scholarly journals Adaptive genetic variation mediates bottom-up and top-down control in an aquatic ecosystem

2015 ◽  
Vol 282 (1812) ◽  
pp. 20151234 ◽  
Author(s):  
Seth M. Rudman ◽  
Mariano A. Rodriguez-Cabal ◽  
Adrian Stier ◽  
Takuya Sato ◽  
Julian Heavyside ◽  
...  
Keyword(s):  
Genetic Variation ◽  
Intraspecific Variation ◽  
Phenotypic Variation ◽  
Evolutionary Dynamics ◽  
Trophic Levels ◽  
Community Genetics ◽  
Top Down ◽  
Black Cottonwood ◽  
Bottom Up

Research in eco-evolutionary dynamics and community genetics has demonstrated that variation within a species can have strong impacts on associated communities and ecosystem processes. Yet, these studies have centred around individual focal species and at single trophic levels, ignoring the role of phenotypic variation in multiple taxa within an ecosystem. Given the ubiquitous nature of local adaptation, and thus intraspecific variation, we sought to understand how combinations of intraspecific variation in multiple species within an ecosystem impacts its ecology. Using two species that co-occur and demonstrate adaptation to their natal environments, black cottonwood ( Populus trichocarpa ) and three-spined stickleback ( Gasterosteus aculeatus ), we investigated the effects of intraspecific phenotypic variation on both top-down and bottom-up forces using a large-scale aquatic mesocosm experiment. Black cottonwood genotypes exhibit genetic variation in their productivity and consequently their leaf litter subsidies to the aquatic system, which mediates the strength of top-down effects from stickleback on prey abundances. Abundances of four common invertebrate prey species and available phosphorous, the most critically limiting nutrient in freshwater systems, are dictated by the interaction between genetic variation in cottonwood productivity and stickleback morphology. These interactive effects fit with ecological theory on the relationship between productivity and top-down control and are comparable in strength to the effects of predator addition. Our results illustrate that intraspecific variation, which can evolve rapidly, is an under-appreciated driver of community structure and ecosystem function, demonstrating that a multi-trophic perspective is essential to understanding the role of evolution in structuring ecological patterns.

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.

Sensory regulation of quadrupedal locomotion: a top-down or bottom-up control system?

2012 ◽  
Vol 108 (3) ◽  
pp. 709-711 ◽  
Author(s):  
Yann Thibaudier ◽  
Marie-France Hurteau
Keyword(s):  
Control System ◽  
Central Pattern Generators ◽  
Top Down ◽  
Bottom Up ◽  
Sensory Inputs ◽  
Sensory Regulation ◽  
Before And After ◽  
Pattern Generators

Propriospinal pathways are thought to be critical for quadrupedal coordination by coupling cervical and lumbar central pattern generators (CPGs). However, the mechanisms involved in relaying information between girdles remain largely unexplored. Using an in vitro spinal cord preparation in neonatal rats, Juvin and colleagues ( Juvin et al. 2012 ) have recently shown sensory inputs from the hindlimbs have greater influence on forelimb CPGs than forelimb sensory inputs on hindlimb CPGs, in other words, a bottom-up control system. However, results from decerebrate cats suggest a top-down control system. It may be that both bottom-up and top-down control systems exist and that the dominance of one over the other is task or context dependent. As such, the role of sensory inputs in controlling quadrupedal coordination before and after injury requires further investigation.

Role of top-down and bottom-up forces on the invasibility of intertidal macroalgal assemblages

2013 ◽  
Vol 76 ◽  
pp. 178-186 ◽  
Author(s):  
Fátima Vaz-Pinto ◽  
Celia Olabarria ◽  
Francisco Arenas
Keyword(s):  
Top Down ◽  
Bottom Up

Computational Models of Learning Mechanisms in Psychosis

2017 ◽  
Author(s):  
Andreas Heinz
Keyword(s):  
Mental Disorders ◽  
Psychiatric Disorders ◽  
Computational Models ◽  
The Self ◽  
Psychotic Experiences ◽  
Learning Mechanisms ◽  
Top Down ◽  
Bottom Up ◽  
Surrounding World

Psychotic experiences may best be described as an alteration in the self-ascription of thoughts and actions, which is associated with a profoundly altered experience of oneself and the surrounding world. Computational models of key symptoms of psychiatric disorders are discussed with respect to the attribution of salience and self-relatedness to otherwise irrelevant stimuli and the role of top-down modelling in the generation of delusions. Top-down and bottom-up approaches in understanding mental disorders and their computational models are compared and critically reflected.

The role of the third sector working with the hard and soft structures of public–private partnerships to promote individual health and reinvigorated, healthier communities

2020 ◽  
pp. 301-318
Author(s):  
Tony Chasteauneuf ◽  
Tony Thornton ◽  
Dean Pallant
Keyword(s):  
Health Outcomes ◽  
Local Authority ◽  
Third Sector ◽  
Public Private Partnerships ◽  
Top Down ◽  
Bottom Up ◽  
The Third ◽  
Individual Health ◽  
The Third Sector

This chapter discusses the role of the third sector working with the hard and soft structures of public–private partnerships to promote healthier individuals and communities. It considers how a recommitment to the 'local authority' of citizens and beneficiaries offers the possibility of revitalised and healthier individuals and reinvigorated and healthier communities, which are unachievable through the hard and soft structures of the commissioner/provider statutory approach. The chapter then identifies the pivotal dynamic of one-to-one relationships in these processes and their association with health outcomes (emotional, physical, and spiritual) alongside the opportunities and challenges in agencies engaging/re-engaging with the agency of citizens and beneficiaries. It explores the tension between the 'agency' of citizens and beneficiaries that constitutes bottom-up power and 'agencies' with top-down power. The chapter also looks at the benefits of embracing the expertise and investment of individuals and their communities in their personal and shared lives, how this can be supported and how it can be undermined.

Tourism as a Pathway to the Good Life: Comparing the Top–Down and Bottom–Up Effects

2018 ◽  
Vol 58 (5) ◽  
pp. 866-876 ◽  
Author(s):  
Chun-Chu Chen ◽  
Sukjoon Yoon
Keyword(s):  
Life Satisfaction ◽  
Good Life ◽  
Structural Model ◽  
Well Being ◽  
Potential Contribution ◽  
The Good Life ◽  
Novelty Seeking ◽  
Top Down ◽  
Bottom Up

This research examined the relationships among tourism, well-being, and novelty-seeking as a personality trait based on the top–down and bottom–up theories of well-being. A structural model that includes a direct effect of novelty-seeking on life satisfaction (top–down influence) and an indirect effect through tourism experiences (bottom–up influence) were proposed and tested using a sample of 556 American residents. Results showed that novelty-seekers were well aware of travel benefits and traveled more frequently. It was also found that the top–down influence of novelty-seeking on life satisfaction was significantly greater than the bottom–up influence. These findings highlight the crucial role of personality as a predictor of well-being as well as the importance of applying positive psychology principles to further enhance the potential contribution of tourism experiences to tourists’ well-being.

The Move towards Gender Equality and Political Participation in Jordan

2018 ◽  
Vol 98 (2) ◽  
pp. 203-224
Author(s):  
Schirin Fathi
Keyword(s):  
Political Participation ◽  
Gender Equality ◽  
Social Contract ◽  
Special Consideration ◽  
Top Down ◽  
Bottom Up ◽  
Societal Development ◽  
Special Circumstances ◽  
Women's Political Participation

Abstract This paper aims to trace the development of women’s political participation in Jordan and the efforts exerted in a top-down and bottom-up approach towards gender equality. Special consideration is accorded to the constitution, in its function as a social contract mirroring societal developments and the role of the monarchy and its available tools to influence decisions and nudge societal development in ways deemed necessary. At the same time the constraints imposed on Jordan due to its special circumstances are pinpointed.

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