population regulation
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2022 ◽  
Vol 247 ◽  
pp. 106180
Author(s):  
Paul M. Regular ◽  
Alejandro D. Buren ◽  
Karen S. Dwyer ◽  
Noel G. Cadigan ◽  
Robert S. Gregory ◽  
...  

2021 ◽  
Vol 288 (1965) ◽  
Author(s):  
Thomas J. Hitchcock ◽  
Andy Gardner

Recent years have seen an explosion of theoretical and empirical interest in the role that kin selection plays in shaping patterns of sexual conflict, with a particular focus on male harming traits. However, this work has focused solely on autosomal genes, and as such it remains unclear how demography modulates the evolution of male harm loci occurring in other portions of the genome, such as sex chromosomes and cytoplasmic elements. To investigate this, we extend existing models of sexual conflict for application to these different modes of inheritance. We first analyse the general case, revealing how sex-specific relatedness, reproductive value and the intensity of local competition combine to determine the potential for male harm. We then analyse a series of demographically explicit models, to assess how dispersal, overlapping generations, reproductive skew and the mechanism of population regulation affect sexual conflict across the genome, and drive conflict between nuclear and cytoplasmic genes. We then explore the effects of sex biases in these demographic parameters, showing how they may drive further conflicts between autosomes and sex chromosomes. Finally, we outline how different crossing schemes may be used to identify signatures of these intragenomic conflicts.


2021 ◽  
Author(s):  
◽  
Enrique Arturo Mundaca

<p><b>The importance of habitat structure has been historically discussed in terms of its influence on diversity, distribution and abundance of living organisms. In this regard, the population fluctuations of any particular species, particularly outbreaking insect species, can be expected to be profoundly influenced by the structure of the habitat. A set of ecological hypotheses, such as, the associational resistance, plant decoy, habitat heterogeneity and resource concentration have implicitly included the structure of the habitat determined by the structure (size, density, physical location) of the host plant and other surrounding plant species. Moreover, type, quality and availability of resources, in addition to the presence of other interacting organisms, e.g. competitors, predators and parasites, have also been considered determining factors in the population fluctuation of outbreaking species. The aim of this thesis is to contribute to the understanding of how the outbreaks of the kowhai moth, U. polygonalis maorialis, relate to the physical structure of the habitat, the availability of resources, specific host plants and to natural enemies.</b></p> <p>In the first experimental chapter of my thesis I studied the fluctuations of the U. polygonalis maorialis larvae and their impacts on the defoliation levels of Sophora spp. plants. I carried out a survey in urban and suburban areas of Wellington city. I examined levels of defoliation of the host plants and population fluctuations in terms of a set of biotic and abiotic variables. These variables were selected in order to cover a range of measures of habitat structure, resource availability and invertebrate community. I modelled such responses to find which variables better explained the observed defoliation and larval population fluctuations. The best fitted model showed that levels of observed defoliation were explained by the structure of the vegetation surrounding the main host plant (vertical and horizontal) and the species of host plant. Population fluctuations of the kowhai moth were explained by the following predicting variables: density of natural enemies, structure of the vegetation surrounding the main host plant (vertical and horizontal), host plant size, level of habitat disturbance, type of habitat (urban/suburban) and the Sophora spp.</p> <p>In my second experimental chapter, I focused on the importance of availability of resources to explain observed densities of U. polygonalis maorialis and phytophagous insects. In my observational experiment I tested the resource concentration hypothesis and the natural enemies hypothesis, by studying the fluctuations of U. polygonalis maorialis larvae on individuals of Sophora microphylla plants located in gardens across Wellington city. Larval densities were found to be higher on smaller plants than large plants, whereas natural enemies did not show specific responses to plant size. In my manipulative experiment I originally aimed for the establishment of U. polygonalis maorialis in the experimental plots. Unfortunately, these were not colonised by U. polygonalis maorialis, instead I studied phytophagous insects that colonised the plots. I found no differences among the S. microphylla treatments for the levels of establishment of phytophagous invertebrates. On the contrary, the amount of nil records was high and there was an overall high variability among treatments and low rate of establishment throughout the sampling season. Nevertheless, natural enemies were found to occur more often at higher densities in plots with lower plant density in only two specific dates.</p> <p>Uresiphita polygonalis maorialis is the main defoliator of Sophora spp in New Zealand. In this context I studied the feeding and oviposition preferences of the moth for the three most commonly found species of Sophora plants in Wellington city. Sophora tetraptera was the preferred species chosen by the female moth. The same species was also the most palatable and preferred when confronted to S. microphylla and S. prostrata. These patterns observed in controlled conditions are coincident with observations made in the field throughout the study.</p> <p>Within the set of variables determined by the invertebrate community, the influence of natural enemies on an herbivorous population is one of the most important in terms of population regulation. In my last experimental chapter I found a positive correlation among the parasitism by M. pulchricornis and U. polygonalis maorialis larval densities, which opens the possibilities for future research to explore the potential existence of population regulation mechanisms between these two taxa.</p> <p>Overall, the results of my thesis highlight the importance of understanding the influence of the structure of the habitat, types of resources provided by plants and natural enemies in determining the fluctuations of outbreaking insect species.</p>


2021 ◽  
Author(s):  
◽  
Enrique Arturo Mundaca

<p><b>The importance of habitat structure has been historically discussed in terms of its influence on diversity, distribution and abundance of living organisms. In this regard, the population fluctuations of any particular species, particularly outbreaking insect species, can be expected to be profoundly influenced by the structure of the habitat. A set of ecological hypotheses, such as, the associational resistance, plant decoy, habitat heterogeneity and resource concentration have implicitly included the structure of the habitat determined by the structure (size, density, physical location) of the host plant and other surrounding plant species. Moreover, type, quality and availability of resources, in addition to the presence of other interacting organisms, e.g. competitors, predators and parasites, have also been considered determining factors in the population fluctuation of outbreaking species. The aim of this thesis is to contribute to the understanding of how the outbreaks of the kowhai moth, U. polygonalis maorialis, relate to the physical structure of the habitat, the availability of resources, specific host plants and to natural enemies.</b></p> <p>In the first experimental chapter of my thesis I studied the fluctuations of the U. polygonalis maorialis larvae and their impacts on the defoliation levels of Sophora spp. plants. I carried out a survey in urban and suburban areas of Wellington city. I examined levels of defoliation of the host plants and population fluctuations in terms of a set of biotic and abiotic variables. These variables were selected in order to cover a range of measures of habitat structure, resource availability and invertebrate community. I modelled such responses to find which variables better explained the observed defoliation and larval population fluctuations. The best fitted model showed that levels of observed defoliation were explained by the structure of the vegetation surrounding the main host plant (vertical and horizontal) and the species of host plant. Population fluctuations of the kowhai moth were explained by the following predicting variables: density of natural enemies, structure of the vegetation surrounding the main host plant (vertical and horizontal), host plant size, level of habitat disturbance, type of habitat (urban/suburban) and the Sophora spp.</p> <p>In my second experimental chapter, I focused on the importance of availability of resources to explain observed densities of U. polygonalis maorialis and phytophagous insects. In my observational experiment I tested the resource concentration hypothesis and the natural enemies hypothesis, by studying the fluctuations of U. polygonalis maorialis larvae on individuals of Sophora microphylla plants located in gardens across Wellington city. Larval densities were found to be higher on smaller plants than large plants, whereas natural enemies did not show specific responses to plant size. In my manipulative experiment I originally aimed for the establishment of U. polygonalis maorialis in the experimental plots. Unfortunately, these were not colonised by U. polygonalis maorialis, instead I studied phytophagous insects that colonised the plots. I found no differences among the S. microphylla treatments for the levels of establishment of phytophagous invertebrates. On the contrary, the amount of nil records was high and there was an overall high variability among treatments and low rate of establishment throughout the sampling season. Nevertheless, natural enemies were found to occur more often at higher densities in plots with lower plant density in only two specific dates.</p> <p>Uresiphita polygonalis maorialis is the main defoliator of Sophora spp in New Zealand. In this context I studied the feeding and oviposition preferences of the moth for the three most commonly found species of Sophora plants in Wellington city. Sophora tetraptera was the preferred species chosen by the female moth. The same species was also the most palatable and preferred when confronted to S. microphylla and S. prostrata. These patterns observed in controlled conditions are coincident with observations made in the field throughout the study.</p> <p>Within the set of variables determined by the invertebrate community, the influence of natural enemies on an herbivorous population is one of the most important in terms of population regulation. In my last experimental chapter I found a positive correlation among the parasitism by M. pulchricornis and U. polygonalis maorialis larval densities, which opens the possibilities for future research to explore the potential existence of population regulation mechanisms between these two taxa.</p> <p>Overall, the results of my thesis highlight the importance of understanding the influence of the structure of the habitat, types of resources provided by plants and natural enemies in determining the fluctuations of outbreaking insect species.</p>


2021 ◽  
Vol 9 ◽  
Author(s):  
Elena Kmetova–Biro ◽  
Emilian Stoynov ◽  
Ivelin Ivanov ◽  
Hristo Peshev ◽  
Simeon Marin ◽  
...  

The current study presents and analyses the results from the recently completed 11-year-establishment phase, following the start of the local re-introduction of the Griffon Vulture (Gyps fulvus) in Kotlenska Planina SPA and Sinite Kamani Nature Park in the Eastern Balkan Mountains of Bulgaria in the period 2010-2020. As a result of the re-introduction efforts and release of 153 individuals, the Griffon Vulture has been successfully reproducing again in the Eastern Balkan Mountains since 2016, after more than 40-50 years of absence. At 2020, the local population consists of some 80 local and up to 80-115 birds, together with sojourn individuals. Amongst them, 23-25 breeding pairs, located in five different colonies and two more frequently used roosting sites. The current average productivity remains relatively low: 0.41 fledglings/territorial pair and fledging success of 0.61 fledglings/breeding pair between 2016 and 2020, but shows a trend to increase with time and the growing experience of the young locally re-introduced population. The mortality confirmed between 2010-2021 accounts for 33%, mostly due to electrocution as a post-release effect in the first six months following their release. Our data show that the newly established population in the Eastern Balkan Mountains mostly forages on feeding sites, having a comparatively small 95% home range: 281.88 ± 91 km2 and 50% core area: 6.6 ± 2.28 km2 (range 4.7–8.5 km2). We, therefore, consider the establishment phase of the re-introduction of Griffon Vulture in this particular site as successfully completed, but management should continue. Furthermore, the area of the Eastern Balkan Mountains can currently be regarded as a "source" for the species within the source-sink population regulation concept in the national and Balkan context.


Author(s):  
John Soghigian ◽  
Todd Livdahl

Abstract Although parasites are by definition costly to their host, demonstrating that a parasite is regulating its host abundance in the field can be difficult. Here we present an example of a gregarine parasite, Ascogregarina taiwanensis Lien and Levine (Apicomplexa: Lecudinidae), regulating its mosquito host, Aedes albopictus Skuse (Diptera: Culicidae), in Bermuda. We sampled larvae from container habitats over 2 yr, assessed parasite prevalence, and estimated host abundance from egg counts obtained in neighboring ovitraps. We regressed change in average egg count from 1 yr to the next on parasite prevalence and found a significant negative effect of parasite prevalence. We found no evidence of host density affecting parasite prevalence. Our results demonstrate that even for a parasite with moderate virulence, host regulation can occur in the field.


2021 ◽  
Vol 11 (1) ◽  
pp. 67-75
Author(s):  
A. I. Mikhailov ◽  
A. E. Bobyrev ◽  
T. I. Bulgakova ◽  
A. D. Sheremetyev

2020 ◽  
pp. 50-93
Author(s):  
Amrita Chhachhi

This article explores the convergence and contradictions between the two hegemonic projects of neoliberalism and Hindutva and the reinforcement/reconstruction of patriarchal gender relations in relation to welfare. Analysis of some key social policies and specific legal interventions show the fusion of the two in the construction of the family/nation/gender related to population regulation, governance of populations, the forging of a paternal contract, the move from welfare to financialization and the undermining of labour rights through regulatory and disciplinary labour codes. The convergence of neoliberalism and Hindutva results in a shift from rights-based entitlements to further commodification and digital financialization and the creation of a hindutvatised neoliberal subjectivity. Keywords: Neoliberal authoritarianism, Hindutva, Welfare, Gender, Labour


2020 ◽  
Vol 18 (5) ◽  
pp. 401-415
Author(s):  
Wojciech Szeligiewicz

Richard Butler’s Tourism Area Life Cycle (TALC) model proposes a specified view on the qualitative changes in the number of tourists N in the area over time and the environmental, social and economic processes taking place there simultaneously. N changes follow S-shaped curve up to stagnation phase. Such a course was adopted in the TALC model, assuming that the tourist population at this stage develops in accordance with a logistic model derived from ecology. This work aimed to recall the properties of the logistic model and the ecological assumptions underlying it, and some of the consequences of incorporating the logistic model into the TALC model. An attempt has also been made to link other TALC aspects with ecology. In particular, reference is made to the graph on the right side of the logistic equation of the TALC model as a function of N with the phases of evolution of the tourist area marked, which reminds that the most attractive area is the original area, i.e. when N is small, as it is characterized by the highest per capita growth of the tourist population. According to this figure, as N increases, there is a linear decrease in attractiveness despite the investments introduced according to the TALC model scenario, i.e. they do not reverse this trend. The same diagram can be used to show some elementary differences between ecotourism and mass tourism. The issues of population regulation were also raised, including the density-dependent self-regulation, the Allee effect, the concept of environmental capacity and r and K strategies. It was also pointed out that the experience gained in the field of population modelling in ecology could help to model tourist populations.


Author(s):  
Suleiman Ahmed Isa ◽  
Muhtari Ladan Jangebe ◽  
Aminu Bala Yabo ◽  
Halimatu Maiakwai Lamido

Background: Walking is a common form of low intensity exercise that is suitable for most sedentary population. Regulation of blood lipids is an important mechanism by which physical exercise reduces cardiovascular risk. Aim: This study aimed to determine whether low intensity exercise modulates cardiometabolic risk markers in previously sedentary individuals. Methods: Twenty sedentary adults (12 males and 8 females) participated in an eight weeks low intensity exercise. The exercise consisted of brisk walking for 45 minutes, 3 times per week for 8 weeks under supervision. Serum glucose, anthropometric parameters, blood pressure and lipid profile were determined at baseline and after four, six and eight weeks of the exercise programme. Results: There was a non-significant decrease in body mass index


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