scholarly journals Individual differences determine the strength of ecological interactions

2020 ◽  
Vol 117 (29) ◽  
pp. 17068-17073 ◽  
Author(s):  
Jason I. Griffiths ◽  
Dylan Z. Childs ◽  
Ronald D. Bassar ◽  
Tim Coulson ◽  
David N. Reznick ◽  
...  
Keyword(s):  
Body Size ◽  
Evolutionary Dynamics ◽  
Size Structure ◽  
Empirical Studies ◽  
Biotic Interactions ◽  
Ecological Interactions ◽  
Intraspecific Interactions ◽  
Different Populations ◽  
The Impact

Biotic interactions are central to both ecological and evolutionary dynamics. In the vast majority of empirical studies, the strength of intraspecific interactions is estimated by using simple measures of population size. Biologists have long known that these are crude metrics, with experiments and theory suggesting that interactions between individuals should depend on traits, such as body size. Despite this, it has been difficult to estimate the impact of traits on competitive ability from ecological field data, and this explains why the strength of biotic interactions has empirically been treated in a simplistic manner. Using long-term observational data from four different populations, we show that large Trinidadian guppies impose a significantly larger competitive pressure on conspecifics than individuals that are smaller; in other words, competition is asymmetric. When we incorporate this asymmetry into integral projection models, the predicted size structure is much closer to what we see in the field compared with models where competition is independent of body size. This difference in size structure translates into a twofold difference in reproductive output. This demonstrates how the nature of ecological interactions drives the size structure, which, in turn, will have important implications for both the ecological and evolutionary dynamics.

A comparison of pre-industrial and present-day changes in Bosmina and Daphnia size structure from soft-water Ontario lakes

2010 ◽  
Vol 67 (4) ◽  
pp. 754-762 ◽  
Author(s):  
Jennifer B. Korosi ◽  
Andrew M. Paterson ◽  
Anna M. DeSellas ◽  
John P. Smol
Keyword(s):  
Body Size ◽  
Size Structure ◽  
South Central ◽  
Zooplankton Size ◽  
Copepod Predation ◽  
Post Impact ◽  
North Temperate Lakes ◽  
Impact Data ◽  
Shield Lakes

Understanding the long-term controls on cladoceran size structure has important implications for aquatic ecosystems. Although there has been considerable interest in zooplankton size trends for Canadian Shield lakes, data are not available for zooplankton size structure prior to the period of anthropogenic disturbances. Here, we present pre- and post-impact size data for the common pelagic cladocerans Bosmina and Daphnia for 44 well-studied Shield lakes in south-central Ontario (Canada). We show that Daphnia were larger and that the length of Bosmina body appendages (mucrones and antennules) was longer in pre-industrial times than they are today. The reduction in Bosmina appendage length we observed may suggest a reduction in copepod predation pressure since pre-industrial times. Reduced maximum body size in Daphnia is a predicted response to a warming climate in north temperate lakes; however, we suggest that alternate explanations, specifically acidification and subsequent recovery following emission reductions, should also be explored as the primary drivers of Daphnia size changes in this lake set. Overall, our results highlight the importance of pre-impact data for understanding the long-term controls on cladoceran body size from pre-1850 to present.

A comparative analysis of the implications of the Islamic religion on corporate capital structures of firms in emerging market countries

2014 ◽  
Vol 7 (3) ◽  
pp. 277-287 ◽  
Author(s):  
Theresa Gunn ◽  
Joshua Shackman
Keyword(s):  
Emerging Market ◽  
Empirical Studies ◽  
Short Term ◽  
Content Type ◽  
Corporate Capital ◽  
Muslim Countries ◽  
Total Debt ◽  
Islamic Religion ◽  
The Impact

Purpose – The purpose of this study is to examine the impact of the Muslim religion on firm capital structure. Design/methodology/approach – The authors compare financing patterns in Muslim versus non-Muslim countries using 658 firms in 16 countries covering a period of seven years. Findings – No significant differences between Muslim and non-Muslim countries were found in terms of total debt ratios. However, significant differences were found in the choice of short-term versus long-term debt, with firms in Muslim countries showing a strong preference for short-term debt. Research limitations/implications – The findings confirm existing theories on the impact of the Islamic religion on short-term versus long-term debt preferences. However, the findings concerning the lack of an impact of the Islamic religion on total debt preferences are surprising and contrary to existing theories. Practical implications – Firms in Muslim countries appear to have the flexibility to adopt overall leverage ratios comparable to those in non-Muslim countries. However, firms in Muslim countries may be disadvantaged in that there appear to be impediments to the use of long-term debt. Originality/value – This paper presents one of the first empirical studies of the impact of the Muslim religion on corporate financing choices across a large cross-section of firms in Muslim and non-Muslim countries.

Antitakeover Provisions and Shareholder Wealth: A Survey of the Literature

2014 ◽  
Vol 49 (4) ◽  
pp. 933-956 ◽  
Author(s):  
Miroslava Straska ◽  
H. Gregory Waller
Keyword(s):  
Good Governance ◽  
Empirical Studies ◽  
Shareholder Wealth ◽  
Current Debate ◽  
Firm Characteristics ◽  
Policy Changes ◽  
Governance Practices ◽  
The Impact ◽  
Long Term Studies

AbstractWe survey theoretical and empirical research on antitakeover provisions, focusing on the relation between antitakeover provisions and shareholder value. We divide the empirical studies based upon the evidence that they provide: short-term event studies, studies on performance and policy changes around adopting antitakeover provisions or passing state antitakeover laws, studies on the impact of antitakeover provisions on takeovers, studies on the relation between antitakeover provisions and firm characteristics, and long-term studies on the relation between antitakeover provisions and firm performance or policies. We also discuss the place of antitakeover provisions in the current debate about “good governance” practices.

scholarly journals Plasmid co-infection: linking biological mechanisms to ecological and evolutionary dynamics

2021 ◽  
Vol 377 (1842) ◽  
Author(s):  
Claudia Igler ◽  
Jana S. Huisman ◽  
Berit Siedentop ◽  
Sebastian Bonhoeffer ◽  
Sonja Lehtinen
Keyword(s):  
Evolutionary Dynamics ◽  
Theoretical Work ◽  
Plasmid Copy Number ◽  
Biological Processes ◽  
Ecological Interactions ◽  
Biological Mechanisms ◽  
Plasmid Copy ◽  
Host Interactions ◽  
Evolutionary Epidemiology ◽  
The Impact

As infectious agents of bacteria and vehicles of horizontal gene transfer, plasmids play a key role in bacterial ecology and evolution. Plasmid dynamics are shaped not only by plasmid–host interactions but also by ecological interactions between plasmid variants. These interactions are complex: plasmids can co-infect the same cell and the consequences for the co-resident plasmid can be either beneficial or detrimental. Many of the biological processes that govern plasmid co-infection—from systems that exclude infection by other plasmids to interactions in the regulation of plasmid copy number—are well characterized at a mechanistic level. Modelling plays a central role in translating such mechanistic insights into predictions about plasmid dynamics and the impact of these dynamics on bacterial evolution. Theoretical work in evolutionary epidemiology has shown that formulating models of co-infection is not trivial, as some modelling choices can introduce unintended ecological assumptions. Here, we review how the biological processes that govern co-infection can be represented in a mathematical model, discuss potential modelling pitfalls, and analyse this model to provide general insights into how co-infection impacts ecological and evolutionary outcomes. In particular, we demonstrate how beneficial and detrimental effects of co-infection give rise to frequency-dependent selection on plasmid variants. This article is part of the theme issue ‘The secret lives of microbial mobile genetic elements’.

scholarly journals COVID-19 and tourist mobility at destinations: a literature review and emerging research agenda

2021 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
Alba Viana-Lora ◽  
Antoni Domènech ◽  
Aaron Gutiérrez
Keyword(s):  
Literature Review ◽  
Research Agenda ◽  
Empirical Studies ◽  
Future Research ◽  
Content Type ◽  
Future Research Agenda ◽  
The Future ◽  
Short And Long Term ◽  
The Impact

PurposeThis paper aims to review conceptual and empirical studies that analyse the impact of the pandemic on mobility and tourism behaviour at destinations in order to identify proposals, forecasts and recommendations to guide the future research agenda on the subject.Design/methodology/approachThis study used a systematic literature review to synthesise information from scientific articles published in journals indexed in the Web of Science database related to tourism mobility at destinations during the COVID-19 pandemic.FindingsThis article found that, according to the existing literature, the COVID-19 pandemic is acting as a catalyst for the sustainable transition of tourism. Although the findings reveal a lack of empirical research on the impact of the pandemic on tourism mobility at destinations, the article synthesizes the short- and long-term impacts of the pandemic and sets out the future research agenda on tourist mobility at destinations.Originality/valueTo the best of the authors' knowledge, this is the first systematic review of the impact of the pandemic on mobility and tourism behaviour at destinations that attempts to describe the emerging challenges and the agenda for future research.

scholarly journals Long-term experimental evolution of HIV-1 reveals effects of environment and mutational history

PLoS Biology ◽  
2020 ◽  
Vol 18 (12) ◽  
pp. e3001010
Author(s):  
Eva Bons ◽  
Christine Leemann ◽  
Karin J. Metzner ◽  
Roland R. Regoes
Keyword(s):  
Evolutionary Dynamics ◽  
Fitness Landscape ◽  
Large Population ◽  
Parallel Evolution ◽  
Cell Types ◽  
Drug Pressure ◽  
Evolutionary Paths ◽  
The Impact ◽  
Hiv 1

An often-returning question for not only HIV-1, but also other organisms, is how predictable evolutionary paths are. The environment, mutational history, and random processes can all impact the exact evolutionary paths, but to which extent these factors contribute to the evolutionary dynamics of a particular system is an open question. Especially in a virus like HIV-1, with a large mutation rate and large population sizes, evolution is expected to be highly predictable if the impact of environment and history is low, and evolution is not neutral. We investigated the effect of environment and mutational history by analyzing sequences from a long-term evolution experiment, in which HIV-1 was passaged on 2 different cell types in 8 independent evolutionary lines and 8 derived lines, 4 of which involved a switch of the environment. The experiments lasted for 240–300 passages, corresponding to approximately 400–600 generations or almost 3 years. The sequences show signs of extensive parallel evolution—the majority of mutations that are shared between independent lines appear in both cell types, but we also find that both environment and mutational history significantly impact the evolutionary paths. We conclude that HIV-1 evolution is robust to small changes in the environment, similar to a transmission event in the absence of an immune response or drug pressure. We also find that the fitness landscape of HIV-1 is largely smooth, although we find some evidence for both positive and negative epistatic interactions between mutations.

Adaptation

2016 ◽  
Author(s):  
Andrew P. Hendry
Keyword(s):  
Genetic Variation ◽  
Adaptive Evolution ◽  
Evolutionary Dynamics ◽  
Natural Populations ◽  
Phenotypic Change ◽  
Adaptive Landscapes ◽  
Local Environments ◽  
Short And Long Term ◽  
Different Populations

This chapter outlines how to conceptualize and predict adaptive evolution based on information about selection and genetic variation. It introduces and explains adaptive landscapes, a concept that has proven useful in guiding the understanding of evolution. The chapter also reviews empirical data to answer fundamental questions about adaptation in nature, including to what extent short- and long-term evolution is predictable, how fast is phenotypic change, to what extent is adaptation constrained by genetic variation, and how well adapted natural populations are to their local environments. Moving beyond selection and adaptation within populations, the chapter shows how eco-evolutionary dynamics will be shaped by biological diversity: that is, different populations and species have different effects on their environment.

scholarly journals Size-based ecological interactions drive food web responses to climate warming

2018 ◽  
Author(s):  
Max Lindmark ◽  
Jan Ohlberger ◽  
Magnus Huss ◽  
Anna Gårdmark
Keyword(s):  
Life History ◽  
Body Size ◽  
Food Web ◽  
Population Size ◽  
Climate Warming ◽  
Size Structure ◽  
Physiological Responses ◽  
Size Variation ◽  
Food Chains ◽  
Ecological Interactions

AbstractPredicting the impacts of climate change on animal populations and communities requires understanding of feedbacks between direct physiological responses and indirect effects via ecological interactions. Food-dependent body growth and within-species size variation have major effects on dynamics of populations and communities through feedbacks between individual performance and population size structure. Moreover, evidence suggests a link between temperature and population size structure, but we lack an understanding of how this is mediated by species interactions when life history processes are food-dependent. Here, we use a dynamic stage-structured biomass model with food-, size- and temperature-dependent life history processes to assess how temperature affects coexistence, stability and size structure in a tri-trophic food chain. We show that predator biomass densities decline with warming either gradually or in the form of collapses, depending on which consumer life stage they predominantly feed on. Collapses occur when warming destabilizes the community and induces alternative stable states via Allee effects, which emerge when predators promote their own food source through predation. By contrast, warming at low temperatures stabilizes the community as limit cycles turn to fixed point dynamics, unless predators feed only on juveniles. Elevated costs of being large in warmer environments accelerate the decline in predator persistence and mean body size of the community. These results suggest that predator persistence in warmer climates may be lower than previously acknowledged when accounting for size- and food-dependence of life history processes, and that interactions within and between species can mediate the effects of warming on food web stability.SignificanceClimate warming is altering the dynamics and structure of aquatic ecosystems worldwide. Predicting food web reorganization under rising temperatures requires an understanding of physiological responses and ecological interactions of organisms, both of which depend on body size. We show that size variation within species, food-dependent growth and ecological interactions critically affect how food chains respond to warming. Specifically, warming can stabilize or destabilize food chains and expose predators to increased risk of sudden collapses, resulting in alternative stable food web states. Increasing temperatures can cause abrupt reductions in mean community body size, primarily due to loss of top predators. The potential loss of biodiversity and shifts in ecosystem stability are among the major challenges caused by a warming climate.

scholarly journals Genomic signatures of inbreeding and genetic load in a threatened rattlesnake

2021 ◽  
Author(s):  
Alexander Ochoa ◽  
H. Lisle Gibbs
Keyword(s):  
Threatened Species ◽  
Empirical Studies ◽  
Genetic Load ◽  
Population History ◽  
Deleterious Mutations ◽  
Genetic Rescue ◽  
Isolated Populations ◽  
Genome Wide ◽  
The Impact

Theory predicts that threatened species living in small populations will experience high levels of inbreeding that will increase their negative genetic load but recent work suggests that the impact of load may be minimized by purging resulting from long term population bottlenecks. Empirical studies that examine this idea using genome-wide estimates of inbreeding and genetic load in threatened species are limited. Here we use genome resequencing data to compare levels of inbreeding, levels of genetic load and population history in threatened Eastern massasauga rattlesnakes (Sistrurus catenatus) which exist in small isolated populations and closely-related yet outbred Western massasauga rattlesnakes (S. tergeminus). In terms of inbreeding, S. catenatus genomes had a greater number of ROHs of varying sizes indicating sustained inbreeding through repeated bottlenecks when compared to S. tergeminus. At the species level, outbred S. tergeminus had higher genome-wide levels of genetic load in the form of greater numbers of derived deleterious mutations compared to S. catenatus presumably due to long-term purging of deleterious mutations in S. catenatus. In contrast, mutations that escaped the “drift sieve” and were polymorphic within S. catenatus populations were more abundant and more often found in homozygote genotypes than in S. tergeminus suggesting a reduced efficiency of purifying selection in smaller S. catenatus populations. Our results support an emerging idea that the historical demography of a threatened species has a significant impact on the type of genetic load present which impacts implementation of conservation actions such as genetic rescue.

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