scholarly journals Variation in space and time: a long-term examination of density-dependent dispersal in a woodland rodent

2019 ◽  
Author(s):  
Simon T. Denomme-Brown ◽  
Karl Cottenie ◽  
J. Bruce Falls ◽  
E. Ann Falls ◽  
Ronald J. Brooks ◽  
...  
Keyword(s):  
Time Series ◽  
Population Density ◽  
Local Density ◽  
Spatial Scales ◽  
Deer Mice ◽  
Population Densities ◽  
Density Dependent ◽  
Regional Population ◽  
The Relationship ◽  
Density Dependent Dispersal

AbstractDispersal is a fundamental ecological process that can be affected by population density, yet studies report contrasting effects of density on propensity to disperse. Additionally, the relationship between dispersal and density is seldom examined using densities measured at different spatial scales or over extensive time-series. We used 51-years of trapping data to examine how dispersal by wild deer mice (Peromyscus maniculatus) was affected by changes in both local and regional population densities. We examined these patterns over both the entire time-series and also in ten-year shifting windows to determine whether the nature and strength of the relationship changed through time. Probability of dispersal decreased with increased local and regional population density, and the negative effect of local density on dispersal was more pronounced in years with low regional densities. Additionally, the strength of negative density-dependent dispersal changed through time, ranging from very strong in some decades to absent in other periods of the study. Finally, while females were less likely to disperse, female dispersal was more density-dependent than male dispersal. Our study shows that the relationship between density and dispersal is not temporally static and that investigations of density-dependent dispersal should consider both local and regional population densities.

Variability in Grouping in the Eastern Grey Kangaroo, Macropus giganteus I. Group Density and Group Size

1984 ◽  
Vol 11 (3) ◽  
pp. 423 ◽  
Author(s):  
CJ Southwell
Keyword(s):  
Seasonal Variation ◽  
Population Density ◽  
Group Size ◽  
Spatial Dispersion ◽  
Population Densities ◽  
Forest Habitat ◽  
Open Forest ◽  
Grey Kangaroo ◽  
Group Density ◽  
The Relationship

The effects of season, population density and habitat on group density and group size in the eastern grey kangaroo were examined. In an open forest habitat, both group density and group size increased significantly with population density, but no seasonal variation was detected for either parameter. The relationship with population density was logarithmic for group density and exponential for group size. In a tall shrubland habitat both group density and group size increased with population density, but the range of population densities sampled was too narrow for the nature of the relationships to be determined. Group density was significantly higher, and group size significantly lower, in the tall shrubland than in the open forest. Possible reasons for this difference in spatial dispersion between habitats are discussed.

scholarly journals Incidence, Population Density, and Spatial Heterogeneity of Plant-Parasitic Nematodes in Corn Fields in Ohio

Plant Disease ◽  
2018 ◽  
Vol 102 (12) ◽  
pp. 2453-2464 ◽  
Author(s):  
Abasola C. M. Simon ◽  
Horacio D. Lopez-Nicora ◽  
Laura E. Lindsey ◽  
Terry L. Niblack ◽  
Pierce A. Paul
Keyword(s):  
Population Density ◽  
Spatial Scales ◽  
Management Strategies ◽  
Parasitic Nematodes ◽  
Growth Stages ◽  
Plant Parasitic Nematodes ◽  
Population Densities ◽  
Sampling Protocols ◽  
Corn Fields ◽  
Plant Parasitic

Soil samples were collected from 425 corn fields in 28 Ohio counties between growth stages V3 and V6 during the 2013 and 2014 growing seasons. Ten morphological groups of plant-parasitic nematodes, namely spiral, lesion, lance, dagger, stunt, pin, ring, stubby-root, cyst, and “tylenchids” (several genera morphologically similar to members of the subfamily Tylenchinae [NCBI Taxonomy] including Cephelenchus, Filenchus, Malenchus, and Tylenchus) were identified. Eight species belonging to six of these groups were characterized. Spiral, tylenchids, lesion, pin, lance, stunt, and dagger nematodes were detected in 94, 96, 80, 57, 48, 48, and 37% of the fields, respectively, whereas the stubby-root, cyst, and ring nematodes were present in fewer than 14% of the samples. Averaged across fields, the spiral, tylenchids, and pin nematodes had the highest mean population densities. For all groups, incidence and population density varied among counties, and in some cases, among soil regions and cropping practices. Both population parameters were heterogeneous at multiple spatial scales, with the lowest heterogeneity among soil regions and the highest among fields within county and soil region. Estimated variances at the soil region level were not significantly different from zero for most of the nematodes evaluated. Stunt and lance were two of the most variable groups at all tested spatial scales. In general, the population densities were significantly more heterogeneous at the field level than at the county level. Findings from this study will be useful for developing sampling protocols and establishing on-farm trials to estimate losses and evaluate nematode management strategies.

scholarly journals The relationship between anthropogenic dust and population over global semi-arid regions

2016 ◽  
Vol 16 (8) ◽  
pp. 5159-5169 ◽  
Author(s):  
Xiaodan Guan ◽  
Jianping Huang ◽  
Yanting Zhang ◽  
Yongkun Xie ◽  
Jingjing Liu
Keyword(s):  
Population Density ◽  
Arid Regions ◽  
Population Change ◽  
Dominant Role ◽  
Positive Contribution ◽  
Regional Population ◽  
Semi Arid Region ◽  
The Impact ◽  
The Relationship ◽  
Semi Arid

Abstract. Although anthropogenic dust has received more attention from the climate research community, its dominant role in the production process is still not identified. In this study, we analysed the relationship between anthropogenic dust and population density/change over global semi-arid regions and found that semi-arid regions are major source regions in producing anthropogenic dust. The results showed that the relationship between anthropogenic dust and population is more obvious in cropland than in other land cover types (crop mosaics, grassland, and urbanized regions) and that the production of anthropogenic dust increases as the population density grows to more than 90 persons km−2. Four selected semi-arid regions, namely East China, India, North America, and North Africa, were used to explore the relationship between anthropogenic dust production and regional population. The most significant relationship between anthropogenic dust and population occurred in an Indian semi-arid region that had a greater portion of cropland, and the high peak of anthropogenic dust probability appeared with 220 persons km−2 of population density and 60 persons km−2 of population change. These results suggest that the influence of population on production of anthropogenic dust in semi-arid regions is obvious in cropland regions. However, the impact does not always have a positive contribution to the production of anthropogenic dust, and overly excessive population will suppress the increase of anthropogenic dust. Moreover, radiative and climate effects of increasing anthropogenic dust need more investigation.

USING RADIOCARBON DATA TO CHRONOLOGICALLY CONTROL POPULATION DENSITY ESTIMATES DERIVED FROM SYSTEMATICALLY COLLECTED INTRA-SETTLEMENT DISTRIBUTIONAL DATA

Radiocarbon ◽  
2020 ◽  
pp. 1-21
Author(s):  
Brandon T Ritchison
Keyword(s):  
Population Density ◽  
Important Variable ◽  
Archaeological Sites ◽  
Archaeological Record ◽  
Population Densities ◽  
Density Estimates ◽  
Archaeological Material ◽  
Radiocarbon Data ◽  
Regional Population ◽  
Fine Time

ABSTRACT Population density is an important variable in the development of social complexity. Estimating population densities from the archaeological record requires combining estimates of population, area, and time. Archaeological population estimates tend to be reported as a maximum population derived from the total accumulation of discrete archaeological material types, usually ceramics or radiocarbon (14C) dates. However, given the palimpsest nature of the archaeological record at recurrently occupied archaeological sites, these maximal, total estimates are, at best, a poor reflection of contemporaneous populations. I present a method for calculating average yearly population densities for occupations at a large, multicomponent site using a combination of distributional data and 60 14C dates. By employing this method at other sites in the same region, modeling intra-regional population dynamics at fine time scales will be possible.

scholarly journals Lack of Anonymity and Secondary Traumatic Stress in Rural Nurses

2021 ◽  
Vol 21 (1) ◽  
pp. 183-201
Author(s):  
Marilyn A. Swan ◽  
Barbara B. Hobbs
Keyword(s):  
Population Density ◽  
Traumatic Stress ◽  
Secondary Traumatic Stress ◽  
Secondary Trauma ◽  
Health Care Facilities ◽  
Population Densities ◽  
Rural Nursing ◽  
The Social ◽  
Rural Nurses ◽  
The Relationship

Purpose:  The purpose was to determine the prevalence of lack of anonymity (LA) and secondary traumatic stress (STS) among nurses; determine if nurses’ LA and STS differ by population density and examine the relationship between lack of anonymity and STS. Design and Method:  A descriptive correlational study examined LA and STS in a random sample of 271 nurses from counties with differing population densities (rural, micropolitan and metropolitan) of a Midwestern US State.  A 3-group design was used to examine the relationship between LA and STS in nurses, living and working in these counties. Data on lack of anonymity, secondary trauma and demographics were collected through online questionnaires.   Findings:  Rural nurses had a higher prevalence of LA than micropolitan and metropolitan nurses.  While the prevalence of STS among rural nurses was higher than either micropolitan or metropolitan nurses; there was no difference in STS among the three population groups.  Lack of anonymity and STS were related; however, analysis revealed that LA and STS are inversely correlated, indicating that as LA increases, STS decreases.  A majority of rural nurses (90%) reported living in a rural community prior to their 18th birthday. Conclusions:  Rural nurses experience STS at similar rates as their metropolitan and micropolitan counterparts, indicating that population density may not be a factor related to the development of STS. LA appears to have a positive effect on reducing STS in rural nurses. Clinical Relevance:  The study advanced the understanding of LA and STS among nurses who live and work in different population densities.  The social support within rural health care facilities and communities may play a role in mitigating the effects of indirect stress. Keywords: rural, rural nursing, lack of anonymity, traumatic stressDOI:  https://doi.org/10.14574/ojrnhc.v21i1.651  

scholarly journals A Two-Component Regulator Mediates Population-Density-Dependent Expression of the Bradyrhizobium japonicum Nodulation Genes

2002 ◽  
Vol 184 (6) ◽  
pp. 1759-1766 ◽  
Author(s):  
John Loh ◽  
Dasharath P. Lohar ◽  
Brett Andersen ◽  
Gary Stacey
Keyword(s):  
Gene Expression ◽  
Population Density ◽  
Conditioned Medium ◽  
Bradyrhizobium Japonicum ◽  
Response Regulator ◽  
High Population ◽  
Wild Type ◽  
Population Densities ◽  
Density Dependent ◽  
Culture Density

ABSTRACT Bradyrhizobium japonicum nod gene expression was previously shown to be population density dependent. Induction of the nod genes is highest at low culture density and repressed at high population densities. This repression involves both NolA and NodD2 and is mediated by an extracellular factor found in B. japonicum conditioned medium. NolA and NodD2 expression is maximal at high population densities. We demonstrate here that a response regulator, encoded by nwsB, is required for the full expression of the B. japonicum nodYABC operon. In addition, NwsB is also required for the population-density-dependent expression of both nolA and nodD2. Expression of nolA and nodD2 in the nwsB mutant remained at a basal level, even at high culture densities. The nwsB defect could be complemented by overexpression of a second response regulator, NodW. Consistent with the fact that NolA and NodD2 repress nod gene expression, the expression of a nodY-lacZ fusion in the nwsB mutant was unaffected by culture density. In plant assays with GUS fusions, nodules infected with the wild type showed no nodY-GUS expression. In contrast, nodY-GUS expression was not repressed in nodules infected with the nwsB mutant. Nodule competition assays between the wild type and the nwsB mutant revealed that the addition of conditioned medium resulted in a competitive advantage for the nwsB mutant.

scholarly journals Apparent negative density-dependent dispersal in tsetse (Glossina spp) is an artefact of inappropriate analysis

2020 ◽  
Author(s):  
John W. Hargrove ◽  
John Van Sickle ◽  
Glyn A. Vale ◽  
Eric R. Lucas
Keyword(s):  
Genetic Material ◽  
Population Estimates ◽  
Effective Population ◽  
Population Densities ◽  
Density Dependent ◽  
Rate Of Increase ◽  
Fundamental Misunderstanding ◽  
Geographic Separation ◽  
Density Dependent Dispersal

AbstractAnalysis of genetic material from field-collected tsetse (Glossina spp) in ten study areas has been used to predict that the distance (δ) dispersed per generation increases as effective population densities (De) decrease, displaying negative density dependent dispersal (NDDD). This result is an artefact arising primarily from errors in estimates of S, the area occupied by a subpopulation, and thereby in De, the effective subpopulation density. The fundamental, dangerously misleading, error lies in the assumption that S can be estimated as the area (Ŝ) regarded as being covered by traps. Errors in the estimates of δ are magnified because variation in estimates of S is greater than for all other variables measured, and accounts for the greatest proportion of variation in δ. The errors result in anomalously high correlations between δ and S, and the appearance of NDDD, with a slope of −0.5 for the regressions of log(δ) on log(e), even in simulations where dispersal has been set as density independent. A complementary mathematical analysis confirms these findings. Improved error estimates for the crucial parameter b, the rate of increase in genetic distance with increasing geographic separation, suggest that three of the study areas should have been excluded because b is not significantly greater than zero. Errors in census population estimates result from a fundamental misunderstanding of the relationship between trap placement and expected tsetse catch. These errors are exacerbated through failure to adjust for variations in trapping intensity, trap performance, and in capture probabilities between geographical situations and between tsetse species. Claims of support in the literature for NDDD are spurious. There is no suggested explanation for how NDDD might have evolved. We reject the NDDD hypothesis and caution that the idea should not be allowed to influence policy on tsetse and trypanosomiasis control.Author summaryGenetic analysis of field-sampled tsetse (Glossina spp) has been used to suggest that, as tsetse population densities decrease, rates of dispersal increase – displaying negative density dependent dispersal (NDDD). It is further suggested that NDDD might apply to all tsetse species and that, consequently, tsetse control operations might unleash enhanced invasion of areas cleared of tsetse, prejudicing the long-term success of control campaigns. We demonstrate that NDDD in tsetse is an artefact consequent on multiple errors of analysis and interpretation. The most serious of these errors stems from a fundamental misunderstanding of the way in which traps sample tsetse, resulting in huge errors in estimates of the areas sampled by the traps, and occupied by the subpopulations being sampled. Errors in census population estimates are made worse through failure to adjust for variations in trapping intensity, trap performance, and in capture probabilities between geographical situations, and between tsetse species. The errors result in the appearance of NDDD, even in modelling situations where rates of dispersal are expressly assumed independent of population density. We reject the NDDD hypothesis and caution that the idea should not be allowed to influence policy on tsetse and trypanosomiasis control.

scholarly journals Density dependence on multiple spatial scales maintains spatial variation in both abundance and traits

2019 ◽  
Author(s):  
Koen J. van Benthem ◽  
Meike J. Wittmann
Keyword(s):  
Population Density ◽  
Spatial Variation ◽  
Local Density ◽  
Fitness Function ◽  
Spatial Scales ◽  
Mutual Effect ◽  
Equilibrium Density ◽  
Mate Finding ◽  
Density Patch

AbstractPopulation density affects fitness through various processes, such as mate finding and competition. The fitness of individuals in a population can in turn affect its density, making population density a key quantity linking ecological and evolutionary processes. Density effects are, however, rarely homogeneous. Different life-history processes can be affected by density over different spatial scales. In birds, for example, competition for food may depend on the number of birds nesting in the direct vicinity, while competition for nesting sites may occur over larger areas. Here we investigate how the effects of local density and of density in nearby patches can jointly affect the emergence of spatial variation in abundance as well as phenotypic diversification. We study a two-patch model that is described by coupled ordinary differential equations. The patches have no intrinsic differences: they both have the same fitness function that describes how an individual’s fitness depends on density in its own patch as well as the density in the other patch. We use a phase-space analysis, combined with a mathematical stability analysis to study the long-term behaviour of the system. Our results reveal that the mutual effect that the patches have on each other can lead to the emergence and long-term maintenance of a low and a high density patch. We then add traits and mutations to the model and show that different selection pressures in the high and low density patch can lead to diversification between these patches. Via eco-evolutionary feedbacks, this diversification can in turn lead to changes in the long-term population densities: under some parameter settings, both patches reach the same equilibrium density when mutations are absent, but different equilibrium densities when mutations are allowed. We thus show how, even in the absence of differences between patches, interactions between them can lead to differences in long-term population density, and potentially to trait diversification.

The relation of population densities of the antagonist, Laetisaria arvalis, to seedling diseases of table beet incited by Pythium ultimum

1986 ◽  
Vol 32 (2) ◽  
pp. 156-159 ◽  
Author(s):  
S. Bruce Martin ◽  
G. S. Abawi ◽  
H. C. Hoch
Keyword(s):  
Low Temperature ◽  
Population Density ◽  
Disease Incidence ◽  
Pythium Ultimum ◽  
Quadratic Model ◽  
Damping Off ◽  
Population Densities ◽  
Field Soils ◽  
Laetisaria Arvalis ◽  
The Relationship

Sclerotia of Laetisaria arvalis were added to raw or steamed table beet field soils infested with Pythium ultimum and other low-temperature Pythium spp. to determine the relationship between soil population densities of the antagonist to disease incidence. Decrease in disease incidence of table beet seedlings and final Pythium spp. inoculum densities were linearly related to increasing population density of the antagonist in raw field soils. In P. ultimum infested steamed soils, decreasing disease incidence was also related to increasing population densities of L. arvalis, but the relationship was curvilinear and was described by a quadratic model. The latter models also described the decrease in P. ultimum inoculum densities with increasing levels of the antagonist. Percentages of healthy plants (those surviving the pre- and post-emergence damping-off disease phases) were increased approximately 20% in raw soils containing 100 sclerotia of L. arvalis per gram soil in comparison with those of unamended soils. However, in Pythium infested steamed soils, percentages of healthy plants in soil amended with 100 sclerotia of L. arvalis per gram soil were increased by 40–60%.

Mucuna deeringiana (Bort) Merr. vs. the corm weevil, Cosmopolites sordidus Germar (Coleoptera: Curculionidae), in plantains

1969 ◽  
Vol 89 (3-4) ◽  
pp. 201-210
Author(s):  
Amparo Salazar ◽  
Alberto Pantoja ◽  
Juan Ortiz
Keyword(s):  
Population Dynamics ◽  
Population Density ◽  
Management Practices ◽  
Production Costs ◽  
Cosmopolites Sordidus ◽  
Adult Density ◽  
High Population Density ◽  
Population Densities ◽  
Insect Density ◽  
The Relationship

The effect of the legume Mucuna deeringiana on Cosmopolites sordidus population dynamics and damage was studied in two planting systems: intercropping with mucuna and mucuna as green mulch before establishing the plantain. The relationship between C. sordidus adult density and larval damage was also studied. The presence of M. deeringiana affected the incidence of C. sordidus.The data suggest that C. sordidus adults are attracted by M. deeringiana, but additional studies are needed to better understand the relationship between the legume and the insect. The presence of M. deeringiana did not affect plantain height, stem diameter, or sucker production if the legume was eliminated four months after planting. However, management practices to establish and cultivate the legume increased production costs. Although C. sordidus population densities were low during most of the year, a high population density was recorded from November to January. A second population explosion was recorded between June and August. The highest insect density recorded was 3.5 insects per trap.

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