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1.
Habitat fragmentation is expected to disrupt dispersal, and thus we explored how patch metrics of landscape structure, such as percolation thresholds used to define landscape connectivity, corresponded with dispersal success on neutral landscapes. We simulated dispersal as either a purely random process (random direction and random step lengths) or as an area-limited random walk (random direction, but movement limited to an adjacent cell at each dispersal step) and quantified dispersal success for 1000 individuals on random and fractal landscape maps across a range of habitat abundance and fragmentation. Dispersal success increased with the number of cells a disperser could search (m), but poor dispersers (m<5) searching via area-limited dispersal on fractal landscapes were more successful at locating suitable habitat than random dispersers on either random or fractal landscapes. Dispersal success was enhanced on fractal landscapes relative to random ones because of the greater spatial contagion of habitat. Dispersal success decreased proportionate to habitat loss for poor dispersers (m=1) on random landscapes, but exhibited an abrupt threshold at low levels of habitat abundance (p<0.1) for area-limited dispersers (m<10) on fractal landscapes. Conventional metrics of patch structure, including percolation, did not exhibit threshold behavior in the region of the dispersal threshold. A lacunarity analysis of the gap structure of landscape patterns, however, revealed a strong threshold in the variability of gap sizes at low levels of habitat abundance (p<0.1) in fractal landscapes, the same region in which abrupt declines in dispersal success were observed. The interpatch distances or gaps across which dispersers must move in search of suitable habitat should influence dispersal success, and our results suggest that there is a critical gap-size structure to fractal landscapes that interferes with the ability of dispersers to locate suitable habitat when habitat is rare. We suggest that the gap structure of landscapes is a more important determinant of dispersal than patch structure, although both are ultimately required to predict the ecological consequences of habitat fragmentation. 相似文献
2.
Steven Walters 《Landscape Ecology》2007,22(6):867-881
Understanding the impacts of habitat fragmentation on dispersal is an important issue in landscape and conservation ecology.
Here I examine the effects of fine- to broad-scale patterns in landscape structure on dispersal success of organisms with
differing life-history traits. An individual-based model was used to simulate dispersal of amphibian-like species whose movements
were driven by land cover and moisture conditions. To systematically control spatial pattern, a landscape model was created
by merging simulated land cover maps with synthetic topographic surfaces. Landscapes varied in topographic roughness and spatial
contagion in agriculture and urban land cover. Simulations included three different species types that varied in their maximum
potential dispersal distances by 1-, 2-, or 4-fold. Two sets of simulations addressed effects of varying aspects of landscape
structure on dispersal success. In the first set of simulations, which incorporated variable distances between breeding patches,
dispersal success was lowest for all species types when anthropogenic cover was patchily distributed. In the second set, with
interpatch distances held constant as landscape composition varied, dispersal success decreased as anthropogenic cover became
spatially contagious. Both sets revealed strong main effects of species characteristics, interpatch distances and landscape
composition on dispersal success; furthermore, scale-dependent patterns in land cover and moisture gradients had a stronger
effect on longer- than shorter-ranging species types. Taken together, these simulations suggest that heuristic conservation
strategies could potentially be developed based on important but limited life history information. 相似文献
3.
There exists a gradient in dispersal behavior from passive to active, which reflects organisms’ dependence upon currents vs. self-propelled movement. We asked: Do currents modify organism–landscape interactions to influence recruitment success along this dispersal gradient? Using a spatially-explicit cellular model, we simulated the recruitment success of three generalized dispersal strategies (walkers, swimmers, and drifters) through hierarchically structured benthic landscapes. We evaluated the relative recruitment success (recruited population size, overall area occupied, time to recruit) of the three dispersal strategies in similar landscapes, as well as the consequences of varying the total proportion of habitat suitable for recruitment, and the scale and pattern of habitat patchiness on recruitment success. In the presence of currents, swimmers and drifters generally recruited over larger areas and in less time than walkers. Differences among the dispersal strategies’ recruitment success were most pronounced when an intermediate number of good habitat cells (16–48% of landscape) were broadly dispersed across the landscape. Although recruitment success always increased with increasing proportion of good habitat, drifters were more sensitive, and swimmers less sensitive, to these landscape changes than walkers. We also found that organisms dispersing within currents typically responded non-linearly (logarithmically or exponentially) to increasing proportion of total good habitat, whereas walkers more often responded linearly. 相似文献
4.
The tallgrass prairie of North America has undergone widespread habitat loss and fragmentation (<4% remains). The Flint Hills
region of Kansas and Oklahoma is the largest tallgrass prairie remaining and therefore provides an opportunity to study the
population genetic structure of grassland species in a relatively contiguous landscape and set a baseline for evaluating changes
when the habitat is fragmented. We adopted a landscape genetics approach to identify how landscape structure affected dispersal,
population genetic structure, and landscape connectivity of the Eastern Yellowbelly Racer (Coluber constrictor flaviventris) across a 13,500-km2 landscape in northeastern Kansas, USA. The racer population had high allelic diversity, high heterozygosity, and was maintaining
migration-drift equilibrium. Autocorrelation between genetic and geographic distance revealed that racers exhibited restricted
dispersal within 3 km, and isolation-by-distance. Significant isolation-by-distance occurred at broad regional scales (>100 km),
but because of sufficient gene flow between locations, we were unable to define discrete subpopulations using Bayesian clustering
analyses. Resistance distance, which considers the permeability of habitats, did not explain significant variation in genetic
distance beyond Euclidean distance alone, suggesting that racers are not currently influenced by landscape composition. In
northeastern Kansas, racers appear to be an abundant and continuously distributed snake that perceives the landscape as well
connected with no cover type currently impeding snake dispersal or gene flow. 相似文献
5.
How should we measure landscape connectivity? 总被引：9，自引：0，他引：9
The methods for measuring landscape connectivity have never been compared or tested for their responses to habitat fragmentation. We simulated movement, mortality and boundary reactions across a wide range of landscape structures to analyze the response of landscape connectivity measures to habitat fragmentation. Landscape connectivity was measured as either dispersal success or search time, based on immigration into all habitat patches in the landscape. Both measures indicated higher connectivity in more fragmented landscapes, a potential for problematic conclusions for conservation plans. We introduce cell immigration as a new measure for landscape connectivity. Cell immigration is the rate of immigration into equal-sized habitat cells in the landscape. It includes both within- and between-patch movement, and shows a negative response to habitat fragmentation. This complies with intuition and existing theoretical work. This method for measuring connectivity is highly robust to reductions in sample size (i.e., number of habitat cells included in the estimate), and we hypothesize that it therefore should be amenable to use in empirical studies. The connectivity measures were weakly correlated to each other and are therefore generally not comparable. We also tested immigration into a single patch as an index of connectivity by comparing it to cell immigration over the landscape. This is essentially a comparison between patch-scale and landscape-scale measurement, and revealed some potential for patch immigration to predict connectivity at the landscape scale. However, this relationship depends on the size of the single patch, the dispersal characteristics of the species, and the amount of habitat in the landscape. We conclude that the response of connectivity measures to habitat fragmentation should be understood before deriving conclusions for conservation management. 相似文献
6.
Spiders associated with the meadow and tree canopies of orchards respond differently to habitat fragmentation 总被引：1，自引：0，他引：1
John D. Herrmann Debra Bailey Gabriela Hofer Felix Herzog Martin H. Schmidt-Entling 《Landscape Ecology》2010,25(9):1375-1384
The response of animal communities to habitat quality and fragmentation may vary depending on microhabitat associations of
species. For example, sensitivity of species to woody habitat fragmentation should increase with their degree of association
with woody plants. We investigated effects of local and landscape factors on spider communities in different microhabitats
within Swiss apple orchards. We expected a stronger negative effect of woody habitat fragmentation on spiders inhabiting tree
canopies compared to spiders living in the meadow. The 30 orchards that we sampled varied in woody habitat amount and isolation
at landscape and patch scales. Local factors included management intensity and plant diversity. Spiders associated with meadow
were affected by plant diversity, but not by fragmentation. In contrast, spiders associated with canopies responded to isolation
from other woody habitats. Surprisingly, we found both positive and negative effects of habitat isolation on local abundance.
This indicates that differences in dispersal and/or biotic interactions shape the specific response to habitat isolation.
The relative importance of local and landscape factors was in accordance with the microhabitat of the spiders. Thus, considering
microhabitat associations can be important for identifying processes that would be overlooked if sampling were pooled for
the whole habitat. 相似文献
7.
Matthew J. Smith Matthew G. Betts Graham J. Forbes Daniel G. Kehler Maryse C. Bourgeois Stephen P. Flemming 《Landscape Ecology》2011,26(5):709-721
Landscape composition and configuration, often termed as habitat loss and fragmentation, are predicted to reduce species population
viability, partly due to the restriction of movement in the landscape. Unfortunately, measuring the effects of habitat loss
and fragmentation on functional connectivity is challenging because these variables are confounded, and often the motivation
for movement by target species is unknown. Our objective was to determine the independent effects of landscape connectivity
from the perspective of a mature forest specialist—the northern flying squirrel (Glaucomys sabrinus). To standardize movement motivation, we translocated 119 squirrels, at varying distances (0.18–3.8 km) from their home range
across landscapes representing gradients in both habitat loss and fragmentation. We measured the physical connectedness of
mature forest using an index of connectivity (landscape coincidence probability). Patches were considered connected if they
were within the mean gliding distance of a flying squirrel. Homing success increased in landscapes with a higher connectivity
index. However, homing time was not strongly predicted by habitat amount, connectivity index, or mean nearest neighbour and
was best explained as a simple function of sex and distance translocated. Our study shows support for the independent effects
of landscape configuration on animal movement at a spatial scale that encompasses several home ranges. We conclude that connectivity
of mature forest should be considered for the conservation of some mature forest specialists, even in forest mosaics where
the distinction between habitat and movement corridors are less distinct. 相似文献
8.
Can landscape indices predict ecological processes consistently? 总被引：36，自引：0，他引：36
The ecological interpretation of landscape patterns is one of the major objectives in landscape ecology. Both landscape patterns and ecological processes need to be quantified before statistical relationships between these variables can be examined. Landscape indices provide quantitative information about landscape pattern. Response variables or process rates quantify the outcome of ecological processes (e.g., dispersal success for landscape connectivity or Morisita's index for the spatial distribution of individuals). While the principal potential of this approach has been demonstrated in several studies, the robustness of the statistical relationships against variations in landscape structure or against variations of the ecological process itself has never been explicitly investigated. This paper investigates the consistency of correlations between a set of landscape indices (calculated with Fragstats) and three response variables from a simulated dispersal process across heterogeneous landscapes (cell immigration, dispersal success and search time) against variation in three experimental treatments (control variables): habitat amount, habitat fragmentation and dispersal behavior. I found strong correlations between some landscape indices and all three response variables. However, 68% of the statistical relationships were highly inconsistent and sometimes ambiguous for different landscape structures and for differences in dispersal behavior. Correlations between one landscape index and one response variable could range from highly positive to highly negative when derived from different spatial patterns. I furthermore compared correlation coefficients obtained from artificially generated (neutral) landscape models with those obtained from Landsat TM images. Both landscape representations produced equally strong and weak statistical relationships between landscape indices and response variables. This result supports the use of neutral landscape models in theoretical analyses of pattern-process relationships. 相似文献
9.
Bosco Laura Wan Ho Yi Cushman Samuel A. Arlettaz Raphaël Jacot Alain 《Landscape Ecology》2019,34(1):105-117
Context
Herbicide treatments in viticulture can generate highly contrasting mosaics of vegetated and bare vineyards, of which vegetated fields often provide better conditions for biodiversity. In southern Switzerland, where herbicides are applied at large scales, vegetated vineyards are limited in extent and isolated from one another, potentially limiting the distribution and dispersal ability of organisms.
ObjectivesWe tested the separate and interactive effects of habitat amount and fragmentation on invertebrate abundance using a multi-scale framework, along with additional environmental factors. We identified which variables at which scales were most important in predicting patterns of invertebrate abundance.
MethodsWe used a factorial design to sample across a gradient of habitat amount (area of vegetated vineyards, measured as percentage of landscape PLAND) and fragmentation (number of vegetated patches, measured as patch density PD). Using 10 different spatial scales, we identified the factors and scales that most strongly predicted invertebrate abundance and tested potential interactions between habitat amount and fragmentation.
ResultsHabitat amount (PLAND index) was most important in predicting invertebrate numbers at a field scale (50 m radius). In contrast, we found a negative effect of fragmentation (PD) at a broad scale of 450 m radius, but no interactive effect between the two.
ConclusionsThe spatial scales at which habitat amount and fragmentation affect invertebrates differ, underpinning the importance of spatially explicit study designs in disentangling the effects between habitat amount and configuration. We showed that the amount of vegetated vineyards has more influence on invertebrate abundance, but that fragmentation also contributed substantially. This suggests that efforts for augmenting the area of vegetated vineyards is more beneficial for invertebrate numbers than attempts to connect them.
相似文献10.
A new, multi-scaled graph visualization approach: an example within the playa wetland network of the Great Plains 总被引：1，自引：1，他引：0
We employed a sliding-window approach at multiple scales (window sizes and dispersal distances) to calculate seven standard graph-theoretical metrics within a subset of a large, freshwater wetland network. In contrast to most graph analyses, which quantify connectivity at a single (global) scale or at a patch-level scale, a multi-scaled, sliding-window approach provides an assessment that bridges these two approaches to examine patch clusters. As a case study we focused on a subset of a habitat patch network in a ~20,000 km2 area encompassing 2,782 playa wetlands in the panhandle of Texas. Playas are seasonal wetlands of the southern Great Plains of North America that form a network of regional habitat resources for wildlife. The large size of this network meant that global metrics failed to capture localized properties, so we used contour mapping to visualize continuous surfaces as functions of playa density, linkage density, and other topological traits at different window sizes and dispersal distances. This technique revealed spatial patterns in the components (i.e., the network properties of regions of the landscape at a given dispersal scale), with the spatial scale of habitat clustering varying with the size of the sliding window and dispersal distance. Using a tool familiar to landscape ecology (sliding-window methodology) in a novel way (to examine ecological networks at multiple scales), our approach provides a way to represent ecologically determined local-scale graph properties and illustrates how a multi-scaled approach is useful in examining habitat connectivity to investigate graph properties. 相似文献
11.
The spatial extent at which landscape structure best predicts population response, called the scale of effect, varies across species. An ability to predict the scale of effect of a landscape using species traits would make landscape study design more efficient and would enable landscape managers to plan at the appropriate scale. We used an individual based simulation model to predict how species traits influence the scale of effect. Specifically, we tested the effects of dispersal distance, reproductive rate, and informed movement behavior on the radius at which percent habitat cover best predicts population abundance in a focal area. Scale of effect for species with random movement behavior was compared to scale of effect for species with three (cumulative) levels of information use during dispersal: habitat based settlement, conspecific density based settlement, and gap-avoidance during movement. Consistent with a common belief among researchers, dispersal distance had a strong, positive influence on scale of effect. A general guideline for empiricists is to expect the radius of a landscape to be 4?C9 times the median dispersal distance or 0.3?C0.5 times the maximum dispersal distance of a species. Informed dispersal led to greater increases in population size than did increased reproductive rate. Similarly, informed dispersal led to more strongly decreased scales of effect than did reproductive rate. Most notably, gap-avoidance resulted in scales that were 0.2?C0.5 times those of non-avoidant species. This is the first study to generate testable hypotheses concerning the mechanisms underlying the scale at which populations respond to the landscape. 相似文献
12.
Strong relations between population trends and spatial distribution have been suggested at the regional scale: declining species
should have more fragmented distributions because decline causes range retractions towards optimal habitats, whereas increasing
species should have more aggregated distributions, because colonization processes are constrained by distance. Most analyses
of the effects of land use changes on animal populations are diachronic studies of population dynamics or synchronic studies
of species habitat selection. Few studies take simultaneously into account temporal changes in habitat distribution and changes
in species spatial distribution. We applied the above rationale to the landscape scale and analysed how population declines,
increases or stability, as diagnosed in a long term study, correlate with population connectivity or fragmentation at that
scale. We used data on changes in faunal distribution and information on temporal changes in the vegetation in a Mediterranean
area that had been subjected to land abandonment. We found that species declining at the landscape scale had retracting fragmented
distributions and that expanding species had expanding continuous distributions. However, for the latter, we suggest that
the factors involved are related to landscape structure and not to dispersal mediated meta-population processes, which are
of little relevance at this local scale. We also show that even species that are numerically stable can show fragmentation
of their distribution and major spatial distribution shifts in response to land use changes, especially in species that have
low occurrence levels or that are associated with transitory habitats such as heterogeneous shrublands (e.g. Sylvia melanocephala). Studying the spatial structure of species distribution patterns at the landscape scale may provide information about population
declines and increases both at the regional and the landscape scale and can improve our understanding of short-term risks
of local extinction. 相似文献
13.
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
14.
Terhi Riutta Eleanor M. Slade Michael D. Morecroft Daniel P. Bebber Yadvinder Malhi 《Landscape Ecology》2014,29(6):949-961
Forest ecosystems have been widely fragmented by human land use, inducing significant microclimatic and biological changes at the forest edge. If we are to rigorously assess the ecological impacts of habitat fragmentation, there is a need to effectively quantify the amount of edge habitat within a landscape, and to allow this to be modelled for individual species and processes. Edge effect may extend only a few metres or as far as several kilometres, depending on the species or process in question. Therefore, rather than attempting to quantify the amount of edge habitat by using a fixed, case-specific distance to distinguish between edge and core, the area of habitat within continuously-varying distances from the forest edge is of greater utility. We quantified the degree of fragmentation of forests in England, where forests cover 10 % of the land area. We calculated the distance from within the forest patches to the nearest edge (forest vs. non-forest) and other landscape indices, such as mean patch size, edge density and distance to the nearest neighbour. Of the total forest area, 37 % was within 30 m and 74 % within 100 m of the nearest edge. This highlights that, in fragmented landscapes, the habitats close to the edge form a considerable proportion of the total habitat area. We then show how these edge estimates can be combined with ecological response functions, to allow us to generate biologically meaningful estimates of the impacts of fragmentation at a landscape scale. 相似文献
15.
Landscape connectivity and animal behavior: functional grain as a key determinant for dispersal 总被引：2，自引：0，他引：2
Landscape connectivity can be viewed from two perspectives that could be considered as extremes of a gradient: functional
connectivity (refers to how the behavior of a dispersing organism is affected by landscape structure and elements) and structural
connectivity (depends on the spatial configuration of habitat patches in the landscape like vicinity or presence of barriers).
Here we argue that dispersal behavior changes with landscape configuration stressing the evolutionary dimension that has often
been ignored in landscape ecology. Our working hypothesis is that the functional grain of resource patches in the landscape
is a crucial factor shaping individual movements, and therefore influencing landscape connectivity. Such changes are likely
to occur on the short-term (some generations). We review empirical studies comparing dispersal behavior in landscapes differing
in their fragmentation level, i.e., with variable resource grain. We show that behavioral variation affecting each of the
three stages of the dispersal process (emigration, displacement or transfer in the matrix, and immigration) is indeed likely
to occur according to selective pressures resulting from changes in the grain of the landscape (mortality or deferred costs).
Accordingly, landscape connectivity results from the interaction between the dispersal behavior of individuals and the grain
of each particular landscape. The existence of this interaction requires that connectivity estimates (being based on individual-based
models, least cost distance algorithms, and structural connectivity metrics or even Euclidian distance) should be carefully
evaluated for their applicability with respect to the required level of precision in species-specific and landscape information. 相似文献
16.
Acknowledgment that the matrix matters in conserving wildlife in human-modified landscapes is increasing. However, the complex
interactions of habitat loss, habitat fragmentation, habitat condition and land use have confounded attempts to disentangle
the relative importance of properties of the landscape mosaic, including the matrix. To this end, we controlled for the amount
of remnant forest habitat and the level of fragmentation to examine mammal species richness in human-modified landscapes of
varying levels of matrix development intensity and patch attributes. We postulated seven alternative models of various patch
habitat, landscape and matrix influences on mammal species richness and then tested these models using generalized linear
mixed-effects models within an information theoretic framework. Matrix attributes were the most important determinants of
terrestrial mammal species richness; matrix development intensity had a strong negative effect and vegetation structural complexity
of the matrix had a strong positive effect. Distance to the nearest remnant forest habitat was relatively unimportant. Matrix
habitat attributes are potentially a more important indicator of isolation of remnant forest patches than measures of distance
to the nearest patch. We conclude that a structurally complex matrix within a human-modified landscape can provide supplementary
habitat resources and increase the probability of movement across the landscape, thereby increasing mammal species richness
in modified landscapes. 相似文献
17.
Context
Land use changes have modified the extent and structure of native vegetation, resulting in fragmentation of native species habitat. Connectivity is increasingly seen as a requirement for effective conservation in these landscapes, but the question remains: ‘connectivity for which species?’.Objective
The aim of this study was to develop and then apply a rapid, expert-based, dispersal guild approach where species are grouped on similar fine-scale dispersal behaviour (such as between scattered trees) and habitat characteristics.Methods
Dispersal guilds were identified using clustering techniques to compare dispersal and habitat parameters elicited from experts. We modelled least-cost paths and corridors between patches and individual movement probabilities within these corridors for each of the dispersal guilds using Circuitscape. We demonstrate our approach with a case study in the Tasmanian Northern Midlands, Australia.Results
The dispersal guild approach grouped the 12 species into five dispersal guilds. The connectivity modelling of those five guilds found that broadly dispersing species in this landscape, such as medium-sized carnivorous mammals, were unaffected by fragmentation while from the perspective of the three dispersal guilds made up of smaller mammals, the landscape appeared highly fragmented.Conclusions
Our approach yields biologically defensible outputs that are broadly applicable, particularly for conservation planning where data and resources are limited. It is a useful first step in multi-species conservation planning which aims to identify those species most in need of conservation efforts.18.
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
19.
Bevan W. Ernst 《Landscape Ecology》2014,29(6):963-978
Habitat connectivity is an essential component of biodiversity conservation. Simulated landscapes were manipulated to quantify the impact of changes to the amount, fragmentation and dispersion of habitat on a widely applied landscape connectivity metric, the probability of connectivity index. Index results for different landscape scenarios were plotted against the dispersal distances used for their calculation to create connectivity response curves for each scenario. Understanding index response to controlled changes in landscape structure at a range of spatial scales can be used to give context to comparison of alternative landscape management scenarios. Increased amounts of habitat, decreased fragmentation and decreased inter-patch distances resulted in increased connectivity index values. Connectivity response curves demonstrated increases in assessed connectivity for scenarios with continuous corridors or “stepping stone” connectors. The sensitivity of connectivity response curves to controlled changes in landscape structure indicate that this approach is able to detect and distinguish between different types of landscape changes, but that delineation of habitat and method of quantifying dispersal probability incorporate assumptions that must be recognized when interpreting results to guide landscape management. Representing landscape connectivity in this manner allows for the impacts of alternative landscape management strategies to be compared visually through comparative plots, or statistically through the parameters that describe connectivity response curves. 相似文献
20.
Tim Diekötter Hans Baveco Paul Arens Carmen Rothenbühler Regula Billeter Daniela Csencsics Riccardo De Filippi Frederik Hendrickx Marjan Speelmans Paul Opdam Marinus J. M. Smulders 《Landscape Ecology》2010,25(3):449-461
Habitat fragmentation has been generally regarded detrimental to the persistence of many species, especially those with limited dispersal abilities. Yet, when exactly habitat elements become functionally disconnected very much depends on the dispersal ability of a species in combination with the landscape’s composition in which it occurs. Surprisingly, for many small and ground-walking generalists knowledge at what spatial scale and to what extent landscape structure affects dispersal is very scarce. Because it is flightless, the bush cricket Pholidoptera griseoaptera may be regarded susceptible to fragmentation. We applied habitat occupancy surveys, population genetic analyses and movement modelling to investigate the performance of P. griseoaptera in an agricultural mosaic landscape with suitable habitat patches of varying size and isolation. Despite its presumed dispersal limitation we could show that P. griseoaptera occupied the majority of suitable habitats, including small and isolated patches, showed a very low and non-significant genetic differentiation (F ST = 0.0072) and, in the model, managed to colonize around 73% of all suitable habitat patches within one generation under weak and strong landscape-effect scenarios. We conclude that P. griseoaptera possesses the behavioural attributes (frequent inter-patch dispersal) necessary to persist in this landscape characterized by a patchy distribution of habitat elements. Yet, sound recommendations to landscape planning and conservation require more research to determine whether this represents a general behaviour of the species or a behavioural adaptation to this particular landscape. 相似文献