Town population size and structuring into villages and households drive infectious disease risks in pre-healthcare Finland

Social life is often considered to cost in terms of increased parasite or pathogen risk. However, evidence for this in the wild remains equivocal, possibly because populations and social groups are often structured, which affects the local transmission and extinction of diseases. We test how the structuring of towns into villages and households influenced the risk of dying from three easily diagnosable infectious diseases—smallpox, pertussis and measles—using a novel dataset covering almost all of Finland in the pre-healthcare era (1800–1850). Consistent with previous results, the risk of dying from all three diseases increased with the local population size. However, the division of towns into a larger number of villages decreased the risk of dying from smallpox and to some extent of pertussis but it slightly increased the risk for measles. Dividing towns into a larger number of households increased the length of the epidemic for all three diseases and led to the expected slower spread of the infection. However, this could be seen only when local population sizes were small. Our results indicate that the effect of population structure on epidemics, disease or parasite risk varies between pathogens and population sizes, hence lowering the ability to generalize the consequences of epidemics in spatially structured populations, and mapping the costs of social life, via parasites and diseases.

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Trade-off between local transmission and long-range dispersal drives infectious disease outbreak size in spatially structured populations

PLoS Computational Biology ◽

10.1371/journal.pcbi.1008009 ◽

2020 ◽

Vol 16 (7) ◽

pp. e1008009 ◽

Cited By ~ 1

Author(s):

Elisa Benincà ◽

Thomas Hagenaars ◽

Gert Jan Boender ◽

Jan van de Kassteele ◽

Michiel van Boven

Keyword(s):

Infectious Disease ◽

Long Range ◽

Disease Outbreak ◽

Structured Populations ◽

Infectious Disease Outbreak ◽

Trade Off ◽

Spatially Structured Populations ◽

Local Transmission ◽

Outbreak Size

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Population-size estimators and unequal catchability in painted turtles

Canadian Journal of Zoology ◽

10.1139/z97-220 ◽

1998 ◽

Vol 76 (3) ◽

pp. 458-465 ◽

Cited By ~ 17

Author(s):

Nicola Koper ◽

Ronald J Brooks

Keyword(s):

Population Size ◽

Sampling Methods ◽

Ecological Research ◽

Closed Population ◽

Painted Turtles ◽

Population Size Estimates ◽

Population Sizes ◽

Almost All ◽

Size Estimates ◽

True Population

Most methods of estimating population size from mark-recapture data assume equal catchability. Failure to meet this assumption may have profound effects on population-size estimates. We used 3 sampling methods to compare population-size estimates derived from Petersen, Schumacher and Eschmeyer, and Jolly-Seber models with the true size of a closed population of painted turtles (Chrysemys picta) in Algonquin Park, Ontario. We found significant variation in capture probabilities, and almost all population-size estimates were far below the true population size. To try to improve the accuracy of the estimates, we applied 4 techniques commonly recommended for reducing bias when catchability is unequal: (i) changing sampling methods, (ii) using several sampling methods simultaneously, (iii) dividing the population by sex, and (iv) calculating population sizes using the computer program CAPTURE. None of the 4 methods reduced the error that resulted from unequal catchability in any of the estimates sufficiently for these methods to be suitable for management of populations or for ecological research.

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Fragmentation helps evolutionary rescue in highly connected habitats

10.1101/2020.10.29.360842 ◽

2020 ◽

Author(s):

Matteo Tomasini ◽

Stephan Peischl

Keyword(s):

Genetic Variation ◽

Gene Flow ◽

Environmental Conditions ◽

Structured Populations ◽

Adaptive Introgression ◽

Spatially Structured Populations ◽

Species Survival ◽

Evolutionary Rescue ◽

The Face ◽

Population Sizes

AbstractGenetic variation and population sizes are critical factors for successful adaptation to novel environmental conditions. Gene flow between sub-populations is a potent mechanism to provide such variation and can hence facilitate adaption, for instance by increasing genetic variation or via adaptive introgression. On the other hand, if gene flow between different habitats is too strong, locally beneficial alleles may not be able to establish permanently. In the context of evolutionary rescue, intermediate levels of gene flow are therefore often optimal for maximizing a species chance for survival in meta-populations without spatial structure. To which extent and under which conditions gene flow facilitates or hinders evolutionary rescue in spatially structured populations remains unresolved. We address this question and show that detrimental effects of gene flow can become negligible in spatially structured populations subject to a gradual deterioration of environmental conditions. If the number of sub-populations is sufficiently large, we find a positive relationship between the amount of gene flow and the survival chance of the population. A counter-intuitive conclusion is that increased fragmentation can facilitate species survival in the face of severe environmental change if migration is common but limited to neighboring sub-populations.

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The influence of fluctuating population densities on evolutionary dynamics

10.1101/444273 ◽

2018 ◽

Author(s):

Hanja Pisa ◽

Joachim Hermisson ◽

Jitka Polechova

Keyword(s):

Ecological Niche ◽

Evolutionary Dynamics ◽

Structured Populations ◽

Population Densities ◽

Ecological Literature ◽

Spatially Structured Populations ◽

Trade Offs ◽

Population Sizes ◽

And Migration ◽

Maintenance Of Diversity

AbstractThe causes and consequences of fluctuating population densities are an important topic in ecological literature. Yet, the effects of such fluctuations on maintenance of variation in spatially structured populations have received little analytic treatment. We analyze what happens when two habitats coupled by migration not only differ in their trade-offs in selection but also in their demographic stability – and show that equilibrium allele frequencies can change significantly due to ecological feedback arising from locally fluctuating population sizes. When an ecological niche exhibits such fluctuations, these drive an asymmetry in the relative impact of gene flow, and therefore, the equilibrium frequency of the locally adapted type decreases. Our results extend the classic conditions on maintenance of diversity under selection and migration by including the effect of fluctuating population densities. We find simple analytic conditions in terms of the strength of selection, immigration, and the extent of fluctuations between generations in a continent-island model. Whereas weak fluctuations hardly affect coexistence, strong recurrent fluctuations lead to extinction of the type better adapted to the fluctuating niche – even if the invader is locally maladapted. There is a disadvantage to specialization to an unstable habitat, as it makes the population vulnerable to swamping from more stable habitats.

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Demography of the northern quoll (Dasyurus hallucatus) in the most arid part of its range

Journal of Mammalogy ◽

10.1093/jmammal/gyz092 ◽

2019 ◽

Vol 100 (4) ◽

pp. 1191-1198

Author(s):

Lorna Hernandez-Santin ◽

Judy A Dunlop ◽

Anne W Goldizen ◽

Diana O Fisher

Keyword(s):

Population Size ◽

Habitat Quality ◽

Local Population ◽

Population Characteristics ◽

Population Declines ◽

Population Size Estimates ◽

Population Sizes ◽

Harsh Climate ◽

Rocky Habitats ◽

Carnivorous Marsupial

Abstract The northern quoll (Dasyurus hallucatus) is a carnivorous marsupial that has suffered severe population declines over the last 50 years and is now listed as Endangered. The Pilbara region of Western Australia is a semi-arid area that represents an extreme of the northern quoll’s range. The overall objective of this study was to assess population characteristics of northern quolls at two rocky sites in the Pilbara, focusing on body condition, reproductive timing, population size, and sex-specific survival. We interpret these in the context of variation in habitat quality and the harsh climate. We found that reproduction occurred later in the year than in populations at more mesic locations where quolls have been previously studied, although their life history and demography were otherwise similar to that in other parts of their range. Contrary to our expectations, post-mating mortality of males was not complete. Population sizes differed between sites, suggesting that these rocky habitats varied in habitat quality. We suggest that local population size estimates can guide decisions on the relative importance of sites to ensure the long-term conservation of the species, given impacts of mining and the imminent invasion of introduced cane toads (Rhinella marina).

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Evolutionary bet-hedging in structured populations

Journal of Mathematical Biology ◽

10.1007/s00285-021-01597-z ◽

2021 ◽

Vol 82 (5) ◽

Author(s):

Christopher E. Overton ◽

Kieran J. Sharkey

Keyword(s):

Local Population ◽

Evolutionary Process ◽

Environmental Variation ◽

Structured Populations ◽

Bet Hedging ◽

Large Populations ◽

Subdivided Populations ◽

Population Sizes ◽

Unexplored Area ◽

Evolutionary Graph Theory

AbstractAs ecosystems evolve, species can become extinct due to fluctuations in the environment. This leads to the evolutionary adaption known as bet-hedging, where species hedge against these fluctuations to reduce their likelihood of extinction. Environmental variation can be either within or between generations. Previous work has shown that selection for bet-hedging against within-generational variation should not occur in large populations. However, this work has been limited by assumptions of well-mixed populations, whereas real populations usually have some degree of structure. Using the framework of evolutionary graph theory, we show that through adding competition structure to the population, within-generational variation can have a significant impact on the evolutionary process for any population size. This complements research using subdivided populations, which suggests that within-generational variation is important when local population sizes are small. Together, these conclusions provide evidence to support observations by some ecologists that are contrary to the widely held view that only between-generational environmental variation has an impact on natural selection. This provides theoretical justification for further empirical study into this largely unexplored area.

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Effect of Pheromone Blend Components, Sex Ratio, and Population Size on the Mating of Cadra cautella (Lepidoptera: Pyralidae)

Journal of Insect Science ◽

10.1093/jisesa/ieaa128 ◽

2020 ◽

Vol 20 (6) ◽

Author(s):

Abeysinghe Mudiyanselage Prabodha Sammani ◽

Dissanayaka Mudiyanselage Saman Kumara Dissanayaka ◽

Leanage Kanaka Wolly Wijayaratne ◽

William Robert Morrison

Keyword(s):

Sex Ratio ◽

Population Size ◽

Management Practices ◽

Mating Disruption ◽

Current Knowledge ◽

Mating Status ◽

Cadra Cautella ◽

Synthetic Chemicals ◽

Population Sizes ◽

Lepidoptera Pyralidae

Abstract The almond moth Cadra cautella (Walker), a key pest of storage facilities, is difficult to manage using synthetic chemicals. Pheromone-based management methods remain a high priority due to advantages over conventional management practices, which typically use insecticides. Cadra cautella females release a blend of pheromone including (Z, E)-9,12-tetradecadienyl acetate (ZETA) and (Z)-9-tetradecadien-1-yl acetate (ZTA). The effect of these components on mating of C. cautella and how response varies with the population density and sex ratio remain unknown. In this study, the mating status of C. cautella was studied inside mating cages under different ratios of ZETA and ZTA diluted in hexane and at different population sizes either with equal or unequal sex ratio. The lowest percentage of mated females (highest mating disruption [MD] effects), corresponding to roughly 12.5%, was produced by a 5:1 and 3.3:1 ratio of ZETA:ZTA. Populations with equal sex ratio showed the lowest percentage of mated females, at 20% and 12.5% under lower and higher density, respectively. The next lowest percentage of mated females was produced when the sex ratio was set to 1: 2 and 2:1 male:female, with just 25% and 22.5% of moths mated, respectively. This study shows that mating status of C. cautella is influenced by ZETA:ZTA ratio, sex ratio, and population size. This current knowledge would have useful implications for mating disruption programs.

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EFFECTS OF POPULATION SIZE AND SELECTION INTENSITY ON SHORT-TERM RESPONSE TO SELECTION FOR POSTWEANING GAIN IN MICE

Genetics ◽

10.1093/genetics/73.3.513 ◽

1973 ◽

Vol 73 (3) ◽

pp. 513-530

Author(s):

J P Hanrahan ◽

E J Eisen ◽

J E Legates

Keyword(s):

Population Size ◽

Selection Response ◽

Selection Intensity ◽

Realized Heritability ◽

Family Selection ◽

Effective Population ◽

Population Sizes ◽

Selection For ◽

Selection Intensities ◽

Term Response

ABSTRACT The effects of population size and selection intensity on the mean response was examined after 14 generations of within full-sib family selection for postweaning gain in mice. Population sizes of 1, 2, 4, 8 and 16 pair matings were each evaluated at selection intensities of 100% (control), 50% and 25% in a replicated experiment. Selection response per generation increased as selection intensity increased. Selection response and realized heritability tended to increase with increasing population size. Replicate variability in realized heritability was large at population sizes of 1, 2 and 4 pairs. Genetic drift was implicated as the primary factor causing the reduced response and lowered repeatability at the smaller population sizes. Lines with intended effective population sizes of 62 yielded larger selection responses per unit selection differential than lines with effective population sizes of 30 or less.

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Estimation of Catchabilities and Population Sizes of Lobsters

Journal of the Fisheries Research Board of Canada ◽

10.1139/f63-006 ◽

1963 ◽

Vol 20 (1) ◽

pp. 59-88 ◽

Cited By ~ 26

Author(s):

J. E. Paloheimo

Keyword(s):

Environmental Factors ◽

Population Size ◽

Atlantic Coast ◽

Temperature Data ◽

New Method ◽

Bottom Temperature ◽

Population Size Estimates ◽

Population Sizes ◽

Estimate Population Size ◽

Size Estimates

Techniques of estimating population size, level of fishing, and the degree of dependence of fishing success on environmental factors are examined on the basis of tagging, catch and effort data. A new method is developed to estimate population size from catch, effort, and temperature data when the catchability varies with temperature.The methods of estimation discussed are applied to data collected from a number of lobster fisheries on Canada's Atlantic coast. Analysis confirms a relationship between the catchability of lobsters and bottom temperature. Differences in this relationship are found between areas and between tagged and untagged lobsters within areas. It is suggested that these differences are attributable to the differences in densities as well as to aggregations of lobsters and fishing. The effect of these aggregations on population size estimates is considered.Calculated average catchabilities at comparable temperatures are different for different areas. These differences are correlated with the numbers of trap hauls per day per square miles fished. It is suggested that the differences in the catchabilities might be due to interactions between units of gear not predicted by the customary relationship between catch and effort.

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