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1.
In fragmented landscapes, the likelihood that a species occupies a particular habitat patch is thought to be a function of
both patch area and patch isolation. Ecologically scaled landscape indices (ESLIs) combine a species’ ecological profile,
i.e., area requirements and dispersal ability, with indices of patch area and connectivity. Since their introduction, ESLIs
for area have been modified to incorporate patch quality. ESLIs for connectivity have been modified to incorporate niche breadth,
which may influence a species’ ease in crossing the non-habitat matrix between patches. We evaluated the ability of 4 ESLIs,
the original and modified indices of area and connectivity, to explain patterns in patch occupancy of 5 forest rodents. Occupancy
of eastern gray squirrels ( Sciurus carolinensis), North American red squirrels ( Tamiasciurus hudsconicus), fox squirrels ( Sciurus niger), white-footed mice ( Peromyscus leucopus), and eastern chipmunks ( Tamias striatus) was modeled at 471 sites in 35 landscapes sampled from the upper Wabash River basin in Indiana. Models containing ESLIs
received support for gray squirrels, red squirrels, and chipmunks. Modified ESLIs were important in models for red squirrels.
However, none of the models demonstrated high predictive ability. Incorporating habitat quality and using surrogate measures
of dispersal can have important effects on model results. Additionally, different responses of species to area, isolation,
and habitat quality suggest that generalizing patterns of metapopulation dynamics was not justified, even across closely related
species. 相似文献
2.
Conservation of populations in fragmented habitats is often based on spatially realistic metapopulation theory, which predicts
negative relationships between patch extinction and area and patch colonization and isolation. Cost-distance metrics have
been developed to integrate habitat quality into measures of connectivity, and thus may improve predictive power of the area-isolation
paradigm. Few studies use empirical data to compare predictive performance of complex cost-distance metrics to simple metrics
relying on Euclidean distances. We used 3 years of presence–absence data to examine relative influence of habitat quality,
habitat area, and connectivity on occupancy and extinction rates for Poliocitellus franklinii (Franklin’s ground squirrel), a rare grassland species of conservation concern. We calculated connectivity using nearest-neighbor
(NN) and incidence function model (IFM) metrics based on Euclidean and cost-distances. Habitat quality, area, and connectivity
were all positive predictors for occupancy, but only isolation was a positive predictor of extinction. P. franklinii does not appear to be a tallgrass prairie obligate, but the species distribution is limited by isolation of suitable grassland
habitat. A simple NN metric measuring Euclidean distance between a target area and nearest occupied source outperformed IFM
(Euclidean and cost-distance) in predicting occupancy and extinction for P. franklinii. Although NN metrics are criticized for considering only the contribution of the source nearest to a target, this simplicity
may be acceptable when measuring connectivity for rare species with few occupied habitat patches within dispersal distance. 相似文献
3.
The distribution and abundance of a species may be simultaneously influenced by both local-scale habitat features and the
broader patch and landscape contexts in which these populations occur. Different factors may influence patch occupancy (presence–absence)
versus local abundance (number of individuals within patches), and at different scales, and thus ideally both occupancy and
abundance should be investigated, especially in studies that seek to understand the consequences of land management on species
persistence. Our study evaluated the relative influences of variables associated with the local habitat patch, hillside (patch
context), and landscape context on patch occupancy and abundance of the collared lizard ( Crotaphytus collaris) within tallgrass prairie managed under different fire and grazing regimes in the northern Flint Hills of Kansas, USA. Using
a multi-model information-theoretic approach that accounted for detection bias, we found that collared lizard abundance and
occupancy was influenced by factors measured at both the local habitat and landscape scales. At a local scale, collared lizard
abundance was greatest on large rock ledges that had lots of crevices, high vegetation complexity, and were located higher
up on the hillslope. At the landscape scale, collared lizard abundance and occupancy were both higher in watersheds that were
burned frequently (1–2 year intervals). Interestingly, grazing only had a significant effect on occupancy and abundance within
less frequently burned (4-year burn interval) watersheds. Our results suggest that, in addition to the obvious habitat needs
of this species (availability of suitable rock habitat), land-management practices have the potential to influence collared
lizard presence and abundance in the grasslands of the Flint Hills. Thus, mapping the availability of suitable habitat is
unlikely to be sufficient for evaluating species distributions and persistence in such cases without consideration of landscape
management and disturbance history. 相似文献
4.
Classical metapopulation models do not account for temporal changes in the suitability of habitat patches. In reality, however,
the carrying capacity of most habitat types is not constant in time due to natural succession processes. In this study, we
modeled plant metapopulation persistence in a successional landscape with disappearing and emerging habitat patches, based
on a realistic dune slack landscape at the Belgian–French coast. We focused on the effects of the variation of different plant
traits on metapopulation persistence in this changing landscape. Therefore, we used a stage based stochastic metapopulation
model implemented in RAMAS/Metapop, simulating a large variation in plant traits but keeping landscape characteristics such
as patch turnover rate and patch lifespan constant. The results confirm the conclusions of earlier modeling work that seed
dispersal distance and seed emigration rate both have an important effect on metapopulation persistence. We also found that
high population growth rate or high recruitment considerably decreased the extinction risk of the metapopulation. Additionally,
a long plant life span had a strong positive effect on metapopulation persistence, irrespective of the plant's dispersal capacity
and population growth rate. Plant species that invest in life span require less investment in offspring and dispersal capacity
to avoid extinction, even in dynamic landscapes with deterministic changes in habitat quality. Moreover, metapopulations of
long-lived plant species were found to be much less sensitive to high levels of environmental stochasticity than short-lived
species. 相似文献
5.
In fragmented landscapes, a species?? dispersal ability and response to habitat condition are key determinants of persistence. To understand the relative importance of dispersal and condition for survival of Nephrurus stellatus (Gekkonidae) in southern Australia, we surveyed 92 woodland remnants three times. This gecko favours early post-fire succession conditions so may be at risk of extinction in the long-unburnt agricultural landscape. Using N-mixture models, we compared the influence of four measures of isolation, patch area and two habitat variables on the abundance and occurrence of N. stellatus, while taking into account detection probability. Patch occupancy was high, despite the long-term absence of fire from most remnants. Distance to the nearest occupied site was the most informative measure of patch isolation, exhibiting a negative relationship with occupancy. Distance to a nearby conservation park had little influence, suggesting that mainland?Cisland metapopulation dynamics are not important. Abundance and occurrence were positively related to ?%-cover of spinifex ( Triodia), indicating that niche-related factors may also contribute to spatial dynamics. Patterns of patch occupancy imply that N. stellatus has a sequence of spatial dynamics across an isolation gradient, with patchy populations and source-sink dynamics when patches are within 300?m, metapopulations at intermediate isolation, and declining populations when patches are separated by >1?C2?km. Considering the conservation needs of the community, habitat condition and connectivity may need to be improved before fire can be reintroduced to the landscape. We speculate that fire may interact with habitat degradation and isolation, increasing the risk of local extinctions. 相似文献
6.
The effects of habitat area and fragmentation are confounded in many studies. Since a reduction in habitat area alone reduces
patch size and increases patch isolation, many studies reporting fragmentation effects may really be documenting habitat-area
effects. We designed an experimental landscape system in the field, founded on fractal neutral landscape models, to study
arthropod community responses to clover habitat in which we adjusted the level of fragmentation independently of habitat area.
Overall, habitat area had a greater and more consistent effect on morphospecies richness than fragmentation. Morphospecies
richness doubled between 10 and 80% habitat, with the greatest increase occurring up to 40% habitat. Fragmentation had a more
subtle and transient effect, exhibiting an interaction at intermediate levels of habitat only at the start of the study or
in the early-season (June) survey. In these early surveys, morphospecies richness was higher in clumped 40–50% landscapes
but higher in fragmented landscapes at 60–80% habitat. Rare or uncommon species are expected to be most sensitive to fragmentation
effects, and we found a significant interaction with fragmentation at intermediate levels of habitat for these types of morphospecies
in early surveys. Although the effects of fragmentation are expected to amplify at higher trophic levels, all trophic levels
exhibited a significant fragmentation effect at intermediate levels of habitat in these early surveys. Predators/parasitoids
were more sensitive to habitat area than herbivores, however. Thus, our results confirm that habitat area is more important
than fragmentation for predicting arthropod community responses, at least in this agricultural system. 相似文献
7.
The importance of the spatial as well as the temporal structure of habitat patches for urban biodiversity has been recognised,
but rarely quantified. In dynamic environments the rate of habitat destruction and recreation (i.e. the landscape turnover
rate), the minimum amount of potential habitat, its spatial configuration as well as the environmental conditions determining
habitat quality are crucial factors for species occurrence. We analysed species responses to environmental parameters and
to the spatio-temporal configuration of urban brownfield habitats in a multi-species approach (37 plant and 43 insect species).
Species presence/absence data and soil parameters, site age, vegetation structure and landscape context were recorded by random
stratified sampling at 133 study plots in industrial areas in the city of Bremen (Germany). Based on the field data, we predicted
species occurrences by species distribution models using a multi-model inference approach. Predicted species communities were
driven by successional age both at the scale of a single building lot and at the landscape scale. Minimum average succession
time of brownfield habitats required to support all and especially regionally rare species depended on the proportion of available
open space; the larger the potential habitat area the faster the acceptable turnover. Most plant, grasshopper, and leafhopper
species modelled could be maintained at an intermediate turnover rate (mean age of 10–15 years) and a proportion of open sites
of at least 40%. Our modelling approach provides the opportunity of inferring optimal spatio-temporal landscape configurations
for urban conservation management from patch scale species-environment relationships. The results indicate that urban planning
should incorporate land use dynamics into the management of urban biodiversity.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. 相似文献
8.
Patch geometry and habitat quality among patches are widely recognized as important factors affecting population dynamics in fragmented landscapes. Little is known, however, about the influence of within-patch habitat quality on population dynamics. In this paper, we investigate the relative importance of patch geometry and within-patch habitat quality in determining population dynamics using a spatially explicit, agent-based model. We simulate two mobile species that differ in their species traits: one resembles a habitat specialist and the other a habitat generalist. Habitat quality varies continuously within habitat patches in space (and time). The results show that spatial variation in within-patch quality, together with patch area, controls population abundance of the habitat specialist. In contrast, the population size of the generalist species depends on patch area and isolation. Temporal variation in within-patch quality is, however, less influential in driving the population resilience of both species. We conclude that specialist species are more sensitive than generalist species to within-patch variation in habitat quality. The patch area-isolation paradigm, developed in metapopulation theory, should incorporate variation in within-patch habitat quality, particularly for habitat specialists. 相似文献
9.
Metapopulation models are frequently used for analysing species–landscape interactions and their effect on structure and dynamic
of populations in fragmented landscapes. They especially support a better understanding of the viability of metapopulations.
In such models, the processes determining metapopulation viability are often modelled in a simple way. Animals’ dispersal
between habitat fragments is mostly taken into account by using a simple dispersal function that assumes the underlying process
of dispersal to be random movement. Species-specific dispersal behaviour such as a systematic search for habitat patches is
likely to influence the viability of a metapopulation. Using a model for metapopulation viability analysis, we investigate
whether such specific dispersal behaviour affects the predictions of ranking orders among alternative landscape configurations
rated regarding their ability to carry viable metapopulations. To incorporate dispersal behaviour in the model, we use a submodel
for the colonisation rates which allows different movement patterns to be considered (uncorrelated random walk, correlated
random walk with various degrees of correlation, and loops). For each movement pattern, the landscape order is determined
by comparing the resulting mean metapopulation lifetime Tm of different landscape configurations. Results show that landscape orders can change considerably between different movement
patterns. We analyse whether and under what circumstances dispersal behaviour influences the ranking orders of landscapes.
We find that the ‘competition between patches for migrants’ – i.e. the fact that dispersers immigrating into one patch are
not longer available as colonisers for other patches – is an important factor driving the change in landscape ranks. The implications
of our results for metapopulation modelling, planning and conservation are discussed. 相似文献
10.
Tradable biodiversity credit systems provide flexible means to resolve conflicts between development and conservation land-use
options for habitats occupied by threatened or endangered species. We describe an approach to incorporate the influence of
habitat fragmentation into the conservation value of tradable credits. Habitat fragmentation decreases gene flow, increases
rates of genetic drift and inbreeding, and increases probabilities of patch extinction. Importantly, tradable credit systems
will change the level of fragmentation over time for small and/or declining populations. We apply landscape equivalency analysis
(LEA), a generalizable, landscape-scale accounting system that assigns conservation value to habitat patches based on patch
contributions to abundance and genetic variance at landscape scales. By evaluating habitat trades using two models that vary
the relationship between dispersal behaviors and landscape patterns, we show that LEA provides a novel method for limiting
access to habitat at the landscape-scale, recognizing that the appropriate amount of migration needed to supplement patch
recruitment and to offset drift and inbreeding will vary as landscape pattern changes over time. We also found that decisions
based on probabilities of persistence alone would ignore changes in migration, genetic drift, and patch extinction that result
from habitat trades. The general principle of LEA is that habitat patches traded should make at least equivalent contributions
to rates of recruitment and migration estimated at a landscape scale. Traditional approaches for assessing the “take” and
“jeopardy” standards under the Endangered Species Act based on changes in abundance and probability of persistence may be
inadequate to prevent trades that increase fragmentation. 相似文献
11.
Habitat specificity indices reflect richness ( α) and/or distinctiveness ( β) components of diversity. The latter may be defined by α and γ (landscape) diversity in two alternative ways: multiplicatively () and additively (). We demonstrate that the original habitat specificity concept of Wagner and Edwards (Landscape Ecol 16:121–131, 2001) consists of three independent components: core habitat specificity (uniqueness of the species composition), patch area and
patch species richness. We describe habitat specificity as a family of indices that may include either area or richness components,
or none or both, and open for use of different types of mean in calculation of core habitat specificity. Core habitat specificity
is a beta diversity measure: the effective number of completely distinct communities in the landscape. Habitat specificity
weighted by species number is a gamma diversity measure: the effective number of species that a patch contributes to landscape
richness. We compared 12 habitat specificity indices by theoretical reasoning and by use of field data (vascular plant species
in SE Norwegian agricultural landscapes). Habitat specificity indices are strongly influenced by weights for patch area and
patch species richness, and the relative contribution of rare vs. common species (type of mean). The relevance of properties
emphasized by each habitat specificity index for evaluation of patches in a biodiversity context is discussed. Core habitat
specificity is emphasized as an ecologically interpretable measure that specifically addresses patch uniqueness while habitat
specificity weighted by species number combines species richness and species composition in ways relevant for conservation
biological assessment.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. 相似文献
12.
Knowledge of variation in vascular plant species richness and species composition in modern agricultural landscapes is important
for appropriate biodiversity management. From species lists for 2201 land-type patches in 16 1-km 2 plots five data sets differing in sampling-unit size from patch to plot were prepared. Variation in each data set was partitioned
into seven sources: patch geometry, patch type, geographic location, plot affiliation, habitat diversity, ecological factors,
and land-use intensity. Patch species richness was highly predictable (75% of variance explained) by patch area, within-patch
heterogeneity and patch type. Plot species richness was, however, not predictable by any explanatory variable, most likely
because all studied landscapes contained all main patch types – ploughed land, woodland, grassland and other open land – and
hence had a large core of common species. Patch species composition was explained by variation along major environmental complex
gradients but appeared nested to lower degrees in modern than in traditional agricultural landscapes because species-poor
parts of the landscape do not contain well-defined subsets of the species pool of species-rich parts. Variation in species
composition was scale dependent because the relative importance of specific complex gradients changed with increasing sampling-unit
size, and because the amount of randomness in data sets decreased with increasing sampling-unit size. Our results indicate
that broad landscape structural changes will have consequences for landscape-scale species richness that are hard or impossible
to predict by simple surrogate variables. 相似文献
13.
We examined the effects of matrix structure and movement responses of organisms on the relationships between 7 patch isolation metrics and patch immigration. Our analysis was based on simulating movement behaviour of two generic disperser types (specialist and generalist) across mosaic landscapes containing three landcover types: habitat, hospitable matrix and inhospitable matrix. Movement, mortality and boundary crossing probabilities of simulated individuals were linked to the landcover and boundary types in the landscapes. The results indicated that area-based isolation metrics generally predict patch immigration more reliably than distance-based isolation metrics. Relationships between patch isolation metrics and patch immigration varied between the two generic disperser types and were affected by matrix composition or matrix fragmentation. Patch immigration was always affected by matrix composition but not by matrix fragmentation. Our results do not encourage the generic use of patch isolation metrics as a substitute for patch immigration, in particular in metapopulation models where generic use may result in wrong projections of the survival probability of metapopulations. However, our examination of the factors affecting the predictive potential of patch isolation metrics should facilitate interpretation and comparison of existing patch isolation studies. Future patch isolation studies should include information about landscape structure and the dispersal distance and dispersal behaviour of the organism of interest.This revised version was published online in May 2005 with corrections to the Cover Date. 相似文献
14.
Understanding the driving forces behind the distribution of threatened species is critical to set priorities for conservation
measures and spatial planning. We examined the distribution of a globally threatened bird, the corncrake ( Crex crex), in the lowland floodplains of the Rhine River, which provide an important breeding habitat for the species. We related
corncrake distribution to landscape characteristics (area, shape, texture, diversity) at three spatial scales: distinct floodplain
units (“floodplain scale”), circular zones around individual observations (“home range scale”), and individual patches (“patch
scale”) using logistic regression. Potential intrinsic spatial patterns in the corncrake data were accounted for by including
geographic coordinates and an autocovariate as predictors in the regression analysis. The autocovariate was the most important
predictor of corncrake occurrence, probably reflecting the strong conspecific attraction that is characteristic of the species.
Significant landscape predictors mainly pertained to area characteristics at the patch scale and the home range scale; the
probability of corncrake occurrence increased with potential habitat area, patch area, and nature reserve area. The median
potential habitat patch size associated with corncrake occurrence was 11.3 ha; 90% of the corncrake records were associated
with patches at least 2.2 ha in size. These results indicate that the corncrake is an area-sensitive species, possibly governed
by the males’ tendency to reside near other males while maintaining distinct territories. Our results imply that corncrake
habitat conservation schemes should focus on the preservation of sufficient potential habitat area and that existing management
measures, like delayed mowing, should be implemented in relatively large, preferably contiguous areas. 相似文献
15.
There is debate among ecologists about whether total habitat area or patch arrangement contributes most to population and/or
community responses to fragmented or patchy landscapes. We tested the relative effects of patch area and isolation for predicting
bird occurrence in a naturally patchy landscape in the Bear River Mountains of Northern Utah, USA. We selected focal patches
(mountain meadows) ranging in elevation from 1,920 to 2,860 m and in size from 0.6 to 182 ha. Breeding birds were sampled
in each focal meadow during the summers of 2003 and 2004 using variable-distance point transects. Logistic regression and
likelihood-based model selection were used to determine the relationship between likelihood of occurrence of three bird species
(Brewer’s sparrow, vesper sparrow, and white-crowned sparrow) and area, isolation, and proximity metrics. We used model weights
and model-averaged confidence intervals to assess the importance of each predictor variable. Plots of area versus isolation
were used to evaluate complex relationships between the variables. We found that meadow area was the most important variable
for explaining occurrence for two species, and that isolation was the most important for the other. We also found that the
absolute distance was more appropriate for evaluating isolation responses than was the species-specific proximity metric.
Our findings add clarity to the debate between ecologists regarding the relative importance of area and isolation in species
responses to patchy landscapes. 相似文献
16.
Land-bridge islands formed by dam construction are considered to be “experimental” systems for studying the effects of habitat
loss and fragmentation, offering many distinct advantages over terrestrial fragments. The Thousand Island Lake in Southeast
China is one such land-bridge system with more than 1000 islands. Based on a field survey of vascular plant richness on 154
land-bridge islands during 2007–2008, we examined the effects of island and landscape attributes on plant species richness
and patterns of species nestedness. We also examined the different responses of plant functional groups (classified according
to growth form and shade tolerance) to fragmentation. We found that island area explained the greatest amount of variation
in plant species richness. Island area and shape index positively affected species diversity and the degree of nestedness
exhibited by plant communities while the perimeter to area ratio of the islands had a negative effect. Shade-tolerant plants
were the most sensitive species group to habitat fragmentation. Isolation negatively affected the degree of nestedness in
herb and shade-intolerant plants including species with various dispersal abilities in the fragmented landscape. Based on
these results, we concluded that the effects of habitat loss and fragmentation on overall species richness depended mostly
on the degree of habitat loss, but patterns of nestedness were generated from different ecological mechanisms due to species-specific
responses to different characteristics of habitat patches. 相似文献
17.
The viability of metapopulations in fragmented landscapes has become a central theme in conservation biology. Landscape fragmentation
is increasingly recognized as a dynamical process: in many situations, the quality of local habitats must be expected to undergo
continual changes. Here we assess the implications of such recurrent local disturbances for the equilibrium density of metapopulations.
Using a spatially explicit lattice model in which the considered metapopulation as well as the underlying landscape pattern
change dynamically, we show that equilibrium metapopulation density is maximized at intermediate frequencies of local landscape
disturbance. On both sides around this maximum, the metapopulation may go extinct. We show how the position and shape of the
intermediate viability maximum is responding to changes in the landscape’s overall habitat quality and the population’s propensity
for local extinction. We interpret our findings in terms of a dual effect of intensified landscape disturbances, which on
the one hand exterminate local populations and on the other hand enhance a metapopulation’s capacity for spreading between
habitat clusters. 相似文献
18.
ContextThe classical theory of island biogeography explains loss of species in fragmented landscapes as an effect of remnant patch size and isolation. Recently this has been challenged by the habitat amount and habitat continuum hypotheses, according to which persistence in modified landscapes is related to total habitat amount rather than habitat configuration or the ability of species to use all habitats to varying degrees. Distinguishing between these theories is essential for effective conservation planning in modified landscapes.ObjectiveIdentify which factors of habitat type, amount and configuration predict the persistence of a keystone woodland specialist, the eastern bettong Bettongia gaimardi, in a fragmented landscape.MethodIn the Midlands region of Tasmania we carried out camera surveys at 62 sites in summer and winter. We included habitat and landscape features to model whether habitat amount or patch size and isolation influenced the presence of the eastern bettong, and to measure effects of habitat quality.ResultsHabitat amount within a 1 km buffer was a better predictor of occupancy than patch size and isolation. Occupancy was also affected by habitat quality, indicated by density of regenerating stems.ConclusionOur results support the habitat amount hypothesis as a better predictor of presence. For a species that is able to cross the matrix between remnant patches and utilise multiple patches, the island biogeography concept does not explain habitat use in fragmented landscapes. Our results emphasize the value of small remnant patches for conservation of the eastern bettong, provided those patches are in good condition. 相似文献
19.
Management of tropical marine environments calls for interdisciplinary studies and innovative methodologies that consider processes occurring over broad spatial scales. We investigated relationships between landscape structure and reef fish assemblage structure in the US Virgin Islands. Measures of landscape structure were transformed into a reduced set of composite indices using principal component analyses (PCA) to synthesize data on the spatial patterning of the landscape structure of the study reefs. However, composite indices (e.g., habitat diversity) were not particularly informative for predicting reef fish assemblage structure. Rather, relationships were interpreted more easily when functional groups of fishes were related to individual habitat features. In particular, multiple reef fish parameters were strongly associated with reef context. Fishes responded to benthic habitat structure at multiple spatial scales, with various groups of fishes each correlated to a unique suite of variables. Accordingly, future experiments should be designed to test functional relationships based on the ecology of the organisms of interest. Our study demonstrates that landscape-scale habitat features influence reef fish communities, illustrating promise in applying a landscape ecology approach to better understand factors that structure coral reef ecosystems. Furthermore, our findings may prove useful in design of spatially-based conservation approaches such as marine protected areas (MPAs), because landscape-scale metrics may serve as proxies for areas with high species diversity and abundance within the coral reef landscape. 相似文献
20.
Tick density and population dynamics are important factors in the ecological processes involved in pathogen circulation in
a habitat. These characteristics of tick populations are closely linked to habitat suitability, which reflects the limiting
ecological factors and landscape features affecting tick populations; however, little work has been done on the regional assessment
of habitat suitability. In this study, a regional model for the distribution and abundance of the tick Ixodes ricinus in central Spain is developed. An occurrence and an abundance model were constructed; climate and vegetation variables were
found to be the main predictors of both occurrence and density in a relatively homogeneous matrix of habitat patches, whereas
topographical variables were found to have small contributions and were therefore discarded. The residuals of the abundance
model showed good correlation with the isolation of each patch. The predictive power of the abundance model was greatly enhanced
by inclusion of the traversability (a measure of the permeability of each patch to the propagules of the metapopulation) and
recruitment (an index of the relative importance of each patch to the traffic through the entire habitat network). The removal
from the landscape of the patches whose recruitment values were in the top 10% has a critical effect on tick density, an effect
not observed when patches are removed at random. These results indicate that permanent tick populations can be sustained only
in landscapes containing a minimum network of viable sites. Graph theory and measurements of patch isolation should prove
to be important elements in the forecasting of tick abundance and the management of the features underlying the landscape
ecology of tick populations and pathogen circulation in the field. 相似文献
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