Multi-scale processes in metapopulations : Contributions of stage structure, rescue effect, and correlated extinctions

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Distance exams : can targeted warnings discourage cheating?

During the COVID-19 sanitary crisis of 2020, many exams were hastily moved to online mode. This revived a much-needed debate on the privacy issues of online proctoring of exams, while the validity and fairness of unproctored exams were increasingly questioned. In a randomized control trial, we send a targeted warning to half of the students who were identified as cheaters in previous exams. We then compare their cheating behavior at the final exam to the group of unwarned cheaters. Preliminary results show that the warning proves effective but does not completely annihilates cheating as the cheating strategies of some students become more sophisticated. We conclude that switching traditional exams to online mode should come with proctoring. When proctoring is not possible, credible and effective anti-cheating technologies should be deployed, together with adequate warnings

“Living on the edge” : the role of field margins for common vole (Microtus arvalis) populations in recently colonised Mediterranean farmland

Acknowledgments RRP was supported by a PhD-studentship from the University of Valladolid (co-funded by Banco Santander, RR 30/04/2014). Financial support was provided by ECOCYCLES (BIODIVERSA 2008, Era-net European project, EUI2008-03658 and NERC NE/G002045/1 to XL) and ECOVOLE projects (CGL2012-35348; Ministerio de Economía y Competitividad of Spain). The article also contributes to project ECOTULA (CGL2015-66962-C2-1-R). We held all the necessary licenses and permits for conducting this work (JJLL, FM and RRP held animal experimentation permits of level B for Spain, and a capture permit was provided by the Consejería de Fomento y Medio Ambiente, Junta de Castilla y León (Expte: EP/CYL/665/2014)). We thank two anonymous reviewers for providing and constructive comments to improve the manuscript.Peer reviewedPublisher PD

When do young birds disperse? : Tests from studies of golden eagles in Scotland

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Density- and age-dependent reproduction partially compensates culling efforts of invasive non-native American mink

Management strategies of wildlife species must pay due regard to density dependent changes in vital rates. Knowledge of density dependent relationships is sparse for most species but such knowledge ought to inform adaptive management. Using data from a large-scale, 6 years of control effort of the invasive non-native American mink (Neovison vison) in Scotland, we analysed density dependent changes in reproduction as revealed by placental scar counts in culled females. Control strongly reduced mink density but it varied substantially over time and space, reflecting variation in when control was initiated in each river section. We used hurdle statistical models to simultaneously relate the probability of conception, litter size and female age to prevailing mink density in river sections where the female was culled. Both the probability of conceiving a litter (average 0.81) and litter size (average 5.52 pups) increased as the density of females, but not males, declined. In addition, there was a senescent decline in both components of fecundity, which given culling of mink and subsequent reinvasions, resulted in a younger population, adding further to density dependent compensation in fecundity. There was no evidence of depensation, even at the lowest density. The predicted combined impact of changes in density and age structure could lead to an increase in fecundity of up to 2.1 pups per female occupying or reinvading the controlled area. Control strategies must be sufficiently adaptable and robust in order to overcome this compensation and suppress densities of mink and other invasive mammals

Invasive crayfish reduce food limitation of alien American mink and increase their resilience to control

Trophic relationships between invasive species in multiply invaded ecosystems may reduce food limitation relative to more pristine ecosystems and increase resilience to control. Here, we consider whether invasive predatory American mink Neovison vison are trophically subsidized by invasive crayfish. We collated data from the literature on density and home range size of mink populations in relation to the prevalence of crayfish in the diet of mink. We then tested the hypothesis that populations of an invasive predator reach higher densities and are more resilient to lethal control when they have access to super-abundant non-native prey, even in the absence of changes in density dependence, hence compensatory capacity. We found a strong positive relationship between the proportion of crayfish in mink diet and mink population density, and a negative relationship between the proportion of crayfish in mink diet and mink home range size, with crayfish contribution to mink diet reflecting their abundance in the ecosystem. We then explored the consequence of elevated mink density by simulating a hypothetical eradication program with a constant harvest in a Ricker model. We found that mink populations were more resilient to harvest in the presence of crayfish. As a result, the simulated number of mink harvested to achieve eradication increased by 500 % in the presence of abundant crayfish if carrying capacity increased by 630 %. This led to a threefold increase in time to eradication under a constant harvest and an approximately 20-fold increase in the cumulative management cost. Our results add to evidence of inter-specific positive interactions involving invasive species, and our simple model illustrates how this increases management cost

The value of considering demographic contributions to connectivity - a review

Connectivity is a central concept in ecology, wildlife management, and conservation science. Understanding the role of connectivity in determining species persistence is increasingly important in the face of escalating anthropogenic impacts on climate and habitat. These connectivity augmenting processes can severely impact species distributions and community and ecosystem functioning. One general definition of connectivity is that it is an emergent process arising from a set of spatial interdependencies between individuals or populations, and increasingly realistic representations of connectivity are being sought. Generally, connectivity consists of a structural component, relating to the distribution of suitable and unsuitable habitat, and a functional component, relating to movement behavior, yet the interaction of both components often better describes ecological processes. Additionally, although implied by ‘movement', demographic measures such as the occurrence or abundance of organisms are regularly overlooked when quantifying connectivity. Integrating such demographic contributions based on the knowledge of species distribution patterns is critical to understanding the dynamics of spatially structured populations. Demographically-informed connectivity draws from fundamental concepts in metapopulation ecology while maintaining important conceptual developments from landscape ecology, and the methodological development of spatially-explicit hierarchical statistical models that have the potential to overcome modeling and data challenges. Together, this offers a promising framework for developing ecologically realistic connectivity metrics. This review synthesizes existing approaches for quantifying connectivity and advocates for demographically-informed connectivity as a general framework for addressing current problems across ecological fields reliant on connectivity-driven processes such as population ecology, conservation biology and landscape ecology. Using supporting simulations to highlight the consequences of commonly made assumptions that overlook important demographic contributions, we show that even small amounts of demographic information can greatly improve model performance. Ultimately, we argue demographic measures are central to extending the concept of connectivity and resolves long-standing challenges associated with accurately quantifying the influence of connectivity on fundamental ecological processes.Publisher PDFPeer reviewe

The Value of Considering Demographic Contributions to Connectivity: A Review

Connectivity is a central concept in ecology, wildlife management, and conservation science. Understanding the role of connectivity in determining species persistence is increasingly important in the face of escalating anthropogenic impacts on climate and habitat. These connectivity augmenting processes can severely impact species distributions and community and ecosystem functioning. One general definition of connectivity is that it is an emergent process arising from a set of spatial interdependencies between individuals or populations, and increasingly realistic representations of connectivity are being sought. Generally, connectivity consists of a structural component, relating to the distribution of suitable and unsuitable habitat, and a functional component, relating to movement behavior, yet the interaction of both components often better describes ecological processes. Additionally, although implied by \u27movement\u27, demographic measures such as the occurrence or abundance of organisms are regularly overlooked when quantifying connectivity. Integrating such demographic contributions based on the knowledge of species distribution patterns is critical to understanding the dynamics of spatially structured populations. Demographically-informed connectivity draws from fundamental concepts in metapopulation ecology while maintaining important conceptual developments from landscape ecology, and the methodological development of spatially-explicit hierarchical statistical models that have the potential to overcome modeling and data challenges. Together, this offers a promising framework for developing ecologically realistic connectivity metrics. This review synthesizes existing approaches for quantifying connectivity and advocates for demographically-informed connectivity as a general framework for addressing current problems across ecological fields reliant on connectivity-driven processes such as population ecology, conservation biology and landscape ecology. Using supporting simulations to highlight the consequences of commonly made assumptions that overlook important demographic contributions, we show that even small amounts of demographic information can greatly improve model performance. Ultimately, we argue demographic measures are central to extending the concept of connectivity and resolves long-standing challenges associated with accurately quantifying the influence of connectivity on fundamental ecological processes

Dampening prey cycle overrides the impact of climate change on predator population dynamics : a long-term demographic study on tawny owls

Funded by ERA-Net BiodivERsA NERC. Grant Numbers: NE/E010660/1, NE/F021402/1, NE/G002045/1Peer reviewedPublisher PD

Essays in Industrial Organization, with Applications to the Electricity and Digital Markets

Le résumé en français n'a pas été communiqué par l'auteur.Le résumé en anglais n'a pas été communiqué par l'auteur