Patches Of Different Quality Research Articles

Steady-state dynamics in a two-patch population model with and without Allee effect

Most biological populations reside in landscapes that consist of many different patches of different quality. Different species differ in their movement behavior, habitat preference and growth rates. Historically, mathematical models for population dynamics have made many simplifying assumptions, such as a single patch or homogeneous landscapes. Recent models have begun to implement landscape heterogeneity and individual movement characteristics, but many of those are based on logistic growth and linear analysis of the zero state. We consider a two-patch model with more general growth functions that can include Allee effects. We prove the existence of steady states and classify their qualitative behavior. In some special cases, we explicitly calculate their stability and use these results to give conditions for when the system exhibits bistability, i.e., the coexistence of locally stable states. We also study bifurcations with respect to the size of habitat patches and give conditions for forward and backward bifurcations.

Rethinking the old hypothesis that new housing construction has an impact on the vector control of Triatoma infestans: A metapopulation analysis

Triatoma infestans (Hemiptera: Reduviidae) is a hematophagous insect, vector of the parasite Trypanosoma cruzi, etiological agent of the Chagas disease. In the south of La Rioja, Argentina, the persistent infestation by triatomines encouraged a program of construction of brand new dwellings in rural areas since 2008, to reduce infestation. According to the metapopulation theory approach, each dwelling was considered to be a patch with different degrees of quality concerning the availability of shelters for T. infestans. Accordingly, brand new dwellings (BNDs) are considered of lower quality for triatomines, compared to traditional dwellings (TDs). The main objective of this study was to analyse the occupancy in patches of different quality and to evaluate the effect of BNDs in the control of T. infestans. 397 patches from three departments of the southern part of La Rioja province were analysed during the period from 2014 to 2017. Six samplings were carried out to estimate the occupancy by T. infestans in patches assigned with different qualities. During the studied period, changes in the occupancy status of the patches among samplings were recorded, and the metapopulation variables which affect the occupancy of T. infestans were analysed. The results showed that all patches, even those considered of lower quality and smaller size, were occupied by T. infestans in a range from 3.8% to 25.5%. In general, the probability of T. infestans occupancy among samplings showed no difference among all studied patches. The occupancy of patches by T. infestans was associated with “department”, “number of patches” and “number of positive patches in the radius of 400 m” (analysis GEE models). However, “patch quality”, “size”, and “distance” showed no effect on T. infestans occupancy. 44.1% of patches with BND were occupied at least once during the study period. Some of these showed “persistent occupancy” by T. infestans. No differences in the T. infestans occupancy between BNDs and TDs were observed. These results allowed us to analyse the impact of the new housing construction as a vector control measure in the metapopulation context of La Rioja province.

Evolutionarily stable movement strategies in reaction-diffusion models with edge behavior.

Many types of organisms disperse through heterogeneous environments as part of their life histories. For various models of dispersal, including reaction-advection-diffusion models in continuously varying environments, it has been shown by pairwise invasibility analysis that dispersal strategies which generate an ideal free distribution are evolutionarily steady strategies (ESS, also known as evolutionarily stable strategies) and are neighborhood invader strategies (NIS). That is, populations using such strategies can both invade and resist invasion by populations using strategies that do not produce an ideal free distribution. (The ideal free distribution arises from the assumption that organisms inhabiting heterogeneous environments should move to maximize their fitness, which allows a mathematical characterization in terms of fitness equalization.) Classical reaction diffusion models assume that landscapes vary continuously. Landscape ecologists consider landscapes as mosaics of patches where individuals can make movement decisions at sharp interfaces between patches of different quality. We use a recent formulation of reaction-diffusion systems in patchy landscapes to study dispersal strategies by using methods inspired by evolutionary game theory and adaptive dynamics. Specifically, we use a version of pairwise invasibility analysis to show that in patchy environments, the behavioral strategy for movement at boundaries between different patch types that generates an ideal free distribution is both globally evolutionarily steady (ESS) and is a global neighborhood invader strategy (NIS).

Effect of Dung Quantity and Quality on Greenhouse Gas Fluxes From Tropical Pastures in Kenya

AbstractTo improve estimates of agricultural greenhouse gas emissions in sub‐Saharan Africa, we measured over six individual periods of 25–29 days fluxes of methane (CH4), carbon dioxide (CO2), and nitrous oxide (N2O) with subdaily time resolution from dung patches of different quality (C/N ratio: 23–41) and quantity (0.5 and 1.0 kg) on a Kenyan rangeland during dry and wet seasons. Methane emissions peaked following dung application, whereas N2O and CO2 fluxes from dung patches were similar to fluxes from rangeland soils receiving no N additions. Greenhouse gas emissions scaled linearly with dung quantity during both seasons. Dung with a low (23) C/N ratio produced up to 10 times more CH4 than dung with a high (41) C/N ratio. Overall, CH4 emission factors (EFs) ranged from 0.001 to 0.042%, lower than those derived in temperate regions. Cumulative CO2 and N2O emissions were similar for all treatments across the different seasons. The N2O EF ranged from 0 to 0.01%, less than 1% of the Intergovernmental Panel on Climate Change Tier 1 default EF (2%) for N2O emissions from dung and urine patches, likely because of the low dung N content (9.7–16.5 g N kg−1 dry matter). However, these results were consistent with the updated cattle dung EF (0.2%) developed for Kenya in 2016/2017 (EF database ID# 422665). In view of the wide range of climates, soils, and management practices across sub‐Saharan Africa, development of robust GHG EFs from dung patches for SSA requires additional studies.

Ecosystem Services from Small Forest Patches in Agricultural Landscapes

In Europe, like in many temperate lowlands worldwide, forest has a long history of fragmentation and land use change. In many places, forest landscapes consist of patches of different quality, age, size and isolation, embedded in a more or less intensively managed agricultural matrix. As potential biodiversity islets, small forest patches (SFP) may deliver several crucial ecosystem services to human society, but they receive little attention compared to large, relatively intact forest patches. Beyond their role as a biodiversity reservoir, SFP provide important in situ services such as timber and wild food (game, edible plants and mushrooms) production. At the landscape scale, SFP may enhance the crop production via physical (obstacle against wind and floods) and biological (sources of pollinators and natural enemies) regulation, but may, on the other hand, also be involved in the spread of infectious diseases. Depending on their geographic location, SFP can also greatly influence the water cycle and contribute to supply high-quality water to agriculture and people. Globally, SFP are important carbon sinks and are involved in nutrient cycles, thus play a role in climate change mitigation. Cultural services are more related to landscape values than to SFP per se, but the latter may contribute to the construction of community identity. We conclude that SFP, as local biodiversity hotspots in degraded landscapes, have the potential to deliver a wide range of ecosystem services and may even be crucial for the ecological intensification of agro-ecosystems. There is thus an urgent need to increase our knowledge about the relationships between biodiversity and ecosystem services delivered by these SFP in agricultural landscapes.

Dispersal evolution and resource matching in a spatially and temporally variable environment.

Metapopulations may consist of patches of different quality, and are often disturbed by extrinsic processes causing variation of patch quality. The persistence of such metapopulations then depends on the species' dispersal strategy. In a temporally constant environment, the evolution of dispersal rates follows the resource matching rule, i.e. at the evolutionarily stable dispersal strategy the number of competitors in each patch matches the resource availability in each patch. Here, we investigate how the distribution of individuals resulting from convergence stable dispersal strategies would match the distribution of resources in an environment which is temporally variable due to extrinsic disturbance. We develop an analytically tractable asexual model with two qualities of patches. We show that convergence stable dispersal rates are such that resource matching is predicted in expectation before habitat quality variation, and that the distribution of individuals undermatches resources after habitat quality variation. The overall flow of individuals between patches matches the overall flow of resources between patches resulting from environmental variation. We show that these conclusions can be generalized to organisms with sexual reproduction, and to a metapopulation with three qualities of patches when there is no mutational correlation between dispersal rates.

Providing insights on habitat connectivity for male brown bears: A combination of habitat suitability and landscape graph-based models

The combined study of movement patterns and habitat selection, behaviors that are affected by landscape structure, is of critical importance for effective conservation of wildlife. In the same context, maintaining connectivity is a key component for facilitating movement and ensuring species persistence. The brown bear is a wide-ranging predator that moves across large areas, crossing various habitats of different quality. Here, we provide a methodological framework that allowed us to explore the relative importance of habitat quality upon movement patterns and connectivity. First, we developed habitat-suitability models by using telemetry data of eight male brown bears (12,893 radio-locations) collected in Greece. Next, we combined habitat-suitability maps with real movement data to develop graph models that represent movement networks as inter-connected patches of different quality. Network analyses revealed that movement networks demonstrate some well-studied properties regarding their structure and robustness (i.e. scale-free and small-world), providing insights on the contribution of patches of different quality to connectivity. Less suitable patches were found to play a critical role for facilitating brown bear's movement and landscape connectivity. Our findings raise the importance of considering the entire habitat of brown bear in conservation planning rather than isolated patches of high quality, as it might have been revealed by simple habitat-suitability models. Our results highlight the need of assessing the importance of the intervening matrix for facilitating connectivity and movement specifically in the case of large and highly mobile species that do not perceive landscape as strictly dichotomous.

Habitat‐specific demography and source–sink dynamics in a population of Siberian jays

1. There are a number of models describing population structure, many of which have the capacity to incorporate spatial habitat effects. One such model is the source-sink model, that describes a system where some habitats have a natality that is higher than mortality (source) and others have a mortality that exceeds natality (sink). A source can be maintained in the absence of migration, whereas a sink will go extinct. 2. However, the interaction between population dynamics and habitat quality is complex, and concerns have been raised about the validity of published empirical studies addressing source-sink dynamics. In particular, some of these studies fail to provide data on survival, a significant component in disentangling a sink from a low quality source. Moreover, failing to account for a density-dependent increase in mortality, or decrease in fecundity, can result in a territory being falsely assigned as a sink, when in fact, this density-dependent suppression only decreases the population size to a lower level, hence indicating a 'pseudo-sink'. 3. In this study, we investigate a long-term data set for key components of territory-specific demography (mortality and reproduction) and their relationship to habitat characteristics in the territorial, group-living Siberian jay (Perisoreus infaustus). We also assess territory-specific population growth rates (r), to test whether spatial population dynamics are consistent with the ideas of source-sink dynamics. 4. Although average mortality did not differ between sexes, habitat-specific mortality did. Female mortality was higher in older forests, a pattern not observed in males. Male mortality only increased with an increasing amount of open areas. Moreover, reproductive success was higher further away from human settlement, indicating a strong effect of human-associated nest predators. 5. Averaged over all years, 76% of the territories were sources. These territories generally consisted of less open areas, and were located further away from human settlement. 6. The source-sink model provides a tool for modelling demography in distinct habitat patches of different quality, which can aid in identifying key habitats within the landscape, and thus, reduce the risk of implementing unsound management decisions.

Large‐scale Input Matching by Urban Feral Pigeons (Columba livia)

AbstractIdeal Free Distribution (IFD) theory predicts the number of animals choosing habitats of differing quality. Most experimental tests of the IFD have been conducted at small spatial scales (i.e. smaller than maximum daily movement of animals) by comparing the number of animals foraging at adjacent food patches of different quality. Urban pigeons (Columba livia) feed in large, open aggregations, and can distribute according to predictions of the IFD at alternative food patches. In this study, we test IFD predictions over a much larger spatial scale by comparing the abundance of urban feral pigeons at four sites spread over the city centre of Montréal, Québec, Canada, to the amount of anthropogenically provided food in each site. We found that the pigeons’ distribution among the four sites qualitatively matched that of resources available at these sites. After controlling for the effect of stochastic variation in food resources, two pair‐wise comparisons between sites indicated undermatching, one indicated matching and three indicated overmatching of consumers to resources. These results suggest that the pigeons inhabiting the downtown area of Montréal may behave as a single population that distributes qualitatively among foraging sites in proportion to the quantity of food offered, and that deviations from expectations cannot be attributed simply to stochastic variation in the food levels at the sites.

Performance of a clonal species in patchy environments: effects of environmental context on yield at local and whole-plant scales

Yield of the clonal plant Glechoma hederacea was compared at different spatial scales, in heterogeneous and homogeneous environments providing the same amount of nutrients. For the heterogeneous treatments, environments were created with different patch sizes and different degrees of contrast in nutrient concentration between patches of different quality. Total clone yield differed by almost 2.5-fold across treatments, being highest in environments with large patches and high contrast, lowest in environments with small patches and high contrast, and intermediate under homogeneous conditions. Compared with plants in homogeneous conditions, there were significant increases or decreases in yield at all scales of measurement in many of the heterogeneous treatments. These effects on yield reflected a combination of local responses to growing conditions and modification of these responses due to physiological integration with other parts of the plant growing in contrasting conditions, supporting the proposal of de Kroon et al. (2005 New Phytol 166:73–82). The results show that plant yield at all scales is strongly dependent on environmental context, and that maximum yield can only be realized under a limited range of heterogeneous conditions.

HARVEST RATES AND PATCH-USE STRATEGY OF EGYPTIAN FRUIT BATS IN ARTIFICIAL FOOD PATCHES

The amount of food left by a forager after feeding in a depletable patch of known volume, the giving-up density (GUD), estimates the quitting harvest rate. I constructed a feeder for measuring GUD in Egyptian fruit bats (Rousettus aegyptiacus). The feeder contained liquid food mixed with pieces of hose that interfered with the drinking behavior of the bats and forced them to work progressively harder to obtain more food as the depth of the liquid in the feeder decreased. Harvest rates in bats using these feeders declined with time. When presented with feeders containing different initial food densities, the bats equalized GUD and consumed proportionately more food from rich patches than from poor ones. Thus, the bats recognized patches of different quality and foraged following a fixed quitting harvest rate patch-use strategy.

Fine scale distribution of ectomycorrhizal fungi and roots across substrate layers including coarse woody debris in a mixed forest.

• Ectomycorrhizal (ECM) fungi are widespread plant root symbionts in boreal forests, but information is lacking on the fine scale distribution of roots and fungi in substrate patches of different quality, including coarse woody debris (CWD). • Wood and soil cores were taken systematically both horizontally and vertically through decayed logs and underlying soil layers in a mixed forest. Root tips were counted and ECM fungi identified by morphotyping and sequencing. • The abundance of root tips and ECM fungi was highly variable on a 5-cm scale. Most species were replaced on a 50-cm scale. Detrended correspondence analysis demonstrated strong preference of resupinate thelephoroid and athelioid fungi and Sebacinaceae for CWD, whereas ascomycetes and euagarics appeared more frequently in mineral soil. Clavulicium delectabile was determined to be an ECM fungus for the first time. • ECM fungi occupy different niches and show variable distribution patterns. CWD plays an important role as a habitat both for roots and ECM fungi. We suggest sampling larger soil cores and selecting random root tips in future studies. Sequencing is a powerful tool in ECM community studies.

The effects of habitat manipulation on population distribution and foraging behavior in meadow voles

Individuals, free to choose between different habitat patches, should settle among them such that fitness is equalized. Alternatives to this ideal free distribution result into fitness differences among the patches. The concordance between fitnesses and foraging costs among inhabitants of different quality patches, demonstrated in recent studies, suggests that the mode of habitat selection and the resulting fitness patterns may have important implications to the resource use of a forager and to the survival of its prey. We studied how coarse scale selection between habitat patches of different quality and quitting harvest rate in these patches are related to each other and to fine scale patch use in meadow voles (Microtus pennsylvanicus). To demonstrate these relationships, we manipulated habitat patches within large field enclosures by mowing vegetative cover and adding supplemental food according to a 2×2 factorial design. We tracked vole population densities, collected giving‐up densities (GUDs, a measure of patch quitting harvest rate), and monitored the removal of seeds from lattice grids with 1.5 m intervals (an index of fine‐scale space use) in the manipulated habitat patches. Changes in habitat quality induced changes in habitat use at different spatial scales. In preferred habitats with intact cover, voles were despotic and GUDs were low, but increased with the addition of food. In contrast, voles in less‐preferred mowed habitats settled into an ideal free distribution, GUDs were high and uninfluenced by the addition of food. Seed removal was enhanced by the presence of cover but inhibited by supplemental food. Across all treatments, vole densities and GUDs were strongly correlated making it impossible to separate their effects on seed removal rates. However, this relationship broke down in unmowed habitats, where GUDs rather than vole density primarily influenced seed removal by voles. GUDs and seed removal correlated with predation on tree seedlings formerly planted into the enclosures, demonstrating the mechanisms between coarse‐scale habitat manipulations and community level consequences on a forager's prey.

Measuring urban habitat fragmentation: an example from the Black Country, UK

The processes of urbanisation have left a fragmented mosaic of habitat patches of varying size, shape and character with the result that from location to location the number and quality of contacts between patches varies considerably. Traditional measurements of this habitat fragmentation, and its converse, connectivity, have rarely looked at the landscape as a whole but instead have simplified it to specific landscape subsets, or else have looked at area-to-area relationships through generalising the landscape into homogeneous pixels or grids. In this paper the character of the whole landscape is examined at scales appropriate to the spatial variability of the urban environment. Using a direct measurement of patch-to-patch contact all contacts between all patches are examined and the relationship between all contiguous and connecting habitats is quantified. This is further refined to look at connections between patches of different quality, a measure that highlights the adverse effects of urbanisation as a whole on landscape connections between quality habitats.

Effects of resource distribution, patch spacing, and preharvest information on foraging decisions of northern bobwhites

We investigated patch assessment by northern bobwhites (Colinus virginianus) in an experimental arena where the distribution of resources in patches, preharvest information about these patches, and spacing of patches varied. We found that preharvest information about patch quality and a bimodal distribution of patch rewards allowed birds to selectively exploit patches high in resources. In contrast, uniform distribution of patch qualities and lack of preharvest information caused birds to forage nonselectively among patches. Birds distinguished among patches of different quality when these patches were spaced 1 3 m apart, but failed to react to patch quality differences when patches were 0 or S m apart We also found a strong effect of the level of patch depletion on foraging decisions: as resources in die arena became scarce, birds increasingly foraged selectively in die most profitable patches. Foraging decisions of bobwhites are biased by die way they experience and memorize a spatially and temporally variable environment. The relative cost of this cognitive bias (i.e., lost opportunity) is nonlinearty related to die mean resource density in die environment and to die difference between this mean density and die resource density in die exploited patch. Cognitive bias should be considered when evaluating patch assessment capabilities of foragers in complex environments.

Female Mate Choice Tactics in A Resource‐Based Mating System: Field Tests of Alternative Models

In this study we test theoretical models of female mate choice tactics in natural populations of pine engravers, Ips pini (Say) (Coleoptera: Scolytidae), a species with a resource-based mating system and high search costs. We first develop distinguishing predictions for each of four models of mate choice: random, comparison tactics, and fixed and adjustable thresholds. These predictions relate to commonly collected field data that include the visiting behavior of females and the quality of accepted and rejected mates. Using these types of data, we conclude that pine engravers use an adjustable threshold mate choice tactic because females often accepted the first male encountered, rarely revisited males, visited similar numbers of males in patches of different quality, accepted higher-quality males than those they rejected even on their first encounter with a male in a patch, and had higher acceptance thresholds in high-quality patches than in low-quality patches. This adjustable threshold tactic is consistent with a one-step decision rule and is predicted to occur in species such as pine engravers in which search costs are high and females have information about patch quality before beginning a search in a patch.