Do We Need to Use Bats as Bioindicators?

Bats show responses to anthropogenic stressors linked to changes in other ecosystem components such as insects, and as K-selected mammals, exhibit fast population declines. This speciose, widespread mammal group shows an impressive trophic diversity and provides key ecosystem services. For these and other reasons, bats might act as suitable bioindicators in many environmental contexts. However, few studies have explicitly tested this potential, and in some cases, stating that bats are useful bioindicators more closely resembles a slogan to support conservation than a well-grounded piece of scientific evidence. Here, we review the available information and highlight the limitations that arise in using bats as bioindicators. Based on the limited number of studies available, the use of bats as bioindicators is highly promising and warrants further investigation in specific contexts such as river quality, urbanisation, farming practices, forestry, bioaccumulation, and climate change. Whether bats may also serve as surrogate taxa remains a controversial yet highly interesting matter. Some limitations to using bats as bioindicators include taxonomical issues, sampling problems, difficulties in associating responses with specific stressors, and geographically biased or delayed responses. Overall, we urge the scientific community to test bat responses to specific stressors in selected ecosystem types and develop research networks to explore the geographic consistency of such responses. The high cost of sampling equipment (ultrasound detectors) is being greatly reduced by technological advances, and the legal obligation to monitor bat populations already existing in many countries such as those in the EU offers an important opportunity to accomplish two objectives (conservation and bioindication) with one action.

Evaluating policy-relevant surrogate taxa for biodiversity conservation: a case study from British Columbia, Canada

Conservation efforts often lead to a small proportion of species receiving a disproportionate amount of attention. This bias in funding may help or hinder broader goals of biodiversity conservation depending on the surrogacy value of the well-funded species. Surrogate species are selected to represent other taxa in a shared environment when it would be costly or impractical to obtain information on individual taxa. We compared the surrogacy value of common groups of taxa implicated in conservation — game species, carnivores, non-game species, and other species. Using a publicly available data set of species–habitat associations, we compared the surrogacy value for 1012 species and 64 habitat types in British Columbia, Canada. We used a conditional entropy metric to quantify pairwise associations between species via their occurrence in different habitat types. Our analysis reveals that game and non-game species surrogacy groups do not significantly differ in either the frequency of captured pairwise associations or their coverage of species. These results suggest that funding game species conservation is likely conferring some benefits to non-game species, but optimal habitat-based conservation outcomes will come from a combination of taxa. This analysis provides an important step in influencing management decisions for the preservation of biodiversity in British Columbia.

Development of a Metric of Aquatic Invertebrates for Volunteers (MAIV): A Simple and Friendly Biotic Metric to Assess Ecological Quality of Streams

Citizen science activities, involving local people in volunteer-supported and sustainable monitoring programs, are common. In this context, the objective of the present work was to develop a simple Metric of Aquatic Invertebrates for Volunteers (MAIV), including a user-friendly tool that can be easily accessed by volunteers, and to evaluate the efficiency of a volunteer monitoring program following an audit procedure. To obtain MAIV values, macroinvertebrate communities were reduced to 18 surrogate taxa, which represented an acceptable compromise between simplicity, efficiency, and reproducibility of the data, compared to the regular Water Framework Directive monitoring. When compared to results obtained with the National Classification System of Portugal, MAIV accurately detected moderate, poor, and bad ecological status. Thus, MAIV can be used by volunteers as a complement to the official monitoring program, as well as a prospective early warning tool for local problems related to ecological quality. Volunteers were students supervised by their teachers. Results obtained by volunteers were compared to results obtained by experts on macroinvertebrate identification to measure the efficiency of the procedure, by counting gains and losses on sorting, and identification. Characteristics of groups of volunteers (age and school level) did not influence significantly the efficiency of the procedure, and generally results of volunteers and experts matched.

Surrogate taxa and fossils as reliable proxies of spatial biodiversity patterns in marine benthic communities

Rigorous documentation of spatial heterogeneity (β-diversity) in present-day and preindustrial ecosystems is required to assess how marine communities respond to environmental and anthropogenic drivers. However, the overwhelming majority of contemporary and palaeontological assessments have centred on single higher taxa. To evaluate the validity of single taxa as community surrogates and palaeontological proxies, we compared macrobenthic communities and sympatric death assemblages at 52 localities in Onslow Bay (NC, USA). Compositional heterogeneity did not differ significantly across datasets based on live molluscs, live non-molluscs, and all live organisms. Death assemblages were less heterogeneous spatially, likely reflecting homogenization by time-averaging. Nevertheless, live and dead datasets were greater than 80% congruent in pairwise comparisons to the literature estimates of β-diversity in other marine ecosystems, yielded concordant bathymetric gradients, and produced nearly identical ordinations consistently delineating habitats. Congruent estimates from molluscs and non-molluscs suggest that single groups can serve as reliable community proxies. High spatial fidelity of death assemblages supports the emerging paradigm of Conservation Palaeobiology. Integrated analyses of ecological and palaeontological data based on surrogate taxa can quantify anthropogenic changes in marine ecosystems and advance our understanding of spatial and temporal aspects of biodiversity.

Anthropogenic stress alters community concordance at the river-riparian interface

Organisms often respond in similar ways to environmental or spatial gradients, particularly at large spatial scales, but patterns at finer scales and across ecotones are less certain. It is important to understand these relationships at multiple spatial scales, as managers often need suitable surrogate taxa for conservation and monitoring purposes. We explored whether community concordance at the river-riparian interface was decoupled by increasing anthropogenic stress (a gradient of local land-use intensity) at 15 sites over three years within the LTER site, Rhine-Main Observatory, a low mountain river system in central Germany. We assessed concordance between four organism groups: riparian spiders and carabid beetles, benthic macroinvertebrates, and combined aquatic macrophytes and riparian plants. This represented three different linkages: (1) predator-prey, (2) direct competition, and (3) habitat associations. While there were no correlations in richness patterns, multivariate community structure was highly concordant between all groups. Anthropogenic stress strongly reduced links between riparian spiders and carabid beetles, likely resulting from their shared resource requirements. However, increasing concordance occurred between plants and other groups. We posit that patterns may be resulting from two processes: (1) linkages between directly competing species decouple with increasing anthropogenic stress, and (2) stronger coupling may occur between habitat providers and dependent species when overall habitat complexity is reduced. These results highlight the complex manner in which anthropogenic stress can influence ecosystems and the importance of considering community structure when exploring biodiversity patterns in basic and applied ecological research, particularly at small scales and for surrogate taxa development.

Anthropogenic stress alters community concordance at the river-riparian interface

Organisms often respond in similar ways to environmental or spatial gradients, particularly at large spatial scales, but patterns at finer scales and across ecotones are less certain. It is important to understand these relationships at multiple spatial scales, as managers often need suitable surrogate taxa for conservation and monitoring purposes. We explored whether community concordance at the river-riparian interface was decoupled by increasing anthropogenic stress (a gradient of local land-use intensity) at 15 sites over three years within the LTER site, Rhine-Main Observatory, a low mountain river system in central Germany. We assessed concordance between four organism groups: riparian spiders and carabid beetles, benthic macroinvertebrates, and combined aquatic macrophytes and riparian plants. This represented three different linkages: (1) predator-prey, (2) direct competition, and (3) habitat associations. While there were no correlations in richness patterns, multivariate community structure was highly concordant between all groups. Anthropogenic stress strongly reduced links between riparian spiders and carabid beetles, likely resulting from their shared resource requirements. However, increasing concordance occurred between plants and other groups. We posit that patterns may be resulting from two processes: (1) linkages between directly competing species decouple with increasing anthropogenic stress, and (2) stronger coupling may occur between habitat providers and dependent species when overall habitat complexity is reduced. These results highlight the complex manner in which anthropogenic stress can influence ecosystems and the importance of considering community structure when exploring biodiversity patterns in basic and applied ecological research, particularly at small scales and for surrogate taxa development.

Using oligochaeta assemblages as an indicator of environmental changes

We designed a field survey (the entire river length; not dammed: First and Second plateaus; dammed: Third Plateau) to test the hypothesis that the cascade of reservoirs promoted a reduction in species richness and changed the composition of Oligochaeta assemblage along the Iguaçu River. Changes in environmental variables and in richness and composition of Oligochaeta were summarized by Canonic Correspondence Analysis. Along the Iguaçu River, conductivity, and altitude decreased, whereas temperature increased. Oligochaeta composition showed a significant spatial variation, with higher abundances of the family Tubificidae and the genus Dero (Naididae) occurring in the First Plateau. In the Second and Third plateaus, few species were dominant, with increases in the presence of species of Naididae below dams. We found a clear decrease in species richness along the Iguaçu River. Moreover, we found that Oligochaeta assemblage was influenced by some environmental variables such as altitude, conductivity, substrate type and temperature, and by anthropogenic activities (human occupation and damming). The results supported the use of Oligochaeta as surrogate taxa to predict environmental changes along impacted (dammed and eutrophic) rivers. The validity of this was indicated by the strong and significant gradient registered, from the headwater to mouth of the Iguaçu River.