The fluctuating world of a tundra predator guild: bottom-up constraints overrule top-down species interactions in winter

Marianne Stoessel; Bodil Elmhagen; Mikael Vinka; Peter Hellström; Anders Angerbjörn

doi:10.1111/ecog.03984

Positive species interactions strengthen in a high-CO 2 ocean

Proceedings of The Royal Society B Biological Sciences ◽

10.1098/rspb.2021.0475 ◽

2021 ◽

Vol 288 (1954) ◽

pp. 20210475

Author(s):

Camilo M. Ferreira ◽

Sean D. Connell ◽

Silvan U. Goldenberg ◽

Ivan Nagelkerken

Keyword(s):

Ocean Acidification ◽

Primary Productivity ◽

Species Interactions ◽

Keystone Species ◽

Predatory Fish ◽

Positive Interactions ◽

Rocky Reef ◽

Top Down ◽

Bottom Up ◽

Food Web Interactions

Negative interactions among species are a major force shaping natural communities and are predicted to strengthen as climate change intensifies. Similarly, positive interactions are anticipated to intensify and could buffer the consequences of climate-driven disturbances. We used in situ experiments at volcanic CO 2 vents within a temperate rocky reef to show that ocean acidification can drive community reorganization through indirect and direct positive pathways. A keystone species, the algal-farming damselfish Parma alboscapularis, enhanced primary productivity through its weeding of algae whose productivity was also boosted by elevated CO 2 . The accelerated primary productivity was associated with increased densities of primary consumers (herbivorous invertebrates), which indirectly supported increased secondary consumers densities (predatory fish) (i.e. strengthening of bottom-up fuelling). However, this keystone species also reduced predatory fish densities through behavioural interference, releasing invertebrate prey from predation pressure and enabling a further boost in prey densities (i.e. weakening of top-down control). We uncover a novel mechanism where a keystone herbivore mediates bottom-up and top-down processes simultaneously to boost populations of a coexisting herbivore, resulting in altered food web interactions and predator populations under future ocean acidification.

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Short Note: Paradigms need hypothesis testing: no evidence for top-down forcing on Adélie and emperor penguin populations

Antarctic Science ◽

10.1017/s0954102008001260 ◽

2008 ◽

Vol 20 (4) ◽

pp. 391-392 ◽

Cited By ~ 7

Author(s):

Christophe Barbraud ◽

Cedric Cotte

Keyword(s):

Southern Ocean ◽

Species Interactions ◽

Research Effort ◽

Marine Ecosystem ◽

Short Note ◽

Emperor Penguin ◽

Ecological Research ◽

Top Down ◽

Bottom Up ◽

Ecosystem Interactions

In their recent review article “Paradigm lost, or is top-down forcing no longer significant in the Antarctic marine ecosystem?” Ainley et al. (2007) questioned why Southern Ocean marine ecologists apparently have shifted to a central paradigm where bottom-up forcing by physics and climate change has become the single most important driver of food web dynamics in the Southern Ocean. Ainley et al. (2007) suggest that top-down forcing (forcing by biotic processes) is no longer considered in the interpretation of ecological research results aimed at understanding ecosystem processes of the Southern Ocean. Based on two examples from the literature they suggest that population trends could better be explained by including species interactions in the modelling rather than by changes in climate related physical processes alone. Nicol et al. (2007) questioned the paradigm shift proposed by Ainley et al. (2007) and made a broad review of the ecological research conducted in the Southern Ocean ecosystems. They concluded that there has been considerable research effort into ecosystem interactions over the last 25 years in the Southern Ocean, and that there seems little evidence that there has been an almost complete shift in paradigms; rather both bottom-up and top-down processes are recognized to govern ecosystems functioning.

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Environmental fluctuations restrict eco-evolutionary dynamics in predator–prey system

Proceedings of The Royal Society B Biological Sciences ◽

10.1098/rspb.2015.0013 ◽

2015 ◽

Vol 282 (1808) ◽

pp. 20150013 ◽

Cited By ~ 26

Author(s):

Teppo Hiltunen ◽

Gökçe B. Ayan ◽

Lutz Becks

Keyword(s):

Species Interactions ◽

Community Dynamics ◽

Evolutionary Dynamics ◽

Temporal Dynamics ◽

Rapid Evolution ◽

Interactive Effects ◽

Top Down ◽

Bottom Up ◽

Evolutionary Response ◽

Environmental Fluctuations

Environmental fluctuations, species interactions and rapid evolution are all predicted to affect community structure and their temporal dynamics. Although the effects of the abiotic environment and prey evolution on ecological community dynamics have been studied separately, these factors can also have interactive effects. Here we used bacteria–ciliate microcosm experiments to test for eco-evolutionary dynamics in fluctuating environments. Specifically, we followed population dynamics and a prey defence trait over time when populations were exposed to regular changes of bottom-up or top-down stressors, or combinations of these. We found that the rate of evolution of a defence trait was significantly lower in fluctuating compared with stable environments, and that the defence trait evolved to lower levels when two environmental stressors changed recurrently. The latter suggests that top-down and bottom-up changes can have additive effects constraining evolutionary response within populations. The differences in evolutionary trajectories are explained by fluctuations in population sizes of the prey and the predator, which continuously alter the supply of mutations in the prey and strength of selection through predation. Thus, it may be necessary to adopt an eco-evolutionary perspective on studies concerning the evolution of traits mediating species interactions.

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Fragment edge and isolation affect the food web: effects on the strength of interactions among trophic guilds

Biota Neotropica ◽

10.1590/1676-0611-bn-2015-0088 ◽

2016 ◽

Vol 16 (2) ◽

Author(s):

Michele Molina Melo ◽

Cristina Magalhães Silva ◽

Carina Santos Barbosa ◽

Maristela Calvente Morais ◽

Paula Eveline Ribeiro D'Anunciação ◽

...

Keyword(s):

Species Interactions ◽

Structural Equation ◽

Species Interaction ◽

Trophic Guilds ◽

Top Down ◽

Bottom Up ◽

Equation Modelling ◽

Predator Interactions ◽

Multiple Species ◽

Patch Scale

Abstract Habitat loss and fragmentation are processes that may affect communities by changing species interactions. These changes occur because the strength of linkages between species is not exclusively dependent on predator and prey traits. Species interaction changes also depend on the spatial context in which they take place. We used structural equation modelling to evaluate effects of these processes at patch-scale on top-down and bottom-up controls in food webs in Atlantic Forest. The model was composed of multiple species, and trophic guilds responded differently to fragment edge and isolation. Changes in bottom-up and top-down controls were mainly related to intermediate predator interactions. Efforts to restore connectivity among fragments should help recover the equilibrium of the trophic interactions by benefiting intermediate predators.

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Incorporating anthropogenic effects into trophic ecology: predator–prey interactions in a human-dominated landscape

Proceedings of The Royal Society B Biological Sciences ◽

10.1098/rspb.2015.1602 ◽

2015 ◽

Vol 282 (1814) ◽

pp. 20151602 ◽

Cited By ~ 55

Author(s):

Ine Dorresteijn ◽

Jannik Schultner ◽

Dale G. Nimmo ◽

Joern Fischer ◽

Jan Hanspach ◽

...

Keyword(s):

Species Interactions ◽

Structural Equation ◽

Trophic Ecology ◽

Camera Traps ◽

Trophic Levels ◽

Apex Predators ◽

Top Down ◽

Large Herbivores ◽

Bottom Up ◽

Combining Data

Apex predators perform important functions that regulate ecosystems worldwide. However, little is known about how ecosystem regulation by predators is influenced by human activities. In particular, how important are top-down effects of predators relative to direct and indirect human-mediated bottom-up and top-down processes? Combining data on species' occurrence from camera traps and hunting records, we aimed to quantify the relative effects of top-down and bottom-up processes in shaping predator and prey distributions in a human-dominated landscape in Transylvania, Romania. By global standards this system is diverse, including apex predators (brown bear and wolf), mesopredators (red fox) and large herbivores (roe and red deer). Humans and free-ranging dogs represent additional predators in the system. Using structural equation modelling, we found that apex predators suppress lower trophic levels, especially herbivores. However, direct and indirect top-down effects of humans affected the ecosystem more strongly, influencing species at all trophic levels. Our study highlights the need to explicitly embed humans and their influences within trophic cascade theory. This will greatly expand our understanding of species interactions in human-modified landscapes, which compose the majority of the Earth's terrestrial surface.

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