Heterogeneity In Population Dynamics Research Articles

Aging and real estate prices in Germany

AbstractExploiting regional heterogeneity in population dynamics across more than 10,000 municipalities in Germany, we provide robust empirical evidence that population aging depresses real estate prices and rents. Using millions of individual real estate listings and detailed demographic data at the municipality level, we estimate that average sales prices in 2020 would have been up to 12% higher if the population age distribution had been the same as in 2008. We show that population aging not only reduces prices but also increases the availability of real estate. In addition, we document substantial heterogeneity in price responses across dwelling type, property characteristics, and urban-rural status, suggesting that lower housing demand and life-cycle dissaving are driving our results. We predict that population aging will continue to exert downward pressure on house prices and exacerbate regional disparities in Germany.

Endogenous spatial heterogeneity in a multi-patch predator-prey system: insights from a field-parameterized model

The causes and consequences of spatial heterogeneity in population dynamics are of both theoretical and practical interest. Previously, we described (Kummel et al., Oikos 122:896–906, 2013) a field system in which predation by ladybugs drives the development of strong spatial heterogeneity among aphid populations living on nearby plants. In this paper, we investigate the detailed mechanisms responsible for this phenomenon. We develop a detailed mathematical model of the system, parameterized by an extensive experimental work showing that ladybugs tend to remain on plants with high aphid numbers and are attracted to plants on which ladybugs are actively feeding. The model reproduces important aspects of the field system and allows us to explore how various behavioral features contribute to these dynamics. The results indicate that spatial heterogeneity results from the random aspect of ladybug foraging that causes some large aphid populations to be under-exploited. For parameter values that are unrealistic for our system, the model displays other types of complex dynamics, including predator swarming and chaos. Our study illustrates how a realistic, carefully parameterized model can connect individual behavior to larger scale spatiotemporal dynamics.

Explaining Spatial Heterogeneity in Population Dynamics and Genetics from Spatial Variation in Resources for a Large Herbivore

Fine-scale spatial variation in genetic relatedness and inbreeding occur across continuous distributions of several populations of vertebrates; however, the basis of observed variation is often left untested. Here we test the hypothesis that prior observations of spatial patterns in genetics for an island population of feral horses (Sable Island, Canada) were the result of spatial variation in population dynamics, itself based in spatial heterogeneity in underlying habitat quality. In order to assess how genetic and population structuring related to habitat, we used hierarchical cluster analysis of water sources and an indicator analysis of the availability of important forage species to identify a longitudinal gradient in habitat quality along the length of Sable Island. We quantify a west-east gradient in access to fresh water and availability of two important food species to horses: sandwort, Honckenya peploides, and beach pea, Lathyrus japonicas. Accordingly, the population clusters into three groups that occupy different island segments (west, central, and east) that vary markedly in their local dynamics. Density, body condition, and survival and reproduction of adult females were highest in the west, followed by central and east areas. These results mirror a previous analysis of genetics, which showed that inbreeding levels are highest in the west (with outbreeding in the east), and that there are significant differences in fixation indices among groups of horses along the length of Sable Island. Our results suggest that inbreeding depression is not an important limiting factor to the horse population. We conclude that where habitat gradients exist, we can anticipate fine-scale heterogeneity in population dynamics and hence genetics.

Spatial structure of roe deer populations: towards defining management units at a landscape scale

Summary A crucial question in wildlife management concerns the definition of ecologically meaningful management units. Management action needs to be co‐ordinated at the appropriate spatial scale. There are few practical tools for delimiting pertinent management units for large mammals such as ungulates. Previous work has favoured a molecular approach to determine genetically distinct units, but this may be too costly for routine management. In addition, recent studies have revealed fine‐scale heterogeneity in population dynamics of free‐ranging ungulates in relation to environmental variability. We combined spatial analysis of environmental heterogeneity (vegetation cover, topography and climate), animal morphology (jaw length) and genetic structure (microsatellites) to define biologically meaningful population units for roe deer Capreolus capreolus in the Belluno province, north‐eastern Italy. Jaw length is a sensitive measure of density‐dependence and a good proxy for spatial and temporal variation in roe deer population growth. Spatial analysis of environmental variables suggested that the study area should be divided into two, or possibly four, biogeographical regions in relation to variation in altitude and habitat type. There was significant spatial variability in jaw length across the province that clustered into two main regions (with shorter jaws in the north compared with the south), which matched the previously defined biogeographical regions. This spatial structuring was also supported by microsatellite analysis, which revealed two genetically distinct populations, one in the north and one in the south. Synthesis and applications. A multiparameter approach, combining environmental information with data on indices of density‐dependence such as jaw length, could be extremely useful for defining ecologically meaningful management units. Indeed, monitoring spatial and temporal variation in jaw length could provide deer managers with a simple way to index population structure and fluctuations in time and space.

Plant phenology, migration and geographical variation in body weight of a large herbivore: the effect of a variable topography

1. A central concept in ruminant foraging ecology is that even slight changes in plant quality affect body growth substantially, because ruminants not only gain more protein and energy but also use less time for rumination when eating high-quality forage. Increased access to highly nutritious forage is thus regarded as an important driving force in the evolution of migration in large herbivores, because the temporal and spatial variation in plant quality is huge. Body weight is in turn a major determinant of reproductive performance and survival in ungulates, and therefore important for population dynamics. 2. In the temperate region, the vertical movement of cervids from a low-elevation winter range to a high-elevation summer range is the most common pattern of migration. Migration to high elevations during summer is regarded as a strategy to increase energy intake among northern temperate ungulates. 3. It has been suggested that there is increased forage quality at high elevation. This leads to the prediction that body weights are positively correlated with the proportion of high-altitude habitat. Alternatively, cervids may benefit due to prolonged access to newly emerged forage as they migrate along an altitudinal gradient. If so, it can be predicted that body weights are highest in regions with the highest diversity of different altitudes. 4. The facing of slopes, i.e. the aspect, is also regarded as an important part of the habitat for deer. Access to north-facing slopes is regarded as favourable because plant quality may be higher on north-facing slopes; access to a variety of different aspects is also favourable because this may lead to a variable snow melt and thus a longer time period with access to high-quality forage. 5. In order to test the above predictions (under points 3 and 4), we analysed the spatial variability of body weight of 8452 female and 12 474 male red deer harvested during 1975-98 from 105 municipalities in Norway. 6. Body weight of red deer was positively related to the diversity of altitudes, and negatively related to the proportion of high-altitude habitat per se. This demonstrated that the altitudinal migration of cervids is not necessarily due to increased forage quality at high elevation, but rather that migrating cervids gain from prolonged access to newly emerging forage along an altitudinal gradient as they migrate to high elevation during early summer. 7. There was also no support for the hypothesis that access to a high proportion of north-facing slopes was favourable; rather, body weight of red deer was correlated with access to a diversity of aspects. There was thus clear evidence that a variable topography, measured as different altitude levels and aspects, was positively related to body weight of red deer. 8. We discuss the possible causes of why an ideal free distribution is not reached, and conclude that phenological differences in plants related to topography can have a large impact on body weights of cervids, and therefore induce considerable spatial heterogeneity in population dynamics.

Spatial Synchrony and Asynchrony in Butterfly Population Dynamics

1. Data from Butterfly Monitoring Scheme (BMS) transect counts were used to investigate the decline in synchrony of population fluctuations with increasing distance between sample units, and to evaluate the relative effects of local and regional scale processes on population fluctuations. 2. Each BMS transect is divided into sections and numbers (densities) of butterflies are recorded separately in each section. Local scale analyses examined population fluctuations on different sections within a single transect. Regional scale analyses examined fluctuations on different transects. 3. At the local scale population dynamics were found to be more closely synchronized between very close population units (sections) than more distant ones. There was considerable variation between data sets but on average this correlation declined relatively quickly over 1-2 km. 4. At the regional scale, where local environmental heterogeneity was averaged out (sections were lumped together within transect sites), the decline in synchrony with increasing distance (up to 200 km) was very small compared with local scale decrease, and populations remain partially synchronized throughout the range studied due to regionally correlated weather patterns. 5. Butterfly dispersal had a significant effect on synchrony at a local scale (several km): the dynamics of populations of relatively mobile species remained correlated over relatively long distances. At the regional level, however, mobility was not a significant factor, implying that widespread environmental stochasticity is of overriding importance at this scale. 6. Although mobility and distance are significant factors in determining population synchrony/asynchrony, the low r 2 values attributable to them indicate that these factors are actually contributing relatively little to the overall dynamics. Butterfly species show local variation in population dynamics, nested within broad scale synchrony which is presumably generated by the climate. Heterogeneity in population dynamics, in local environments, potentially aids metapopulation persistence by buffering the effects of high levels of temporal environmental stochasticity.

Survival, Immigration and Habitat Quality in the Mediterranean Pine Vole

There is evidence that the Mediterranean pine vole does not display population cycles as some microtines do. The aim of our study was to test whether dispersal between populations could be a stabilizing factor of densities of this species. Four populations were studied by capture-recapture in southern France. Two habitats of different quality were sampled. Probabilistic estimators were used to estimate population sizes, survival rates, recruitment and immigration. Densities were similar in all populations but some variations were obvious and not related to habitat quality. Survival was constant throughout the seasons in the high-quality habitat, but not in the low-quality habitat where it decreased critically during spring. Recruitment was low in the former habitat, and almost did not occur in the latter. Immigration was strongly correlated to population size changes and was the factor causing the variations observed between patches of high quality. Immigration allowed the persistence of the population in the patch of low quality at densities similar to the others. A source-sink metapopulation dynamics was inferred from these results. The existence of adaptive dispersal is discussed as a stabilizing factor of population densities in the Mediterranean pine vole. The adaptiveness of dispersal is conditioned by the existence of discontinuous distribution and heterogeneity in population dynamics caused by different habitat quality or variable immigration patterns. The generality of this stabilizing mechanism is discussed in microtine populations.

Spatial and temporal heterogeneity in population dynamics of citrus aphids at a regional scale

AbstractA quick method of evaluating aphid infestations on young clementine trees is developed. It uses visual abundance classes. This method is used to compare the population dynamics of two aphid species in 11 orchards in Corsica (France). The curves describing the succession of the abundance indices on each sampling tree between April and July are compared using principal component analyses.The first three factorial axes illustrate the intensity, precocity and flatness of the infestation curves. For each species, a significant between‐orchard variability is demonstrated by comparing the mean factorial coordinates of the sampling trees of the different orchards. The validity of such methods for analyzing the demographic strategies of phytophagous and entomophagous insects at a large scale is discussed.

The effects of spatial heterogeneity in population dynamics

The dynamics of a population inhabiting a heterogeneous environment are modelled by a diffusive logistic equation with spatially varying growth rate. The overall suitability of an environment is characterized by the principal eigenvalue of the corresponding linearized equation. The dependence of the eigenvalue on the spatial arrangement of regions of favorable and unfavorable habitat and on boundary conditions is analyzed in a number of cases.