共查询到20条相似文献,搜索用时 31 毫秒
1.
Threshold levels of habitat composition for the presence of the long-tailed tit (Aegithalos caudatus) in a boreal landscape 总被引:4,自引:0,他引:4
We assessed the habitat patch occupancy of a deciduous-mixed forest specialist, the long-tailed tit (Aegithalos caudatus), in a 1000 km2 conifer dominated landscape in relation to two landscape parameters, namely proportion and isolation of suitable habitat. Data from five consecutive spring seasons were used and within habitat variation controlled for. The occurrence of long-tailed tits was positively related to the amount of habitat within 1 km2 (p=0.0007) and negatively related to the distance between habitat patches (p<0.0001). When combined, the two variables explained >78% of the variation in local patch occupancy. There were distinct thresholds in these landscape variables for the probability of local long-tailed tit presence. In the model the probability increased from 0.1 to 0.8 when interpatch distance decreased from 500 to 100 m with 5% total habitat coverage. With a total proportion of 15% suitable habitat, the same probability jump occurred when interpatch distance changed from 900 to 500 m. The general importance of defined measurements and quantified threshold levels for species conservation and landscape management is discussed. 相似文献
2.
In fragmented landscapes, plant species persistence depends on functional connectivity in terms of pollen flow to maintain
genetic diversity within populations, and seed dispersal to re-colonize habitat patches following local extinction. Connectivity
in plants is commonly modeled as a function of the physical distance between patches, without testing alternative dispersal
vectors. In addition, pre- and post-dispersal processes such as seed production and establishment are likely to affect patch
colonization rates. Here, we test alternative models of potential functional connectivity with different assumptions on source
patch effects (patch area and species occupancy) and dispersal (relating to distance among patches, matrix composition, and
sheep grazing routes) against empirical patch colonization rates at the community level (actual functional connectivity),
accounting for post-dispersal effects in terms of structural elements providing regeneration niches for establishment. Our
analyses are based on two surveys in 1989 and in 2009 of 48 habitat specialist plants in 62 previously abandoned calcareous
grassland patches in the Southern Franconian Alb in Bavaria, Germany. The best connectivity model S
i
, as identified by multi-model inference, combined distance along sheep grazing routes including consistently and intermittently
grazed patches with mean species occupancy in 1989 as a proxy for pre-dispersal effects. Community-level patch colonization
rates depended to equal degrees on connectivity and post-dispersal process. Our study highlights that actual functional connectivity
of calcareous grassland communities cannot be approximated by structural connectivity based on physical distance alone, and
modeling of functional connectivity needs to consider pre- and post-dispersal processes. 相似文献
3.
Pablo González-Moreno Joan Pino David Carreras Corina Basnou Iván Fernández-Rebollar Montserrat Vilà 《Landscape Ecology》2013,28(5):891-903
Landscape pattern might be an important determinant of non-native plant invasions because it encompasses components influencing the availability of non-native plant propagules and disturbance regimes. We aimed at exploring the relative role of patch and landscape characteristics, compared to those of habitat type and regional human influence on non-native plant species richness. For this purpose, we identified all non-native plant species in 295 patches of four coastal habitat types across three administrative regions in NE Spain differing in the degree of human influence. For each patch, we calculated several variables reflecting habitat patch geometry (size and shape), landscape composition (distribution of land-cover categories) and landscape configuration (arrangement of patches). The last two groups of variables were calculated at five different spatial extents. Landscape composition was by far the most important group of variables associated with non-native species richness. Natural areas close to diverse and urban landscapes had a high number of non-native species while surrounding agricultural areas could buffer this effect. Regional human influence was also strongly associated with non-native species richness while habitat type was the least important factor. Differences in sensitivity of landscape variables across spatial extents proved relevant, with 100 m being the most influential extent for most variables. These results suggest that landscape characteristics should be considered for performing explicit spatial risk analyses of plant invasions. Consequently, the management of invaded habitats should focus not only at the stand scale but also at the highly influential neighbouring landscape. Prior to incorporate landscape characteristics into management decisions, sensitivity analyses should be taken into account to avoid inconsistent variables. 相似文献
4.
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
5.
Mira Kattwinkel Barbara Strauss Robert Biedermann Michael Kleyer 《Landscape Ecology》2009,24(7):929-941
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
6.
Dispersal traits determine plant response to habitat connectivity in an urban landscape 总被引:1,自引:1,他引:0
Identification of trait syndromes that make species vulnerable to habitat fragmentation is essential in predicting biodiversity
change. Plants are considered particularly vulnerable if their capacities for persistence in and for dispersal among local
habitats are low. Here we investigated the influence of easily measured functional traits on the presence of 45 plant species
in an urban landscape in north-west Germany where patches were separated by distances consistent with regular plant dispersal
range. To describe the spatial configuration of patches we calculated species-specific patch connectivities. Then we assessed
plant connectivity responses in distribution models calculated from connectivities and environmental predictors. Twenty (45%)
of the analysed species showed a positive connectivity response after accounting for species-specific habitat requirements.
These species differed from non-responsive species by functional traits associated with dispersal, including reduced seed
numbers and higher terminal velocities relative to non-responsive species. Persistence traits played however no role which
we attribute to the environmental conditions of urban habitats and their spatiotemporal characteristics. Our study underlines
that even ruderal plants experience dispersal limitation and demonstrates that easily measured functional traits may be used
as indicators of fragmentation vulnerability in urban systems allowing generalizations to larger species sets. 相似文献
7.
Edge geometry influences patch-level habitat use by an edge specialist in south-eastern Australia 总被引:1,自引:1,他引:0
We investigated patterns in habitat use by the noisy miner (Manorina melanocephala) along farmland-woodland edges of large patches of remnant vegetation (>300 ha) in the highly fragmented box-ironbark woodlands
and forests of central Victoria, Australia. Noisy miners exclude small birds from their territories, and are considered a
significant threat to woodland bird communities in the study region. Seventeen different characteristics of edge habitat were
recorded, together with the detection or non-detection of noisy miners along 129 500-m segments of patch edge. Habitat characteristics
ranged from patch-level factors related to patch-edge geometry to site-level floristic factors. Backward (stepwise) logistic
regression analyses were used to identify habitat characteristics that were associated with the occupancy of a site by noisy
miners. After accounting for the effects of spatial autocorrelation on the occurrence of noisy miners along edges, we identified
projections of remnant vegetation from the patch edge into the agricultural matrix (e.g., corners of patches, peninsulas of
vegetation) and clumps of trees in the agricultural matrix within 100 m of the edge as significant predictors of the occupancy
of edges by noisy miners. This relationship was also confirmed in two other geographically and floristically distinct habitats
within Victoria. The use of edges with projections by noisy miners may confer advantages in interspecific territorial defence.
In light of these results, we advocate revegetation strategies that attempt to enclose projections within 100 m of the edge,
with fencing placed out to this new boundary, to reduce the likelihood of colonisation and domination of an edge by noisy
miners. Our study highlights the need for greater consideration to be given to the patterns in habitat use by aggressive edge
specialists, particularly in relation to patch-edge geometry and other human-induced components of landscapes. 相似文献
8.
Petra Janečková Štěpán Janeček Jitka Klimešová Lars Götzenberger Jan Horník Jan Lepš Francesco de Bello 《Landscape Ecology》2017,32(4):791-805
Context
Landscape fragmentation significantly affects species distributions by decreasing the number and connectivity of suitable patches. While researchers have hypothesized that species functional traits could help in predicting species distribution in a landscape, predictions should depend on the type of patches available and on the ability of species to disperse and grow there.Objectives
To explore whether different traits can explain the frequency of grassland species (number of occupied patches) and/or their occupancy (ratio of occupied to suitable patches) across a variety of patch types within a fragmented landscape.Methods
We sampled species distributions over 1300 grassland patches in a fragmented landscape of 385 km2 in the Czech Republic. Relationships between functional traits and species frequency and occupancy were tested across all patches in the landscape, as well as within patches that shared similar management, wetness, and isolation.Results
Although some traits predicting species frequency also predicted occupancy, others were markedly different, with competition- and dispersal-related traits becoming more important for occupancy. Which traits were important differed for frequency and occupancy and also differed depending on patch management, wetness, and isolation.Conclusions
Plant traits can provide insight into plant distribution in fragmented landscapes and can reveal specific abiotic, biotic, and dispersal processes affecting species occurrence in a patch type. However, the importance of individual traits depends on the type of suitable patches available within the landscape.9.
We investigated the role of patch attributes and context on patch occupancy of the Lower Keys marsh rabbit (Sylvilagus palustris hefneri). The Lower Keys marsh rabbit is a federally endangered lagomorph endemic to the Lower Keys of Florida. The marsh rabbit occurs in subpopulations on patches of high marsh that interact to form a metapopulation. Between March 1991 and July 1993, all known patches of high marsh in the Lower Keys were surveyed for presence or absence of marsh rabbit pellets three times per year. Of the 59 habitat patches, 20 had pellets present during all of the surveys (occupied patches), 22 had pellets present during at least one survey (variable patches), and 17 never had any pellets present (empty). Ten variables were measured at each of the 59 patches; seven of these variables concerned attributes of the patch (food, cover, patch size), and three were patch context variables (distance of patch to other patches, distance of patch to other features). Two discriminant function analysis (DFA) were performed. The first DFA compared empty patches to occupied patches (both variably and consistently occupied). Patch isolation explained the most variation in patch occupancy followed by area. The second DFA compared the variably occupied sites with the consistently occupied sites, and patch attributes variables involving the type and height of vegetation were significant. Management efforts for the Lower Keys marsh rabbit should be aimed at both improving habitat quality and decreasing distance between patches. 相似文献
10.
Effects of patch attributes, barriers, and distance between patches on the distribution of a rock-dwelling rodent (Lagidium viscacia) 总被引:1,自引:0,他引:1
We tested whether size of habitat patches and distance between patches are sufficient to predict the distribution of the mountain
vizcacha Lagidium viscacia a large, rock-dwelling rodent of the Patagonian steppe Argentina, or whether information on other patch and landscape characteristics
also is required. A logistic regression model including the distance between rock crevices and depth of crevices, distance
between a patch and the nearest occupied patch, and whether or not there was a river separating it from the nearest occupied
patch was a better predictor of patch occupancy by mountain vizcachas than was a model based only on patch size and distance
between patches. Our results indicate that a simple metapopulation analysis based on size of habitat patches and distance
between patches may not provide an accurate representation of regional population dynamics if patches vary in habitat quality
independently of patch size and features in the matrix alter connectivity.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
11.
Habitat fragmentation strongly affects insect species diversity and community composition, but few studies have examined landscape
effects on long term development of insect communities. As mobile consumers, insects should be sensitive to both local plant
community and landscape context. We tested this prediction using sweep-net transects to sample insect communities for 8 years
at an experimentally fragmented old-field site in northeastern Kansas, USA. The site included habitat patches undergoing secondary
succession, surrounded by a low turf matrix. During the first 5 years, plant richness and cover were measured in patches.
Insect species richness, total density, and trophic diversity increased over time on all transects. Cover of woody plants
and perennial forbs increased each year, adding structural complexity to successional patches and potentially contributing
to increased insect diversity. Within years, insect richness was significantly greater on transects through large successional
patches (5000 m2) than on transects through fragmented arrays of 6 medium-sized (total area 1728 m2) or 15 small (480 m2) patches. However, plant cover did not differ among patch types and was uncorrelated with insect richness within years. Insect
richness was strongly correlated with insect density, but trophic and α diversities did not differ among patch types, indicating
that patch insect communities were subsets of a common species pool. We argue that differences in insect richness resulted
from landscape effects on the size of these subsets, not patch succession rates. Greater insect richness on large patches
can be explained as a community-level consequence of population responses to resource concentration. 相似文献
12.
Context
The habitat amount hypothesis has rarely been tested on plant communities. It remains unclear how habitat amount affect species richness in habitat fragments compared to island effects such as isolation and patch size.Objectives
How do patch size and spatial distribution compared to habitat amount predict plant species richness and grassland specialist plant species in small grassland remnants? How does sampling area affect the prediction of spatial variables on species richness?Methods
We recorded plant species density and richness on 131 midfield islets (small remnants of semi-natural grassland) situated in 27 landscapes in Sweden. Further, we tested how habitat amount, compared to focal patch size and distance to nearest neighbor predicted species density and richness of plants and of grassland specialists.Results
A total of 381 plant species were recorded (including 85 grassland specialist species). A combination of patch size and isolation was better in predicting both density and richness of species compared to habitat amount. Almost 45% of species richness and 23% of specialist species were explained by island biogeography parameters compared to 19 and 11% by the amount of habitat. A scaled sampling method increased the explanation level of island biogeography parameters and habitat amount.Conclusions
Habitat amount as a concept is not as good as island biogeography to predict species richness in small habitats. Priority in landscape planning should be on larger patches rather than several small, even if they are close together. We recommend a sampling area scaled to patch size in small habitats.13.
A comparison of metrics predicting landscape connectivity for a highly interactive species along an urban gradient in Colorado, USA 总被引:1,自引:1,他引:0
Many organisms persist in fragmented habitat where movement between patches is essential for long-term demographic and genetic
stability. In the absence of direct observation of movement, connectivity or isolation metrics are useful to characterize
potential patch-level connectivity. However, multiple metrics exist at varying levels of complexity, and empirical data on
species distribution are rarely used to compare performance of metrics. We compared 12 connectivity metrics of varying degrees
of complexity to determine which metric best predicts the distribution of prairie dog colonies along an urban gradient of
385 isolated habitat patches in Denver, Colorado, USA. We found that a modified version of the incidence function model including
area-weighting of patches and a cost-weighted distance surface best predicted occupancy, where we assumed roads were fairly
impermeable to movement, and low-lying drainages provided dispersal corridors. We also found this result to be robust to a
range of cost weight parameters. Our results suggest that metrics should incorporate both patch area and the composition of
the surrounding matrix. These results provide guidance for improved landscape habitat modeling in fragmented landscapes and
can help identify target habitat for conservation and management of prairie dogs in urban systems. 相似文献
14.
Cultural landscapes of Germany are patch-corridor-matrix mosaics for an invasive megaforb 总被引:1,自引:0,他引:1
Predicting the vulnerability of landscapes to both the initial colonisation and the subsequent spread of invasive species
remains a major challenge. The aim of this study was to assess the relative importance of sub-patch level factors and landscape
factors for the invasion of the megaforb Heracleum mantegazzianum. In particular, we tested which factors affect the presence in suitable habitat patches and the cover-percentage within invaded
patches. For this purpose, we used standard (logistic) regression modelling techniques. The regression analyses were based
on inventories of suitable habitat patches in 20 study areas (each 1 km2) in cultural landscapes of Germany. The cover percentage in invaded patches was independent from landscape factors, except
for patch shape, and even unsatisfactorily explained by sub-patch level factors included in the analysis (R
2 = 0.19). In contrast, presence of H. mantegazzianum was affected by both local and landscape factors. Woody habitat structure decreased the occurrence probability, whereas vicinity
to transport corridors (rivers, roads), high habitat connectivity, patch size and perimeter-area ratio of habitat patches
had positive effects. The significance of corridors and habitat connectivity shows that dispersal of H. mantegazzianum through the landscape matrix is limited. We conclude that cultural landscapes of Germany function as patch-corridor-matrix
mosaics for the spread of H. mantegazzianum. Our results highlight the importance of landscape structure and habitat configuration for invasive spread. Furthermore,
this study shows that both local and landscape factors should be incorporated into spatially explicit models to predict spatiotemporal
dynamics and equilibrium stages of plant invasions. 相似文献
15.
Matrix quality affects probability of persistence in habitat patches in landscape simulation models while empirical studies
show that both urban and agricultural land uses affect forest birds. However, due to the fact that forest bird abundance and
species richness can be strongly influenced by local habitat factors, it is difficult to analyze matrix effects without confounding
effects from such factors. Given this, our objectives were to (1) relate human-dominated land uses to forest bird abundance
and species richness without confounding effects from other factors; (2) determine the scale at which forest birds respond
to the matrix; and (3) identify whether certain bird migratory strategies or habitat associations vary in richness or abundance
as a function of urban and agriculture land uses. Birds were surveyed at a single point count site 100 m from the edge of
23 deciduous forest patches near Ottawa, Ontario. Land uses surrounding each patch were measured within increasingly large
circles from 200 to 5000 m radius around the bird survey site. Regression results suggest that effects of urban and agricultural
land uses on forest birds (1) are not uniformly positive or negative, (2) can occur at different spatial scales, and (3) differentially
affect certain groups of species. In general, agriculture appeared to affect species at a broad spatial scale (within 5 km),
while urban land use had an impact at both a narrower spatial scale (within 1.8 km) and at the broad scale. Neotropical and
short distance migrant birds seemed to be the most sensitive to land use intensification within the matrix. Limiting urban
land use within approximately 200–1800 m of forest patches would be beneficial for Neotropical migrant birds, which are species
of growing conservation concern in temperate North America. 相似文献
16.
The understanding and prediction of the responses of animal populations to habitat fragmentation is a central issue in applied
ecology. The identification of habitat variables associated to patch occupancy is particularly important when habitat quality
is affected by human activities. Here, we analyze the influence of patch and landscape characteristics on patch occupancy
by the subterranean herbivorous rodent Ctenomys porteousi. Patch occupancy was monitored in a network of 63 habitat patches identified by satellite imagery analysis which extends
along almost the whole distributional range for C. porteousi. Suitable habitat for the occurrence of C. porteousi is highly fragmented and represents <10% of the total area in its distributional range. The distribution of C. porteousi in the patch network is affected not only by characteristics of the habitat patches, but also by those of the surrounding
landscape matrix. Significant differences between occupied and empty patches were found in several environmental variables.
Overall, occupied patches were larger, less vegetated, more connected, and had larger neighbor patches than empty patches.
A stepwise procedure on a generalized linear model selected four habitat variables that explain patch occupancy in C. porteousi; it included the effects of habitat quality in the matrix surrounding the patch, average vegetation cover in the patch, minimum
vegetation cover in the matrix surrounding the patch, and the area of the nearest neighbor patch. These results indicate that
patch occupancy in C. porteousi is strongly influenced by the availability and quality of habitat both in the patch and in the surrounding landscape matrix. 相似文献
17.
Effects of different matrix representations and connectivity measures on habitat network assessments
Assessing landscape connectivity is important to understand the ecology of landscapes and to evaluate alternative conservation strategies. The question is though, how to quantify connectivity appropriately, especially when the information available about the suitability of the matrix surrounding habitat is limited. Our goal here was to investigate the effects of matrix representation on assessments of the connectivity among habitat patches and of the relative importance of individual patches for the connectivity within a habitat network. We evaluated a set of 50 × 50 km2 test areas in the Carpathian Mountains and considered three different matrix representations (binary, categorical and continuous) using two types of connections among habitat patches (shortest lines and least-cost paths). We compared connections, and the importance of patches, based on (1) isolation, (2) incidence-functional, and (3) graph measures. Our results showed that matrix representation can greatly affect assessments of connections (i.e., connection length, effective distance, and spatial location), but not patch prioritization. Although patch importance was not much affected by matrix representation, it was influenced by the connectivity measure and its parameterization. We found the biggest differences in the case of the integral index of connectivity and equally weighted patches, but no consistent pattern in response to changing dispersal distance. Connectivity assessments in more fragmented landscapes were more sensitive to the selection of matrix representation. Although we recommend using continuous matrix representation whenever possible, our results indicated that simpler matrix representations can be also used as a proxy to delineate those patches that are important for overall connectivity, but not to identify connections among habitat patches. 相似文献
18.
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
19.
Ecological connectivity is the foundation of maintaining urban biodiversity and ecosystem health. Identifying and managing ecological (connectivity) networks can help maintain the stability of urban ecosystems. However, few studies have explored the cluster effect in the ecological network caused by the imbalance in connectivity strength between habitat patches, which is not conducive to the in-depth restoration of ecological networks. In the present study, a typical urban area, Shenzhen, was used as an example to analyze the important habitats in the city based on the focal species and to identify an ecological network. Habitat patch clusters in the ecological network were explored based on random walk network community detection. These are clusters of closely connected habitat lands. Finally, we analyzed existing urban policies for the protection of clusters and the points to be repaired in the network. The results showed that 50 ecological corridors connected 39 habitats in the study area, which further formed seven habitat patch clusters. Most of the clusters were well-protected by existing policies. Nineteen barrier points were identified between the clusters, and their restoration helped strengthen the connectivity between clusters. This study provides a reference for future urban ecological restoration. 相似文献
20.
Spatial dynamics of the knob-tailed gecko Nephrurus stellatus in a fragmented agricultural landscape
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