and endangered species if phylogenetic relationships are taken into consideration.

Testing surrogacy assumptions: can threatened and endangered plants be grouped by biological similarity and abundances?

There is renewed interest in implementing surrogate species approaches in conservation planning due to the large number of species in need of management but limited resources and data. One type of surrogate approach involves selection of one or a few species to represent a larger group of species requiring similar management actions, so that protection and persistence of the selected species would result in conservation of the group of species. However, among the criticisms of surrogate approaches is the need to test underlying assumptions, which remain rarely examined. In this study, we tested one of the fundamental assumptions underlying use of surrogate species in recovery planning: that there exist groups of threatened and endangered species that are sufficiently similar to warrant similar management or recovery criteria. Using a comprehensive database of all plant species listed under the U.S. Endangered Species Act and tree-based random forest analysis, we found no evidence of species groups based on a set of distributional and biological traits or by abundances and patterns of decline. Our results suggested that application of surrogate approaches for endangered species recovery would be unjustified. Thus, conservation planning focused on individual species and their patterns of decline will likely be required to recover listed species.

South African ecotoxicology — present status and future prognosis

Toxicology studies the interactions of a chemical substance with individual organisms, whereas ecotoxicology is a multidisciplinary approach incorporating ecology and other disciplines, e.g. chemistry, microbiology, etc., to determine responses of individuals, populations and whole ecosystems to stressors such as chemicals. We present here the current status of toxicity testing in South Africa and propose a future prognosis for such tests. We propose a path forward for the development of ecotoxicology in South Africa and also globally. Toxicity testing issues dealt with are the use of surrogate species as opposed to indigenous species, their comparative tolerances, and the selection of relevant endpoints as measures of toxicity. Ecotoxicological considerations need to address the following key ecological realities: tolerance (both physiological acclimation and genetic adaptation), trophic redundancies, resilience, compensation (e.g. density dependence), evolution, and recovery. We believe that predictive ecotoxicology will play a major role in the future management of ecosystems that are constantly changing. We also believe that such management must be proactive to the point of intervention to create desired change, specifically the maintenance of ecosystem services.

A Critical Assessment of the Use of Surrogate Species in Conservation Planning in the Sacramento-San Joaquin Delta, California (U.S.A.)

Conservation biology has provided wildlife managers with a wealth of concepts and tools for use in conservation planning; among them is the surrogate species concept. Over the past 20 years, a growing body of empirical literature has demonstrated the limited effectiveness of surrogates as management tools, unless it is first established that the target species and surrogate will respond similarly to a given set of environmental conditions. Wildlife managers and policy makers have adopted the surrogate species concept, reflecting the limited information available on most species at risk of extirpation or extinction and constraints on resources available to support conservation efforts. We examined the use of surrogate species, in the form of cross-taxon response-indicator species (that is, one species from which data are used to guide management planning for another, distinct species) in the Sacramento-San Joaquin Delta, California (U.S.A.). In that system there has been increasing reliance on surrogates in conservation planning for species listed under federal or state endangered species acts, although the agencies applying the surrogate species concept did not first validate that the surrogate and target species respond similarly to relevant environmental conditions. During the same period, conservation biologists demonstrated that the surrogate concept is generally unsupported by ecological theory and empirical evidence. Recently developed validation procedures may allow for the productive use of surrogates in conservation planning, but, used without validation, the surrogate species concept is not a reliable planning tool.

Ecological risk of anthropogenic pollutants to reptiles: Evaluating assumptions of sensitivity and exposure

A large data gap for reptile ecotoxicology still persists; therefore, ecological risk assessments of reptiles usually incorporate the use of surrogate species. This necessitates that (1) the surrogate is at least as sensitive as the target taxon and/or (2) exposures to the surrogate are greater than that of the target taxon. We evaluated these assumptions for the use of birds as surrogates for reptiles. Based on a survey of the literature, birds were more sensitive than reptiles in less than 1/4 of the chemicals investigated. Dietary and dermal exposure modeling indicated that exposure to reptiles was relatively high, particularly when the dermal route was considered. We conclude that caution is warranted in the use of avian receptors as surrogates for reptiles in ecological risk assessment and emphasize the need to better understand the magnitude and mechanism of contaminant exposure in reptiles to improve exposure and risk estimation.

Sensitivity of Lamprey Ammocoetes to Six Chemicals

As part of the ecological risk assessment for Portland Harbor Superfund site, a study was conducted to address the question of whether the use of surrogate species in the risk assessment would be protective of lamprey ammocoetes. The study evaluated the acute toxicity of six chemicals: pentachlorophenol, copper, diazinon, aniline, naphthalene, and lindane; these chemicals represent the toxic modes of action of oxidative phosphorylation uncoupler, gill dysfunction, acetylcholinesterase inhibitor, polar narcosis, narcosis, and central nervous system interference, respectively. Field-collected lamprey ammocoetes were exposed to each of the six chemicals in a definitive 96-h flow-through acute water-only toxicity test. LC(50)s were calculated for pentachlorophenol at 31 μg/l, copper at 46 μg/l, diazinon at 8.9 mg/l, and aniline at 430 mg/l. Species sensitivity distributions based on LC(50)s for aquatic organisms indicated that lamprey ammocoetes were relatively sensitive to pentachlorophenol (15th percentile). The sensitivity of lamprey ammocoetes to copper approximated the average of aquatic species tested (46th percentile). Lamprey ammocoetes were relatively insensitive to diazinon and aniline (72nd and 90th percentile, respectively). The 96-h LC(50) for naphthalene was estimated at 10 mg/l, based on 50% mortality in the highest concentration. Based on a comparison with LC(50)s for four other fish species, ranging from 2.0 to 6.6 mg/l, lamprey ammocoetes were relatively insensitive to naphthalene. A 96-h LC(50) could not be derived for lindane, with 12.5% mortality in the highest test concentration of 2.68 mg/l. LC(50)s for numerous other fish species ranged from 0.001 to 0.24 mg/l, indicating that lamprey ammocoetes were relatively insensitive to lindane. The study concluded that the use of surrogate species in the ecological risk assessment for Portland Harbor would be protective of lamprey ammocoetes.

The Use of Surrogate Species in Risk Assessment: Using Life History Data to Safeguard Against False Negatives

The use of surrogate species is an important tool in predicting the effects of management decisions or the establishment of protective measures for endangered/threatened species. While relying on a handful of model species to predict the fate of scores of distantly related target species has been criticized, a quantitative measure linking life history traits and population predictions has been sorely missing. We derive here a closed-form expression aimed at determining conditions under which sublethal effects of a toxicant on surrogate species population outcomes will reliably predict outcomes of target (listed) species. We develop a critical threshold in fecundity reduction above which the surrogate species outcomes indicate positive population growth, while the listed species is driven to extinction. Thus we have established a means of determining conditions under which we are prone to making a "Type II" error in assessing ecological risk using surrogate species. Finally, we use the derived expression and life history data to compare outcomes from four different commonly used fish surrogate species (round goby, fathead minnow, smallmouth bass, cutthroat trout) and their target listed species (Chinook and Coho salmon). We illustrate that all four surrogate species fail to predict population outcomes for the listed species in cases of as little as 15% fecundity reduction due to toxicant exposure. Furthermore, surrogate species reliability is a function of toxicant level, so that some species are reliable at some levels but not at others. We discuss the implications of these findings, and outline further analyses that occur as a natural extension of the criteria developed here.

Simple to sample: Vascular plants as surrogate group in a nature reserve

Summary One of the basic tools to quantify biodiversity is based on the use of surrogate species. Such groups of species are easily assessed and may reflect the diversity of other important and less easily detectable taxa (cross-taxon surrogacy). Among these key groups of species, the vascular plant flora has great potential in determining diversity of other groups, since in terrestrial ecosystems it constitutes the bulk of total biomass and provides the physical structure for other organisms. The cross-taxon congruence of species diversity (species richness and species composition) among vascular plants, bryophytes, lichens, fungi, oligochaetes, butterflies and birds was investigated with special attention to testing the potential role of vegetation as surrogate for the other studied taxa. The 271 ha Nature Reserve “Bosco di S. Agnese” (Tuscany, Italy) characterised by evergreen Mediterranean woodlands, scrublands, garigues, xeric grasslands and cultivations was used as study area. A multi-scale sampling design, based on a restricted random selection of plots, was used to get information about vascular plants, bryophytes, lichens, fungi, oligochaetes, butterflies and birds. The congruence in species richness and composition among the different taxa was tested by Spearman rank correlation coefficient. Most of the pair-wise comparisons showed weak and statistically not significant correlations for both species richness and compositional data, indicating a limited cross-taxon congruence. Species richness of vascular plants was significantly correlated only to that of birds and butterflies. Compositional patterns were congruent only between vascular plants and butterflies. The results of this study indicated that neither vascular plants nor any other taxonomic group is a valid surrogate in this nature reserve.

Using Hydrogen Isotopes to Assign Origins of Bats in the Eastern United States

Stable hydrogen isotopes (dDs) in metabolically inert tissues such as feathers and hair provide a set of endogenous markers that may be useful for establishing migratory connectivity in animals. We tested the assumption of a clear relationship between dD values of growing-season–weighted average precipitation (dDp) derived from 2 geographic information system (GIS) models or latitude (LAT) and dD values in bat hair (dDh), and examined intra- and interspecific variation in dDh of 4 bat species in the eastern United States. We analyzed 251 hair samples from 1 long-distance migrant (eastern red bat [Lasiurus borealis]) and 3 regional migrants (Indiana bat [Myotis sodalis], northern long-eared bat [M. septentrionalis], and little brown bat [M. lucifugus]) captured during the reproductive period (pregnancy and lactation) when bats are resident. LAT explained more of the variation in dDh than dDp derived from either of the GIS-based models, although 1 model of dDp performed better for some species. We found significant intraspecific differences in the relationships between dDh and LAT and between dDh and estimates of dDp derived from Bowen et al. (dDpB) for L. borealis, and significant variation in the regression equations of dDh and LAT and dDh and dDp among species for adult females and adult males. Stable hydrogen isotope analysis may be a valuable tool for studying migratory connectivity in bats, but significant intra- and interspecific variatio ni ndDh values suggests that pooling across sex and age categories and use of surrogate species should be avoided.

Protectiveness of species sensitivity distribution hazard concentrations for acute toxicity used in endangered species risk assessment

A primary objective of threatened and endangered species conservation is to ensure that chemical contaminants and other stressors do not adversely affect listed species. Assessments of the ecological risks of chemical exposures to listed species often rely on the use of surrogate species, safety factors, and species sensitivity distributions (SSDs) of chemical toxicity; however, the protectiveness of these approaches can be uncertain. We comprehensively evaluated the protectiveness of SSD first and fifth percentile hazard concentrations (HC1, HC5) relative to the application of safety factors using 68 SSDs generated from 1,482 acute (lethal concentration of 50%, or LC50) toxicity records for 291 species, including 24 endangered species (20 fish, four mussels). The SSD HC5s and HCls were lower than 97 and 99.5% of all endangered species mean acute LC50s, respectively. The HC5s were significantly less than the concentrations derived from applying safety factors of 5 and 10 to rainbow trout (Oncorhynchus mykiss) toxicity data, and the HCls were generally lower than the concentrations derived from a safety factor of 100 applied to rainbow trout toxicity values. Comparison of relative sensitivity (SSD percentiles) of broad taxonomic groups showed that crustaceans were generally the most sensitive taxa and taxa sensitivity was related to chemical mechanism of action. Comparison of relative sensitivity of narrow fish taxonomic groups showed that standard test fish species were generally less sensitive than salmonids and listed fish. We recommend the use of SSDs as a distribution-based risk assessment approach that is generally protective of listed species.