Variation In Population Density Research Articles

SURVIVAL CAPACITY OF Arcobacter butzleri INOCULATED IN POULTRY MEAT AT TWO DIFFERENT REFRIGERATION TEMPERATURES.

Arcobacter spp. are emerging enteropathogens and potential zoonotic agents that can be transmitted by food and water, being considered a public health risk. The high isolation rate of these bacteria from poultry products suggests that it may be a major source of human infections. One hallmark for differentiating the genus Arcobacter fromCampylobacter includes their growing capacity at low temperatures (15-30 °C) under aerobic conditions. However, little is known about the population density variation of these bacteria at different refrigeration temperatures. The aim of this study was to determine the survival behavior of two different Arcobacter butzleri concentrations (104 CFU/mL and 107 CFU/mL) inoculated on chicken legs and held at two different refrigeration temperatures (4 and 10 °C) throughout storage time. Results have shown that A. butzleri had growing capacity both at 4 and 10 °C. No statistical difference between the survival trends was found for both bacterial concentrations and temperatures tested. This study shows that A. butzleri is a robust species with regard to storage temperature, and represents a potential health risk for poultry meat consumers.

Kajian Isu Pemekaran di Kota Medan: Tinjauan Berdasarkan Kondisi Ketimpangan Wilayah

<p class="Abstract"><em>Generally, disparities between regions and inter-regions happened because of concentration, agglomeration, external factors, globalization, internal factor, grouping, critical growth or polar development, institution involvement in economic activities. Initially development in Medan concentrated in several sub districts as the center of government and trade activities. Based on long-term development plan of Medan 2006-2025, stated that development policy in Medan not notice of the regional gap. Disparities development between north and south of Medan are the problems for segregation issue at fourth sub-districts in the northern part of Medan. The purpose of this research is to analyze the gap condition in economic, social demography and the infrastructure’s service in Medan related to the emergence of segregation issue in North Medan. The analysis that used in research is descriptive statistic analysis, analysis of statistical correlation, crosstab analysis, and verification of statistic results using interview method so that at the end of the research will be generated economic, social demography and infrastructure services index for every sub-district in the Medan to know the development difference. </em><em>The result of correlation analysis shows that there was a correlation between disparity and segregation issue. Descriptive analysis produce the index for 4 sub districts in north side have the medium category while 17 sub districts in the south have a good category. Crosstab analysis shows that there is a correlation between disparities condition and the emergence of segregation issue. Crosstab analysis also shows that variable education facilities (senior high school), population density, and labor variables show the disparity condition significantly.</em></p>

Spatial variation in osteon population density at the human femoral midshaft: histomorphometric adaptations to habitual load environment.

Intracortical remodeling, and the osteons it produces, is one aspect of the bone microstructure that is influenced by and, in turn, can influence its mechanical properties. Previous research examining the spatial distribution of intracortical remodeling density across the femoral midshaft has been limited to either considering only small regions of the cortex or, when looking at the entirety of the cortex, considering only a single individual. This study examined the spatial distribution of all remodeling events (intact osteons, fragmentary osteons, and resorptive bays) across the entirety of the femoral midshaft in a sample of 30 modern cadaveric donors. The sample consisted of 15 males and 15 females, aged 21-97years at time of death. Using geographic information systems software, the femoral cortex was subdivided radially into thirds and circumferentially into octants, and the spatial location of all remodeling events was marked. Density maps and calculation of osteon population density in cortical regions of interest revealed that remodeling density is typically highest in the periosteal third of the bone, particularly in the lateral and anterolateral regions of the cortex. Due to modeling drift, this area of the midshaft femur has some of the youngest primary tissue, which consequently reveals that the lateral and anterolateral regions of the femoral midshaft have higher remodeling rates than elsewhere in the cortex. This is likely the result of tension/shear forces and/or greater strain magnitudes acting upon the anterolateral femur, which results in a greater amount of microdamage in need of repair than is seen in the medial and posterior regions of the femoral midshaft, which are more subject to compressive forces and/or lesser strain magnitudes.

Existence of spatial patterns in reaction–diffusion systems incorporating a prey refuge

Abstract. In real-world ecosystem, studies on the mechanisms of spatiotemporal pattern formation in a system of interacting populations deserve special attention for its own importance in contemporary theoretical ecology. The present investigation deals with the spatial dynamical system of a two-dimensional continuous diffusive predator–prey model involving the influence of intra-species competition among predators with the incorporation of a constant proportion of prey refuge. The linear stability analysis has been carried out and the appropriate condition of Turing instability around the unique positive interior equilibrium point of the present model system has been determined. Furthermore, the existence of the various spatial patterns through diffusion-driven instability and the Turing space in the spatial domain have been explored thoroughly. The results of numerical simulations reveal the dynamics of population density variation in the formation of isolated groups, following spotted or stripe-like patterns or coexistence of both the patterns. The results of the present investigation also point out that the prey refuge does have significant influence on the pattern formation of the interacting populations of the model under consideration.

Variability in Population Density Is Paralleled by Large Differences in Foraging Efficiency in Chimpanzees (Pan troglodytes)

The assumption that population density restricts the foraging efficiency of individuals in the population via increased competition for resources underpins socioecological models of female social relationships in primates. We examined this assumption by comparing quantitative measures of foraging efficiency in two communities of chimpanzees (Pan troglodytes schweinfurthii) that inhabit the same contiguous forest in Kibale National Park, Uganda, but differ substantially in size and density. To calculate net caloric gain rates (our measure of foraging efficiency) we obtained data directly from focal follows of individual chimpanzees on 1) residency time in a feeding patch, 2) feeding rate in the patch, 3) the nutrient content of the items fed upon, and 4) the distance walked between feeding patches. We collected foraging efficiency data over 1059 h at Ngogo and 961 h at Kanyawara. We found that individuals in the high-density community (Ngogo) had higher mean foraging efficiency values than those in the low-density community (Kanyawara), and that foraging efficiency varied less over time at Ngogo when assessed over the time scales of individual feeding/traveling bouts and of daily net caloric gain rates. Fluctuation in net caloric gain rates on a monthly time scale was greater at Ngogo than at Kanyawara, but this was likely due to the nutritional effects of a mast fruiting event by one of the most important species at the site. These findings suggest that high population density at Ngogo has not precluded high foraging efficiency. The classic view of increased population density inevitably increasing feeding competition and reducing foraging efficiency likely underemphasizes the ability of primates, especially those in rich habitats, to maximize caloric intake.

Diffusion-driven instabilities and emerging spatial patterns in patchy landscapes

Spatial variation in population densities across a landscape is a feature of many ecological systems, from self-organised patterns on mussel beds to spatially restricted insect outbreaks. It occurs as a result of environmental variation in abiotic factors and/or biotic factors structuring the spatial distribution of populations. However the ways in which abiotic and biotic factors interact to determine the existence and nature of spatial patterns in population density remain poorly understood. Here we present a new approach to studying this question by analysing a predator–prey patch-model in a heterogenous landscape. We use analytical and numerical methods originally developed for studying nearest-neighbour (juxtacrine) signalling in epithelia to explore whether and under which conditions patterns emerge. We find that abiotic and biotic factors interact to promote pattern formation. In fact, we find a rich and highly complex array of coexisting stable patterns, located within an enormous number of unstable patterns. Our simulation results indicate that many of the stable patterns have appreciable basins of attraction, making them significant in applications. We are able to identify mechanisms for these patterns based on the classical ideas of long-range inhibition and short-range activation, whereby landscape heterogeneity can modulate the spatial scales at which these processes operate to structure the populations.

Ecology of Conus on Seychelles reefs at mid-twentieth century: comparative habitat use and trophic roles of co-occurring congeners

This comparative ecological study of 33 species of the predatory gastropod Conus in coral reef-associated habitats in Seychelles emphasizes variation in species composition, diversity, and population density with environmental attributes, and use of food and space resources by co-occurring congeners. Topographically simple but physically harsh intertidal benches supported eight or nine species of generally small body size [mean shell length (SL) 22 mm] but relatively high population density (0.2 m−2). Structurally more complex, physically benign, subtidal coral reef platforms supported more species (7–19, mean = 12) of much broader size range and larger mean SL (41 mm), but at lower population densities (0.02–0.14 m−2). Most species (85 %) preyed on polychaete worms. One preyed exclusively on a hemichordate worm, two on fishes, and three on gastropods. In general, species specialized more on different prey taxa than different microhabitats. These results are generally consistent with those previously reported for Conus spp. assemblages in similar habitats elsewhere in the tropical Indo-Pacific. They support the hypotheses that (1) resource partitioning, especially of food resources but also of microhabitats, facilitates assemblages of numerous co-occurring Conus spp. and their avoidance of interspecific competition, and (2) ecological differentiation has contributed importantly to the striking Cenozoic adaptive radiation of Conus. The fieldwork, in 1957–1958, also provides baseline data for future studies of how changing marine environmental conditions affect coral reef-associated biotas.

Population structure and dispersal patterns in Scottish Golden Eagles Aquila chrysaetos revealed by molecular genetic analysis of territorial birds

Conservation management of species distributed across fragmented habitats requires consideration of population genetic structure and relative levels of genetic diversity throughout the relevant geographical range. The Golden Eagle Aquila chrysaetos is monitored within Scotland to ensure its survival in the face of land‐use pressure, persecution and future climate change. In this study we constructed DNA profiles for 271 individual birds using a collection of over 1600 moulted feathers collected from 148 territories, representing 34% of known Scottish territories in the largest population genetic study of Golden Eagles undertaken to date. The results, based on data from 10 nuclear microsatellite loci, revealed previously unreported genetic structure between the islands of the Outer Hebrides and the rest of Scotland (FST = 0.03), together with evidence of reduced genetic diversity in the Outer Hebridean population compared with mainland Scotland. Analysis of gene flow supports a hypothesis of limited, predominantly male‐mediated, dispersal from the Outer Hebrides to mainland Scotland. The persistence of this pattern is discussed with respect to variation in population density and persecution pressure across Scotland. A finding of non‐random mating within the Outer Hebrides is interpreted as evidence of natal philopatry that was revealed by more intensive sampling in these islands, and is likely to be accentuated by the apparent degree of isolation of the islands from the rest of Scotland.

Molecular and functional characteristics of streptomycete communities in relation to soil factors and potato common scab

Naturally-occurring disease-suppressive soils provide control of plant pathogens via the activities of indigenous microbes. While all soils contain antagonistic microbes, there is little systematic understanding of the correlates of variation in indigenous antagonist populations and on their relationships with plant diseases. We characterized the population densities, inhibitory capacities, and phylogenetic composition of soil streptomycete communities in a potato field over time in relation to edaphic factors, antagonist inoculation, and potato common scab severities. Antagonistic Streptomyces populations were highly variable in time and space. Similarly, metagenomic analyses of streptomycete communities showed extensive spatial and temporal variation in composition. Soil characteristics (pH, potassium, organic matter, nitrate, and phosphorous) sometimes explained up to 50% of the spatial variation in Streptomyces population densities, proportion of inhibitory isolates, or pathogen suppressive capacity among locations in the field. Soil pH was positively correlated with common scab severity, and negatively correlated with the proportion of pathogen-inhibitory Streptomyces among locations in the field. This suggests that high pH may have direct beneficial effects on pathogen populations and disease development, and/or indirect effects on pathogen populations via reductions in pathogen-inhibitory Streptomyces populations. Mean pathogen suppressive capacity of antagonistic Streptomyces was negatively correlated with common scab disease. Streptomyces inoculants had no discernible effect on streptomycete community composition, antagonistic capacities, or potato common scab severities, likely reflecting poor colonization of inoculants. Further understanding of the relationships between indigenous antagonist populations and plant diseases will be important to harnessing the potential of indigenous communities to contribute to sustainable disease management.

Genetic diversity and gene flow within and between two different habitats ofPrimula merrilliana(Primulaceae), an endangered distylous forest herb in eastern China

Understanding whether and how different habitats shape population genetics is a fundamental question and a specific goal for evolutionary and conservation biology research. This study examined genetic diversity and gene flow within and between mountain and foothill habitats of Primula merrilliana, an endangered distylous forest herb in eastern China. Eleven population characteristics, including area, size and density variation, from the two habitats were also investigated. Mountain populations had significantly higher mean genetic diversity than foothill populations, which may be explained by stronger self-incompatibility breeding system, more opportunity to use elevational shifts to track suitable sites under conditions of climate change and more heterogeneous environments in the former habitat, rather than by the differences of population size, gene flow and genetic drift intensity between them. Genetic analysis revealed that two distinct lineages, corresponding to the two habitats, diverged at China's ‘Last Glaciation’ (11 700–67 500 yr BP), suggesting this divergence was probably triggered by warmer climates during inter- (or post-) glacial periods. Low unidirectional gene flow from mountain to foothill habitats, chiefly by seed dispersal, played a more important role in overall gene flow between habitats than within-habitat gene flow. Within habitats, pollen contributes more substantially to gene flow than seed dispersal, especially in foothill habitats, possibly due to higher individual density and larger population sizes. These results have implications for the conservation in this and similar landscape areas and indicate the need to protect suitable habitats with wide elevational spans and sufficient size to permit ecological and elevational shifts in response to climatic changes.

Mega-regions in the Philippines: Accounting for special economic zones and global-local dynamics

Mega-regions have emerged as ‘new engines’ of global economic growth, characterized by incessant movement of global and local capital. Considering this, this study offers a spatiodemographic approach that defines mega-regions beyond static state-delimited urban boundaries, and considers the global-local dynamics that underlie its formations. Focusing on the Philippines, one of the fastest growing economies in Southeast Asia, we discuss emergent mega-regions and analyze their recent and future trajectories using municipal-level demographic variables (population density, percentage change across Censal years 1990, 2000, 2010) along with special economic zones. Results show the rise of multiple mega-regions in varying degrees of spatial expansion and development from the mega-conurbation of Metro Manila and surrounding regions to emergent provincial mega-regions. Also, the patterns of special economic zones illustrate the spatial expressions of globalization in restructuring mega-regional landscapes in the Philippines. The paper hopes to encourage urban analyses that seek ways of theorizing and accounting for mobilities and global-local networks to guide socially just and sustainable planning.

Detectability of landscape effects on recolonization increases with regional population density.

Variation in population size over time can influence our ability to identify landscape-moderated differences in community assembly. To date, however, most studies at the landscape scale only cover snapshots in time, thereby overlooking the temporal dynamics of populations and communities. In this paper, we present data that illustrate how temporal variation in population density at a regional scale can influence landscape-moderated variation in recolonization and population buildup in disturbed habitat patches. Four common insect species, two omnivores and two herbivores, were monitored over 8 years in 10 willow short-rotation coppice bio-energy stands with a four-year disturbance regime (coppice cycle). The population densities in these regularly disturbed stands were compared to densities in 17 undisturbed natural Salix cinerea (grey willow) stands in the same region. A time series approach was used, utilizing the natural variation between years to statistically model recolonization as a function of landscape composition under two different levels of regional density. Landscape composition, i.e. relative amount of forest vs. open agricultural habitats, largely determined the density of re-colonizing populations following willow coppicing in three of the four species. However, the impact of landscape composition was not detectable in years with low regional density. Our results illustrate that landscape-moderated recolonization can change over time and that considering the temporal dynamics of populations may be crucial when designing and evaluating studies at landscape level.

Spatial variation in population density affects dispersal behavior in brush mice

Population density can influence all three phases of natal dispersal: departure from the place of birth, searching the landscape, and selecting a new site in which to settle. The direction of the effect of density on dispersal should be affected by the relative costs and benefits of living in an area with high population density. Animals may benefit from high population density due to mate availability and predator risk dilution, but may also face increased competition in high density areas. These conflicting mechanisms should influence the pattern of change in population density between pre‐ and post‐dispersal locations: do dispersing individuals choose to move to areas of higher or lower population density than that at their natal site? We examined the influence of density on dispersal in brush mice (Peromyscus boylii). We documented pre‐ and post‐dispersal locations of individuals using both radio telemetry and live‐trapping, and used a spatially explicit capture–recapture model to estimate density across the landscape. We also tested for a relationship between dispersal distance and local population density at the natal site. Animals tended to settle in areas with higher population densities than where they were born. This pattern held when landscape‐level changes in population density were incorporated: the magnitude of change in local population density between the pre‐ and post‐dispersal locations of a given individual tended to be greater than would be explained by increasing population density across the landscape alone. Further, dispersal distances were shorter when local natal population density was higher.

Interactions between density, home range behaviors, and contact rates in the Channel Island fox (Urocyon littoralis).

Many of the mechanisms underlying density-dependent regulation of populations, including contest competition and disease spread, depend on contact among neighboring animals. Understanding how variation in population density influences the frequency of contact among neighboring animals is therefore an important aspect to understanding the mechanisms underlying, and ecological consequences of, density-dependent regulation. However, contact rates are difficult to measure in the field and may be influenced by density through multiple pathways. This study explored how local density affects contact rates among Channel Island foxes (Urocyon littoralis) through two pathways: changes in home range size and changes in home range overlap. We tracked 40 radio-collared foxes at four sites on San Clemente Island, California. Fox densities at the four sites ranged from 2.8 ± 1.28 to 42.8 ± 9.43 foxes/km2. Higher fox densities were correlated with smaller home ranges (R2 = 0.526, F1,38 = 42.19, P < 0.001). Thirty foxes wore collars that also contained proximity loggers, which recorded the time and duration of occasions when collared foxes were within 5 m of one another. Contact rates between neighboring fox dyads were positively correlated with home range overlap (R2 = 0.341, P = 0.008), but not fox density (R2 = 0.012, P = 0.976). Individuals at high densities had more collared neighbors with overlapping home ranges (R2 = 0.123, P = 0.026) but not an increase in the amount of contact between individual neighbors. This study was the first time contact rates were directly measured and compared to density and home range overlap. Results suggest that foxes exhibit a threshold in their degree of tolerance for neighbors, overlap is a reliable index of the amount of direct contact between island foxes, and disease transmission rates will likely scale with fox density.

Latitudinal variations in biometry and population density of a Mediterranean solitary coral

AbstractCorrelations between solar radiation, sea surface temperature (SST), biometry, and population density were assessed along a wide latitudinal gradient in the non‐zooxanthellate solitary coral Caryophyllia inornata. Biometric parameters were more strongly correlated with temperature than with solar radiation as in previous studies on Mediterranean solitary corals. With increasing SST, populations were characterized by bigger polyps, and consequently by a higher percent area coverage and mass per square meter. Population abundance was not correlated with SST, similarly to the non‐zooxanthellate solitary Leptopsammia pruvoti. Instead, the population density of the zooxanthellate solitary Balanophyllia europaea decreases with increasing SST. When extrapolating the relationships between biological parameters of the three species and SST, according to the projected seawater temperature increase, a higher tolerance to temperature for non‐zooxanthellate species seems to be confirmed.

New record of some freshwater mussels (Bivalvia: Unionidae) from north-east Bangladesh

A total of 6 species of freshwater mussels under the family Unionidae, order- Unionoida were collected, which are new records for Bangladesh. The information on the distribution and ecology, population density and seasonal variation of Lamellidens phenchooganjensis, L. indawgyiensis, L. generosus, Parreysia (Parreysia) favidens var. assamensis, P. (P.) var. marcens and P. (P.) var. viridula were provided in this paper. Population density and morphometric parameters were measured. Moreover, economic importance and economic role were stated.Bangladesh J. Zool. 41(1): 29-42, 2013

Sample and population exponents of generalized Taylor’s law

Taylor's law (TL) states that the variance V of a nonnegative random variable is a power function of its mean M; i.e., V = aM(b). TL has been verified extensively in ecology, where it applies to population abundance, physics, and other natural sciences. Its ubiquitous empirical verification suggests a context-independent mechanism. Sample exponents b measured empirically via the scaling of sample mean and variance typically cluster around the value b = 2. Some theoretical models of population growth, however, predict a broad range of values for the population exponent b pertaining to the mean and variance of population density, depending on details of the growth process. Is the widely reported sample exponent b ≃ 2 the result of ecological processes or could it be a statistical artifact? Here, we apply large deviations theory and finite-sample arguments to show exactly that in a broad class of growth models the sample exponent is b ≃ 2 regardless of the underlying population exponent. We derive a generalized TL in terms of sample and population exponents b(jk) for the scaling of the kth vs. the jth cumulants. The sample exponent b(jk) depends predictably on the number of samples and for finite samples we obtain b(jk) ≃ k = j asymptotically in time, a prediction that we verify in two empirical examples. Thus, the sample exponent b ≃ 2 may indeed be a statistical artifact and not dependent on population dynamics under conditions that we specify exactly. Given the broad class of models investigated, our results apply to many fields where TL is used although inadequately understood.

Seasonal variations of population density of root knot nematode, Meloidogyne incognita as affected by different cropping sequences

Seasonal variations of population density of root knot nematode, Meloidogyne incognita as affected by different cropping sequences

Population Dynamics of an Insect Herbivore over 32 Years are Driven by Precipitation and Host-Plant Effects: Testing Model Predictions.

The interaction between the arroyo willow, Salix lasiolepis Bentham, and its specialist herbivore, the arroyo willow stem-galling sawfly, Euura lasiolepis Smith (Hymenoptera: Tenthredinidae), was studied for 32 yr in Flagstaff, AZ, emphasizing a mechanistic understanding of insect population dynamics. Long-term weather records were evaluated to provide a climatic context for this study. Previously, predictive models of sawfly dynamics were developed from estimates of sawfly gall density made between 1981 and 2002; one model each for drier and wetter sites. Predictor variables in these models included winter precipitation and the Palmer Drought Severity Index, which impact the willow growth, with strong bottom-up effects on sawflies. We now evaluate original model predictions of sawfly population dynamics using new data (from 2003-2012). Additionally, willow resources were evaluated in 1986 and in 2012, using as criteria clone area, shoot density, and shoot length. The dry site model accounted for 40% of gall population density variation between 2003 and 2012 (69% over the 32 yr), providing strong support for the bottom-up, mechanistic hypothesis that water supply to willow hosts impacts sawfly populations. The current drying trend stressed willow clones: in drier sites, willow resources declined and gall density decreased by 98%. The wet site model accounted for 23% of variation in gall population density between 2003 and 2012 (48% over 30 yr), consistent with less water limitation. Nonetheless, gall populations were reduced by 72%.

The determinants of sexual freedom from 1990 to 2010

With sexual freedom represented by the changing definition of marriage in the news lately, the question this article seeks to answer is what drives the issue of sexual freedom. This article focuses on the hypothesized link between sexual freedom and possible explanatory factors. Data are obtained from 1990 to 2010. The examination of data shows that median income, ideology, median age, population density and religion variables are significant in understanding sexual freedom in the United States.