Local species immigration,extinction, and turnover of butterflies in relation to habitat area and habitat isolation

Temporal dynamics of insect communities in terrestrial habitat fragments have been rarely studied. Here it was tested whether immigration, extinction, and turnover of butterfly species change with area and isolation of 31 calcareous grasslands. The area ranged from 0.03 to 5.14 ha, the isolation index from 2,100 to 86,000 (edge-to-edge distance 55–1,894 m). In both study years (1996, 2000), the total number of individuals (16,466, 15,101) and species (60, 54) sampled across all sites were similar and number of species increased with area in both years indicating an equilibrium. Rates of extinction (38% for habitat specialists vs. 20% for generalists) and turnover (51% vs. 35%) were higher, and rates of immigration (11% vs. 30%) were lower for habitat specialists than for generalists. Extinction and turnover rates decreased with increasing fragment size for both specialist (n =25 species) and generalist (n =36) butterflies, but specialists showed a significantly steeper decrease with increasing fragment size than generalists. Immigration rates increased with area. As a result, species number of habitat specialists declined in small habitats but not in large habitats between 1996 and 2000. No significant impact of habitat isolation on the butterfly community was found. The data suggest that large habitat fragments are of special importance for the conservation of the specialized, most endangered butterfly species. Habitat isolation appears to be less important, as butterflies can cope with the habitat mosaic in our study region.Due to an error in the citation line, this revised PDF (published in December 2003) deviates from the printed version, and is the correct and authoritative version of the paper.     

Island theory, matrix effects and species richness patterns in habitat fragments

Island biogeography theory, created initially to study diversity patterns on islands, is often applied to habitat fragments. A key but largely untested assumption of this application of theory is that landscape matrix species composition is non‐overlapping with that of the islands. We tested this assumption in successional old field patches in a closely mowed matrix, and because our patches are appropriately viewed as sets of contiguous habitat units we studied patterns of species richness per unit area. Previous studies at our site did not find that diversity patterns on patch ‘islands’ conformed to predictions of island biogeography theory. Our results indicate that when matrix species are removed from the patch samples, diversity patterns conform better to theory. We suggest that classical island theory remains an appropriate tool to study diversity patterns in fragmented habitats, but that allowances should be made for spill‐over colonization of ‘islands’ from the ‘sea’.     

Winter bird communities in the northern Negev: species dispersal patterns, habitat use and implications for habitat conservation

Bird habitat conservation may require different management strategies for different seasonal bird assemblages. We studied habitat use by winter birds in forest and scrubland habitat patches in the northern Negev, Israel. Our goal was to assess whether differences in responses to landscape and habitat structure between breeding and non-breeding seasons require changes in future conservation plans that have been suggested for the Negev breeding bird community. We evaluated habitat and area effects on bird abundance and distribution and tested whether species habitat use during winter involves niche shifts. Compared with breeding birds, a larger proportion of winter bird species occupied both scrubland and forest. As in summer, forest bird species responded to habitat structure, whereas scrubland species were associated with both habitat structure and area. Resident birds disperse into habitats in which they were not present during summer. Consequently, for several species, the correlation between bird densities and environmental factors showed a better fit at the landscape rather than at the habitat scale. In addition, rather than niche shift, birds actually extended their niche breadth. Nest site selection may constrain bird distribution into a realized niche, smaller than their fundamental niche. Despite the scale differences in habitat use, the similar species diversity patterns between seasons suggest that both winter and summer birds would benefit from conservation of scrub patches larger than 50 ha, and enrichment of foliage layers within the planted forests.     

Plant distribution patterns related to species characteristics and spatial and temporal habitat heterogeneity in a network of ditch banks

In this study we investigated the relationship between the distributionpatterns of a number of herbaceous plant species and the isolation and age ofhabitat patches. The study was conducted for a network of ditch banks in anagricultural landscape in The Netherlands. Thirteen plant species were selectedrepresenting contrasting dispersal and seed bank characteristics. Isolation ofhabitat patches was determined by the distance to the nearest occupied patchandby the number of occupied patches in circles of increasing radius around thepatches. Age was the number of years since the creation of the ditches. In amultiple logistic regression model the separate effects of age of the habitatand the spatial variables were analyzed. A number of habitat variables wereusedto correct the effect of habitat quality. We concluded that distributionpatterns of plant species were mainly determined by habitat quality and thepresence of seed sources at short distances (< 25 m). Thisconclusion was independent of the dispersal characteristics of the species.Mostspecies had higher occupation frequencies in older than younger ditch banks.Only species with persistent seeds had comparable occupation probabilities inolder and younger habitat patches, indicating the importance of the soil seedbank as a source of colonization after large-scale disturbances. The effect ofage and management on the occupation probabilities of the species was oftendiminished in the regression model, probably due to correlation between somehabitat variables and the age of the patches.     

贵州花溪大学城破碎化林地中鸟类群落的小岛屿效应

小岛屿效应打破了传统的种-面积关系认知,是当前岛屿生物地理学与生境破碎化领域的研究热点之一。然而,目前的研究缺乏以人类干扰度较高的城市破碎化生境为载体来探究小岛屿效应问题。本研究以贵州花溪大学城30个面积0.25 ~ 290.40 hm2的残存自然林地为研究区,在2017至2021年的鸟类繁殖季对林地中的鸟类进行调查。共记录到鸟类98种,隶属于11目41科。剔除高空飞行、非森林鸟类及偶然出现的物种后,不同斑块中的鸟类物种数介于12至49种之间,平均每个斑块24种。在R软件中利用“sars”包构建4种关键种-面积回归模型发现,先平后升的两段式回归模型是预测种-面积关系的最佳模型。该模型显示,在面积阈值1.16 hm2之上,物种丰富度随着面积的增加逐渐增多,符合传统岛屿生物地理学提出的面积效应;但是,在面积阈值1.16 hm2之下,物种丰富度不随面积发生显著变化,表现出小岛屿效应的特征。小岛屿效应的形成可能与喀斯特特殊地貌环境、食物资源或“中转站”、“垫脚石”等生态功能相关,其具体发生机制尚有待进一步研究。根据本研究结果,建议在城市规划建设时尽可能保护自然林地并设计绿色过渡带,在优先保护大林地斑块的同时不应忽视对具有重要生态价值的小林地斑块的保护。     

Seed,dispersal, microsite,habitat and recruitment limitation: identification of terms and concepts in studies of limitations

Recently, there is an increase in number of studies concerned with the effect of various types of limitations on species local population size and distribution pattern at the landscape scale. The terminology used to describe these limitations is, however, very inconsistent. Since the different terms often appear in conclusions of the papers, the inconsistency in their use obscures the message of these papers. In this study, we review the current uses of these terms, identify the basic concepts involved in the discussion of a limitation and link the concepts with the currently used terms. Finally, we discuss the experimental approaches used to assess the different types of limitations. We differentiated four basic concepts resulting from the combination of limitation by environment versus ability to grow and spread, and two spatial scales (local and regional scale). The two concepts at each spatial scale are expected to form a gradient of all possible combinations of the two respective types of limitations. In the considerations of various experimental approaches used to assess these limitations, we conclude that sowing experiments, i.e. seed addition into existing populations or seed introduction into unoccupied habitats, are the only reliable types of evidence for the different types of limitations.     

Woody species colonisation in relation to habitat productivity

A study was conducted to analyse the effect of habitat productivity on woody species colonisation. Three soil types were distinguished: a relatively poor sandy soil type (1), a somewhat richer sandy type (2) and a relatively rich sandy loamy type (3). Chronosequences were established on these three soil types of 38 (type 1), 20 (type 2) and 54 years (type 3) after abandonment. In total 117 vegetation relevées were used to analyse life form change and species responses during old field succession via regression models. On the rich soil type the colonisation rate of woody species was slower than on the poor soil type. This can be explained by higher abundances of perennial species during the first 20 years after abandonment on the rich soil type in contrast to the poor soil type. Perennial species may delay the woody species colonisation. First they close the bare ground which inhibits germination and next they compete with woody seedlings for light, water and nutrients. The effect of habitat productivity on woody species colonisation can only be determined appropriately by taking life history traits into account. Early successional 'pioneer' woody species dispersed by wind have less difficulties colonising old fields than late successional 'forest' species; they colonise old fields prior to the development of a dense perennial sward. Forest species depend on animals to be dispersed which are attracted by vegetation structure. In ± 30 years on the poor soil type and in ± 45 years on the rich soil type woody species become dominant relative to other life forms. Forest species like Quercus robur L. invaded relatively early (<5 years) in contrast to other studies which probably coincides with the distance to seed sources (forest edges).     

Seed dispersal networks in tropical forest fragments: Area effects,remnant species,and interaction diversity

Seed dispersal interactions involve key ecological processes in tropical forests that help to maintain ecosystem functioning. Yet this functionality may be threatened by increasing habitat loss, defaunation, and fragmentation. However, generalist species, and their interactions, can benefit from the habitat change caused by human disturbance while more specialized interactions mostly disappear. Therefore, changes in the structure of the local, within fragment, networks can be expected. Here we investigated how the structure of seed dispersal networks changes along a gradient of increasing habitat fragmentation. We analyzed 16 bird seed dispersal assemblages from forest fragments of a biodiversity-rich ecosystem. We found significant species–, interaction–, and network–area relationships, yet the later was determined by the number of species remaining in each community. The number of frugivorous bird and plant species, their interactions, and the number of links per species decreases as area is lost in the fragmented landscape. In contrast, network nestedness has a negative relationship with fragment area, suggesting an increasing generalization of the network structure in the gradient of fragmentation. Network specialization was not significantly affected by area, indicating that some network properties may be invariant to disturbance. Still, the local extinction of partner species, paralleled by a loss of interactions and specialist–specialist bird–plant seed dispersal associations, suggests the functional homogenization of the system as area is lost. Our study provides empirical evidence for network–area relationships driven by the presence/absence of remnant species and the interactions they perform.     

Microhabitat segregation and physiological differences in co-occurring tiger beetle species,Cicindela oregona and Cicindela tranquebarica

Summary The daily movements of two co-occurring tiger beetle species were monitored in conjunction with changes in microclimate along streams in Northeast Arizona. Cicindela oregona and C. tranquebarica temporarily segregated across areas of beach exhibiting different microclimates. C. oregona progressively moved from the dry upper beach to the wet stream edge as beach temperatures increased and humidity decreased. The actively foraged throughout the day in this moist habitat at air temperatures between 25 and 38°C. C. tranquebarica remained on the dry, upper portions of the beach and shuttled between sun and shade at air temperatures above 35°C. Only when stream edge temperatures exceeded 30°C was tranquebarica found in this subhabitat. Both species exhibited physiological tolerances in the laboratory that were consistent with their microhabitat preferences in the field. Although both species had similar high lethal temperatures (47–48°C) in saturated air, oregona died at lower temperatures (39–43°C) than tranquebarica (46–47°C) under dry (0% RH) conditions. C. oregona was considerably more active than tranquebarica at body temperatures below 30°C and exhibited higher levels of active metabolism between 25 and 40°C. In addition, C. tranquebarica exhibited significantly lower water loss rates than oregona at 30, 35 and 40°C.     

Species numbers,area, and habitat diversity on the habitat-islands of Mizorogaike pond,Japan

Species-area relationships of flowering plants were analyzed on the habitat-islands (hummocks on a floating bog) of Mizorogaike Pond, Japan. Three habitat units (Sphagnum cuspidatum unit,Sphagnum palustre unit, and fallen leaves unit) in which habitat conditions were homogeneous and a group of habitat-specific species occurred were recognized on the hummocks. Six hummock types were determined according to various combinations of the three habitat units. The most fundamental species-area relationships in which size itself affects the number of species were shown by hummocks with only one habitat unit. The species-area relationships for hummocks with two or three habitat units included the effects of habitat diversity in addition to size. The speciesarea curve for all hummocks was an average of these relationships. It is concluded that area in species-area relationships affects species numbers in two ways: number of habitat units and size of each habitat unit.     

Bird communities in rainforest fragments: guild responses to habitat variables in Tabasco,Mexico

The effects of habitat loss and fragmentation in tropical forests are difficult to separate, as they usually occur concurrently. In the state park La Sierra, in Tabasco, Mexico, the rainforest is being cleared for pasture, and fragments are being used by local inhabitants. This study examined the response of bird feeding guilds to habitat characteristics, including human disturbance, in five fragments of different sizes (1 ∼ 4,500 ha, 2 ∼ 150 ha, and 2 ∼ 80 ha). Using point count observations, 125 species were recorded and were grouped into 11 feeding guilds. As expected, the largest fragment had higher species richness and abundances than the smaller fragments. However, five habitat features differed significantly among fragment sizes, including tree density, the number of tree stumps and the number of trails. Thus the larger fragment was also less disturbed. Fragment size alone was significant only for scavenger species richness, and for the abundance of bark gleaning insectivores and insectivore/nectarivores. Raptors were more diverse and abundant in the large fragment and less disturbed sites. Arboreal frugivores and bark or foliage gleaning insectivores, depended on higher trees and less disturbed sites. A better understanding of the mechanisms that affect persistence is essential for the planning of conservation actions.     

Age and size of European saltmarshes and the population genetic consequences for ground beetles

Enzyme and dispersal polymorphisms of the saltmarsh carabid beetles Pogonus chalceus and Dicheirotrichus gustavii were studied in European populations varying in size and in isolation in space and time. D. gustavii, a constantly fullwinged species, has a larger genetic diversity and a smaller genetic differentiation between populations than the wing-polymorphic P. chalceus. Clear relationships between population or site characteristics and genetic structure were not observed, except for the special position taken by some small populations in both species. The dispersal power of P. chalceus in small populations is larger than in large populations, suggesting that these populations are unstable and/or young. Small populations, however, do not always show a lower genetic diversity than large populations, as would be expected from genetic drift. Dispersal power in P. chalceus declines with increasing age of the saltmarsh, probably due to continuous emigration of winged individuals. Age and size of saltmarshes, although difficult to study independently, both appear to be important in determining the genetic structure of saltmarsh beetles. Maximum diversity in both parameters is therefore recommended as an optimal nature conservation strategy. Received: 22 September 1997 / Accepted: 29 December 1997     

The effects of habitat complexity on the macroinvertebrates colonising wood substrates in a lowland stream

Summary Woody debris is a major structural component of south-eastern Australian lowland streams, and the decayed wood substrates provide a structurally complex habitat for macroinvertebrate colonization. I tested for the presence of a species richness-habitat complexity relationship for macroinvertebrate species inhabiting the surfaces of decayed submerged logs (snags) in a lowland stream in northern Victoria. The species-habitat complexity relationship is defined as the increase in species richness due to increased structural complexity of a habitat when area is held constant. The response of macroinvertebrates to seven treatments of artificial and natural substrates of differing levels and types of structural complexity were examined using cluster analyses and MANOVAs. These analyses revealed a significant species-habitat complexity relationship. In addition, a comparison of species evenness between simple and complex habitats supported the hypothesis that more complex habitats contained more species because they possessed more resources. Analysis of species richness, though informative, masked the complexity of species responses revealed by multivariate analyses of species abundances. These analyses showed that different species groups selected different microhabitats on snags, particularly in response to the level of sediment deposition, which was greater on more structurally complex snags. In comparison with the benthos, snags were significantly richer in species abundances, possibly related to low levels of dissolved oxygen in benthic habitats.     

The importance of streamside sandbars to ground beetle (Coleoptera, Carabidae) communities in a deciduous forest

We used pitfall traps to sample ground beetles on sandbars along a small woodland stream and in the adjacent floodplain forest (Oglethorpe Co., GA, USA). We captured a total of 1,477 ground beetles representing 41 species. Twenty-two species were exclusive to sandbars, while eight were found only in the forested habitat. Ground beetles were captured in significantly greater numbers from sandbars, especially Brachinus janthinipennis and Omophron americanum. The B. janthinipennis record represents a new state record for the species. This study demonstrates that many unique species can be found in specialized microhabitats and emphasizes the need for biodiversity assessment surveys to include a wide range of these microhabitats within a survey area. In addition, it appears that many generalist forest species might use sandbars seasonally to exploit available resources. The U.S. Government's right to retain a non-exclusive, royalty-free license in and to any copyright is acknowledged.     

Effects of seagrass habitat fragmentation on juvenile blue crab survival and abundance

Seagrasses form temporally dynamic, fragmented subtidal landscapes in which both large- and small-scale habitat structure may influence faunal survival and abundance. We compared the relative influences of seagrass (Zostera marina L.) habitat fragmentation (patch size and isolation) and structural complexity (shoot density) on juvenile blue crab (Callinectes sapidus Rathbun) survival and density in a Chesapeake Bay seagrass meadow. We tethered crabs to measure relative survival, suction sampled for crabs to measure density, and took seagrass cores to measure shoot density in patches spanning six orders of magnitude (ca. 0.25-30,000 m²) both before (June) and after (September) seasonally predictable decreases in seagrass structural complexity and increases in seagrass fragmentation. We also determined if juvenile blue crab density and seagrass shoot density varied between the edge and the interior of patches. In June, juvenile blue crab survival was not linearly related to seagrass patch size or to shoot density, but was significantly lower in patches separated by large expanses of unvegetated sediment (isolated patches) than in patches separated by <1 m of unvegetated sediment (connected patches). In September, crab survival was inversely correlated with seagrass shoot density. This inverse correlation was likely due to density-dependent predation by juvenile conspecifics (i.e. cannibalism); juvenile blue crab density increased with seagrass shoot density, was inversely correlated with crab survival, and was greater in September than in June. Shoot density effects on predator behavior and on conspecific density also likely caused crab survival to be lower in isolated patches than in connected patches in June. Isolated patches were either large (patch area >3000 m²) or very small (<1 m²). Large isolated patches had the lowest shoot densities, which may have allowed predators to easily find tethered crabs. Very small isolated patches had the highest shoot densities and consequently a high abundance of predators (=juvenile conspecifics). Though shoot density did not differ between the edge and the interior of patches, crabs were more abundant in the interior of patches than at the edge. These results indicate that seagrass fragmentation does not have an overriding influence on juvenile blue crab survival and density, and that crab cannibalism and seasonal changes in landscape structure may influence relationships between crab survival and seagrass habitat structure. Habitat fragmentation, structural complexity, faunal density, and time all must be incorporated into future studies on faunal survival in seagrass landscapes.     

Population dynamics of Agrimonia eupatoria and Geum rivale,two perennial grassland species

The population dynamics of two polycarpic perennials,Agrimonia eupatoria and Geum rivale, characteristic ofsemi-natural grasslands in Scandinavia, were examined in south-eastern Sweden.The perennial forbs were studied for several years in two populations each,located in habitats characteristic for the species in the study area.Demographic transition probabilities varied significantly between populationsand among years for the species. Transition matrix modelling yielded-values (population growth rates) that ranged from 0.89 to 1.14 forA. eupatoria and from 0.94 to 1.04 for G.rivale. The elasticity analysis showed that stasis in the adultstageclasses contributed most to . The life-table response experimentanalysis produced similar results as the elasticity analysis, where stasistogether with progression in the adult stage classes made a large contributionto the observed spatial variation in . Simulations of expected time toextinction were in the order of centuries for the study populations. Seedlingrecruitment was enhanced by seed addition and small scale disturbance inpopulations. For the intermediately abundant and more patchily distributedA. eupatoria, a regional survey of local populations wasconducted in the study area which revealed that most populations wererelativelysmall (< 100 individuals) and restricted to grassland fragments in roadverges. Furthermore, an attempt was made to estimate fruit dispersal from localpopulations.     

Dung beetles in continuous forest, forest fragments and in an agricultural mosaic habitat island at Los Tuxtlas, Mexico

With the aim of determining what kind of landscape mosaics might sustainmaximum diversity and minimum species loss, dung beetles were sampled withbaited pitfall traps to compare species richness and species composition in atract of continuous forest, forest fragments and a habitat island consisting ofa mosaic of forest and arboreal crops in Los Tuxtlas, southern Mexico. Wecaptured 7332 dung beetles representing 33 species. Similar numbers of specieswere captured in the three habitats. However, 56% of individuals were capturedin the continuous forest, 29% in the mosaic habitat and 15% in the forestfragments. Eight species (Canthon femoralis,Copris laeviceps, Canthidium centrale,Onthophagus batesi, Deltochilumpseudoparile, O. rhinolophus, Canthonviridis vazquezae and Dichotomius satanus) accounted for 90% of thecaptures, but their relative dominance varied among habitats. A clear trend wasevident in the number of dung beetles captured in the dung processing guilds(rollers/tunnelers) as well as in the diurnal and nocturnal guilds, withcaptures decreasing from the continuous forest to the mosaic habitat to theforest fragments. A similar trend was detected in detection rates for medium andsmall size dung producing mammals. Species richness of forest fragments andmosaic habitat did not differ from that found in the continuous forest, butthese habitats differ significantly in species richness from isolated shaded andunshaded plantations, linear strips of vegetation, the forest–pasture edge andpastures according to rarefaction analysis. The co-occurrence of the continuousforest, the mosaic habitat and the cluster of forest fragments in closeproximity seems to be preserving a diverse assemblage of dung beetle species inthe local landscape.     

The scale-dependent importance of habitat factors and dispersal limitation in structuring Great Lakes shoreline plant communities

Niche-based and neutral models of community structure posit distinct mechanisms underlying patterns in community structure; correlation between species’ distributions and habitat factors points to niche assembly while spatial pattern independent of habitat suggests neutral assembly via dispersal limitation. The challenge is to disentangle the relative contributions when both processes are operating, and to determine the scales at which each is important. We sampled shoreline plant communities on an island in Lake Michigan, varying the extent and the grain of sampling, and used both distance-based correlation methods and variance partitioning to quantify the proportion of the variation in plant species composition that was attributable to habitat factors and to spatial configuration independent of habitat. Our results were highly scale dependent. We found no distance decay of plant community similarity at the island scale (1−33 km). All of the explained variation (32%) in species composition among samples at this scale was attributed to habitat factors. However, at a site intensively sampled at a smaller scale (5−1,200 m), similarity of species composition did decay with distance. Using a coarse sampling grain (transects), habitat factors explained 40% of the variation, but the purely spatial component explained a comparable 22%. Analyzing plots within transects revealed variation in species composition that was still jointly determined by habitat and spatial factors (18 and 11% of the variance, respectively). For both grain sizes, most of the habitat component was spatially structured, reflecting an abrupt alongshore transition from sandy dunes to cobble beach. Space per se explained more variation in species composition at a second site where the habitat transition was more gradual; here, habitat acted as a less selective filter, allowing the signal of dispersal limitation to be detected more readily. We conclude that both adaptation to specific habitat factors and habitat-independent spatial position indicative of dispersal limitation determine plant species composition in this system. Our results support the prediction that dispersal limitation—a potentially, but not necessarily, neutral driver—is relatively more important at smaller scales.     

Effects of habitat edges on American lobster abundance and survival

Habitat edges frequently possess distinct ecological conditions that affect interactions such as competition and predation. Within a species' preferred habitat, the structural complexity and resource availability of adjacent habitats may influence the effect of edges on ecological processes. In nearshore waters of New England, American lobsters (Homarus americanus) inhabit fragmented cobble reefs that often are bordered by unvegetated sediment and occasionally by seagrass. We determined whether proximity to cobble patch edges, microhabitat characteristics within cobble habitat, and the type of habitat adjacent to cobble patches (seagrass or unvegetated sediment) influence the density and survival of juvenile and adult American lobsters in Narragansett Bay, Rhode Island, USA. We surveyed naturally occurring cobble patches and artificial cobble reefs to determine how the odds of finding lobsters varied with distance from the edge and habitat type. Additionally, we tethered lobsters at different distances from the edge inside and outside of cobble patches to determine how lobster relative survival varied with edge proximity and habitat type. In cobble habitat, the odds of finding large lobsters (adolescents and adults > 40 mm carapace length (CL)) were highest near patch edges regardless of adjacent habitat type, whereas smaller lobsters (e.g. emergent juveniles 15-25 mm CL) were more abundant in patch interiors when seagrass bordered cobble patches. The odds of finding lobsters also increased with the relative amount of cobble cover within patches. In predation experiments, lobster relative survival after 6 h was lowest outside of cobble and increased toward cobble patch interiors, but after 24 h this trend disappeared or reversed. Seagrass appeared to offer greater refuge for lobsters than did unvegetated sediment. Our results suggest that proximity to patch edges influences lobster distribution and survival, and that edge effects on lobsters vary with life history phase and with the type of habitat adjacent to cobble patches.     

Effect of alfalfa habitat change on dispersal behavior of Harmonia axyridis Pallas and Hippodamia variegata Goeze (Coleoptera: Coccinellidae)

An alfalfa grassland landscape was divided into 36 plots during 2014 season in Yuanzhou District of Guyuan city in Ningxia Hui Autonomous Region of P.R. China. In these three times repeated experiments, treatment of habitat fragmentation was divided into two grades: continuity (H = 0.0) and fragmentation (H = 1.0), and their habitat loss rate was divided into 6 grades: 90, 80, 70, 50, 20 and 0%. Considering habitat loss 0% of the plot as the reference, as a result of sweeping net and visual methods, results showed that the flight distance of the Harmonia axyridis was much higher than that of the Hippodamia variegata both in fragmentation and continuous habitats. In the alfalfa landscape, H. axyridis moved more by flying, while H. variegata moved more by crawling. There was a threshold effect that affected the movement behavior of lady beetles between 70 and 100% of the habitat loss. The population of the two species of lady beetles in the continuous habitat was higher than that in the habitat fragmentation and was more obvious in 70 and 50% plots of the habitat loss. The dispersal rate of the two species of lady beetles inside plots was higher than outside of the experimental plots, which reflected the low diffusivity of the ladybeetle. Habitat fragmentation affected the dispersal, migration and construction of two species of lady beetles on different spatial scales by disturbing the spread of natural enemies and searching for prey.