Resilience and stability of freshwater invertebrate communities across space and time

Understanding ecosystem response to environmental change is one of the biggest challenges in ecology. Studies of the biological factors and environmental drivers underpinning change in communities through space and time are essential for predicting responses to increasing anthropogenic pressures on ecosystems. Ecosystems encompass numerous interactions within and across levels of biological organization and are inextricably linked to human societies. This thesis addresses ecosystem change from the perspectives of ecological and social-ecological resilience, ecosystem stability, and adaptive capacity. Drawing on ecological resilience theory, promising methods for assessing social-ecological resilience were identified. Following this, the concept of adaptive capacity was refined, operationalized, and distinguished from ecological resilience and stability. Indicators of adaptive capacity, namely compositional stability, functional redundancy, and response diversity were measured in invertebrate communities in Swedish freshwater. I quantified drivers of stability across time and space in Swedish lakes and documented positive correlations between functional redundancy and response diversity at a broad spatial scale in Swedish streams. These indicators were influenced by physiochemical variables, and pervasive anthropogenic disturbances in the landscape. The results highlight the importance of studying long-term and spatially extensive changes in biotic communities using a framework that integrates different aspects of ecosystem resilience to environmental change

A Quantitative Framework for Assessing Ecological Resilience

Quantitative approaches to measure and assess resilience are needed to bridge gaps between science, policy, and management. In this paper, we suggest a quantitative framework for assessing ecological resilience. Ecological resilience as an emergent ecosystem phenomenon can be decomposed into complementary attributes (scales, adaptive capacity, thresholds, and alternative regimes) that embrace the complexity inherent to ecosystems. Quantifying these attributes simultaneously provides opportunities to move from the assessment of specific resilience within an ecosystem toward a broader measurement of its general resilience. We provide a framework that is based on reiterative testing and recalibration of hypotheses that assess complementary attributes of ecological resilience. By implementing the framework in adaptive approaches to management, inference, and modeling, key uncertainties can be reduced incrementally over time and learning about the general resilience of dynamic ecosystems maximized. Such improvements are needed because uncertainty about global environmental change impacts and their effects on resilience is high. Improved resilience assessments will ultimately facilitate an optimized use of limited resources for management

Long‐term population dynamics of dreissenid mussels (Dreissena polymorpha and D. rostriformis): a cross‐system analysis

Dreissenid mussels (including the zebra mussel Dreissena polymorpha and the quagga mussel D. rostriformis) are among the world's most notorious invasive species, with large and widespread ecological and economic effects. However, their long‐term population dynamics are poorly known, even though these dynamics are critical to determining impacts and effective management. We gathered and analyzed 67 long‐term (>10 yr) data sets on dreissenid populations from lakes and rivers across Europe and North America. We addressed five questions: (1) How do Dreissena populations change through time? (2) Specifically, do Dreissena populations decline substantially after an initial outbreak phase? (3) Do different measures of population performance (biomass or density of settled animals, veliger density, recruitment of young) follow the same patterns through time? (4) How do the numbers or biomass of zebra mussels or of both species combined change after the quagga mussel arrives? (5) How does body size change over time? We also considered whether current data on long‐term dynamics of Dreissena populations are adequate for science and management. Individual Dreissena populations showed a wide range of temporal dynamics, but we could detect only two general patterns that applied across many populations: (1) Populations of both species increased rapidly in the first 1–2 yr after appearance, and (2) quagga mussels appeared later than zebra mussels and usually quickly caused large declines in zebra mussel populations. We found little evidence that combined Dreissena populations declined over the long term. Different measures of population performance were not congruent; the temporal dynamics of one life stage or population attribute cannot generally be accurately inferred from the dynamics of another. We found no consistent patterns in the long‐term dynamics of body size. The long‐term dynamics of Dreissena populations probably are driven by the ecological characteristics (e.g., predation, nutrient inputs, water temperature) and their temporal changes at individual sites rather than following a generalized time course that applies across many sites. Existing long‐term data sets on dreissenid populations, although clearly valuable, are inadequate to meet research and management needs. Data sets could be improved by standardizing sampling designs and methods, routinely collecting more variables, and increasing support

Effect of ground temperature and nest differences on productivity and worker size in Atta cephalotes (Hymenoptera Formicidae)

Atta cephalotes is one of the few species that does better in grassy pastures and secondary growth and their abundance, persistent foraging, and that they collect from a lot of different tree species has earned them the reputation of huge agricultural pests. A. cephalotes are poikilotherms meaning their internal body temperature fluctuates greatly with temperature. For this reason, it has been purported that these leaf-cutter ants will only collect leaf fragments at certain temperatures and that different sized workers have different temperature tolerances. The objective of this study was to look for relationships between temperature, productivity, and worker size in nests in Monteverde, Costa Rica. It was found that some nests’ productivity was more responsive to changes in temperature and that nest and temperature interact to predict worker size during foraging. Because of A. cephalotes’ large impact on the ecosystem in Monteverde (whether viewed as good or bad), it is important and interesting to know more about what regulates the speed of their foraging. Atta cephalotes es una especie que se desarrolla mejor en los pastos y en los bosques de crecimiento secundario y su abundancia, forrajeo persistente, y el hecho que recolectan muchos tipos de árboles diferentes les da la reputación de grandes pestes agrícolas. A. cephalotes es una especie poiquilotermia lo que significa que la temperatura interna de su cuerpo fluctúa con la temperatura ambiental. Por esta razón, se piensa que las hormigas que cortan-hojas solamente recogen los fragmentos de las hojas durante las temperaturas específicas y que los trabajadores de los diferentes tamaños tienen tolerancias de temperatura diferentes. El objetivo de este estudio fue entender las relaciones entre la temperatura, la productividad, y el tamaño de trabajadores de esta especie en Monteverde, Costa Rica. Descubrí que la productividad de algunos nidos fue más afectada por la temperatura que otros. También que la temperatura e identidad del nido interactúan para predecir el tamaño de los trabajadores durante el forrajeo. Dado el impacto grande que tiene Atta cephalotes en los ecosistemas de Monteverde (ya sea visto como bueno o malo), es importante e interesante saber más de lo que limita y acelera el forrajeo.https://digitalcommons.usf.edu/tropical_ecology/1102/thumbnail.jp

Effect of ground temperature and nest differences on productivity and worker size in Atta cephalotes (Hymenoptera Formicidae)

Atta cephalotes is one of the few species that does better in grassy pastures and secondary growth and their abundance, persistent foraging, and that they collect from a lot of different tree species has earned them the reputation of huge agricultural pests. A. cephalotes are poikilotherms meaning their internal body temperature fluctuates greatly with temperature. For this reason, it has been purported that these leaf-cutter ants will only collect leaf fragments at certain temperatures and that different sized workers have different temperature tolerances. The objective of this study was to look for relationships between temperature, productivity, and worker size in nests in Monteverde, Costa Rica. It was found that some nests’ productivity was more responsive to changes in temperature and that nest and temperature interact to predict worker size during foraging. Because of A. cephalotes’ large impact on the ecosystem in Monteverde (whether viewed as good or bad), it is important and interesting to know more about what regulates the speed of their foraging. Atta cephalotes es una especie que se desarrolla mejor en los pastos y en los bosques de crecimiento secundario y su abundancia, forrajeo persistente, y el hecho que recolectan muchos tipos de árboles diferentes les da la reputación de grandes pestes agrícolas. A. cephalotes es una especie poiquilotermia lo que significa que la temperatura interna de su cuerpo fluctúa con la temperatura ambiental. Por esta razón, se piensa que las hormigas que cortan-hojas solamente recogen los fragmentos de las hojas durante las temperaturas específicas y que los trabajadores de los diferentes tamaños tienen tolerancias de temperatura diferentes. El objetivo de este estudio fue entender las relaciones entre la temperatura, la productividad, y el tamaño de trabajadores de esta especie en Monteverde, Costa Rica. Descubrí que la productividad de algunos nidos fue más afectada por la temperatura que otros. También que la temperatura e identidad del nido interactúan para predecir el tamaño de los trabajadores durante el forrajeo. Dado el impacto grande que tiene Atta cephalotes en los ecosistemas de Monteverde (ya sea visto como bueno o malo), es importante e interesante saber más de lo que limita y acelera el forrajeo.https://digitalcommons.usf.edu/tropical_ecology/1102/thumbnail.jp

Parallels of quantum superposition in ecological models: from counterintuitive patterns to eco-evolutionary interpretations of cryptic species

Abstract Background Superposition, i.e. the ability of a particle (electron, photon) to occur in different states or positions simultaneously, is a hallmark in the subatomic world of quantum mechanics. Although counterintuitive at first sight, the quantum world has potential to inform macro-systems of people and nature. Using time series and spatial analysis of bird, phytoplankton and benthic invertebrate communities, this paper shows that superposition can occur analogously in redundancy analysis (RDA) frequently used by ecologists. Results We show that within individual ecosystems single species can be associated simultaneously with different orthogonal axes in RDA models, which suggests that they operate in more than one niche spaces. We discuss this counterintuitive result in relation to the statistical and mathematical features of RDA and the recognized limitations with current traditional species concepts based on vegetative morphology. Conclusion We suggest that such “quantum weirdness” in the models is reconcilable with classical ecosystems logic when the focus of research shifts from morphological species to cryptic species that consist of genetically and ecologically differentiated subpopulations. We support our argument with theoretical discussions of eco-evolutionary interpretations that should become testable once suitable data are available

Drivers of long-term invertebrate community stability in changing Swedish lakes

Research on ecosystem stability has had a strong focus on local systems. However, environmental change often occurs slowly at broad spatial scales, which requires regional-level assessments of long-term stability. In this study, we assess the stability of macroinvertebrate communities across 105 lakes in the Swedish “lakescape.” Using a hierarchical mixed-model approach, we first evaluate the environmental pressures affecting invertebrate communities in two ecoregions (north, south) using a 23 year time series (1995–2017) and then examine how a set of environmental and physical variables affect the stability of these communities. Results show that lake latitude, size, total phosphorus and alkalinity affect community composition in northern and southern lakes. We find that lake stability is affected by species richness and lake size in both ecoregions and alkalinity and total phosphorus in northern lakes. There is large heterogeneity in the patterns of community stability of individual lakes, but relationships between that stability and environmental drivers begin to emerge when the lakescape, composed of many discrete lakes, is the focal unit of study. The results of this study highlight that broad-scale comparisons in combination with long time series are essential to understand the effects of environmental change on the stability of lake communities in space and time

A Quantitative Framework for Assessing Ecological Resilience

Quantitative approaches to measure and assess resilience are needed to bridge gaps between science, policy, and management. In this paper, we suggest a quantitative framework for assessing ecological resilience. Ecological resilience as an emergent ecosystem phenomenon can be decomposed into complementary attributes (scales, adaptive capacity, thresholds, and alternative regimes) that embrace the complexity inherent to ecosystems. Quantifying these attributes simultaneously provides opportunities to move from the assessment of specific resilience within an ecosystem toward a broader measurement of its general resilience. We provide a framework that is based on reiterative testing and recalibration of hypotheses that assess complementary attributes of ecological resilience. By implementing the framework in adaptive approaches to management, inference, and modeling, key uncertainties can be reduced incrementally over time and learning about the general resilience of dynamic ecosystems maximized. Such improvements are needed because uncertainty about global environmental change impacts and their effects on resilience is high. Improved resilience assessments will ultimately facilitate an optimized use of limited resources for management

A quantitative framework for assessing ecological resilience

Quantitative approaches to measure and assess resilience are needed to bridge gaps between science, policy, and management. In this paper, we suggest a quantitative framework for assessing ecological resilience. Ecological resilience as an emergent ecosystem phenomenon can be decomposed into complementary attributes (scales, adaptive capacity, thresholds, and alternative regimes) that embrace the complexity inherent to ecosystems. Quantifying these attributes simultaneously provides opportunities to move from the assessment of specific resilience within an ecosystem toward a broader measurement of its general resilience. We provide a framework that is based on reiterative testing and recalibration of hypotheses that assess complementary attributes of ecological resilience. By implementing the framework in adaptive approaches to management, inference, and modeling, key uncertainties can be reduced incrementally over time and learning about the general resilience of dynamic ecosystems maximized. Such improvements are needed because uncertainty about global environmental change impacts and their effects on resilience is high. Improved resilience assessments will ultimately facilitate an optimized use of limited resources for management.publishedVersio

Adaptive capacity in ecosystems

Understanding the adaptive capacity of ecosystems to cope with change is crucial to management. However, unclear and often confusing definitions of adaptive capacity make application of this concept difficult. In this paper, we revisit definitions of adaptive capacity and operationalize the concept. We define adaptive capacity as the latent potential of an ecosystem to alter resilience in response to change. We present testable hypotheses to evaluate complementary attributes of adaptive capacity that may help further clarify the components and relevance of the concept. Adaptive sampling, inference and modeling can reduce key uncertainties incrementally over time and increase learning about adaptive capacity. Such improvements are needed because uncertainty about global change and its effect on the capacity of ecosystems to adapt to social and ecological change is high