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1.
Due to their specialised habitat requirements, butterflies are particularly vulnerable to habitat loss and fragmentation. Understanding the drivers of local abundances of species is essential for their effective conservation in fragmented landscapes. We investigated factors affecting population densities of an endangered European butterfly, the Violet Copper ( Lycaena helle), occurring in a small metapopulation near the city of Kraków, southern Poland. The environmental parameters tested as predictors of the local densities of the species included both the variables associated with spatial structure of habitats such as patch sizes, their isolation and fragmentation as well as those potentially reflecting habitat quality. Patch area and vegetation height turned out to be the only factors significantly influencing L. helle densities, both having a positive effect. The positive impact of patch area is a bit surprising, since its relationship with population densities is typically negative in butterflies. In our study system it is likely to derive from source-sink dynamics as the smaller habitat patches are apparently too small to sustain viable local populations. In turn, the positive influence of vegetation height implies that the ongoing succession does not deteriorate the quality of the recently abandoned meadows yet, whereas higher turf may provide better sheltering places. The loss of almost half of L. helle habitat patches in the study area in recent years is alarming. However, its inclusion into the Natura 2000 system should help to conserve the species as long as this act is followed by proper management of its habitats. 相似文献
2.
Habitat size, habitat isolation and habitat quality are regarded as the main determinants of butterfly occurrence in fragmented
landscapes. To analyze the relationship between the occurrence of the butterfly Cupido minimus and these factors, patch occupancy of the immature stages in patches of its host plant Anthyllis
vulneraria was studied in the nature reserve Hohe Wann in Bavaria (Germany). In 2001 and 2002, 82 A.
vulneraria patches were surveyed for the presence of C. minimus larvae. The occurrence was largely affected by the size of the food plant patches. In a habitat model that uses multiple logistic
regression, the type of management and habitat connectivity are further determinants of species distribution. Internal and
temporal validation demonstrate the stability and robustness of the developed habitat models. Additionally, it was proved
that the colonization rate of C. minimus was significantly influenced by the distance to the next occupied Anthyllis patch. Concerning long-term survival of (meta-) populations in fragmented landscapes, the results show that lower habitat
quality may be compensated by higher connectivity between host plant patches.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. 相似文献
3.
Temporal changes in allele frequencies are often assumed in studies addressing the history of populations affected by different anthropogenic and natural impacts at different time scales. Yet, few studies directly compare the genetic composition of populations over time spans of more than 10 years. Therefore, to test the genetic effects of 15 years of population isolation in the butterfly Lycaena helle, we analysed 472 individuals from 27 samples, of which nine were collected in 1991 and 18 in 2006. Sampling was performed in five mountain regions (Pyrenees, Massif Central, Jura, Vosges and Ardennes). Genetic analyses were performed using five polymorphic microsatellites. Old and new samples of identical or neighbouring populations revealed similar genetic differentiations among these five mountain regions. A comparatively strong genetic differentiation among populations combined with a high amount of private alleles for each mountain area was detected, but mountain‐specific alleles were in most cases identical in 1991 and 2006. Nevertheless, the obtained data also indicate moderate changes between 1991 and 2006 in the species’ genetic structure – genetic differentiation among local populations increased marginally and allele frequencies showed corresponding modifications. A significant decline in genetic diversity was not detectable, and nine private alleles exclusive to a single mountain region were only detected in samples from the year 1991, whereas eleven were only observed in the individuals collected in 2006. These observations might indicate the results of genetic drift within isolated populations. 相似文献
4.
Fragmentation, deterioration, and loss of habitat patches threaten the survival of many insect species. Depending on their
trophic level, species may be differently affected by these factors. However, studies investigating more than one trophic
level on a landscape scale are still rare. In the present study we analyzed the effects of habitat size, isolation, and quality
for the occurrence and population density of the endangered leaf beetle Cassida canaliculata Laich. (Coleoptera: Chrysomelidae) and its egg parasitoid, the hymenopteran wasp Foersterella reptans Nees (Hymenoptera: Tetracampidae). C. canaliculata is strictly monophagous on meadow sage ( Salvia pratensis), while F. reptans can also parasitize other hosts. Both size and isolation of habitat patches strongly determined the occurrence of the beetle.
However, population density increased to a much greater extent with increasing host plant density ( = habitat quality) than
with habitat size. The occurrence probability of the egg parasitoid increased with increasing population density of C. canaliculata. In conclusion, although maintaining large, well-connected patches with high host plant density is surely the major conservation
goal for the specialized herbivore C. canaliculata, also small patches with high host plant densities can support viable populations and should thus be conserved. The less
specialized parasitoid F. reptans is more likely to be found on patches with high beetle density, while patch size and isolation seem to be less important. 相似文献
5.
Habitat fragmentation is a major cause of species rarity and decline because it increases local population extinctions and
reduces recolonisation rates of remnant patches. Although two major patch characteristics (area and connectivity) have been
used to predict distribution patterns in fragmented landscapes, other factors can affect the occurrence of a species as well
as the probability of it becoming extinct. In this paper, we study the spatial structure and dynamics of the butterfly Iolana iolas in a 75-patch network of its host plant ( Colutea hispanica) to determine the relative importance of patch area, connectivity and habitat quality characteristics on occupancy, extinction
and density over the period 2003–2006. Occupancy in 2003, incidence (proportion of years occupied) and probability of extinction
were mostly affected by patch area. Smaller patches were less likely to be occupied because they had a higher probability
of extinction, partly due to environmental stochasticity. The density of I. iolas was negatively related to patch area in all study years. Only in 2004 was the density of I. iolas positively influenced by fruit production per plant. Our results suggest that for I. iolas, and probably for other specialist butterflies with clearly delimited resource requirements, metapopulation dynamics can
be satisfactorily predicted using only geometric variables because most habitat characteristics are subsumed in patch area.
However, this hypothesis should be subject to further testing under diverse environmental conditions to evaluate the extent
of its generalisation. 相似文献
6.
Two general approaches have usually been taken towards understanding the distributions and dynamics of localised species in
heterogeneous landscapes, namely habitat characterisation and metapopulation dynamics. We show how habitat and metapopulation
dynamics interact to generate a highly localised distribution of a butterfly, despite the extremely widespread nature of the
butterfly’s host plant. Egg placement, macro-habitat requirements and dispersal were studied for the butterfly Erynnis tages, in North Wales, where it shows a restricted distribution relative to that of its host plant, Lotus corniculatus. Females laid eggs disproportionately on large plants growing in hollows, with intermediate cover of bare ground and high
cover of L. corniculatus. Ideal macro-habitat, studied at 100-m grid resolution, consisted of areas with high host plant densities, sheltered from
wind, with light or no grazing or cutting. These specialised conditions are represented as localised patches in the landscape,
and define the potential habitat network, within which metapopulation dynamics take place. Although there was a moderate (22%)
level of exchange of individual E. tages among local populations, the total number of potential colonists in the whole system was low because source population sizes
were small (≤200 individuals at peak in any site in 1997 and 1998). Four unoccupied but apparently suitable 500-m grid squares
were colonised between 1997 and 1998, and isolated habitat was less likely to be occupied. Overall, our study suggests that
long-term regional persistence of E. tages is very likely to depend on metapopulation processes within the restricted patch network, rather than on the long-term survival
of local populations.
Received: 25 May 1999 / Accepted: 9 August 1999 相似文献
7.
A successful conservation strategy for an insect species should address the habitat requirements of all life stages and all
activities performed by those life stages. In this paper the night-time roosting habitat and behaviour of the endangered damselfly
Coenagrion mercuriale (Odonata: Coenagrionidae) was investigated by marking damselflies with UV fluorescent paint. Night-time observations revealed
that individuals did not roost together and those that were recorded on more than one occasion did not return to the same
spot each night. There was no apparent preference for roosting close to the watercourses. C. mercuriale roosted towards the top of the vegetation and this vegetation was considerably taller than the mean height of the vegetation
in the study area. Adults were strongly associated with two tussock-forming monocots, Juncus inflexus and Deschampsia cespitosa. Differences in the abundance of these plants were shown to result in large differences in the numbers of C. mercuriale roosting in different parts of the site. The importance of providing these structural elements of habitat as part of a wider
conservation strategy for this species is discussed. 相似文献
8.
Few field studies of natural populations have examined the factors influencing local extinctions and colonization of empty habitat patches for a prey species and its predator. In this study, I carried out a census of planthopper ( Prokelisia crocea; Hemiptera: Delphacidae) and egg parasitoid ( Anagrus columbi; Hymenoptera: Mymaridae) incidence and densities in 147 host-plant patches ( Spartina pectinata; Poaceae) over seven planthopper generations in a tall-grass prairie landscape. For both species, the likelihood of going extinct in a patch was related to a number of patch-specific variables: density, temporal variability in density, proportion of hosts parasitized (planthopper only), host-plant density, patch size, patch isolation, and composition of the surrounding matrix. Colonization likelihood was related only to the physical attributes of the patch. There was high patch turnover in this prairie landscape. On average, planthoppers went extinct in 23% of the patches and A. columbi went extinct in 51% of the patches in each generation. For the planthopper, extinction likelihood increased with a decrease in patch size and the proportion of the matrix composed of mudflat. Parasitism of eggs had no effect on the extinction likelihood of local P. crocea populations, suggesting that A. columbi may not play a major role in the patch dynamics of its host. The likelihood of extinction for A. columbi was dependent on factors that spanned three trophic levels. An increase in plant density, decrease in host density and decrease in parasitoid density all increased the likelihood of A. columbi extinction within a patch. The dependency on multiple trophic levels may explain the higher extinction risk for the parasitoid than its host. A. columbi extinction was also affected by the matrix habitat surrounding the patch—the effect was the opposite of that for P. crocea. Finally, vacant patches were colonized at rates of 53% and 34% per generation for the planthopper and parasitoid, respectively. For both species, colonization probabilities decreased with an increase in patch isolation. High host densities in a patch also favored high rates of colonization by A. columbi. I discuss how anthropogenic changes to the prairie landscape can affect the metapopulation dynamics and persistence time of this host-parasitoid interaction. 相似文献
9.
Dispersal is a key ecological process linking metapopulation dynamics in the landscape to distribution patterns at larger spatial scales. In this study, we investigated the landscape occupancy and genetic population structure of a butterfly species, Melanargia galathea. Several landscapes differing in composition and structure were sampled as well as populations at different spatial scales. We found that M. galathea occupied 91.3% of all habitat patches available within a particular landscape, probably due to a dominance of landscape scale processes such as rescue effect and recolonisation. A high level of genetic polymorphism within the sampled populations and a very low amount of genetic differentiation between populations was observed ( Gst=0.034), characteristic of species with high dispersal capacity and/or high density. High dispersal rates ensured considerable gene mixing at the landscape scale while the influence of distance on dispersal success was detected at the regional and continental scales by a significant amount of isolation by distance. We also found that, at the landscape scale, the dispersal of this butterfly species was influenced by the spatial distribution of its habitat patches. ZusammenfassungDie Ausbreitung ist ein ökologischer Schlüsselprozess, der die Metapopulationsdynamik in einer Landschaft mit den Verbreitungsmustern auf einer größeren räumlichen Skala verbindet. In dieser Studie untersuchten wir die Verbreitungsmuster und die genetische Populationsstruktur einer Schmetterlingsart, Melanargia galathea. Es wurden sowohl einige Landschaften beprobt, die sich in der Zusammensetzung und der Struktur unterschieden, als auch Populationen auf verschiedenen räumlichen Skalen. Wir fanden, dass M. galathea 91.3% aller verfügbaren Habitatflecken in einer bestimmten Landschaft besetzte, möglicherweise aufgrund der Dominanz von Landschaftsskalenprozessen wie “Rescue-Effekt” und Rekolonisation. Es wurde ein hoher genetischer Polymorphismuslevel und ein sehr geringer Umfang genetischer Differenzierung innerhalb der beprobten Populationen beobachtet (Gst=0.034), was charakteristisch für Arten mit einer großen Ausbreitungsfähigkeit und/oder hoher Dichte ist. Hohe Ausbreitungsraten sicherten eine beträchtliche Genvermischung auf der Landschaftsskala, während der Einfluss der Entfernung auf den Verbreitungserfolg auf der regionalen und kontinentalen Skala durch einen signifikanten Anteil der Isolation aufgrund von Entfernung festgestellt wurde. Wir fanden auch, dass auf der Landschaftsskala die Ausbreitung dieses Schmetterlings durch die räumliche Verteilung der Habitatflecken beeinflusst wurde. 相似文献
10.
This study examines the predictive accuracy of the population viability analysis package, ALEX (Analysis of the Likelihood of EXtinction). ALEX was used to predict the probability of patch occupancy for two species of small native Australian mammals ( Antechinus agilis and Rattus fuscipes) among 13 patches of suitable habitat in a matrix of plantation pines ( Pinus radiata). The study was retrospective, running each simulation from 1900 until 1997, and the model parameterised without knowledge of the 1997 observed field data of patch occupancy. Predictions were made over eight scenarios for each species, allowing for variation in the amount of dispersal between patches, level of environmental stochasticity, and size of habitat patches. Predicted occupancies were compared to the 1997 field data of patch occupancy using logistic regression, testing H
random, that there was no relationship between observed and predicted occupancy, and H
perfect, that there was a perfect, 1:1 relationship between observed and predicted occupancies. Rejection of H
random and failure to reject H
perfect was taken as a good match between observed and predicted occupancies. Such a match was found for one scenario with R. fuscipes, and no scenarios with A. agilis. In general, patch occupancy was underestimated, with field surveys finding that 9 of the 13 patches were occupied by R. fuscipes and 10 by A. agilis. Nonetheless, PVA predictions were in the right direction, whereby patches predicted to have a high probability of occupancy were generally occupied, and vice versa. A post hoc search over additional scenarios found few scenarios with a better match than the original eight. The results of this study support the notion that PVA is best thought of as a relative, rather than absolute predictor of the consequences of management actions in threatened populations. 相似文献
11.
A widespread decline in biodiversity in agro-ecosystems has been reported for several groups of organisms in Western Europe.
The butterfly fauna was studied in 60 selected semi-natural grasslands in a coniferous-dominated boreal landscape in south-eastern
Sweden. The aim was to investigate how butterfly assemblages were affected by the amount of semi-natural grasslands in the
surrounding landscape. Furthermore, we wanted to determine if semi-natural grasslands in boreal landscapes harboured species
otherwise declining in other parts of Europe. For each study site, the amounts of semi-natural grasslands in the landscape
within radii of 500, 2,000 and 5,000 m were studied. Nine local habitat factors were also recorded. Only the amount of semi-natural
grasslands within a 5,000 m radius could explain a significant part of the variation in butterfly composition, but there was
no clear relationship between the amount of semi-natural grassland and butterfly diversity. Instead, this study showed that
local habitat quality was very important for butterfly diversity at individual sites. Flower abundance, sward height and herb
composition were the most important local factors. Patches surrounded by a small amount of semi-natural grasslands had high
butterfly diversity, contrary to expectations. This may be explained by the fact that forest habitat provides a matrix with
several features suitable for butterflies. The butterfly fauna was rich in species representative of low-productivity grasslands,
species that are declining in other countries in Western Europe. 相似文献
12.
Some species cope with, and survive in, urban areas better than others.From a conservation viewpoint it is important to understand why some species arerare or are excluded in the urban landscape, in order that we might take actionto conserve and restore species. Two ecological factors that might explain thedistribution and abundance of butterfly species in the urban landscape aredispersal ability and the availability of suitable habitat. The influence ofthese factors was assessed by examining the distribution and genetic structureof four grassland butterfly species in the West Midlands conurbation, UK. Thefour species differ in their distribution and abundance, mobility and habitatspecificity. No significant fit to the isolation-by-distance model was found forany of the study species at this spatial scale. Mean F
ST values revealed a non-significant level ofpopulation structuring for two species, Pieris napi (L.)and Maniola jurtina (L.), but moderate and significantpopulation differentiation for Pyronia tithonus (L.) and Coenonympha pamphilus (L.). Results suggest that thesespecies are limited more by the availability of suitable habitat than by theirability to move among habitat patches. Conservation strategies for thesegrassland species should initially focus on the creation and appropriatemanagement of suitable habitat. More sedentary species that have already beenexcluded from the conurbation may require a more complex strategy for theirsuccessful restoration. 相似文献
13.
Prescribed burning is routinely used to improve grazing in Pyrenean rangelands affected by an overall trend of land abandonment. This study considers the environmental variables influencing habitat occupancy by birds and the consequences of the use of fire in range management for bird conservation. Bird use and habitat structure of 11 cover types, the result of specific management regimes, were monitored for two breeding seasons in a mosaic landscape. Three main gradients of avian composition, corresponding to tree cover, shrub volume and grazing intensity, were identified from canonical correspondence analysis. The structure of the bird community seemed more intensely affected by species-specific selection of cover types than by the birds' use of multiple patches. Out of a total of 10 bird species analysed by a simultaneous confidence intervals procedure, four species with an unfavourable conservation status in Europe ( Emberiza cia, Lullula arborea, Saxicola torquata and Lanius collurio) preferred managed grassland. Three types of grassland with shrubs (derived from single or repeated burning) had the highest bird conservation index (taking into account specific status and abundance of the bird assemblage), whereas forests showed middle or low values. The relation ( P = 0.054) of this index to the logarithm of the pastoral value (which includes density and grazing quality of grasses) in currently managed cover types suggests that the objectives of grassland recovery by appropriate management practices and those of bird conservation coincide in our study area. 相似文献
14.
1. Ecological specialists are often regarded as most likely to be threatened by anthropogenic habitat changes but few relevant data are available on changes in the status of widespread species. 2. Grid square distribution maps have been used widely to measure rates of decline and target conservation resources but it is known that coarse grain mapping is not appropriate to identify declines in widespread species that initially contain numerous local populations per grid cell. Changes in the status of widespread species need to be quantified. 3. Present‐day habitat associations, determined from over 2000 transect counts, combined with data on historical and present‐day habitat distributions, reveal that the area of occupancy and population‐level rate of decline of the Small Copper butterfly Lycaena phlaeas is likely to have been of the order of 92 and 89% respectively, in 35 km 2 of North Wales. Similar data on the species' major host plants Rumex acetosa and R. acetosella indicate possible declines in area occupied of 48 and 91%. If a 1‐km 2 grid was applied to the landscape, and if L. phlaeas, R. acetosa, and R. acetosella had occupied all 1‐km 2 cells in the study area in 1901 (non‐limestone cells for R. acetosella only), their declines would only have been recorded as 15, 9, and 35% respectively. 4. Many declining ecological specialists are threatened with extinction because of their initial rarity. At a population level, however, they may or may not be declining faster than less specialised species. The results presented here illustrate that some widespread species may have declined as much as many of Britain's rarities. 相似文献
15.
Patch occupancy by Coenonympha tullia has been surveyed in 166 sites in Northumberland, UK. It was found in 117 of them and absent in 37. Weather conditions were too poor to determine its presence at a further 12 sites. Differences in habitat quality among sites account for patch occupancy as successfully (R2 = 48%) as isolation and patch size jointly (R2 = 46%). This finding has relevance for metapopulation studies as it demonstrates that greater attention should be given to differences in habitat quality among patches beyond their size and distance from one another. Together, habitat quality, patch size and isolation account for 61% of the variation in C. tullia occupancy of sites and discriminant analysis produces a correct classification for > 88% of sites. Habitat quality and patch size jointly account for much the same variance, and result in the same classification of the twelve sites excluded from analysis, as they do in conjunction with patch isolation. This result suggests that there is potential for predicting changes in occupancy of sites from site specific data in the face of changes to biotopes, such as planned exploitation and deterioration of sites from other causes including climate change and management practices. 相似文献
16.
In the past, extensive areas in Drenthe (The Netherlands) were covered by peat bogs and wet heath lands, but nowadays only relatively small fragments are left. During the second half of the 20th century the quality of these fragments decreased, due to lowering of the water table and the input of nutrients. These factors will have a negative effect on the survival of species which are adapted to these stable type of biotopes, like the Black bog ant. The distribution pattern was analysed within a study area of 750 km 2, in order to find out if this species will survive in a landscape where its habitat is severely fragmented. Using multiple logistic regression analysis it appears that size and quality of the habitat patches, as well as openness of the environment, contribute significantly to patch-occupancy. No correlation was found between the probability of a patch being occupied and its distance to the nearest occupied patch. It appears that the spatial cohesion of local populations by means of flying queens is weak or absent on the scale of the study area. Only in parts of the area, where the distance between habitat patches is less than 3 km in open field, a habitat network may still exist. However, with ongoing habitat loss a threshold will be passed and the species will ultimately become extinct. 相似文献
17.
We studied the response to forest fragmentation of a generalist carnivore, the stone marten Martes foina, in highly fragmented landscapes of central Spain. Five different areas ( n = 178 fragments) in central Spain were surveyed. This paper analyses the relationship between fragment use by martens (measured through scat presence) and a series of variables related to the size, isolation and vegetation structure of each fragment by means of stepwise logistic regression. Size and isolation have an important effect on stone marten presence in fragments. Our results were similar to those found for other marten species in landscapes with coarse-grain fragmentation, but they contrast with other studies conducted in landscapes with fine-grain fragmentation. These data suggested that in highly fragmented landscapes, size and isolation factors resulting from forest fragmentation were responsible for determining marten responses, irrespective of their habitat generalism. Management policies for the stone marten in highly fragmented scenarios require the maintenance of large forests near continuous forest tracts in mountains or riparian woodlands. 相似文献
18.
The European natterjack toad ( Bufo calamita) has declined rapidly in recent years, primarily due to loss of habitat, and in Denmark it is estimated that 50% of the isolated
populations are lost each decade. To efficiently manage and conserve this species and its genetic diversity, knowledge of
the genetic structure is crucial. Based on nine polymorphic microsatellite loci, the genetic diversity, genetic structure
and gene flow were investigated at 12 sites representing 5–10% of the natterjack toad localities presently known in Denmark.
The expected heterozygosity ( H
E) within each locality was generally low (range: 0.18–0.43). Further analyses failed to significantly correlate genetic diversity
with population size, degree of isolation and increasing northern latitude, indicating a more complex combination of factors
in determining the present genetic profile. Genetic differentiation was high (overall θ = 0.29) and analyses based on a Bayesian clustering method revealed that the dataset constituted 11 genetic clusters, defining
nearly all sampling sites as distinct populations. Contemporary gene flow among populations was undetectable in nearly all
cases, and the failure to detect a pattern of isolation by distance within major regions supported this apparent lack of a
gene flow continuum. Indications of a genetic bottleneck were found in three populations. The analyses suggest that the remaining
Bufo calamita populations in Denmark are genetically isolated, and represent independent units in a highly fragmented gene pool. Future
conservation management of this species is discussed in light of these results.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. 相似文献
20.
1. Movement mediates the response of populations and communities to landscape and habitat spatial structure, yet movement capability may itself be modified by selection pressures accompanying landscape change. Insect flight morphology can be affected by both the landscape surrounding habitat patches and the distribution of resources within habitat patches. 2. This study investigated the relative influence of local habitat patch conditions and surrounding landscape structure on variation in morphological traits associated with flight in the bog copper ( Lycaena epixanthe), a butterfly endemic to temperate Nearctic peatlands. 3. Eight habitat patches were sampled to assess the influence of the surrounding landscape (connectivity of potential habitat and matrix composition) and patch size (an integrated proxy of resource density and spatial distribution) on investment into flight, measured by thorax and abdomen mass, and wing area. 4. The results revealed an effect of both local habitat conditions and landscape structure on flight‐related morphological traits. Increasing forest cover in the surrounding landscape, indicative of increased habitat patch isolation, corresponded with less mobile phenotypes in both sexes. Surrounding landscapes with more water were also generally associated with less mobile phenotypes. Investment into flight was greater in smaller peatlands in which host plant density is higher and more homogeneously distributed. 5. The present study highlights that morphological traits associated with mobility may be responding to both local habitat patch characteristics and surrounding landscape structure. It also supports the hypothesis that local habitat conditions contribute to morphological variation in butterflies. 相似文献
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