AbstractEstimating distributions for cryptic and highly range‐restricted species induces unique challenges for species distribution modeling. In particular, bioclimatic covariates that are typically used to model species ranges at regional and continental scales may not show strong variation at scales of 100s and 10s of meters. This limits both the likelihood and usefulness of correlated occurrence to data typically used in distribution models. Here, we present analyses of species distributions, at 100 × 100 m resolution, for a highly range restricted salamander species (Shenandoah salamander, Plethodon shenandoah) and a closely related congener (red‐backed salamander, Plethodon cinereus). We combined data across multiple survey types, account for seasonal variation in availability of our target species, and control for repeated surveys at locations– all typical challenges in range‐scale monitoring datasets. We fit distribution models using generalized additive models that account for spatial covariates as well as unexplained spatial variation and spatial uncertainty. Our model accommodates different survey protocols using offsets and incorporates temporal variation in detection and availability resulting from survey‐specific variation in temperature and precipitation. Our spatial random effect was crucial in identifying small‐scale differences in the occurrence of each species and provides cell‐specific estimates of uncertainty in the density of salamanders across the range. Counts of both species were seen to increase in the 3 days following a precipitation event. However, P. cinereus were observed even in extremely wet conditions, while surface activity of P. shenandoah was associated with a more narrow range. Our results demonstrate how a flexible analytical approach improves estimates of both distribution and uncertainty, and identify key abiotic relationships, even at small spatial scales and when scales of empirical data are mismatched. While our approach is especially valuable for species with small ranges, controlling for spatial autocorrelation, estimating spatial uncertainty, and incorporating survey‐specific information in estimates can improve the reliability of distribution models in general.

Making timely management decisions is often hindered by uncertainty. Monitoring reduces two key types of uncertainty. First, it serves to reduce structural uncertainty of how the system works and provides support for expectations of how a system works. Second, it serves to reduce parametric uncertainty of the drivers of system dynamics. By combining monitoring data and quantitative models, we can reduce structural and parametric uncertainty. To demonstrate this, we focus on the Shenandoah salamander (Plethodon shenandoah), a United States Federally Endangered Species. Early work suggested that P. shenandoah extinction risk results from competition with a conspecific (Plethodon cinereus). However, more recent work has found equivocal support for this claim, instead suggesting that abiotic factors, such as moisture and temperature, drive P. shenandoah persistence. Using long-term monitoring data, we find that while competition may play a part in P. shenandoah extinction risk, measures of surface moisture are better predictors of occupancy dynamics. Further, we find decreased detection rates of P. shenandoah when P. cinereus is present, suggesting a conflation of detection probability with actual competition, which cautions against making inference from unadjusted observations of occurrence. Using multiple lines of inquiry allows for more robust understanding of system drivers in the face of high uncertainty, increasing opportunities to manage extinction risk.

Using accurate and precise species-specific parameters in mechanistic models can lead to better predictions of population dynamics and ecosystem function (e.g. nutrient cycling) across a range of environmental conditions. Zooplankton are important in the aquatic food web and for nutrient cycling but are highly diverse, and there is only limited information on specific species. Knowledge of species-specific attributes is patchy. In particular, tropical species are underrepresented in this regard. Here, we gather all the known information about a wide-spread tropical zooplankton member, Ceriodaphnia rigaudi , and add new information from lab and field experiments. We determine feeding rate across a range of food concentrations and food-dependent population growth rate of C. rigaudi . Additionally, we use 16 years of occurrence data from rock pools in Jamaica to explore environmental characteristics of the habitat in which C. rigaudi live. We compare our data to worldwide records of the species attributes and create a reference map of its occurrence.

Resilience, the capacity for a system to bounce-back after a perturbation, is critical for conservation and restoration efforts.Different functional traits have differential effects on system-level resilience.We test this experimentally in a lab system consisting of algae consumed by zooplankton, snails, or both, using an eutrophication event as a perturbation.We examined seston settlement load, chlorophyll-a and ammonium concentration as gauges of resilience.We find that Daphnia magna increased our measures of resilience.But this effect is not consistent across ecosystem measures; in fact D. magna increased the difference between disturbed and undisturbed treatments in seston settlement loads.We have some evidence of shifting reproductive strategy in response to perturbation in D. magna and in the presence of Physa sp..These shifts correspond with altered population levels in D. magna , suggesting feedback loops between the herbivore species.While these results suggest only an ambiguous connection between functional traits to ecosystem resilience, they point to the difficulties in establishing such a link: indirect effects of one species on reproduction of another and different scales of response among components of the system, are just two examples that may compromise the power of simple predictions.

Resilience, the capacity for a system to bounce-back after a perturbation, is critical for conservation and restoration efforts. Different functional traits have differential effects on system-level resilience. We test this experimentally in a lab system consisting of algae consumed by zooplankton, snails, or both, using an eutrophication event as a perturbation. We examined seston settlement load, chlorophyll-a and ammonium concentration as gauges of resilience. We find that Daphnia magna increased our measures of resilience. But this effect is not consistent across ecosystem measures; in fact, D. magna increased the difference between disturbed and undisturbed treatments in seston settlement loads. We have some evidence of shifting reproductive strategy in response to perturbation in D. magna and in the presence of Physa sp. These shifts correspond with altered population levels in D. magna , suggesting feedback loops between the herbivore species. While these results suggest only an ambiguous connection between functional traits to ecosystem resilience, they point to the difficulties in establishing such a link: indirect effects of one species on reproduction of another and different scales of response among components of the system, are just two examples that may compromise the power of simple predictions.

Previous articleNext article No AccessEcologyMeasuring Abundance: Methods for the Estimation of Population Size and Species Richness. Data in the Wild Series. By Graham J. G. Upton. Exeter (United Kingdom): Pelagic Publishing. $97.13 (hardcover); $45.33 (paper). x + 226 p.; ill.; index of examples and general index. ISBN: 978-1-78427-232-6 (hc); 978-1-78427-231-9 (pb); 978-1-78427-233-3 (eb). 2020.Jo A. WerbaJo A. WerbaEcosystem Science & Management, Pennsylvania State University, University Park, Pennsylvania Search for more articles by this author PDFPDF PLUSFull Text Add to favoritesDownload CitationTrack CitationsPermissionsReprints Share onFacebookTwitterLinkedInRedditEmail SectionsMoreDetailsFiguresReferencesCited by The Quarterly Review of Biology Volume 96, Number 3September 2021 Published in association with Stony Brook University Article DOIhttps://doi.org/10.1086/716148 Views: 18Total views on this site For permission to reuse, please contact [email protected]PDF download Crossref reports no articles citing this article.

The dear enemy hypothesis predicts that territorial individuals will be less aggressive toward known neighbors than to strangers. This hypothesis has been well studied and there is a wealth of data demonstrating its prevalence in some taxa. However, a quantitative synthesis is needed to test the generality of the phenomenon, identify key mechanisms driving the behavior, and guide future research. In this study, we conduct a meta-analysis and, we test the importance of the location of intrusion, the type of experiment conducted (field, laboratory, or neutral arenas), and the sex and breeding status of territory holders, on the occurrence of dear enemy behavior. We also test how various ecological and life history traits, such as territory type, stimulus of intrusion, and taxonomic group, affect the magnitude of dear enemy behavior. We find that this phenomenon is common and that taxonomic class and breeding status are correlated with the expression of dear enemy behaviors. Further, we found that the way authors measure aggression influences the likelihood of identifying dear enemy responses, and thus we discuss potential pitfalls of dear enemy studies. Considering this conclusion, we discuss future lines of inquiry that could more directly examine the mechanisms of the dear enemy phenomenon.

ABSTRACT Climate change induced salinization events are predicted to intensify and lead to increased salt stress in freshwater aquatic ecosystems. As a consequence, formerly distinct abiotic conditions and associated biotic communities merge, and the emergence, loss, and persistence of microbial taxa modify the types and rates of ecosystem processes. This study examined how bacterial taxonomic and phylogenetic diversity and ecosystem function respond to acute salinization events where freshwater and estuarine communities and environments coalesce. We hypothesized that when the salinity change outpaces microbial adaptation or saline microbial populations are not yet established in formerly freshwater conditions, then these aquatic communities will exhibit diminished carbon cycling rates, decreased microbial diversity, and altered composition of microbial communities compared to historically freshwater communities. We used an experimental mesocosm approach to determine how salinity and the merging of distinct communities influenced resultant bacterial community structure and function. Each mesocosm represented different salinities (0, 5, 9, 13 psu). Two dispersal treatments, representing aquatic communities sourced from brackish 13 psu ponds and a mix of 13 psu and freshwater ponds, were added to all salinity levels and replicated four times. Results revealed that salinity, but not dispersal, decreased bacterial taxonomic and phylogenetic diversity. Carbon mineralization rates were highest in freshwater conditions and associated to bacterial taxa represented in low relative abundance. Acute salinity changes, such as localized flooding due to storm surge, will more negatively affect freshwater aquatic communities compared to chronic exposure to salinization where the communities have had time to adapt or turnover. IMPORTANCE STATEMENT Climate change induced salinization results in the mixing of formerly distinct environmental conditions and aquatic communities. This study examined the consequence of short-term, acute salinity stress on aquatic bacterial taxonomic and phylogenetic diversity and ecosystem function using an experimental approach. Results revealed that salinity, but not the source of aquatic communities, decreased bacterial taxonomic and phylogenetic diversity. Carbon mineralization rates, which represented ecosystem function, were highest in freshwater conditions and also associated with indicator bacterial taxa in low abundance relative to the total microbial community. Taken together, acute salinity changes will more negatively affect freshwater aquatic communities compared to chronic exposure to salinization where the communities have had time to adapt or turnover resulting in recovered biogeochemical functions.

Sea level rise is mixing formerly isolated freshwater communities with saltwater communities. The structure of these new aquatic communities is jointly controlled by pre- and post-colonization processes. Similarly, since salinity is a strong abiotic determinant of post-colonization survival in coastal systems, changes in salinity will likely impact community composition. In this study, we examine how a strong abiotic gradient affects the diversity and structure of bacterial and zooplankton communities and associated ecosystem functions (decomposition and carbon mineralization). We ran a six week dispersal experiment using mesocosm ponds with four distinct salinity profiles (0, 5, 9, and 13 psu). We find that salinity is the primary driver of both bacterial and zooplankton community composition. We find evidence that as bacterial richness increases so does the amount of decomposition. A phenomenological model suggests carbon mineralization may decrease at mid-salinities; this warrants future work into possible mechanisms for this apparent loss of function. Understanding how salinization changes community structure and ecosystem function maybe paramount for managing and conserving coastal plain ecosystems where salinity is increasing due to sea level rise, saltwater intrusion, storm surges, and drought.