Self-facilitation through ecosystem engineering (i.e., organism modification of the abiotic envir... more Self-facilitation through ecosystem engineering (i.e., organism modification of the abiotic environment) and consumer-resource interactions are both major determinants of spatial patchiness in ecosystems. However, interactive effects of these two mechanisms on spatial complexity have not been extensively studied. We investigated the mechanisms underlying a spatial mosaic of low-tide exposed hummocks and waterlogged hollows on an intertidal mudflat in the Wadden Sea dominated by the seagrass Zostera noltii. A combination of field measurements, an experiment and a spatially explicit model
Regime shifts in ecosystem structure and processes are typically studied from a temporal perspect... more Regime shifts in ecosystem structure and processes are typically studied from a temporal perspective. Yet, theory predicts that in large ecosystems with environmental gradients, shifts should start locally and gradually spread through space. Here we empirically document a spatially propagating shift in the trophic structure of a large aquatic ecosystem, from dominance of large predatory fish (perch, pike) to the small prey fish, the three-spined stickleback. Fish surveys in 486 shallow bays along the 1200 km western Baltic Sea coast during 1979–2017 show that the shift started in wave-exposed archipelago areas near the open sea, but gradually spread towards the wave-sheltered mainland coast. Ecosystem surveys in 32 bays in 2014 show that stickleback predation on juvenile predators (predator–prey reversal) generates a feedback mechanism that appears to reinforce the shift. In summary, managers must account for spatial heterogeneity and dispersal to better predict, detect and confront...
Declines of large predatory fish due to overexploitation are restructuring food webs across the g... more Declines of large predatory fish due to overexploitation are restructuring food webs across the globe. It is now becoming evident that restoring these altered food webs requires addressing not only ecological processes, but evolutionary ones as well, because human-induced rapid evolution may in turn affect ecological dynamics. In the central Baltic Sea, abundances of the mesopredatory fish, the three-spined stickleback (Gasterosteus aculeatus), have increased dramatically during the past decades. Time-series data covering 22 years show that this increase coincides with a decline in the number of juvenile perch (Perca fluviatilis), the most abundant predator of stickleback along the coast. We studied the interaction between evolutionary and ecological effects of this mesopredator take-over, by surveying the armour plate morphology of stickleback and the structure of the associated food web. First, we investigated the distribution of different stickleback phenotypes depending on preda...
Background. Organism biomass is one of the most important variables in ecological studies, making... more Background. Organism biomass is one of the most important variables in ecological studies, making estimations of organism weight one of the most common laboratory tasks. Biomass of small macroinvertebrates is usually estimated as dry (DW) or ash-free dry weight (AFDW); a laborious and time consuming process, that often can be speeded up using easily measured and reliable proxy variables like wet/fresh weight and/or body size. Another common way of estimating AFDW - which is the most accurate but also time-consuming estimate of biologically active tissue weight - is the use of AFDW/DW ratios or conversion factors. So far, however, these ratios typically ignore the possibility that the relative weight of biologically active vs. non-active support tissue (e.g. protective exoskeleton or shell) - and therefore, also the AFDW/DW ratio - may change with body size, as previously shown for taxa like spiders, vertebrates and trees. Methods. We collected samples of aquatic, epibenthic macroinv...
Background Organism biomass is one of the most important variables in ecological studies, making ... more Background Organism biomass is one of the most important variables in ecological studies, making biomass estimations one of the most common laboratory tasks. Biomass of small macroinvertebrates is usually estimated as dry mass or ash-free dry mass (hereafter ‘DM’ vs. ‘AFDM’) per sample; a laborious and time consuming process, that often can be speeded up using easily measured and reliable proxy variables like body size or wet (fresh) mass. Another common way of estimating AFDM (one of the most accurate but also time-consuming estimates of biologically active tissue mass) is the use of AFDM/DM ratios as conversion factors. So far, however, these ratios typically ignore the possibility that the relative mass of biologically active vs. non-active support tissue (e.g., protective exoskeleton or shell)—and therefore, also AFDM/DM ratios—may change with body size, as previously shown for taxa like spiders, vertebrates and trees. Methods We collected aquatic, epibenthic macroinvertebrates ...
Self-facilitation through ecosystem engineering (i.e., organism modification of the abiotic envir... more Self-facilitation through ecosystem engineering (i.e., organism modification of the abiotic environment) and consumer-resource interactions are both major determinants of spatial patchiness in ecosystems. However, interactive effects of these two mechanisms on spatial complexity have not been extensively studied. We investigated the mechanisms underlying a spatial mosaic of low-tide exposed hummocks and waterlogged hollows on an intertidal mudflat in the Wadden Sea dominated by the seagrass Zostera noltii. A combination of field measurements, an experiment and a spatially explicit model
Regime shifts in ecosystem structure and processes are typically studied from a temporal perspect... more Regime shifts in ecosystem structure and processes are typically studied from a temporal perspective. Yet, theory predicts that in large ecosystems with environmental gradients, shifts should start locally and gradually spread through space. Here we empirically document a spatially propagating shift in the trophic structure of a large aquatic ecosystem, from dominance of large predatory fish (perch, pike) to the small prey fish, the three-spined stickleback. Fish surveys in 486 shallow bays along the 1200 km western Baltic Sea coast during 1979–2017 show that the shift started in wave-exposed archipelago areas near the open sea, but gradually spread towards the wave-sheltered mainland coast. Ecosystem surveys in 32 bays in 2014 show that stickleback predation on juvenile predators (predator–prey reversal) generates a feedback mechanism that appears to reinforce the shift. In summary, managers must account for spatial heterogeneity and dispersal to better predict, detect and confront...
Declines of large predatory fish due to overexploitation are restructuring food webs across the g... more Declines of large predatory fish due to overexploitation are restructuring food webs across the globe. It is now becoming evident that restoring these altered food webs requires addressing not only ecological processes, but evolutionary ones as well, because human-induced rapid evolution may in turn affect ecological dynamics. In the central Baltic Sea, abundances of the mesopredatory fish, the three-spined stickleback (Gasterosteus aculeatus), have increased dramatically during the past decades. Time-series data covering 22 years show that this increase coincides with a decline in the number of juvenile perch (Perca fluviatilis), the most abundant predator of stickleback along the coast. We studied the interaction between evolutionary and ecological effects of this mesopredator take-over, by surveying the armour plate morphology of stickleback and the structure of the associated food web. First, we investigated the distribution of different stickleback phenotypes depending on preda...
Background. Organism biomass is one of the most important variables in ecological studies, making... more Background. Organism biomass is one of the most important variables in ecological studies, making estimations of organism weight one of the most common laboratory tasks. Biomass of small macroinvertebrates is usually estimated as dry (DW) or ash-free dry weight (AFDW); a laborious and time consuming process, that often can be speeded up using easily measured and reliable proxy variables like wet/fresh weight and/or body size. Another common way of estimating AFDW - which is the most accurate but also time-consuming estimate of biologically active tissue weight - is the use of AFDW/DW ratios or conversion factors. So far, however, these ratios typically ignore the possibility that the relative weight of biologically active vs. non-active support tissue (e.g. protective exoskeleton or shell) - and therefore, also the AFDW/DW ratio - may change with body size, as previously shown for taxa like spiders, vertebrates and trees. Methods. We collected samples of aquatic, epibenthic macroinv...
Background Organism biomass is one of the most important variables in ecological studies, making ... more Background Organism biomass is one of the most important variables in ecological studies, making biomass estimations one of the most common laboratory tasks. Biomass of small macroinvertebrates is usually estimated as dry mass or ash-free dry mass (hereafter ‘DM’ vs. ‘AFDM’) per sample; a laborious and time consuming process, that often can be speeded up using easily measured and reliable proxy variables like body size or wet (fresh) mass. Another common way of estimating AFDM (one of the most accurate but also time-consuming estimates of biologically active tissue mass) is the use of AFDM/DM ratios as conversion factors. So far, however, these ratios typically ignore the possibility that the relative mass of biologically active vs. non-active support tissue (e.g., protective exoskeleton or shell)—and therefore, also AFDM/DM ratios—may change with body size, as previously shown for taxa like spiders, vertebrates and trees. Methods We collected aquatic, epibenthic macroinvertebrates ...
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Papers by Serena Donadi