Population dynamics of large and small mammals: Graeme Caughley's grand vision

2009 ◽  
Vol 36 (1) ◽  
pp. 1 ◽  
Author(s):  
Charles J. Krebs
Keyword(s):  
Population Dynamics ◽  
Population Control ◽  
Population Increase ◽  
Control Mechanisms ◽  
Relative Role ◽  
Top Down ◽  
Large Herbivores ◽  
Disturbed Systems ◽  
Herbivorous Mammals ◽  
Grand Vision

Ecologists that study the population dynamics of large and small herbivorous mammals operate in two worlds that overlap only partly, and in this paper I address whether the conjecture that these worlds represent two distinct and valid paradigms is currently justified. I argue that large mammals fall into three groups depending on whether they have effective predators or not, and whether they are harvested by humans. Because of human persecution of large predators, more and more large herbivorous mammals are effectively predator-free and are controlled bottom-up by food. But in less disturbed systems, large herbivorous mammals should be controlled top-down by effective predators, and this can lead to a trophic cascade. Small herbivorous mammals have been suggested to be controlled top-down by predators but some experimental evidence has challenged this idea and replaced it with the notion that predation is one of several factors that may affect rates of population increase. Intrinsic control (territoriality, infanticide, social inhibition of breeding) appears to be common in small herbivorous mammals with altricial young but is absent in species with precocial young, in ecosystems with strong stochastic weather variation (deserts) and in areas of human-induced habitat fragmentation in agricultural monocultures. The extrinsic control of large herbivores with precocial young validates part of Graeme Caughley’s Grand Vision, but the relative role of intrinsic and extrinsic mechanisms for small herbivores with altricial young is still controversial. An improved knowledge of population control mechanisms for large and small herbivores is essential for natural resource management.

Attention Biases Visual Activity in Visual Short-term Memory

2014 ◽  
Vol 26 (7) ◽  
pp. 1377-1389 ◽  
Author(s):  
Bo-Cheng Kuo ◽  
Mark G. Stokes ◽  
Alexandra M. Murray ◽  
Anna Christina Nobre
Keyword(s):  
Large Scale ◽  
Short Term Memory ◽  
Control Mechanisms ◽  
Top Down ◽  
Short Term ◽  
Visual Activity ◽  
Visual Short Term Memory ◽  
Large Scale Network ◽  
Visual Areas ◽  
Scale Network

In the current study, we tested whether representations in visual STM (VSTM) can be biased via top–down attentional modulation of visual activity in retinotopically specific locations. We manipulated attention using retrospective cues presented during the retention interval of a VSTM task. Retrospective cues triggered activity in a large-scale network implicated in attentional control and led to retinotopically specific modulation of activity in early visual areas V1–V4. Importantly, shifts of attention during VSTM maintenance were associated with changes in functional connectivity between pFC and retinotopic regions within V4. Our findings provide new insights into top–down control mechanisms that modulate VSTM representations for flexible and goal-directed maintenance of the most relevant memoranda.

scholarly journals Top–Down Attentional Control in Parkinson's Disease: Salient Considerations

2010 ◽  
Vol 22 (5) ◽  
pp. 848-859 ◽  
Author(s):  
Roshan Cools ◽  
Robert Rogers ◽  
Roger A. Barker ◽  
Trevor W. Robbins
Keyword(s):  
Parkinson’S Disease ◽  
Parkinson's Disease ◽  
Attentional Control ◽  
Direct Evidence ◽  
Control Mechanisms ◽  
Set Shifting ◽  
Top Down ◽  
Bottom Up ◽  
Salient Dimension ◽  
Dimensional Salience

Cognitive dysfunction in Parkinson's disease (PD) has been hypothesized to reflect a failure of cortical control. In keeping with this hypothesis, some of the cognitive deficits in PD resemble those seen in patients with lesions in the lateral pFC, which has been associated with top–down attentional control. However, there is no direct evidence for a failure of top–down control mechanisms in PD. Here we fill this gap by demonstrating disproportionate control by bottom–up attention to dimensional salience during attentional set shifting. Patients needed significantly more trials to criterion than did controls when shifting to a low-salient dimension while, remarkably, needing significantly fewer trials to criterion than did controls when shifting to a high-salient dimension. Thus, attention was captured by bottom–up attention to salient information to a greater extent in patients than in controls. The results provide a striking reinterpretation of prior set-shifting data and provide the first direct evidence for a failure of top–down attentional control, resembling that seen after catecholamine depletion in the pFC.

scholarly journals Population dynamics of five riverbed breeding bird species on the lower Drava River, NE Slovenia

Acrocephalus ◽  
2017 ◽  
Vol 38 (174-175) ◽  
pp. 85-126
Author(s):  
Luka Božič ◽  
Damijan Denac
Keyword(s):  
Population Dynamics ◽  
Bird Species ◽  
Breeding Population ◽  
Population Increase ◽  
General Situation ◽  
Breeding Bird ◽  
Main River Channel ◽  
Extreme Flood ◽  
Gravel Bars ◽  
Gravel Bar

AbstractIn 2006–2017, annual censuses of breeding bird species regarded as indicators of natural rivers were carried out on the 38.9 km long lowland stretch of the Drava riverbed between Maribor and Zavrč with altered flow regime due to the operating hydropower plants. Gravel bar habitats were surveyed in four years of the study period by combining orthophoto analysis and analysis of field photographs. Effects of gravel bar management were evaluated based at 20 locations. The Little Ringed PloverCharadrius dubiusoccurred on 39.8% of the gravel bars, but most were occupied only in a few years and held just one breeding pair. Low numbers between 2009 and 2012 (< 30 pairs) were followed by a steep population increase from 2014 onwards to a maximum of 66–73 pairs (1.7–1.9 p/km). Such population dynamics was attributed to the lack of large discharges (>500 m3/s) and consequent overgrowing of riverbed in the first part of the study period, while the increase in the second part was due to the creation of extensive shingle areas (from 20,6 ha in 2009/10 to 37,8 ha in 2014) by the extreme flood in early November 2012, subsequent regular occurrence of large discharges outside the breeding seasons and large-scale removals of woody vegetation. Breeding population of Common SandpiperActitis hypoleucosremained at a rather similar low level (<20 p) during most of the period studied after an initial decline, and did not reflect changes in the overall surface area of riverbed habitats. Contrary to the general situation, the number of breeding pairs on gravel bars subjected to management increased several-fold. Maximum number of pairs on these bars was reached up to four years after the initiation of management measures, as only then the optimal mosaic of early successional stages interspersed with shingle areas developed at main sites. The species was widespread only on lower part of the Drava. KingfisherAlcedo atthiswas fairly widely distributed along the riverbed, but occurred in rather low densities throughout (c. one pair on 2–3 km of the studied riverbed on average), probably as a result of limited bank erosion and consequent overgrowing/lack of suitable nest sites. The population was estimated as stable with effects of harsh winter conditions on breeding numbers in some years. The majority of nest holes were excavated in eroded river banks along the main river channel (77.8%), followed by similar sites located in mouth areas of small tributaries of the Drava (14.8%). Regular breeding of Sand MartinRiparia ripariasince 2012 (up to 259, mostly at only one location annually) was almost exclusively the result of the annual artificial nest site preparation programme. Fairly large gravel bar-breeding population of White WagtailMotacilla alba, monitored since 2013 and predominantly ground nesting in sparsely vegetated areas, seems unusual considering the prevalent breeding habits of the species at the European scale. Conservation implications and guidelines for future management efforts are discussed.

scholarly journals Temporal refuges differ between anthropogenic and natural top down pressures in a subordinate carnivore

2020 ◽  
Author(s):  
Rumaan Malhotra ◽  
Samantha Lima ◽  
Nyeema C. Harris
Keyword(s):  
Human Impacts ◽  
Temporal Response ◽  
Apex Predators ◽  
Top Down ◽  
Anthropogenic Pressures ◽  
Multiple Camera ◽  
Disturbed Systems ◽  
Food Subsidies ◽  
Predator Guild ◽  
Fear Effects

ABSTRACTApex predators structure communities through consumptive and non-consumptive pathways. In the carnivore guild, this can result in a within-guild cascade through the suppression of mesocarnivores. As the top-down influences of apex predators wane due to human-driven declines, landscape level anthropogenic pressures are rising. Human impacts can be analogous to apex predators in that humans can drive increased mortality in both prey species and carnivores, and impact communities through indirect fear effects and food subsidies. Here, we evaluate whether anthropogenic top-down pressures can structure communities in a similar manner as apex predators in shaping the interactions of mesocarnivores. Specifically, we expect anthropogenic forces to induce comparable effects as occurrence of apex predators in driving spatiotemporal partitioning between two mesocarnivores. Using multiple camera-trap surveys, we compared the temporal response of a small carnivore, the raccoon (Procyon lotor), to the larger coyote (Canis latrans) at four sites across Michigan that represented opposing gradients of pressure from humans and apex predators. Contrary to our expectations, we found that raccoons shifted their activity pattern in response to coyotes at sites with higher anthropogenic pressures and exhibited no temporal response at sites with apex predators. Temporal shifts were characterized by raccoons being more diurnal in areas of high coyote activity. We conclude that despite superficial similarities, anthropogenic forces do not replace the function of native apex predators in structuring the mesocarnivore guild. As such, an intact and functioning native predator guild remains necessary to preserve spatiotemporal community structure, in natural and disturbed systems alike.

scholarly journals Population Dynamics and Tree Damage of the Invasive Chestnut Gall Wasp, Dryocosmus kuriphilus, in Its Southernmost European Distributional Range

Insects ◽  
2021 ◽  
Vol 12 (10) ◽  
pp. 900
Author(s):  
Javier Quinto ◽  
María Eva Wong ◽  
Juan Ramón Boyero ◽  
José Miguel Vela ◽  
Martin Aguirrebengoa
Keyword(s):  
Population Dynamics ◽  
Control Mechanisms ◽  
Gall Wasp ◽  
Local Conditions ◽  
Tree Damage ◽  
Dryocosmus Kuriphilus ◽  
Distributional Range ◽  
The Status ◽  
Spatio Temporal ◽  
Over Time

The invasive chestnut gall wasp (CGW), Dryocosmus kuriphilus, the worst pest of chestnut cultivation, has spread worryingly throughout Europe in less than 20 years. Despite the great concern around this pest, little is known about the status in its southernmost distribution in continental Europe. We assessed spatio-temporal patterns in the population dynamics, phenology and tree damage caused by CGW in southern Spain. Likewise, the relationship between these variables and thermal trends was evaluated. We found strong variation in the population dynamics and flight phenology among localities and over time, which were highly influenced by changes in thermal regimes. Specifically, warmer localities and vegetative periods promoted higher population densities, a partial increase in the survival of immature stages, and advanced flight activity. Moreover, tree damage evolved differently over time in each locality, which suggests that local conditions may determine differences in damage evolution. Our findings evidence that great spatio-temporal variability in the CGW populations takes place across invaded areas in its southernmost European distributional range. Although control mechanisms have been introduced, implementation of further control and management measures are critical to cope with this main threat for the chestnut industry and to prevent its spread to nearing chestnut-producing areas.

Too Little Too Late

Dream Denied ◽  
2016 ◽  
Author(s):  
Michaela Soyer
Keyword(s):  
Juvenile Justice ◽  
Inner City ◽  
Justice System ◽  
Juvenile Justice System ◽  
Control Mechanisms ◽  
Top Down ◽  
And Control

Chapter 3 focuses on the youths’ experiences of the punitive and rehabilitative aspects of juvenile justice. This chapter contextualizes depictions of inner-city men as being subject to top-down control mechanisms within a range of alternatives. Left without any support from the juvenile justice system, poverty and violence are as limiting as constant supervision and control.

scholarly journals Re-membering the body: applications of computational neuroscience to the top-down control of regeneration of limbs and other complex organs

2015 ◽  
Vol 7 (12) ◽  
pp. 1487-1517 ◽  
Author(s):  
G. Pezzulo ◽  
M. Levin
Keyword(s):  
Information Processing ◽  
Pattern Formation ◽  
Computational Neuroscience ◽  
Memory System ◽  
The Body ◽  
Signaling Networks ◽  
Control Mechanisms ◽  
Top Down ◽  
The Brain

How do regenerating bodies know when to stop remodeling? Bioelectric signaling networks guide pattern formation and may implement a somatic memory system. Deep parallels may exist between information processing in the brain and morphogenetic control mechanisms.

Predator disease out-break modulates top-down, bottom-up and climatic effects on herbivore population dynamics

2006 ◽  
Vol 9 (4) ◽  
pp. 383-389 ◽  
Author(s):  
Christopher C. Wilmers ◽  
Eric Post ◽  
Rolf O. Peterson ◽  
John A. Vucetich
Keyword(s):  
Population Dynamics ◽  
Top Down ◽  
Climatic Effects ◽  
Bottom Up

scholarly journals Rapid evolution leads to differential population dynamics and top-down control in resurrectedDaphniapopulations

2017 ◽  
Vol 11 (1) ◽  
pp. 96-111 ◽  
Author(s):  
Eyerusalem Goitom ◽  
Laurens J. Kilsdonk ◽  
Kristien Brans ◽  
Mieke Jansen ◽  
Pieter Lemmens ◽  
...  
Keyword(s):  
Population Dynamics ◽  
Rapid Evolution ◽  
Top Down

scholarly journals Top–Down Inhibitory Mechanisms Underlying Auditory–Motor Integration for Voice Control: Evidence by TMS

2020 ◽  
Vol 30 (8) ◽  
pp. 4515-4527 ◽  
Author(s):  
Dongxu Liu ◽  
Guangyan Dai ◽  
Churong Liu ◽  
Zhiqiang Guo ◽  
Zhiqin Xu ◽  
...  
Keyword(s):  
Auditory Feedback ◽  
Brain Activity ◽  
Event Related Potential ◽  
Control Mechanisms ◽  
Top Down ◽  
Vocal Production ◽  
Left Dlpfc ◽  
Dorsolateral Prefrontal ◽  
Pitch Regulation ◽  
Condition C

Abstract The dorsolateral prefrontal cortex (DLPFC) has been implicated in auditory–motor integration for accurate control of vocal production, but its precise role in this feedback-based process remains largely unknown. To this end, the present event-related potential study applied a transcranial magnetic stimulation (TMS) protocol, continuous theta-burst stimulation (c-TBS), to disrupt cortical activity in the left DLPFC as young adults vocalized vowel sounds while hearing their voice unexpectedly shifted upwards in pitch. The results showed that, as compared to the sham condition, c-TBS over left DLPFC led to significantly larger vocal compensations for pitch perturbations that were accompanied by significantly smaller cortical P2 responses. Source localization analyses revealed that this brain activity pattern was the result of reduced activation in the left superior frontal gyrus and right inferior parietal lobule (supramarginal gyrus). These findings demonstrate c-TBS-induced modulatory effects of DLPFC on the neurobehavioral processing of vocal pitch regulation, suggesting that disrupting prefrontal function may impair top–down inhibitory control mechanisms that prevent speech production from being excessively influenced by auditory feedback, resulting in enhanced vocal compensations for feedback perturbations. This is the first study that provides direct evidence for a causal role of the left DLPFC in auditory feedback control of vocal production.

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