scholarly journals Amendment to: populations in environments with a soft carrying capacity are eventually extinct

2021 ◽  
Vol 83 (1) ◽  
Author(s):  
Peter Jagers ◽  
Sergei Zuyev

AbstractThis sharpens the result in the paper Jagers and Zuyev (J Math Biol 81:845–851, 2020): consider a population changing at discrete (but arbitrary and possibly random) time points, the conditional expected change, given the complete past population history being negative, whenever population size exceeds a carrying capacity. Further assume that there is an $$\epsilon > 0$$ ϵ > 0 such that the conditional probability of a population decrease at the next step, given the past, always exceeds $$\epsilon $$ ϵ if the population is not extinct but smaller than the carrying capacity. Then the population must die out.

2017 ◽  
Author(s):  
John Hawks

AbstractHuman populations have a complex history of introgression and of changing population size. Human genetic variation has been affected by both these processes, so that inference of past population size depends upon the pattern of gene flow and introgression among past populations. One remarkable aspect of human population history as inferred from genetics is a consistent “wave” of larger effective population size, prior to the bottlenecks and expansions of the last 100,000 years. Here I carry out a series of simulations to investigate how introgression and gene flow from genetically divergent ancestral populations affect the inference of ancestral effective population size. Both introgression and gene flow from an extinct, genetically divergent population consistently produce a wave in the history of inferred effective population size. The time and amplitude of the wave reflect the time of origin of the genetically divergent ancestral populations and the strength of introgression or gene flow. These results demonstrate that even small fractions of introgression or gene flow from ancient populations may have large effects on the inference of effective population size.


2020 ◽  
Author(s):  
Jérémy Andréoletti ◽  
Antoine Zwaans ◽  
Rachel C. M. Warnock ◽  
Gabriel Aguirre-Fernández ◽  
Joëlle Barido-Sottani ◽  
...  

AbstractPhylodynamic models generally aim at jointly inferring phylogenetic relationships, model parameters, and more recently, population size through time for clades of interest, based on molecular sequence data. In the fields of epidemiology and macroevolution these models can be used to estimate, respectively, the past number of infected individuals (prevalence) or the past number of species (paleodiversity) through time. Recent years have seen the development of “total-evidence” analyses, which combine molecular and morphological data from extant and past sampled individuals in a unified Bayesian inference framework. Even sampled individuals characterized only by their sampling time, i.e. lacking morphological and molecular data, which we call occurrences, provide invaluable information to reconstruct past population sizes.Here, we present new methodological developments around the Fossilized Birth-Death Process enabling us to (i) efficiently incorporate occurrence data while remaining computationally tractable and scalable; (ii) consider piecewise-constant birth, death and sampling rates; and (iii) reconstruct past population sizes, with or without knowledge of the underlying tree. We implement our method in the RevBayes software environment, enabling its use along with a large set of models of molecular and morphological evolution, and validate the inference workflow using simulations under a wide range of conditions.We finally illustrate our new implementation using two empirical datasets stemming from the fields of epidemiology and macroevolution. In epidemiology, we apply our model to the Covid-19 outbreak on the Diamond Princess ship. We infer the total prevalence throughout the outbreak, by taking into account jointly the case count record (occurrences) along with viral sequences for a fraction of infected individuals. In macroevolution, we present an empirical case study of cetaceans. We infer the diversity trajectory using molecular and morphological data from extant taxa, morphological data from fossils, as well as numerous fossil occurrences. Our case studies highlight that the advances we present allow us to further bridge the gap between between epidemiology and pathogen genomics, as well as paleontology and molecular phylogenetics.


2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Yashuai Zhang ◽  
Fang Wang ◽  
Zhenxia Cui ◽  
Min Li ◽  
Xia Li ◽  
...  

Abstract Background One of the most challenging tasks in wildlife conservation and management is clarifying which and how external and intrinsic factors influence wildlife demography and long-term viability. The wild population of the Crested Ibis (Nipponia nippon) has recovered to approximately 4400, and several reintroduction programs have been carried out in China, Japan and Korea. Population viability analysis on this endangered species has been limited to the wild population, showing that the long-term population growth is restricted by the carrying capacity and inbreeding. However, gaps in knowledge of the viability of the reintroduced population and its drivers in the release environment impede the identification of the most effective population-level priorities for aiding in species recovery. Methods The field monitoring data were collected from a reintroduced Crested Ibis population in Ningshan, China from 2007 to 2018. An individual-based VORTEX model (Version 10.3.5.0) was used to predict the future viability of the reintroduced population by incorporating adaptive patterns of ibis movement in relation to catastrophe frequency, mortality and sex ratio. Results The reintroduced population in Ningshan County is unlikely to go extinct in the next 50 years. The population size was estimated to be 367, and the population genetic diversity was estimated to be 0.97. Sensitivity analysis showed that population size and extinction probability were dependent on the carrying capacity and sex ratio. The carrying capacity is the main factor accounting for the population size and genetic diversity, while the sex ratio is the primary factor responsible for the population growth trend. Conclusions A viable population of the Crested Ibis can be established according to population viability analysis. Based on our results, conservation management should prioritize a balanced sex ratio, high-quality habitat and low mortality.


1978 ◽  
Vol 35 (9) ◽  
pp. 1249-1261 ◽  
Author(s):  
G. H. Winters

From recent and historical data the natural mortality rate of adult harp seals (Pagophilus groenlandicus) is estimated to be 0.10 which is within the range of previous estimates (0.08–0.11). New estimates of bedlamer and 0-group natural mortality rates were not significantly different from those of adult seals. Pup production estimates from survival indices agreed well with those from sequential population analyses and indicated a decline from about 350 000 animals in the early 1950s to about 310 000 animals in the early 1970s. Over the same period the 1+ population size declined from 2.5 to 1.1 million animals but has been increasing at the rate of 3%/yr since the introduction of quotas in 1972. The relative contribution of the "Front" production to total ("Front" plus Gulf) production during the past decade has fluctuated from 49 to 87%, the average of 64% being very similar to the 61% obtained previously. These fluctuations suggest some interchange between "Front" and Gulf adults and it is concluded that homing in the breeding areas is a facultative rather than obligatory aspect of seal behavior. Thus the heavier exploitation of the "Front" production is probably sufficiently diffused into the total population to avoid serious effects on "Front" production. The maximum sustainable yield of Northwest Atlantic seals harvested according to recent patterns is estimated to be 290 000 animals (80% pups) from a 1+ population size of 1.8 million animals producing 460 000 pups annually. The sustainable yield at present levels of pup production (335 000 animals) is calculated to be 220 000 animals which is substantially above the present TAC of 180 000 animals and coincides with present harvesting strategies designed to enable the seal hunt to increase slowly towards the MSY level. Key words: mortality, production, sustainable yield, population dynamics, marine mammal


1983 ◽  
Vol 40 (3) ◽  
pp. 267-271 ◽  
Author(s):  
Paul Brodie ◽  
Brian Beck

The increase in population size of the grey seal (Halichoerus grypus) off eastern Canada over the past 20 yr may be attributed to a decrease in shark stocks, their supposed predators. Reduction of the shark population is presumed to have resulted from a directed longline fishery and, of greater significance, from a change in the fishery for swordfish (Xiphias gladius) from selective harpooning to pelagic longlining, which has produced a large bycatch of sharks. The resulting enhanced survival of grey seals is reflected in greater infestation of commercially important fish species by the codworm (Phocanema decipiens).Key words: grey seals, harbour seals, sharks, swordfish, codworm, predation, fisheries


2022 ◽  
pp. 1-27
Author(s):  
Clifford Bohm ◽  
Douglas Kirkpatrick ◽  
Arend Hintze

Abstract Deep learning (primarily using backpropagation) and neuroevolution are the preeminent methods of optimizing artificial neural networks. However, they often create black boxes that are as hard to understand as the natural brains they seek to mimic. Previous work has identified an information-theoretic tool, referred to as R, which allows us to quantify and identify mental representations in artificial cognitive systems. The use of such measures has allowed us to make previous black boxes more transparent. Here we extend R to not only identify where complex computational systems store memory about their environment but also to differentiate between different time points in the past. We show how this extended measure can identify the location of memory related to past experiences in neural networks optimized by deep learning as well as a genetic algorithm.


2002 ◽  
Vol 61 (2) ◽  
pp. 591-607 ◽  
Author(s):  
James Lee ◽  
Cameron Campbell ◽  
Wang Feng

As recently as twenty-five years ago, there were virtually no demographers of China and there was little available data on Chinese demographic behavior. Thus in spite of intense interest in China's population dating back at least to Malthus (1766–1834), his initial understanding, or rather misunderstanding, of Chinese population dynamics remains dominant. While recent research on European population history has confirmed Malthus's observations that European, or at least English, population size was controlled largely by the preventive check, nuptiality, the absence of similar studies of Chinese population history ironically facilitated the persistence of a Malthusian hypothesis that Chinese population size was controlled largely by the positive check, mortality. It is a tribute to the elegance and power of the Malthusian orthodoxy that in spite of the lack of information on Chinese historic demographic behavior and economic performance, many of the most distinguished Western scholars of late imperial China continue to interpret social and economic processes in China during the last three hundred years in Malthusian or neo-Malthusian terms (Elvin 1973; Chao 1986; Huang 1990).


Medicina ◽  
2022 ◽  
Vol 58 (1) ◽  
pp. 87
Author(s):  
Agnieszka Jodzis ◽  
Maciej Walędziak ◽  
Krzysztof Czajkowski ◽  
Anna Różańska-Walędziak

Background: Global access to social media has supposedly changed women’s awareness about the pharmacological and alternative methods of pain relief during vaginal delivery. The purpose of the study was to analyze changes in women’s preference and opinion about different forms of labor analgesia over the past decade. Materials and methods: The study was designed as an anonymous survey with questions about women’s knowledge and preference of different forms of pain relief in labor. The survey was conducted in 2010 and 2020, with data collected from 1175 women in 2010 and 1033 in 2020. Results: There were no differences between 2010 and 2020 in the proportion of women who wanted to receive analgesia in labor, at, respectively 67.9% of women in 2010 and 73.9% in 2020. About 50% of women chose epidural analgesia as the only efficacious method of pain relief in labor both in 2010 and 2020. There were no differences between the two time-points in the distribution of chosen methods of pain relief. In total, 92.3% of women in 2010 and 94.9% in 2020 thought that they should have the possibility of independent choice of analgesia method before the delivery (p < 0.04). Conclusions: A high proportion of Polish women choose EDA over other pharmacological and nonpharmacological methods of pain relief in labor, and this preference has not changed over the last decade. Increasing women’s knowledge about different methods of intrapartum pain relief may lead to wider use of nonpharmacological methods of pain relief.


Author(s):  
Zhongwei Zhao

China constituted one of the earliest civilizations in the world. During most of the past two millennia, China was also one of the most advanced economies and the home of around a quarter of the world’s population. By the start of the first millennium, the Chinese population was already about sixty million. In the next two thousand years, China’s population growth and economic development significantly influenced the world’s population changes and history. Partly for these reasons, in the study of population and social history, China’s historical population growth, demographic regimes, marriage patterns, and household formation systems are frequently used as examples in the discussion of population changes, microsocial structure, and their relationships with natural resources and economic development in past times. Population changes were one of the key components of Chinese history. The size and density of the population, the rise and fall of fertility and mortality, and the increase and decrease of population movements were not only related to demographic factors such as age structure. They were also strongly affected by political and economic conditions, social institutions and cultural traditions, and natural and social environments. Therefore, studies of demographic history, those conducted recently in particular, often shed new light on economic, political, social, and environmental changes in the past. This bibliography, through reviewing major works published in Chinese and English, provides an introduction to China’s main historical population data sources, major research questions, and debates in the study of Chinese population history. It also introduces recent advances in Chinese historical demography and important research findings made by these developments.


2014 ◽  
Author(s):  
Melinda A Yang ◽  
Kelley Harris ◽  
Montgomery Slatkin

We introduce a method for comparing a test genome with numerous genomes from a reference population. Sites in the test genome are given a weight w that depends on the allele frequency x in the reference population. The projection of the test genome onto the reference population is the average weight for each x, w(x). The weight is assigned in such a way that if the test genome is a random sample from the reference population, w(x)=1. Using analytic theory, numerical analysis, and simulations, we show how the projection depends on the time of population splitting, the history of admixture and changes in past population size. The projection is sensitive to small amounts of past admixture, the direction of admixture and admixture from a population not sampled (a ghost population). We compute the projection of several human and two archaic genomes onto three reference populations from the 1000 Genomes project, Europeans (CEU), Han Chinese (CHB) and Yoruba (YRI) and discuss the consistency of our analysis with previously published results for European and Yoruba demographic history. Including higher amounts of admixture between Europeans and Yoruba soon after their separation and low amounts of admixture more recently can resolve discrepancies between the projections and demographic inferences from some previous studies.


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