Heterogeneity In Habitat Quality Research Articles

Spatiotemporal Variation and Driving Factors Analysis of Habitat Quality: A Case Study in Harbin, China

Biodiversity is profoundly influenced by habitat quality, and Harbin, a provincial capital situated in a cold climate zone, stands out as one of China’s regions most susceptible to the repercussions of climate change. To ensure the city’s continued sustainable growth, a thorough assessment of habitat quality must be conducted. This study employs a comprehensive approach integrating the InVEST model, the PLUS model, a landscape pattern analysis, geographic detector, and a geographically weighted regression model. The goal is to assess how land use and habitat quality have changed in Harbin City, investigate factors contributing to spatial heterogeneity in habitat quality, thoroughly examine evolutionary patterns under the inertial development scenario from 2030 to 2050, and propose spatial optimization strategies. There are four key findings. First, from 2000 to 2020, agricultural land and forest were Harbin City’s two most prevalent land use types. The most notable transition occurred from forest to grassland, and the expansion of construction land primarily resulted from its encroachment into agricultural areas. Second, within the area of study, the landscape heterogeneity increased while simultaneously experiencing a decrease in connectivity, and the landscape had a tendency toward a more fragmented spatial distribution. Third, overall habitat quality rose between 2000 and 2020 but declined between 2030 and 2050. There was a “weak in the west and high in the east” distribution pattern in the spatial heterogeneity of habitat quality. Fourth, population density has the most impact on habitat quality, with the NDVI and GDP close behind. Conversely, precipitation and slope had comparatively smaller influences on habitat quality. Natural factors combined had a primarily favorable influence on habitat quality across the research region in terms of spatial distribution. Conversely, population density had a discernibly detrimental impact. Given these findings, this study suggests targeted strategies to optimize habitat quality. These recommendations are relevant not only for biodiversity conservation but also for the development of an ecologically sustainable community, particularly in a cold climate region.

Temporal and spatial responses of landscape patterns to habitat quality changes in the Poyang Lake region, China

Due to intense human activity and landscape configuration changes, evaluating habitat quality is critical for ecosystem service capacity maintenance while promoting human well-being. This study aimed to evaluate and analyze the temporal and spatial responses of landscape patterns to habitat quality changes in the Poyang Lake region. During 2000–2020, the landscape pattern in the Poyang Lake region shifted from agglomeration to fragmentation. Within this period, the area with the highest proportion of habitat quality reached a poor level within the region, and the area with the worst level experienced notable improvement. The concentration of excellent habitat quality areas was evident within the central region of Poyang Lake, as well as in the northeastern and northwestern of the entire region. The proportion of habitat quality improvement surpassed that of habitat degradation, accounting for 32.62% and 17.94%, respectively. Notably, areas characterized by moderate and good habitat quality experienced a significant upgrade to an excellent level by 2020. The results of spatial autocorrelation, as measured by Moran's I index, indicated a consistent positive trend. This value gradually increased over time, suggesting a progressive intensification in the spatial clustering of habitat quality. Furthermore, the spatial heterogeneity in habitat quality was primarily driven by CONTAG, which was the primary influential factor. An enhanced two-factor interaction, surpassing the explanatory force of the factors on their own, was observed through an analysis of the interactions between different combinations of influencing factors. The explanatory force of the CONTAG index indicated a decline in habitat quality in certain local regions. For these areas, we suggest controlling the disorderly development of construction land and transportation systems, strictly prohibiting the illegal occupation of arable land, promoting vegetation restoration, and maintaining landscape patch connectivity.

Modelling the effect of habitat and fishing heterogeneity on the performance of a Total Allowable Catch-regulated fishery

Abstract Fisheries are often characterized by high heterogeneity in the spatial distribution of habitat quality, as well as fishing effort. However, in several fisheries, the objective of achieving a sustainable yield is addressed by limiting Total Allowable Catch (TAC), set as a fraction of the overall population, regardless of the population's spatial distribution and of fishing effort. Here, we use an integral projection model to investigate how stock abundance and catch in the green abalone fishery in Isla Natividad, Mexico, are affected by the interaction of heterogeneity in habitat quality and fishing effort, and whether these interactions change with Allee effects—reproductive failure in a low-density population. We found that high-quality areas are under-exploited when fishing pressure is homogeneous but habitat is heterogeneous. However, this leads to different fishery outcomes depending on the stock's exploitation status, namely: sub-optimal exploitation when the TAC is set to maximum sustainable yield, and stability against collapses when the fishery is overexploited. Concentration of fishing effort in productive areas can compensate for this effect, which, similarly, has opposite consequences in both scenarios: fishery performance increases if the TAC is sustainable but decreases in overexploited fisheries. These results only hold when Allee effects are included.

Identification and extraction of a current urban ecological network in Minhang District of Shanghai based on an optimization method

The urban ecological network has gained substantial interest in the context of urban sustainable development research in recent years. It guides the optimization of the urban ecological spatial layout, which is an important means for inventory development and ecological construction. However, traditional construction methods may not be suitable for urban environments with complex matrices. This can result in the inaccurate extraction of urban ecological networks. This study aimed to improve understanding of the current distribution and composition of key elements in urban ecological networks. In the present study, an optimized evaluation method involving ecological source patches and resistance surfaces was used to identify and extract an urban ecological network. The Minhang District (MhD) of Shanghai formed the study area. The results showed that: (1) There was spatial heterogeneity in habitat quality and the location importance of cores in the MhD. These two factors were inconsistent with the area size. (2) The habitat quality for the same land use types were significantly different. This was because of both vegetation quality and the external environment. (3) The urban ecological network for the MhD had 82 source patches. These were unevenly distributed and mainly concentrated in Pudong. (4) A total of 133 least-cost paths were extracted from between the source patches. However, the cost of least-cost paths were generally high in Puxi. This was not conducive to forming functional connections between patches. This study provided an optimization method for identifying and extracting ecological networks in urban areas by combining Geographical Information System software (GIS), Guidos, Graphab, and the Integrated Valuation of Ecosystem Services and Tradeoffs (InVEST) model. Ecological indicators such as NDVI, the percentage variation of the probability of connectivity (dPC), and habitat quality were applied to improve accuracy. The study findings lay the foundation for further layout optimization and supporting ecological planning.

Quantifying the nature and strength of intraspecific density dependence in Arctic mosquitoes.

Processes that change with density are inherent in all populations, yet quantifying density dependence with empirical data remains a challenge. This is especially true for animals recruiting in patchy landscapes because heterogeneity in habitat quality in combination with habitat choice can obscure patterns expected from density dependence. Mosquitoes (Diptera: Culicidae) typically experience strong density dependence when larvae compete for food, however, effects vary across species and contexts. If populations experience intense intraspecific density-dependent mortality then overcompensation can occur, where the number of survivors declines at high densities producing complex endogenous dynamics. To seek generalizations about density dependence in a widespread species of Arctic mosquito, Aedes nigripes, we combined a laboratory experiment, field observations, and modeling approaches. We evaluated alternative formulations of discrete population models and compared best-performing models from our lab study to larval densities from ponds in western Greenland. Survivorship curves from the lab were the best fit by a Hassell model with compensating density dependence (equivalent to a Beverton-Holt model) where peak recruitment ranged from 8 to 80 mosquitoes per liter depending on resource supply. In contrast, our field data did not show a signal of strong density dependence, suggesting that other processes such as predation may lower realized densities in nature, and that expected patterns may be obscured because larval abundance covaries with resources (cryptic density dependence). Our study emphasizes the importance of covariation between the environment, habitat choice, and density dependence in understanding population dynamics across landscapes, and demonstrates the value of pairing lab and field studies.

Disease or drought: environmental fluctuations release zebra from a potential pathogen-triggered ecological trap.

When a transmission hotspot for an environmentally persistent pathogen establishes in otherwise high-quality habitat, the disease may exert a strong impact on a host population. However, fluctuating environmental conditions lead to heterogeneity in habitat quality and animal habitat preference, which may interrupt the overlap between selected and risky habitats. We evaluated spatio-temporal patterns in anthrax mortalities in a plains zebra (Equus quagga) population in Etosha National Park, Namibia, incorporating remote-sensing and host telemetry data. A higher proportion of anthrax mortalities of herbivores was detected in open habitats than in other habitat types. Resource selection functions showed that the zebra population shifted habitat selection in response to changes in rainfall and vegetation productivity. Average to high rainfall years supported larger anthrax outbreaks, with animals congregating in preferred open habitats, while a severe drought forced animals into otherwise less preferred habitats, leading to few anthrax mortalities. Thus, the timing of anthrax outbreaks was congruent with preference for open plains habitats and a corresponding increase in pathogen exposure. Given shifts in habitat preference, the overlap in high-quality habitat and high-risk habitat is intermittent, reducing the adverse consequences for the population.

Keeping up with the times: Mapping range-wide habitat suitability for endangered species in a changing environment

Biologists and policy-makers have the difficult task of allocating limited resources to habitat conservation and management for endangered species in the face of changing environmental conditions. Satellite remote sensing can inform conservation because it is an efficient means to obtain environmental data over broad spatial and temporal extents. Yet, the challenges of accessing, processing, and analyzing remote sensing data hinder wider application of these techniques in conservation planning. We used Landsat data and hierarchical statistical models to link satellite-derived habitat measurements with abundance of endangered Yuma Ridgway's rails (Rallus obsoletus yumanensis) within the Lower Colorado River Basin and Salton Sink, USA. We addressed many of the challenges facing the application of remote sensing techniques by using the web-based, freely-available Google Earth Engine to process Landsat datasets, apply habitat models, and generate maps to predict habitat suitability at a fine spatial grain (30 m) across the range of the species. These maps are shareable, interactive, and easy to update annually as habitat conditions change using a Google Earth Engine App we developed. Thus, we provide a framework for building habitat suitability models and maps to help target adaptive habitat management over broad extents for sensitive species, enabling biologists to improve conservation and restoration efforts regularly as conditions change in highly variable ecosystems. We demonstrate this approach for Yuma Ridgway's rails, but our methods for merging hierarchical statistical models with open-source mapping software to describe spatial-temporal heterogeneity in habitat quality are applicable to any species, and are especially helpful to species inhabiting highly variable ecosystems.

Behavioral switching in Magellanic woodpeckers reveals perception of habitat quality at different spatial scales

The switching pattern between behavioral modes provides a mechanistic basis for understanding how animals perceive and memorize the habitat quality in their home ranges. We assessed if Magellanic woodpeckers (Campephilus magellanicus) move based on habitat quality at local (neighboring trees) and home range scales. We used state-space models to examine the relationship between remotely-sensed estimates of habitat quality (tree decay) and movement of adult woodpeckers tracked with GPS telemetry in southern Chile. Woodpeckers spent most time (> 80%) in the area-restricted search (ARS) mode in contrast to the exploratory transient mode, characterized by frequent directional displacements (> 50 m). The extent to which individuals switched between behavioral modes was related to habitat quality at different scales. Woodpeckers switched to and remained in the ARS mode when encountering moderate levels of heterogeneity in habitat quality. At very low or high heterogeneity levels, however, individuals switched to and remained in the transient mode, respectively. Likewise, as habitat quality declined locally and across home range, woodpeckers were more likely to adopt a transient mode. Although woodpeckers seemed to easily perceive and memorize habitat quality at different spatial scales, our results suggest that spatial memory will less effective under extreme levels of habitat heterogeneity.

Spatial Assessment of the Potential Impact of Infrastructure Development on Biodiversity Conservation in Lowland Nepal

Biodiversity is declining at an unprecedented rate with infrastructure development being one of the leading causes. New infrastructure, such as roads, provides new access and results in increased land clearing and wildlife hunting. A number of large infrastructure projects, including new roads and rail, are being planned in Nepal. We show the application of readily available remotely sensed data and geospatial tools to assess the potential impact of these future developments on habitat quality under three protection-level scenarios. Our findings reveal that there is currently large spatial heterogeneity in habitat quality across the landscape as a result of current anthropogenic threats, and that three areas in particular could have up to 40% reduction in habitat quality as a result of the planned infrastructure. Further research is required to determine more precisely the impact on key species. Strengthening protected areas and buffer zones will contribute to mitigating degradation to some degree, however, large areas of biologically significant areas outside protected areas will be affected without new controls. Our geographic information systems (GIS) based methodology could be used to conduct studies in data poor developing countries, where rapid infrastructure development across ecological sites are ongoing, in order to make society, policy makers, and development planners aware.

Livestock and the functional habitat of vicuñas in Ecuador: a new puzzle

AbstractWhether interactions between wildlife and livestock are competitive or facilitative is context dependent. Intermediary factors that explain how context (seasonal or regional characteristics of the ecological community) affects these interactions are rarely reported. We compared activity time and density in vicuñas (Vicugna vicugna) introduced into the Chimborazo Faunal Production Reserve (CFPR), Ecuador, to describe how they interact with livestock. We compared vicuña density in wetlands and uplands (two landscape structures) with and without livestock (two conditions) using an isodar approach. We measured, over two seasons, vicuña forage abundance, composition, preference and accessibility, time vicuñas spent vigilant, and their flight distances on approach. We tested optimal foraging theory relating to the hypothesis that time mediates behavior, and found that vicuñas were no less frequently vigilant, nor were flight distances greater, during a wet season or in habitats of greater forage abundance and accessibility. We also found no evidence that vicuña behavior was density dependent; instead, we found that more time was spent vigilant by vicuñas when they foraged near livestock in rainy regions during the dry season. Although forage abundance was similar throughout CFPR during a dry season, better forage quality in areas occupied by livestock may constitute an effect of their facilitating vicuñas. A puzzling finding, because it was not explained by any of the other variables we measured, was that at low densities vicuñas selected habitat irrespective of livestock, and where their density was higher, it was doubly so adjacent to livestock. We conclude that in the CFPR, spatial heterogeneity in habitat quality determines the interactions between livestock and vicuñas. To support recommendations that minimize competition between wildlife and livestock, and to expand on descriptions of the contexts that determine the direction of species interactions, future study may require a wider sampling of the densities of sympatric large herbivores in general, and, in the CFPR, a closer resolution of spatial heterogeneity in forage plant quality.

Information thresholds, habitat loss and population persistence in breeding birds

The combination of spatial structure and non‐linear population dynamics can promote the persistence of coupled populations, even when the average population growth rate of the patches seen in isolation would predict otherwise. This phenomenon has generally been conceptualized and investigated through the movement of individuals among patches that each holds many individuals, as in metapopulation models. However, population persistence can likewise increase as the result of individuals moving among sites (e.g. breeding territories) within in a single patch. Here I examine the latter: individuals making small‐scale informed decisions with respect to where to breed can promote population persistence in poor environments. Based on a simple algebraic model, I demonstrate information thresholds, and predict that greater information use is required for population persistence under lower spatial heterogeneity in habitat quality, all else equal. Second, I implement an individual‐based model to explore prior experience and prospecting on conspecific success within a more complex, and spatially heterogeneous environment. Uniquely, I jointly examine the effects of simulated habitat loss, spatial heterogeneity prior to habitat, and variation in information gathering on population persistence. I find that habitat loss accelerates population quasi‐extinction risk; however, information use reduces extinction probabilities in proportion to the level of information gathering. Per capita reproductive success declines with number of breeding sites, suggesting that information‐mediated Allee effects may contribute to extinction risk. In conclusion, my study suggests that populations in a changing world may be increasingly vulnerable to extinction where patch size and spatial heterogeneity constrain the effectiveness of information‐use strategies.

Carryover effects drive competitive dominance in spatially structured environments

Understanding how changes to the quality of habitat patches affect the distribution of species across the whole landscape is critical in our human-dominated world and changing climate. Although patterns of species' abundances across a landscape are clearly influenced by dispersal among habitats and local species interactions, little is known about how the identity and origin of dispersers affect these patterns. Because traits of individuals are altered by experiences in their natal habitat, differences in the natal habitat of dispersers can carry over when individuals disperse to new habitats and alter their fitness and interactions with other species. We manipulated the presence or absence of such carried-over natal habitat effects for up to eight generations to examine their influence on two interacting species across multiple dispersal rates and different habitat compositions. We found that experimentally accounting for the natal habitat of dispersers significantly influenced competitive outcomes at all spatial scales and increased total community biomass within a landscape. However, the direction and magnitude of the impact of natal habitat effects was dependent upon landscape type and dispersal rate. Interestingly, effects of natal habitats increased the difference between species performance across the landscape, suggesting that natal habitat effects could alter competitive interactions to promote spatial coexistence. Given that heterogeneity in habitat quality is ubiquitous in nature, natal habitat effects are likely important drivers of spatial community structure and could promote variation in species performance, which may help facilitate spatial coexistence. The results have important implications for conservation and invasive species management.

Stock-specific advection of larval walleye (Sander vitreus) in western Lake Erie: Implications for larval growth, mixing, and stock discrimination

Physical processes can generate spatiotemporal heterogeneity in habitat quality for fish and also influence the overlap of pre-recruit individuals (e.g., larvae) with high-quality habitat through hydrodynamic advection. In turn, individuals from different stocks that are produced in different spawning locations or at different times may experience dissimilar habitat conditions, which can underlie within- and among-stock variability in larval growth and survival. While such physically-mediated variation has been shown to be important in driving intra- and inter-annual patterns in recruitment in marine ecosystems, its role in governing larval advection, growth, survival, and recruitment has received less attention in large lake ecosystems such as the Laurentian Great Lakes. Herein, we used a hydrodynamic model linked to a larval walleye (Sander vitreus) individual-based model to explore how the timing and location of larval walleye emergence from several spawning sites in western Lake Erie (Maumee, Sandusky, and Detroit rivers; Ohio reef complex) can influence advection pathways and mixing among these local spawning populations (stocks), and how spatiotemporal variation in thermal habitat can influence stock-specific larval growth. While basin-wide advection patterns were fairly similar during 2011 and 2012, smaller scale advection patterns and the degree of stock mixing varied both within and between years. Additionally, differences in larval growth were evident among stocks and among cohorts within stocks which were attributed to spatiotemporal differences in water temperature. Using these findings, we discuss the value of linked physical–biological models for understanding the recruitment process and addressing fisheries management problems in the world's Great Lakes.

Wild bison as ecological indicators of the effectiveness of management practices to increase forage quality on open rangeland

Habitat manipulations through the use of fire or mechanical treatments are often used to combat woody plant encroachment and increase foraging opportunities for wildlife and livestock. This creates spatial heterogeneity in habitat quality that large herbivores should respond to in ways predicted by ideal free distribution theory. We monitored free-ranging bison to test whether, (1) manipulated habitats offer higher quality forage than habitats in undisturbed rangeland, (2) bison respond through changes in herd composition or activity to differences in habitat quality, and (3) burned and mechanically treated habitats offer similar forage qualities. We found that habitat types burned ∼10 years ago continue to produce higher quality forage as evidenced by bison fecal N concentration (14.4gkg−1 dry mass) than open (10.5gkg−1), closed (10.6gkg−1), or mechanically manipulated habitats (11.7gkg−1). Bison herd composition and activity did not vary across habitat types within seasons, despite some between-season variation in overall group composition with sexual segregation being most evident before mid-summer. For semi-arid rangelands encroached with woody vegetation (e.g. piñon–juniper in the western USA) our evidence from free-ranging bison indicates that burning results in higher quality forage than occurs in both mechanically manipulated and undisturbed habitats. Bison roam widely from water, sample available vegetation continuously, and are long-lived gregarious animals that learn to exploit the spatiotemporal heterogeneity in their large home ranges. Bison also have very similar diets to cattle and so, where bison and cattle are allowed to comingle, we suggest the foraging parameters of free-ranging bison are effective ecological indicators of rangeland quality for both bison and cattle.

Melding kin structure and demography to elucidate source and sink habitats in fragmented landscapes

The source‐sink model undoubtedly is one of the most established paradigms for associating variance in population dynamics with heterogeneity in habitat quality. However, despite extensive theoretical support by the scientific community, the majority of studies seeking empirical validation for this model have lacked sufficient data to distinguish source and sink habitats, particularly for large or secretive mammals. Using relatively long‐term mark‐recapture and genetic data for a generalist mesopredator within a fragmented agricultural ecosystem, we show that use of a two‐stage approach incorporating both genetic and demographic data can be a powerful tool for evaluating the population structure of organisms occupying complex ecological systems. We further demonstrate that a strong concordance exists between demographic attributes and underlying genetic expectations, suggesting evaluation of fine‐scale genetic patterns alone may provide valuable insights into the population dynamics of species. These data have important implications for advancing our ability to quantify heterogeneity in population stability, particularly for large or imperiled species where sufficient demographic data cannot be obtained to parameterize traditional source‐sink models.

Spatial, temporal, and density-dependent components of habitat quality for a desert owl.

Spatial variation in resources is a fundamental driver of habitat quality but the realized value of resources at any point in space may depend on the effects of conspecifics and stochastic factors, such as weather, which vary through time. We evaluated the relative and combined effects of habitat resources, weather, and conspecifics on habitat quality for ferruginous pygmy-owls (Glaucidium brasilianum) in the Sonoran Desert of northwest Mexico by monitoring reproductive output and conspecific abundance over 10 years in and around 107 territory patches. Variation in reproductive output was much greater across space than time, and although habitat resources explained a much greater proportion of that variation (0.70) than weather (0.17) or conspecifics (0.13), evidence for interactions among each of these components of the environment was strong. Relative to habitat that was persistently low in quality, high-quality habitat buffered the negative effects of conspecifics and amplified the benefits of favorable weather, but did not buffer the disadvantages of harsh weather. Moreover, the positive effects of favorable weather at low conspecific densities were offset by intraspecific competition at high densities. Although realized habitat quality declined with increasing conspecific density suggesting interference mechanisms associated with an Ideal Free Distribution, broad spatial heterogeneity in habitat quality persisted. Factors linked to food resources had positive effects on reproductive output but only where nest cavities were sufficiently abundant to mitigate the negative effects of heterospecific enemies. Annual precipitation and brooding-season temperature had strong multiplicative effects on reproductive output, which declined at increasing rates as drought and temperature increased, reflecting conditions predicted to become more frequent with climate change. Because the collective environment influences habitat quality in complex ways, integrated approaches that consider habitat resources, stochastic factors, and conspecifics are necessary to accurately assess habitat quality.

Predicting top predator habitats in the Southwest Indian Ocean

Top predators need to develop optimal strategies of resources and habitats utilization in order to optimize their foraging success. At the individual scale, a predator has to maximize his intake of food while minimizing his cost of foraging to optimize his energetic gain. At the ecosystem scale, we hypothesized that foraging strategies of predators also respond to their general energetic constraints. Predators with energetically costly lifestyles may be constrained to select high quality habitats whereas more phlegmatic predators may occupy both low and high quality habitats. The objectives of this study were 1) to investigate predator responses to heterogeneity in habitat quality with reference to their energetic strategies and 2) to evaluate their responses to contemporaneous versus averaged habitat quality. We collected cetacean and seabird data from an aerial survey in the Southwest Indian Ocean, a region characterized by heterogeneous oceanographic conditions. We classified cetaceans and seabirds into energetic guilds and described their habitats using remotely sensed covariates at contemporaneous and time‐averaged resolutions and static covariates. We used generalized additive models to predict their habitats at the regional scale. Strategies of habitat utilization appeared in accordance with predators energetic constraints. Cetaceans responded to the heterogeneity in habitat quality, with higher densities predicted in more productive areas. However, the costly Delphininae appeared to be more dependent on habitat quality (showing a 1‐to‐13 ratio between the lowest and highest density sectors) than the more phlegmatic sperm and beaked whales (showing only a 1‐to‐3 ratio). For seabirds, predictions primarily reflected colony locations, although the colony effect was stronger for costly seabirds. Moreover, our results suggest that predators may respond better to persistent oceanographic features. To provide a third dimension to habitat quality, cetacean strategies of utilization of the vertical habitat could be related to the distribution of micronekton in the water column.

Fortune favours the aggressive: territory quality and behavioural syndromes in song sparrows, Melospiza melodia

While the relationship between aggression and resource value in competitions for discrete resources is well established, the relationship between aggression and territory quality is less well understood. Territoriality imposes spatial structure on social interactions: if spatial heterogeneity in habitat quality leads to clustering of high- and low-quality territories, and if consistently more aggressive individuals are more likely to obtain higher-quality territories, the resulting clusters of territory holders of similar aggression are likely to influence a wide array of social dynamics in territorial species, particularly when aggressive behaviour is consistently associated with variation in other behaviours, such as boldness. Using 8 years of historical nesting data in a northeastern population of song sparrows, we here determine (1) whether historical nesting success (defined both as clutch size and survival) is spatially clustered; and (2) whether aggression or boldness in first-year territorial males is correlated with the historical clutch size or nest survival of each male's territory. We found significant clustering of both predation risk and large clutch sizes, even when controlling for the identities of historical territory owners. The aggressive behaviour of new territorial males was correlated with historical clutch size, but not with historical nest survival; in contrast, boldness was not correlated with either historical clutch size or nest survival. Thus, spatial variation in habitat quality is correlated with territorial aggression, but territory holders may either prioritize or be unable to assess all variables contributing to territory quality. In addition, a boldness-aggression syndrome does not necessarily result in both behaviours covarying with territory quality.

Environmental, biological and anthropogenic effects on grizzly bear body size: temporal and spatial considerations.

BackgroundIndividual body growth is controlled in large part by the spatial and temporal heterogeneity of, and competition for, resources. Grizzly bears (Ursus arctos L.) are an excellent species for studying the effects of resource heterogeneity and maternal effects (i.e. silver spoon) on life history traits such as body size because their habitats are highly variable in space and time. Here, we evaluated influences on body size of grizzly bears in Alberta, Canada by testing six factors that accounted for spatial and temporal heterogeneity in environments during maternal, natal and ‘capture’ (recent) environments. After accounting for intrinsic biological factors (age, sex), we examined how body size, measured in mass, length and body condition, was influenced by: (a) population density; (b) regional habitat productivity; (c) inter-annual variability in productivity (including silver spoon effects); (d) local habitat quality; (e) human footprint (disturbances); and (f) landscape change.ResultsWe found sex and age explained the most variance in body mass, condition and length (R2 from 0.48–0.64). Inter-annual variability in climate the year before and of birth (silver spoon effects) had detectable effects on the three-body size metrics (R2 from 0.04–0.07); both maternal (year before birth) and natal (year of birth) effects of precipitation and temperature were related with body size. Local heterogeneity in habitat quality also explained variance in body mass and condition (R2 from 0.01–0.08), while annual rate of landscape change explained additional variance in body length (R2 of 0.03). Human footprint and population density had no observed effect on body size.ConclusionsThese results illustrated that body size patterns of grizzly bears, while largely affected by basic biological characteristics (age and sex), were also influenced by regional environmental gradients the year before, and of, the individual’s birth thus illustrating silver spoon effects. The magnitude of the silver spoon effects was on par with the influence of contemporary regional habitat productivity, which showed that both temporal and spatial influences explain in part body size patterns in grizzly bears. Because smaller bears were found in colder and less-productive environments, we hypothesize that warming global temperatures may positively affect body mass of interior bears.

Dragonflies cause spatial and temporal heterogeneity in habitat quality for butterflies

. 1. Mortality caused by natural enemies is an essential but largely overlooked aspect of habitat quality for herbivorous insects. Quantitative data on mortality sources and their spatiotemporal variation are especially scarce for adult insects. 2. Here we report the results of an extensive field study aimed to quantify spatial and seasonal variation in dragonfly predation on adult butterflies in their natural habitats in temperate calcareous grasslands. We rely on direct observations of actual predation events during standardised transect walks. 3. Dragonflies were found to exert high mortality in butterflies. Their impact on butterflies was dependent on predator abundance, which strongly varied among habitat patches and during the season. This suggests that dragonflies can generate substantial spatiotemporal heterogeneity in habitat quality for butterflies in terms of survival. 4. Obtaining prior knowledge of where and when predators are abundant, and avoiding such sites for butterfly conservation, could considerably improve the efficiency of butterfly conservation practices.