Population dynamics and environemental changes during natural irruptions of Australian desert rodents.

1994 ◽  
Vol 21 (5) ◽  
pp. 569 ◽  
Author(s):  
M Predavec
Keyword(s):  
Population Dynamics ◽  
Sand Dune ◽  
Temporal Trend ◽  
Time Lag ◽  
High Turnover ◽  
Seed Availability ◽  
Temporal Correlations ◽  
Desert Rodents ◽  
Over Time ◽  
Population Numbers

Populations of Pseudomys hermannsburgensis and Notomys alexis were studied during a 33-month period (January 1991 to September 1993) in a sand-dune habitat in south-western Queensland. Population numbers of both species fluctuated dramatically over time with an approximately 40-fold difference between periods of lowest and highest abundance. Increased numbers were due primarily to an influx of juveniles to the population. A high turnover of individuals in both populations resulted in low rates of recapture. Numbers of both species were correlated positively with an index of rainfall with a time-lag of four months. P. hermannsburgensis showed spatial and temporal correlations with seed availability, whereas N. alexis displayed a strong, but non-significant, temporal trend with seed availability. These data suggest strongly that natural irruptions of Australian desert rodents are triggered by rainfall and possibly rain-induced food availability.

Population dynamics and habitat use of the long-haired rat (Rattus villosissimus) in south-western Queensland

1994 ◽  
Vol 21 (1) ◽  
pp. 1 ◽  
Author(s):  
M Predavec ◽  
CR Dickman
Keyword(s):  
Population Dynamics ◽  
Habitat Use ◽  
Food Availability ◽  
Sand Dune ◽  
Population Decline ◽  
Radio Tracking ◽  
Spatial Activity ◽  
Secondary Role ◽  
Population Numbers

A population of Rattus villosissimus was studied during an 18-month period in a sand-dune habitat in south-western Queensland. The population numbers fluctuated dramatically during this time. Increases in population numbers were due primarily to immigration, with reproduction playing a secondary role. Rain-induced increases in food availability are the most likely stimuli for these increases. The cause of population decline is not clear from this study, but predation and disease may be important factors. Radio-tracking showed that the spatial activity of the animals was concentrated on the sides of the dunes, and around burrows. Temporal activity is influenced by moonlight, with animals remaining in burrows for long periods of time on bright nights.

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.

scholarly journals Trends in cause-specific readmissions in heart failure with preserved versus reduced and mid-range ejection fraction

2020 ◽  
Vol 41 (Supplement_2) ◽  
Author(s):  
X.T Cui ◽  
E Thunstrom ◽  
U Dahlstrom ◽  
J.M Zhou ◽  
J.B Ge ◽  
...  
Keyword(s):  
Heart Failure ◽  
Ejection Fraction ◽  
Temporal Trend ◽  
Funding Source ◽  
Preserved Ejection Fraction ◽  
Readmission Rates ◽  
P Values ◽  
National Board ◽  
Over Time

Abstract Background It remains unclear whether the readmission of heart failure (HF) patients has decreased over time and how it differs among HF with preserved ejection fraction (EF) (HFpEF) versus reduced EF (HFrEF) and mid-range EF (HFmrEF). Methods We evaluated HF patients index hospitalized from January 2004 to December 2011 in the Swedish Heart Failure Registry with 1-year follow-up. Outcome measures were the first occurring all-cause, cardiovascular (CV) and HF readmissions. Results Totally 20,877 HF patients (11,064 HFrEF, 4,215 HFmrEF, 5,562 HFpEF) were included in the study. All-cause readmission was highest in patients with HFpEF, whereas CV and HF readmissions were highest in HFrEF. From 2004 to 2011, HF readmission rates within 6 months (from 22.3% to 17.3%, P=0.003) and 1 year (from 27.7% to 23.4%, P=0.019) in HFpEF declined, and the risk for 1-year HF readmission in HFpEF was reduced by 7% after adjusting for age and sex (P=0.022). Likewise, risk factors for HF readmission in HFpEF changed. However, no significant changes in cause-specific readmissions were observed in HFrEF. Time to the first readmission did not change significantly from 2004 to 2011, regardless of EF subgroup (all P-values>0.05). Conclusions Although the burden of all-cause readmission remained highest in HFpEF versus HFrEF and HFmrEF, a declining temporal trend in 6-month and 1-year HF readmission rates was found in patients with HFpEF, suggesting that non-HF-related readmission represents a big challenge for clinical practice. Funding Acknowledgement Type of funding source: Foundation. Main funding source(s): The SwedeHF was funded by the Swedish National Board of Health and Welfare, the Swedish Association of Local Authorities and Regions.

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.

scholarly journals The dynamics of questing ticks collected for 164 consecutive months off the vegetation of two landscape zones in the Kruger National Park (1988–2002). Part II. Rhipicephalus appendiculatus and Rhipicephalus zambeziensis

2011 ◽  
Vol 78 (1) ◽  
Author(s):  
Arthur M. Spickett ◽  
Gordon J. Gallivan ◽  
Ivan G. Horak
Keyword(s):  
Population Dynamics ◽  
Relative Humidity ◽  
National Park ◽  
Rhipicephalus Appendiculatus ◽  
Kruger National Park ◽  
Large Herbivore ◽  
Questing Ticks ◽  
Over Time

The study aimed to assess the long-term population dynamics of questing Rhipicephalus appendiculatus and Rhipicephalus zambeziensis in two landscape zones of the Kruger National Park (KNP). Ticks were collected by dragging the vegetation monthly in three habitats (grassland, woodland and gully) at two sites in the KNP (Nhlowa Road and Skukuza) from August 1988 to March 2002. Larvae were the most commonly collected stage of both species. More R. appendiculatus were collected at Nhlowa Road than at Skukuza, with larvae being most abundant from May to August, while nymphs were most abundant from August to December. Larvae were most commonly collected in the gullies from 1991 to 1994, but in the grassland and woodland habitats from 1998 onwards. Nymphs were most commonly collected in the grassland and woodland. More R. zambeziensis were collected at Skukuza than at Nhlowa Road, with larvae being most abundant from May to September, while nymphs were most abundant from August to November. Larvae and nymphs were most commonly collected in the woodland and gullies and least commonly in the grassland (p < 0.01). The lowest numbers of R. appendiculatus were collected in the mid-1990s after the 1991/1992 drought. Rhipicephalus zambeziensis numbers declined after 1991 and even further after 1998, dropping to their lowest levels during 2002. The changes in numbers of these two species reflected changes in rainfall and the populations of several of their large herbivore hosts, as well as differences in the relative humidity between the two sites over time.

scholarly journals Evolution of Cultural Identity Terms in Lay and Academic Sources: Implications for Research and Public Policy

2017 ◽  
Author(s):  
Roxanne Moadel-Attie ◽  
Sheri R. Levy ◽  
Bonita London ◽  
Rami Al-Rfou
Keyword(s):  
Public Policy ◽  
Social Identity ◽  
Cultural Identity ◽  
Time Lag ◽  
Computational Techniques ◽  
Psychosocial Experiences ◽  
The Social ◽  
Usage Patterns ◽  
Google Books ◽  
Over Time

Increasingly, individuals identify as bicultural and multicultural, yet are sometimes externally misclassified, contributing to experiences of invisibility within U.S. society. Using computational techniques, we examined the transmission of cultural identity terms through time, providing some evidence for the changing representation of social identity. We examined the usage patterns of cultural identity terms with the prefixes (mono-, bi-, multi-), modifying the social identity terms: culture, ethnicity, and race (e.g., comparing monocultural, monoethnic and monoracial). For bicultural and multicultural terms, those with -racial suffixes were the earliest used terms, while those with -cultural and -ethnic suffixes gained more popularity recently. We examined the evolution of the higher frequency social identity terms in lay sources (NY Times, Reddit), and found that interracial and multicultural were the most popular over time, peaking recently. We examined the potential time lag in the sequence of identity terms amongst academic (PsycINFO, NIH and NSF Databases), lay (NY Times) and mixed sources (Google Books N-Grams), supporting our hypothesis that newer terms (e.g., multicultural) are first used and gain prevalence in lay sources, then mixed sources, and eventually academic sources. The implications of these findings for research, public policy and psychosocial experiences of individuals are discussed.

scholarly journals Quantifying the relationship between lockdowns, mobility, and effective reproduction number (Rt) during the COVID-19 pandemic in the Greater Toronto Area

2021 ◽  
Vol 21 (1) ◽  
Author(s):  
Christopher Dainton ◽  
Alexander Hay
Keyword(s):  
Public Health ◽  
Secular Trend ◽  
Reproduction Number ◽  
Time Lag ◽  
Correlation Coefficients ◽  
Greater Toronto Area ◽  
Global Mobility ◽  
The Relationship ◽  
Second Wave ◽  
Over Time

Abstract Background The effectiveness of lockdowns in mitigating the spread of COVID-19 has been the subject of intense debate. Data on the relationship between public health restrictions, mobility, and pandemic growth has so far been conflicting. Objective We assessed the relationship between public health restriction tiers, mobility, and COVID-19 spread in five contiguous public health units (PHUs) in the Greater Toronto Area (GTA) in Ontario, Canada. Methods Weekly effective reproduction number (Rt) was calculated based on daily cases in each of the five GTA public health units between March 1, 2020, and March 19, 2021. A global mobility index (GMI) for each PHU was calculated using Google Mobility data. Segmented regressions were used to assess changes in the behaviour of Rt over time. We calculated Pearson correlation coefficients between GMI and Rt for each PHU and mobility regression coefficients for each mobility variable, accounting for time lag of 0, 7, and 14 days. Results In all PHUs except Toronto, the most rapid decline in Rt occurred in the first 2 weeks of the first province-wide lockdown, and this was followed by a slight trend to increased Rt as restrictions decreased. This trend reversed in all PHUs between September 6th and October 10th after which Rt decreased slightly over time without respect to public health restriction tier. GMI began to increase in the first wave even before restrictions were decreased. This secular trend to increased mobility continued into the summer, driven by increased mobility to recreational spaces. The decline in GMI as restrictions were reintroduced coincides with decreasing mobility to parks after September. During the first wave, the correlation coefficients between global mobility and Rt were significant (p < 0.01) in all PHUs 14 days after lockdown, indicating moderate to high correlation between decreased mobility and decreased viral reproduction rates, and reflecting that the incubation period brings in a time-lag effect of human mobility on Rt. In the second wave, this relationship was attenuated, and was only significant in Toronto and Durham at 14 days after lockdown. Conclusions The association between mobility and COVID-19 spread was stronger in the first wave than the second wave. Public health restriction tiers did not alter the existing secular trend toward decreasing Rt over time.

scholarly journals Population Dynamics and Tree Damage of the Invasive Chestnut Gall Wasp, Dryocosmus kuriphilus, in Its Southernmost European Distributional Range

Insects ◽  
2021 ◽  
Vol 12 (10) ◽  
pp. 900
Author(s):  
Javier Quinto ◽  
María Eva Wong ◽  
Juan Ramón Boyero ◽  
José Miguel Vela ◽  
Martin Aguirrebengoa
Keyword(s):  
Population Dynamics ◽  
Control Mechanisms ◽  
Gall Wasp ◽  
Local Conditions ◽  
Tree Damage ◽  
Dryocosmus Kuriphilus ◽  
Distributional Range ◽  
The Status ◽  
Spatio Temporal ◽  
Over Time

The invasive chestnut gall wasp (CGW), Dryocosmus kuriphilus, the worst pest of chestnut cultivation, has spread worryingly throughout Europe in less than 20 years. Despite the great concern around this pest, little is known about the status in its southernmost distribution in continental Europe. We assessed spatio-temporal patterns in the population dynamics, phenology and tree damage caused by CGW in southern Spain. Likewise, the relationship between these variables and thermal trends was evaluated. We found strong variation in the population dynamics and flight phenology among localities and over time, which were highly influenced by changes in thermal regimes. Specifically, warmer localities and vegetative periods promoted higher population densities, a partial increase in the survival of immature stages, and advanced flight activity. Moreover, tree damage evolved differently over time in each locality, which suggests that local conditions may determine differences in damage evolution. Our findings evidence that great spatio-temporal variability in the CGW populations takes place across invaded areas in its southernmost European distributional range. Although control mechanisms have been introduced, implementation of further control and management measures are critical to cope with this main threat for the chestnut industry and to prevent its spread to nearing chestnut-producing areas.

scholarly journals Hippocampus-dependent emergence of spatial sequence coding in retrosplenial cortex

2018 ◽  
Vol 115 (31) ◽  
pp. 8015-8018 ◽  
Author(s):  
Dun Mao ◽  
Adam R. Neumann ◽  
Jianjun Sun ◽  
Vincent Bonin ◽  
Majid H. Mohajerani ◽  
...  
Keyword(s):  
Population Dynamics ◽  
Spatial Learning ◽  
Calcium Imaging ◽  
Place Cell ◽  
Retrosplenial Cortex ◽  
Population Code ◽  
Spatial Activity ◽  
Cellular Calcium ◽  
Hippocampal Lesions ◽  
Over Time

Retrosplenial cortex (RSC) is involved in visuospatial integration and spatial learning, and RSC neurons exhibit discrete, place cell-like sequential activity that resembles the population code of space in hippocampus. To investigate the origins and population dynamics of this activity, we combined longitudinal cellular calcium imaging of dysgranular RSC neurons in mice with excitotoxic hippocampal lesions. We tracked the emergence and stability of RSC spatial activity over consecutive imaging sessions. Overall, spatial activity in RSC was experience-dependent, emerging gradually over time, but, as seen in the hippocampus, the spatial code changed dynamically across days. Bilateral but not unilateral hippocampal lesions impeded the development of spatial activity in RSC. Thus, the emergence of spatial activity in RSC, a major recipient of hippocampal information, depends critically on an intact hippocampus; the indirect connections between the dysgranular RSC and the hippocampus further indicate that hippocampus may exert such influences polysynaptically within neocortex.

Integral projection models

2021 ◽  
pp. 181-196
Author(s):  
Edgar J. González ◽  
Dylan Z. Childs ◽  
Pedro F. Quintana-Ascencio ◽  
Roberto Salguero-Gómez
Keyword(s):  
Population Dynamics ◽  
Environmental Variables ◽  
Linear Models ◽  
Vital Rates ◽  
Matrix Population Models ◽  
Generalised Linear Models ◽  
Integral Projection Models ◽  
Integral Projection ◽  
Over Time

Integral projection models (IPMs) allow projecting the behaviour of a population over time using information on the vital processes of individuals, their state, and that of the environment they inhabit. As with matrix population models (MPMs), time is treated as a discrete variable, but in IPMs, state and environmental variables are continuous and are related to the vital rates via generalised linear models. Vital rates in turn integrate into the population dynamics in a mechanistic way. This chapter provides a brief description of the logic behind IPMs and their construction, and, because they share many of the analyses developed for MPMs, it only emphasises how perturbation analyses can be performed with respect to different model elements. The chapter exemplifies the construction of a simple and a more complex IPM structure with an animal and a plant case study, respectively. Finally, inverse modelling in IPMs is presented, a method that allows population projection when some vital rates are not observed.

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