Effects of food, kinship, and density on the longevity of spiderlings

2021 ◽  
pp. 741-751
Author(s):  
Marta Luciane Fischer ◽  
Lays Cherobim Parolin ◽  
Felipe Marcel Neves ◽  
German Antonio Villanueva-Bonilla ◽  
João Vasconellos-Neto
Keyword(s):  
Population Density ◽  
Laboratory Experiments ◽  
Survival Rates ◽  
Food Resource ◽  
Behavioral Characteristic ◽  
Risk Of Predation ◽  
Large Populations ◽  
Main Factors ◽  
Conspecific Tolerance ◽  
Loxosceles Laeta

Cannibalism is a behavioral characteristic found in a wide variety of animal groups. Although the rates of cannibalism can vary from one group to another, studies indicate that the main factors contributing to an increase in the frequency of such behavior are the availability of food, population density, the behavior and availability of victims, and environmental stress. We carried out different laboratory experiments to assess whether different factors such as the presence or absence of food among siblings and non-siblings, and at different densities among conspecific and heterospecific individuals, affect longevity of recently emerged Brazilian brown recluse (Loxosceles intermedia Mello-Leitão, 1934) and Chilean recluse (Loxosceles laeta (Nicolet, 1849)) spiderlings during periods of starvation. The results revealed that the survivorship of L. laeta during starvation was significantly higher than that of L. intermedia and that the addition of conspecific individuals increased survival rates by 1.5- and 1.6-fold, respectively. The tolerance of conspecifics differed between the two species, and generally, cannibalism was not observed, probably due to the risk of predation and limited consumption by weakened spiders, which coincided with the continued availability of endogenous vitelline reserves, thus indicating that the use of these spiderlings as a food resource may act to regulate starvation in more resistant spiders. The greater longevity and conspecific tolerance of L. laeta may be important factors contributing to the establishment of large populations of this spider in restricted areas, whereas for L. intermedia, hunger probably functions as a trigger for dispersal.

scholarly journals COVID-19 Risk Assessment: Contributing to Maintaining Urban Public Health Security and Achieving Sustainable Urban Development

2021 ◽  
Vol 13 (8) ◽  
pp. 4208
Author(s):  
Jun Zhang ◽  
Xiaodie Yuan
Keyword(s):  
Public Health ◽  
Population Density ◽  
Prevention And Control ◽  
Floating Population ◽  
Sustainable Urban Development ◽  
Risk Level ◽  
Health Security ◽  
Main Factors ◽  
And Control ◽  
Epidemic Risk

As the most infectious disease in 2020, COVID-19 is an enormous shock to urban public health security and to urban sustainable development. Although the epidemic in China has been brought into control at present, the prevention and control of it is still the top priority of maintaining public health security. Therefore, the accurate assessment of epidemic risk is of great importance to the prevention and control even to overcoming of COVID-19. Using the fused data obtained from fusing multi-source big data such as POI (Point of Interest) data and Tencent-Yichuxing data, this study assesses and analyzes the epidemic risk and main factors that affect the distribution of COVID-19 on the basis of combining with logistic regression model and geodetector model. What’s more, the following main conclusions are obtained: the high-risk areas of the epidemic are mainly concentrated in the areas with relatively dense permanent population and floating population, which means that the permanent population and floating population are the main factors affecting the risk level of the epidemic. In other words, the reasonable control of population density is greatly conducive to reducing the risk level of the epidemic. Therefore, the control of regional population density remains the key to epidemic prevention and control, and home isolation is also the best means of prevention and control. The precise assessment and analysis of the epidemic conducts by this study is of great significance to maintain urban public health security and achieve the sustainable urban development.

Adjustment of fecundity and sex ratio in response to social environments in a haplodiploid mite

2022 ◽  
Author(s):  
Nuwan Weerawansha ◽  
Qiao Wang ◽  
Xiong Zhao He
Keyword(s):  
Population Density ◽  
Sex Ratio ◽  
Population Size ◽  
Local Population ◽  
Female Offspring ◽  
Social Environments ◽  
Positive Interaction ◽  
Offspring Sex Ratio ◽  
Offspring Sex ◽  
Large Populations

Animals can adjust reproductive strategies in favour of corporation or competition in response to local population size and density, the two key factors of social environments. However, previous studies usually focus on either population size or density but ignore their interactions. Using a haplodiploid spider mite, Tetranychus ludeni Zacher, we carried out a factorial experiment in the laboratory to examine how ovipositing females adjust their fecundity and offspring sex ratio during their early reproductive life under various population size and density. We reveal that females laid significantly more eggs with increasing population size and significantly fewer eggs with increasing population density. This suggests that large populations favour cooperation between individuals and dense populations increase competition. We demonstrate a significant negative interaction of population size and density that resulted in significantly fewer eggs laid in the large and dense populations. Furthermore, we show that females significantly skewed the offspring sex ratio towards female-biased in small populations to reduce the local mate competition among their sons. However, population density incurred no significant impact on offspring sex ratio, while the significant positive interaction of population size and density significantly increased the proportion of female offspring in the large and dense populations, which will minimise food or space competition as females usually disperse after mating at crowded conditions. These results also suggest that population density affecting sex allocation in T. ludeni is intercorrelated with population size. This study provides evidence that animals can manipulate their reproductive output and adjust offspring sex ratio in response to various social environments, and the interactions of different socio-environmental factors may play significant roles.

Eutrophication

1972 ◽  
Vol 180 (1061) ◽  
pp. 371-382 ◽  
Keyword(s):  
Environmental Factors ◽  
Aquatic Ecosystems ◽  
Sewage Effluent ◽  
Large Reduction ◽  
Water Industry ◽  
Detailed Understanding ◽  
Run Off ◽  
Large Populations ◽  
Main Factors ◽  
The Cost

Eutrophication is enrichment by plant nutrients. Here man-made eutrophication is considered. The chief sources of enrichment are sewage, artificial fertilizers and agricultural wastes. Large populations of plants and animals, alive or dead, cause difficulties in the water industry and may interfere with recreation, especially fishing. Most of the phosphorus and nitrogen can be removed from sewage effluent if the cost is justified. A large reduction of agricultural run-off is impractical but some reduction is possible. The removal of polyphosphates from detergents is a palliative but a suitable replacement which does not pose a threat to the environment is not yet on the market. Though the main factors causing eutrophication are well known, there is little detailed understanding of their interaction with other environmental factors. Consequently it is not yet possible to forecast the exact changes to be expected in aquatic ecosystems, a fact which is illustrated by certain changes in two mildly enriched lakes over the last 27 years.

scholarly journals Effects of Supplemental Food on Parental-Care Strategies and Juvenile Survival of Northern Goshawks

The Auk ◽  
2001 ◽  
Vol 118 (2) ◽  
pp. 352-365 ◽  
Author(s):  
Sarah R. Dewey ◽  
Patricia L. Kennedy
Keyword(s):  
Adult Female ◽  
Survival Rates ◽  
Mortality Factor ◽  
Food Supplementation ◽  
Juvenile Survival ◽  
Nest Attendance ◽  
Additional Food ◽  
Supplemental Food ◽  
Risk Of Predation ◽  
Northern Goshawks

Abstract Using food supplementation, we tested whether food limits juvenile survival in a population of Northern Goshawks (Accipiter gentilis) in northeastern Utah. The influence of additional food on female nest attendance also was investigated because those strategies may influence predation mortality rates of juveniles. We provided supplemental food near 13 nests from close to hatching until close to independence during the 1996 and 1997 breeding seasons. Thirteen additional nests served as controls and received no supplemental food. We compared the following variables at treatment and control nests: (1) adult female mass, (2) nestling mass and size, (3) female nest attendance, and (4) juvenile survival. Following supplemental feeding, adult females from treatment nests were heavier than their control counterparts, and remained closer to the nest during the latter part of the nestling period and throughout the postfledging period. Nestlings from supplemented nests were significantly heavier than those from unsupplemented nests, but results for size measurements were equivocal. Survival rates for treatment nestlings were significantly higher than controls in 1997, but not in 1996. Those results support the hypothesis that food does not limit avian reproductive success on an annual basis. Most deaths in 1997 were the result of starvation or sibling competition. That observation, and the fact that fed nestlings were heavier, is consistent with the idea that treatment nestlings were in improved nutritional condition. Overall patterns of mass and nest-attendance for adult female goshawks supports the hypothesis that female condition and behavior are adjusted in response to food supplies. However, it is less clear what role the females' presence in the nest stand plays in mediating juvenile deaths, because we did not document predation as a primary mortality factor during the two years of this study. The apparent flexibility in female nest attendance behavior suggests that such plasticity may be an adaptation to lower the risk of predation.

Influence of alternative mating tactics on predation risk in the damselfly Calopteryx virgo

2009 ◽  
Vol 87 (8) ◽  
pp. 684-688 ◽  
Author(s):  
Tero Toivanen ◽  
Markus J. Rantala ◽  
Jukka Suhonen
Keyword(s):  
Predation Risk ◽  
Mating Behaviour ◽  
Survival Rates ◽  
Habitat Type ◽  
Spatiotemporal Patterns ◽  
Territorial Male ◽  
Alternative Mating Tactics ◽  
Mating Tactics ◽  
Avian Predators ◽  
Large Populations

Alternative mating tactics are a widespread feature in insects. A typical form of alternative mating behaviour is being a sneaker in the vicinity of a territorial male. Such nonterritorial males have lower mating success, but they may benefit from lower energetic costs and decreased predation risk. In this study, we examined whether nonterritorial male damselflies Calopteryx virgo (L., 1758) are subject to lower predation risk than territorial males. To distinguish predation from other sources of mortality, we used models. The experiment consisted of dried male damselflies settled into the typical perching positions of territorial and nonterritorial males. Also the spatiotemporal patterns of predation risk were studied. The survival of nonterritorial male models was consistently higher than that of territorial male models, which can be attributed to different predation risk. Survival of the models was lower in the presence of avian predators and in large populations. Survival rates were affected by habitat type but did not change during the season. We conclude that nonterritorial male damselflies are less vulnerable to predation and that there may be a trade-off which could potentially make the fitness of sneakers equal to that of territorial males.

GIS Based Spatialization of Population Data in Meijiang River Basin

2013 ◽  
Vol 295-298 ◽  
pp. 2378-2383 ◽  
Author(s):  
Xiang Gui Zeng ◽  
Ge Ying Lai ◽  
Fa Zhao Yi ◽  
Ling Ling Zhang
Keyword(s):  
Land Use ◽  
Population Density ◽  
River Basin ◽  
Population Distribution ◽  
Population Data ◽  
Fusion Technology ◽  
Processing Technologies ◽  
Source Data ◽  
Density Map ◽  
Main Factors

This paper used GIS spatial analysis and data processing technologies and multi-source data fusion technology to spatialize the population data of Meijiang river basin. Land use was selected as the index factor and the settlements as the indicative factor. Selected terrain, roads and rivers were the main influencing factors and were further classified into several sub-factors. During the simulation, we first calculated the weight indexes of sub-factors on the settlements distribution and then fused the indexes to calculate the weight indexes of the main factors. Second we calculated the weight indexes of settlements on the population distribution. Last we fused the weight indexes of the main factors and the weight indexes of settlements to obtain the population density indexes of whole region and then generated the 100m×100m resolution raster population density map.

The fall and rise of bison populations in Wood Buffalo National Park: 1971 to 2003

2005 ◽  
Vol 83 (9) ◽  
pp. 1195-1205 ◽  
Author(s):  
Mark Bradley ◽  
John Wilmshurst
Keyword(s):  
National Park ◽  
Census Data ◽  
Disease Incidence ◽  
Population Decline ◽  
Survival Rates ◽  
Bison Bison ◽  
Adult Survival ◽  
Risk Of Predation ◽  
Increased Risk ◽  
Wood Buffalo National Park

Two hypotheses have been proposed to explain the decline of bison (Bison bison (L., 1758)) abundance in Wood Buffalo National Park (WBNP). The "disease–predation" hypothesis proposes that tuberculosis (Mycobacterium bovis (Karlson and Lessel 1970)) and brucellosis (Brucella abortus (Schmidt 1901)) reduce bison survival and reproduction, resulting in a low-density, predator-regulated equilibrium. The "habitat dispersion hypothesis" proposes that bison in one area of WBNP, the Peace–Athabasca Delta (Delta), have an increased risk of predation because they are concentrated in large meadows with high temporal and spatial predictability. We incorporate bison census data, calf and yearling segregation counts, reproductive rates, adult survival rates, and adult disease incidence in a stochastic population model to show that the historical decline of bison in WBNP would have occurred regardless of disease prevalence. Our model shows that survival of juveniles, the age class that is least susceptible to disease effects, was likely an important determinant of historical changes in population size. We also demonstrate that the population decline was most pronounced in the Delta and that juvenile survival was lower in the Delta, despite evidence that disease incidence was lower in the Delta than in the rest of WBNP. Lastly, the current population trend in WBNP is one of rapid increase, even in the presence of disease.

Space use by female agile antechinus: are teat number and home-range size linked?

2016 ◽  
Vol 43 (4) ◽  
pp. 348 ◽  
Author(s):  
Juliey Beckman ◽  
Alan Lill
Keyword(s):  
Population Density ◽  
Home Range ◽  
Food Resource ◽  
Food Abundance ◽  
Energetic Cost ◽  
Home Ranges ◽  
Female Population ◽  
Eastern Australia ◽  
Minimal Convex ◽  
Teat Number

Context The number of teats that a female agile antechinus (Antechinus agilis) possesses effectively determines her initial litter size. In the Otway Ranges, south-eastern Australia, numerous separate populations in which all females have either six or 10 teats occur fairly close together in similar, contiguous forest at comparable altitudes and latitudes. Six-teat and 10-teat females have a similar mean mass, but the latter have a 1.7 × greater reproductive potential and so should have a greater nutritional requirement while raising young than do six-teat females. Theoretically, they could meet this requirement by occupying larger and/or more exclusive home ranges during breeding than do six-teat females do (provided that their food-resource abundance is comparable), albeit at a greater energetic cost. Aims The aim of the study was to determine whether 10-teat A. agilis females occupied larger and less overlapping home ranges than did six-teat females. To interpret the findings more meaningfully, it was necessary to compare food abundance and habitat characteristics in areas occupied by the two phenotypes. Methods The investigation was conducted in six-teat and 10-teat A. agilis areas in cool temperate forest over 22 months. Population density was determined by mark–recapture methods and arthropod prey biomass and abundance by pitfall trapping. Vegetation structure and plant-taxa abundance and diversity were determined by standard plant-survey methods. Female home-range estimates determined by radio-tracking were based on 95% minimal convex polygons (MCP) and kernel analysis. Home-range overlap was based on 80% MCP range determinations and core areas were calculated from utilisation plots. Key results Female population density was 2.5 × lower in exclusively 10-teat than in exclusively six-teat populations. Radio-tracked 10-teat females’ home ranges less commonly overlapped those of identified female neighbours and, on average, were 1.5 × larger than ranges of six-teat females. Food abundance and composition was similar in six-teat and 10-teat areas, but ground cover was denser and more complex in the latter areas. Conclusions Food-resource availability was similar in the six-teat and 10-teat phenotype areas, so the larger, and probably more exclusive, home ranges of 10-teat females could reflect greater nutritional requirements resulting from having larger litters, and account for their lower population density. Implications The A. agilis teat-number variation pattern in the Otways may be a rare, visible example of ongoing incipient speciation. This makes it of great scientific and conservation value and it is important to document how the phenomenon operates.

scholarly journals Spread of new mutations through space

2022 ◽  
Author(s):  
Kyle Shaw ◽  
Peter Beerli
Keyword(s):  
Population Density ◽  
Population Size ◽  
Simulation Software ◽  
Effective Population ◽  
Random Drift ◽  
Rate Of Spread ◽  
Large Populations ◽  
Discrete Population ◽  
Explicit Simulation ◽  
New Mutations

The terms population size and population density are often used interchangeably, when in fact they are quite different. When viewed in a spatial landscape, density is defined as the number of individuals within a square unit of distance, while population size is simply the total count of a population. In discrete population genetics models, the effective population size is known to influence the interaction between selection and random drift with selection playing a larger role in large populations while random drift has more influence in smaller populations. Using a spatially explicit simulation software we investigate how population density affects the flow of new mutations through a geographical space. Using population density, selectional advantage, and dispersal distributions, a model is developed to predict the speed at which the new allele will travel, obtaining more accurate results than current diffusion approximations provide. We note that the rate at which a neutral mutation spreads begins to decay over time while the rate of spread of an advantageous allele remains constant. We also show that new advantageous mutations spread faster in dense populations.

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