scholarly journals Effects of Resource Availability on Population Density of the Chillie Thrips, Scirtothrips dorsalis HOOD (Thysanoptera: Thripidae), on Grape

1997 ◽  
Vol 32 (2) ◽  
pp. 413-415 ◽  
Author(s):  
Manabu SHIBAO
Keyword(s):  
Population Density ◽  
Resource Availability ◽  
Scirtothrips Dorsalis

Spatial and dietary requirements of the chuditch (Dasyurus geoffroii) in a semiarid climatic zone

2012 ◽  
Vol 34 (1) ◽  
pp. 59 ◽  
Author(s):  
Kelly Rayner ◽  
Brian Chambers ◽  
Brent Johnson ◽  
Keith D. Morris ◽  
Harriet R. Mills
Keyword(s):  
Population Density ◽  
Home Range ◽  
Resource Availability ◽  
Climatic Zone ◽  
Generalist Predator ◽  
Home Ranges ◽  
Jarrah Forest ◽  
Semiarid Zone ◽  
Dietary Requirements ◽  
Management Regimes

Knowledge of the ecology of the chuditch (Dasyurus geoffroii) is largely restricted to its distribution in mesic jarrah forests. There is a need for information regarding its ecology in semiarid zones where rainfall and consequently productivity are lower than mesic forests. Given that spatial requirements are strongly influenced by resource availability, it was expected that the chuditch in the semiarid zone would be present at lower densities and would have larger core home ranges (defined by daytime refuges) than those in the jarrah forests. The diet was also investigated by examining the contents of scats. Chuditch at Forrestania were trapped and six individuals were radio-tracked. The population density was one-third that of the lowest estimate reported from the jarrah forest and core home-range estimates were substantially larger, particularly for males. The diet included mammals, birds, reptiles, invertebrates, plants and rubbish, which was consistent with it being a generalist predator. Chuditch did have greater spatial requirements than in the jarrah forest, therefore different management regimes may be needed for populations occurring in the semiarid zone.

scholarly journals What Drives Life-History Variation in the Livebearing Fish Poeciliopsis prolifica? An Assessment of Multiple Putative Selective Agents

2021 ◽  
Vol 8 ◽  
Author(s):  
Andrea J. Roth-Monzón ◽  
Mark C. Belk ◽  
J. Jaime Zúñiga-Vega ◽  
Jerald B. Johnson
Keyword(s):  
Life History ◽  
Population Density ◽  
Interspecific Competition ◽  
Resource Availability ◽  
Life History Traits ◽  
Life History Evolution ◽  
Embryo Size ◽  
Selective Pressures ◽  
Selective Agents ◽  
Livebearing Fish

Life-history traits are directly linked to fitness, and therefore, can be highly adaptive. Livebearers have been used as models for understanding the evolution of life histories due to their wide diversity in these traits. Several different selective pressures, including population density, predation, and resource levels, can shape life-history traits. However, these selective pressures are usually considered independently in livebearers and we lack a clear understanding of how they interact in shaping life-history evolution. Furthermore, selective pressures such as interspecific competition are rarely considered as drivers of life-history evolution in poeciliids. Here we test the simultaneous effects of several potential selective pressures on life-history traits in the livebearing fish Poeciliopsis prolifica. We employ a multi-model inference approach. We focus on four known agents of selection: resource availability, stream velocity, population density, and interspecific competition, and their effect on four life-history traits: reproductive allocation, superfetation, number of embryos, and individual embryo size. We found that models with population density and interspecific competition alone were strongly supported in our data and, hence, indicated that these two factors are the most important selective agents for most life-history traits, except for embryo size. When population density and interspecific competition increase there is an increase in each of the three life-history traits (reproductive allocation, superfetation, and number of embryos). For individual embryo size, we found that all single-agent models were equivalent and it was unclear which selective agent best explained variation. We also found that models that included population density and interspecific competition as direct effects were better supported than those that included them as indirect effects through their influence on resource availability. Our study underscores the importance of interspecific competitive interactions on shaping life-history traits and suggests that these interactions should be considered in future life-history studies.

scholarly journals COVID-19 TRANSMISSION DYNAMICS IN INDIA WITH EXTENDED SEIR MODEL

2020 ◽  
Author(s):  
BRAHMATHEJA REDDY MALI REDDY ◽  
ANUJ SINGH ◽  
PRADEEP SRIVASTAVA
Keyword(s):  
Critical Care ◽  
Population Density ◽  
Resource Availability ◽  
Transmission Dynamics ◽  
Study Analysis ◽  
Population Mobility ◽  
Seir Model ◽  
Early Implementation ◽  
Rate Study ◽  
Critical Patients

India is one of the most harshly affected countries due to COVID epidemic. Early implementation of lockdown protocols were useful to control certain parameters of transmission dynamics, but the numbers are consistently increasing in later months. India population is divided into different clusters on the basis of population density and population mobility, even varying resource availability and since the recent cases are coming from throughout the country, it allows us to model an overall average of the country. In this study, we try to prove the efficiency of using the SEIR epidemiological model for different rate study analysis for COVID epidemic in India. Along with it we derived newer components for better forecast of the pandemic in India. We found that there is a decrease in R0 value, but still the epidemic is not under control. The percentage of infected patients being admitted into ICU for critical care is around 9.986%, while the chances of recovery of critical patients being admitted to the ICU seem to be slim at 79.9% of the admitted being dead.

Reproduction and survival in Melanoplus sanguinipes (Orthoptera: Acrididae) in response to resource availability and population density: the role of exploitative competition

2003 ◽  
Vol 135 (3) ◽  
pp. 415-426 ◽  
Author(s):  
David H. Branson
Keyword(s):  
Individual Differences ◽  
Population Density ◽  
Resource Availability ◽  
Egg Production ◽  
Resource Competition ◽  
Reproductive Allocation ◽  
Exploitative Competition ◽  
Melanoplus Sanguinipes ◽  
Per Capita ◽  
Competition For Resources

AbstractThe relative importance of exploitative competition for resources on grasshopper reproductive allocation has not been fully examined. Given the large fluctuations in grasshopper densities that periodically occur in western North America, an increased understanding of how grasshopper survival and reproduction vary in response to intraspecific densities and per capita resource availability is important. I examined if exploitative resource competition could explain variation in reproductive allocation in Melanoplus sanguinipes (Fabricius) in response to resource availability and grasshopper population density. I also examined whether individual differences in competitive ability resulted in increased variance in egg production with low per capita resource availability. As expected with exploitative resource competition, per capita resource availability explained a significant amount of the variation in all reproductive characteristics examined. There was no effect of per capita resource availability on survival. Residuals of the regressions of egg production and vitellogenesis versus per capita resource availability did not differ for resource or density treatments, indicating that exploitative competition for resources played a more important role than interference competition in determining reproductive allocation in M. sanguinipes. Individual differences were evident, as variation around the mean of egg production increased with resource limitation. Exploitative competition for resources was important in determining both individual and population-level reproductive responses of grasshoppers to resource availability.

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