Population density of the eastern pygmy-possum in a heath–woodland habitat

2017 ◽  
Vol 65 (6) ◽  
pp. 391 ◽  
Author(s):  
Ross L. Goldingay ◽  
Jo Keohan
Keyword(s):  
Population Dynamics ◽  
Population Density ◽  
Population Models ◽  
Mark Recapture ◽  
Nest Boxes ◽  
Patchy Habitats ◽  
Cercartetus Nanus ◽  
Over Time

The eastern pygmy-possum (Cercartetus nanus) has posed a challenge in attempts to describe its population density due to low rates of capture, preference for patchy habitats and periodic influxes of subadult individuals. We conducted a mark–recapture study of this species using a grid of nest boxes in a 9-ha patch of banksia heath–woodland. We captured 54 adults across the two years of our study. We estimated the density of adult pygmy-possums to be 1.5–4.2 ha–1 from different population models. This is substantially lower than previous estimates in equivalent habitat because we focussed on adults and recognised that they were not confined to the area bounded by our grid. We captured 36 subadults over the two years but they could not be reliably modelled due to extremely low recapture rates, which reflect high rates of dispersal and also mortality. For this reason, only the number of adults should be used to characterise populations of this species. Further study is required to investigate population dynamics over time and to describe the density of eastern pygmy-possums in other habitats.

scholarly journals Within and among-population variation in vital rates and population dynamics in a variable environment

2015 ◽  
Author(s):  
Simone Vincenzi ◽  
Marc Mangel ◽  
Dusan Jesensek ◽  
John Carlos Garza ◽  
Alain J Crivelli
Keyword(s):  
Population Dynamics ◽  
Population Density ◽  
Debris Flows ◽  
Life Histories ◽  
Population Variation ◽  
Population Differences ◽  
Vital Rates ◽  
Marble Trout ◽  
Over Time

Understanding the causes of within- and among-population differences in vital rates, life histories, and population dynamics is a central topic in ecology. To understand how within- and among-population variation emerges, we need long-term studies that include episodic events and contrasting environmental conditions, data to characterize individual and shared variation, and statistical models that can tease apart population-, shared-, and individual contribution to the observed variation. We used long-term tag-recapture data and novel statistical and modeling techniques to investigate and estimate within- and among-population differences in vital rates, life histories and population dynamics of marble trout Salmo marmoratus, a endemic freshwater salmonid with a narrow range. Only ten populations of pure marble trout persist in headwaters of Alpine rivers in western Slovenia. Marble trout populations are also threatened by floods and landslides, which have caused the extinction of two populations in recent years. We estimated and determined causes of variation in growth, survival, and recruitment both within and among populations, and evaluated trade-offs between them. Specifically, we estimated the responses of these traits to variation in water temperature, density, sex, early life conditions, and the occurrence of extreme climatic events (e.g., flash floods and debris flows). We found that the effects of population density on traits were mostly limited to the early stages of life and that individual growth trajectories were established early in life. We found no clear effects of water temperature on survival and recruitment. Population density varied over time, with flash floods and debris flows causing massive mortalities and threatening population persistence. Apart from flood events, variation in population density within streams was largely determined by variation in recruitment, with survival of older fish being relatively constant over time within populations, but substantially different among populations. Marble trout show a fast to slow continuum of life histories, with slow growth associated with higher survival at the population level, possibly determined by food conditions and age at maturity. Our work provides unprecedented insight into the causes of variation in vital rates, life histories, and population dynamics in an endemic species that is teetering on the edge of extinction.

Introduction to Population Models

2021 ◽  
pp. 25-46
Author(s):  
Timothy E. Essington
Keyword(s):  
Population Dynamics ◽  
Population Density ◽  
Population Size ◽  
Population Models ◽  
Change Model ◽  
Density Dependent ◽  
Intrinsic Factors ◽  
Model Understanding ◽  
Dynamics Of Populations ◽  
Simple Models

The chapter “Introduction to Population Models” introduces unstructured population models and shows how model decisions can change model behavior, the different ways that feedbacks can be represented, and how one evaluates the consequences of those feedbacks. The goal here is to show how modeling a single entity, population density, can be done in many different ways, depending on the purpose of the model. Understanding the dynamics of populations remains one of the fundamental goals of ecology. Not surprisingly, many models have contributed to the theory of population dynamics and regulation. The models vary considerably in terms of depth, breadth, intended uses (e.g. prediction vs. generality), and structure. This chapter will largely focus on the behavior of simple models, to see how intrinsic factors can dictate variability in population size. Density-independent and density-dependent models are covered, as well as methods used to understand model behaviors.

scholarly journals Characteristics and Demography of a Free-Ranging Ethiopian Hedgehog, Paraechinus aethiopicus, Population in Qatar

Animals ◽  
2020 ◽  
Vol 10 (6) ◽  
pp. 951
Author(s):  
Carly Pettett ◽  
David W. Macdonald ◽  
Afra Al-Hajiri ◽  
Hayat Al-Jabiry ◽  
Nobuyuki Yamaguchi
Keyword(s):  
Population Dynamics ◽  
Population Characteristics ◽  
Term Survival ◽  
Mark Recapture ◽  
Long Term Survival ◽  
Search Area ◽  
One Year ◽  
Free Ranging ◽  
Over Time

Information on population characteristics of Paraechinusis is valuable for ensuring long term survival of populations, however, studies are currently lacking. Here we investigate the population dynamics of Ethiopian hedgehogs based on a capture-mark-recapture study in Qatar by fitting Jolly-Seber and Cormack-Jolly-Seber models. Over the 19 months of the study, we estimate a mean population of 60 hedgehogs, giving a density of 7 hedgehogs per km2 in our 8.5 km2 search area. The monthly abundance of hedgehogs decreased over the study and although survival was constant over the study period, with a mean monthly rate of 75%, there was a decline in the number of new entrants over time. We also studied these parameters over one year, excluding winter, and found that monthly estimates of juvenile and subadult survival decreased over time. We surmise that survival of juveniles may be a factor in the decrease in abundance and there may be implications for the persistence of this population, with anthropogenic influenced resources playing an important role. We caught between 91.3% and 100% of the estimated population at this site, indicating that our capture methodology was efficient. We conclude that the methodology used here is transferrable to other hedgehog species.

Population dynamics of Hemicycliophora conida as affected by different temperatures and absence of hosts

Nematology ◽  
2020 ◽  
Vol 22 (9) ◽  
pp. 975-983
Author(s):  
Eliyeh Ganji ◽  
Christina Hieronymus ◽  
Maria R. Finckh ◽  
Johannes Hallmann ◽  
Jan H. Schmidt
Keyword(s):  
Population Dynamics ◽  
Population Density ◽  
Host Plant ◽  
Initial Density ◽  
Reproduction Rate ◽  
Base Temperature ◽  
Meloidogyne Hapla ◽  
Root Knot Nematode ◽  
Time Required ◽  
Over Time

Summary The effects of temperature and absence of a host plant on the population dynamics of the sheath nematode, Hemicycliophora conida, were studied under glasshouse conditions. Regarding temperature, population dynamics of H. conida on tomato ‘Moneymaker’ were monitored weekly over a period of 12 weeks. In the first experiment, with an average temperature of 21.4°C, population growth of H. conida continuously increased over time from an initial density of 106 nematodes (100 ml soil)−1 to a final density of 820 nematodes (100 ml soil)−1, resulting in a reproduction rate of 7.7. The time required to complete one generation was 6.5 weeks or 598 temperature degree days at 8°C base temperature (TDD8). A second experiment showed that the development of H. conida on tomato was faster at 22.1°C than at 19.0°C. At 22.1°C, one generation was completed after 6 weeks (= 588 TDD8) compared to 8 weeks (=634 TDD8) at 19.0°C. The higher temperature also resulted in a higher reproduction rate (93 at 22.1°C vs 7.8 at 19.0°C). In the absence of a host plant, the population density of H. conida decreased over time. However, this natural decline was less pronounced than for the root-knot nematode Meloidogyne hapla. In the first experiment, the population density of H. conida decreased within 18 weeks by 89.5%, while M. hapla was already no longer detectable 12 weeks after inoculation. In the second experiment, H. conida decreased by 98.2% within 16 weeks compared to 99.98% for M. hapla.

scholarly journals POPULATION DYNAMICS, AGGLOMERATION ECONOMIES AND MUNICIPAL SIZE: A LONG-TERM ANALYSIS

2020 ◽  
Vol 11 (1) ◽  
Author(s):  
Maria Teresa CIOMMI ◽  
laria ZAMBON ◽  
Luca SALVATI
Keyword(s):  
Population Dynamics ◽  
Spatial Distribution ◽  
Population Density ◽  
Spatial Heterogeneity ◽  
Goodness Of Fit ◽  
Basic Knowledge ◽  
Optimal Size ◽  
Administrative Units ◽  
Over Time

Under the hypothesis that modifications in municipal boundaries and creation (or suppression) of new administrative units reflect a progressive adjustment toward a more balanced distribution of population over space, the present study investigates the long-term relationship (1928-2012) between urban expansion, population dynamics and municipal area in a growing metropolitan region (Athens, Greece). In expanding regions, municipal size is a key variable outlining the amount and spatial concentration of services and infrastructures, resulting to be functionally related to population density, agglomeration factors, land availability to building and characteristic socioeconomic profiles of local communities. A statistical analysis of the relationship between population density and municipal area provides basic knowledge to policy and planning adjustments toward a more balanced spatial distribution of population and land among the local government units. Descriptive statistics, mapping, correlation analysis and linear regressions were used to assess the evolution of such relationship over a sufficiently long time period. The average municipal area in Athens decreased moderately over time, with a slight increase in spatial heterogeneity. Conversely, the average population density per municipality increased more rapidly, with a considerable reduction in spatial heterogeneity. The observed goodness-of-fit of the linear relationship between population density and municipal area increased significantly over time. The empirical results of our study indicate that municipal size has progressively adjusted to population density across metropolitan areas, determining a more balanced spatial distribution of the resident population, which was consolidated by the recent administrative reform of the local authorities in Greece (the so called ‘Kallikratis’ law). Such conditions represent a base for the informed analysis of the spatial structure of local administrative units and they contribute to the debate on the optimal size of municipalities and other administrative districts with relevant impact on both urban and metropolitan scales of governance.

scholarly journals Analysis of 220 Years of Floodplain Population Dynamics in the US at Different Spatial Scales

Water ◽  
2021 ◽  
Vol 13 (2) ◽  
pp. 141
Author(s):  
Firoza Akhter ◽  
Maurizio Mazzoleni ◽  
Luigia Brandimarte
Keyword(s):  
Population Dynamics ◽  
Large Scale ◽  
Spatial Scales ◽  
National Level ◽  
State Level ◽  
Economic Activities ◽  
Protection Measures ◽  
Management Planning ◽  
The Us ◽  
Over Time

In this study, we explore the long-term trends of floodplain population dynamics at different spatial scales in the contiguous United States (U.S.). We exploit different types of datasets from 1790–2010—i.e., decadal spatial distribution for the population density in the US, global floodplains dataset, large-scale data of flood occurrence and damage, and structural and nonstructural flood protection measures for the US. At the national level, we found that the population initially settled down within the floodplains and then spread across its territory over time. At the state level, we observed that flood damages and national protection measures might have contributed to a learning effect, which in turn, shaped the floodplain population dynamics over time. Finally, at the county level, other socio-economic factors such as local flood insurances, economic activities, and socio-political context may predominantly influence the dynamics. Our study shows that different influencing factors affect floodplain population dynamics at different spatial scales. These facts are crucial for a reliable development and implementation of flood risk management planning.

Canadian Exceptionalism: Explaining Differences over Time in Provincial and Federal Voter Turnout

2001 ◽  
Vol 34 (2) ◽  
pp. 299-319 ◽  
Author(s):  
Donley T. Studlar
Keyword(s):  
Regression Analysis ◽  
Population Density ◽  
Multiple Regression Analysis ◽  
Voter Turnout ◽  
The Political ◽  
Federal Level ◽  
Industrial Democracies ◽  
Different Types ◽  
Over Time ◽  
Cross National

Canada is unusual among advanced industrial democracies in having some provinces which regularly have greater voter turnouts for provincial than for federal elections. Provincial and federal turnouts by province in Canada are analyzed for the 1945-1998 period using multiple regression analysis, both for each set of elections and by comparing differences between the two. Federal turnout has declined over the years but provincial turnout appears to have increased slightly. Although the effects found here largely confirm previous findings about the relative effects of different types of variables found for the Canadian federal level only, several of the political explanations previously supported in cross-national research find less support. Instead, region, population density, months since the last federal or provincial election, and season of the year generally have greater and sometimes more consistent effects. This suggests the need for more studies of turnout in democracies at sub-central levels.

Effects of crop sequence and rainfall on population dynamics of Fusarium solani f.sp. phaseoli in soil

1992 ◽  
Vol 70 (10) ◽  
pp. 2005-2008 ◽  
Author(s):  
Robert Hall ◽  
Lana Gay Phillips
Keyword(s):  
Population Dynamics ◽  
Phaseolus Vulgaris ◽  
Population Density ◽  
Fusarium Solani ◽  
Population Densities ◽  
Total Rainfall ◽  
Colony Forming Units ◽  
Bean Crop ◽  
Previous Summer ◽  
Crop Sequence

Evidence is presented that population dynamics of Fusarium solani f.sp. phaseoli in soil depend on the effects of crop sequence and rainfall on parasitic activities of the pathogen. In a rotation trial started in 1978 and conducted over 14 years, population densities (colony-forming units/g) of the fungus in soil remained below 50 in treatments (fallow, repeated corn, repeated soybean) where the preferred host plant (common bean, Phaseolus vulgaris) was not grown. Where bean was grown every 3rd year or every year, population densities reached 475 and 660, respectively, by 1984. Thereafter, population densities of the fungus fluctuated widely from year to year in both rotation and repeated bean treatments. In the rotation treatment, peaks in population density of the pathogen coincided with the years of bean production. In repeated bean plots between 1985 and 1991, population density of the fungus in June was significantly correlated (r = 0.77, p = 0.04) with total rainfall received during the previous summer (June–August). It is postulated that higher rainfall during the growing season of the bean crop stimulated root growth and root infection, leading to the accumulation of higher levels of potential inoculum in infected tissue and the release of higher levels of inoculum into the soil by the following June. Key words: Fusarium solani f.sp. phaseoli, bean, Phaseolus vulgaris, rainfall, crop rotation.

PREDATION BY INSECTS AND SPIDERS INHABITING COLONIAL WEBS OF HYPHANTRIA CUNEA

1972 ◽  
Vol 104 (8) ◽  
pp. 1197-1207 ◽  
Author(s):  
R. F. Morris
Keyword(s):  
Population Dynamics ◽  
Nova Scotia ◽  
North America ◽  
Population Density ◽  
New Brunswick ◽  
Numerical Response ◽  
Initial Number ◽  
Hyphantria Cunea ◽  
The North ◽  
The Mean

AbstractThe number of predators inhabiting nests of Hyphantria cunea Drury was recorded annually for 13 years in four areas in New Brunswick and two areas on the coast of Nova Scotia. The most common groups were the pentatomids and spiders, which sometimes reproduced within the nests, but the mean number per nest was low in relation to the number of H. cunea larvae in the colonies. The rate of predation on fifth-instar larvae was low. Small or timid predators appeared to prey largely on moribund larvae or small saprophagans during the principal defoliating instars of H. cunea.No relationship could be detected between the number of larvae reaching the fifth instar and the number of predators in the colony; nor could any functional or numerical response of the predators to either the initial number of larvae per colony or the population density of colonies be found. It is concluded that the influence of the nest-inhabiting predators is small and relatively stable, and may be treated as a constant in the development of models to explain the population dynamics of H. cunea.H. cunea is a pest in parts of Europe and Asia, where it has been accidentally introduced from North America. The introduction to other continents of the North American predator, Podisus maculiventiis (Say), is discussed briefly.

scholarly journals The influence of microhabitat on the population dynamics of four herbaceous species in a semiarid area of northeastern Brazil

2016 ◽  
Vol 76 (1) ◽  
pp. 45-54 ◽  
Author(s):  
K. A. Silva ◽  
J. M. F. F. Santos ◽  
J. R. Andrade ◽  
E. N. Lima ◽  
U. P. Albuquerque ◽  
...  
Keyword(s):  
Population Dynamics ◽  
Population Size ◽  
Mortality Rates ◽  
Dry Forest ◽  
Northeastern Brazil ◽  
Annual Rainfall ◽  
Herbaceous Species ◽  
Forest Fragment ◽  
Experimental Station ◽  
Over Time

Abstract Variation in annual rainfall is considered the most important factor influencing population dynamics in dry environments. However, different factors may control population dynamics in different microhabitats. This study recognizes that microhabitat variation may attenuate the influence of climatic seasonality on the population dynamics of herbaceous species in dry forest (Caatinga) areas of Brazil. We evaluated the influence of three microhabitats (flat, rocky and riparian) on the population dynamics of four herbaceous species (Delilia biflora, Commelina obliqua, Phaseolus peduncularis and Euphorbia heterophylla) in a Caatinga (dry forest) fragment at the Experimental Station of the Agronomic Research Institute of Pernambuco in Brazil, over a period of three years. D. biflora, C. obliqua and P. peduncularis were found in all microhabitats, but they were present at low densities in the riparian microhabitat. There was no record of E. heterophylla in the riparian microhabitat. Population size, mortality rates and natality rates varied over time in each microhabitat. This study indicates that different establishment conditions influenced the population size and occurrence of the four species, and it confirms that microhabitat can attenuate the effect of drought stress on mortality during the dry season, but the strength of this attenuator role may vary with time and species.

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