PREDATION RISK AFFECTS RELATIVE STRENGTH OF TOP-DOWN AND BOTTOM-UP IMPACTS ON INSECT HERBIVORES

Ecology ◽  
2003 ◽  
Vol 84 (4) ◽  
pp. 1032-1044 ◽  
Author(s):  
Robert F. Denno ◽  
Claudio Gratton ◽  
Hartmut Döbel ◽  
Deborah L. Finke
Keyword(s):  
Predation Risk ◽  
Relative Strength ◽  
Insect Herbivores ◽  
Top Down ◽  
Bottom Up

scholarly journals Bottom‐up vs. top‐down effects on terrestrial insect herbivores: a meta‐analysis

2017 ◽  
Vol 21 (1) ◽  
pp. 138-150 ◽  
Author(s):  
Mayra C. Vidal ◽  
Shannon M. Murphy
Keyword(s):  
Meta Analysis ◽  
Insect Herbivores ◽  
Top Down ◽  
Bottom Up ◽  
Terrestrial Insect

scholarly journals State-dependent changes in olfactory cortical networks via cholinergic modulation

2018 ◽  
Author(s):  
Donald A. Wilson ◽  
Maxime Juventin ◽  
Maria Ilina ◽  
Alessandro Pizzo ◽  
Catia Teixeira
Keyword(s):  
Olfactory Bulb ◽  
Entorhinal Cortex ◽  
Synaptic Input ◽  
Piriform Cortex ◽  
Receptor Activation ◽  
Relative Strength ◽  
Top Down ◽  
Cortical Networks ◽  
Bottom Up ◽  
State Dependent

AbstractActivity in sensory cortical networks reflects both peripheral sensory input and intra‐ and inter-cortical network input. How sensory cortices balance these diverse inputs to provide relatively stable, accurate representations of the external world is not well understood. Furthermore, neuromodulation could alter the balance of these inputs in a state‐ and behavior-dependent manner. Here, we used optogenetic stimulation to directly assay the relative strength of bottom-up (olfactory bulb) and top-down (lateral entorhinal cortex) synaptic inputs to piriform cortex in freely moving rats. Optotrodes in the piriform cortex were used to test the relative strength of these two inputs, in separate animals, with extracellular, monosynaptic evoked potentials. The results suggest a rapid state-dependent shift in the balance of bottom-up and top-down inputs to PCX, with enhancement in the strength of lateral entorhinal cortex synaptic input and stability or depression of olfactory bulb synaptic input during slow-wave sleep compared to waking. The shift is in part due to a state-dependent change in cholinergic tone as assessed with fiber photometry of GCaMP6 fluorescence in basal forebrain ChAT+ neurons, and blockade of the state-dependent synaptic shift with cholinergic muscarinic receptor activation.

Effects of predation risk on elk (Cervus elaphus) landscape use in a wolf (Canis lupus) dominated system

2015 ◽  
Vol 93 (2) ◽  
pp. 99-111 ◽  
Author(s):  
Cristina Eisenberg ◽  
David E. Hibbs ◽  
William J. Ripple
Keyword(s):  
Predation Risk ◽  
Populus Tremuloides ◽  
Cervus Elaphus ◽  
Canis Lupus ◽  
Top Down ◽  
Bottom Up ◽  
The North ◽  
North Fork ◽  
Landscape Use ◽  
Pellet Density

Food acquisition and predation avoidance are key drivers of herbivore behaviour. We investigated the interaction of top-down (predator) and bottom-up (food, fire, thermal) effects by measuring the relationship between wolf (Canis lupus L., 1758) predation risk perceived by elk (Cervus elaphus L., 1758) and elk landscape use. We conducted fecal pellet and wolf scat surveys in three valleys with three wolf population levels (Saint Mary: low; Waterton: moderate; North Fork: high). In the North Fork, 90% of quaking aspen (Populus tremuloides Michx.) stands burned recently; the other valleys had no fire. We created predictive models of elk pellet density that incorporated bottom-up and top-down variables. All valleys had a high elk pellet density (≥10 per 100 m2). Wolf scat density was similar where there was no fire, but one order of magnitude greater in burned areas. Elk pellet density was lower in the North Fork, a predation-related response. In all valleys, site-specific elk density declined as impediments to detecting or escaping wolves increased, and elk avoided aspen, except for North Fork unburned areas. Models that best predicted elk density contained bottom-up and top-down effects. At local scales, high predation risk negatively influence elk occurrence, suggesting that even with minimal wolf exposure elk avoid risky sites.

scholarly journals Does management of a top carnivore influence the response of mesopredators and prey to rainfall in arid ecosystems? Evidence for a Baseline Density theory

2021 ◽  
Author(s):  
Renee L. Brawata
Keyword(s):  
Primary Productivity ◽  
Relative Strength ◽  
Trophic Levels ◽  
Arid Ecosystems ◽  
Top Down ◽  
Down Regulation ◽  
Bottom Up ◽  
Rate Of Increase ◽  
Abundance And Diversity

ABSTRACT The removal of apex carnivores from ecosystems can impact the abundance and diversity of species in lower trophic levels. In arid ecosystems, where “bottom up” forces of primary productivity and resource availability strongly affect trophic interactions, the role of “top down” effects is still much debated. This study explored the potential role of an apex predator, the dingo, as a “top down” trophic regulator in Australian arid ecosystems under different levels of primary productivity and dingo management regimes. Consistent with the theory of top down regulation, strong relationships were found between dingo management, dingo activity and fox activity. Dingoes appeared to suppress fox activity where dingoes were uncontrolled or only opportunistically controlled. At sites where dingoes were absent or in low numbers, fox activity was higher, and this inverse relationship persisted regardless of rainfall. The activity of rabbits and small mammals was lower where dingoes were absent and fox activity was high, while the activity of macropods was higher in the absence of dingoes. Feral cat activity did not differ significantly between sites under different dingo management or between years. These results suggest that management of dingoes is a key determinant of fox activity and the activity of some prey under varying levels of productivity. Evidence from this research showed that while the strength of trophic regulation by dingoes may fluctuate, top down effects occurred both prior to and post significant rainfall events. Following this, top down regulation of fox populations during dry periods at sites where dingoes are retained may enable higher and more stable “baseline” densities of small vertebrates, from which a larger and more rapid rate of increase of these prey during the “boom” periods can occur. Understanding the relative strength and interactions of top down and bottom up forces in regulating populations, and under what ecological states the importance of each changes, is important for the long-term conservation of biodiversity in arid regions.

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