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At large scales, the mechanisms underpinning stability in natural communities may vary in importance due to changes in species composition, mean abundance, and species richness. Here we link species characteristics (niche positions) and community characteristics (richness and abundance) to evaluate the importance of stability mechanisms in 156 butterfly communities monitored across three European countries and spanning five bioclimatic regions. We construct niche-based hierarchical structural Bayesian models to explain first differences in abundance, population stability, and species richness between the countries, and then explore how these factors impact community stability both directly and indirectly (via synchrony and population stability). Species richness was partially explained by the position of a site relative to the niches of the species pool, and species near the centre of their niche had higher average population stability. The differences in mean abundance, population stability, and species richness then influenced how much variation in community stability they explained across the countries. We found, using variance partitioning, that community stability in Finnish communities was most influenced by community abundance, whereas this aspect was unimportant in Spain with species synchrony explaining most variation; the UK was somewhat intermediate with both factors explaining variation. Across all countries, the diversity–stability relationship was indirect with species richness reducing synchrony which increased community stability, with no direct effects of species richness. Our results suggest that in natural communities, biogeographical variation observed in key drivers of stability, such as population abundance and species richness, leads to community stability being limited by different factors and that this can partially be explained due to the niche characteristics of the European butterfly assemblage.

Aim: It is important to understand the factors affecting community stability because ecosystem function is increasingly at risk from biodiversity loss. Here, we evaluate how a key factor, the position of local environmental conditions within the thermal range of the species, influences the stability of butterfly communities at a continental scale.Location: Spain, UK and Finland.Time period: 1999– 2017.Major taxa studied: Butterflies.Methods: We tested the following hypotheses about how species responses to tem-perature anomalies aggregate to influence stability: Hypothesis 1, species have con-trasting responses to local temperature anomalies at opposing edges of their thermal range; hypothesis 2, communities with central thermal range positions have higher community stability; and the impacts of thermal range position on community stabil-ity are driven by hypothesis 3, population asynchrony, or hypothesis 4, additive popu-lation stability. Data were analysed at 876 sites for 157 species.Results: We found some support for hypothesis 1, because there were interactions be-tween thermal range and response to temperature anomalies such that species at dif-ferent range edges could provide weak compensatory dynamics. However, responses were nonlinear, suggesting strong declines with extreme anomalies, particularly at the hot range edge. Hypothesis 2 was supported in part, because community stabil-ity increased with central thermal range positions and declined at the edges, after accounting for species richness and community abundance. Thermal range position was weakly correlated with asynchrony (hypothesis 3) and population stability (hy-pothesis 4), although species richness and population abundance had larger impacts. Main conclusions: Future extreme heat events will be likely to impact species nega-tively across their thermal range, but might be particularly impactful on populations at the hottest end of the thermal range. Thermal range position influenced community stability because range edge communities were stable. However, the prediction of community stability from thermal range position is challenging because of nonlinear responses to temperature, with small temperature anomalies producing weak com-pensatory dynamics, but large extreme events synchronizing dynamics. The UK butterfly monitoring scheme is organized and funded by Butterfly Conservation, the Centre for Ecology and Hydrology, British Trust for Ornithology and the Joint Nature Conservation Committee. The Catalan butterfly monitoring scheme is funded by the Catalan Government, the Barcelona Provincial Council and other local partners. The Catalan butterfly monitoring scheme also incorpo-rates the Andora butterfly monitoring scheme, which is run by Centre d'Estudis de la Neu i la Mutanya d'Andorra (CENMA) and funded by Govern d'Andorra. The Finnish butterfly monitoring scheme is organ-ized and funded by the Finnish Environment Institute (SYKE).

Species can adapt to climate change by adjusting in situ or by dispersing to new areas, and these strategies may complement or enhance each other. Here, we investigate temporal shifts in phenology and spatial shifts in northern range boundaries for 289 Lepidoptera species by using long-term data sampled over two decades. While 40% of the species neither advanced phenology nor moved northward, nearly half (47%) -used one of the two strategies. The strongest positive population trends was observed for the minority of species (13%) that both advanced flight phenology and shifted their northern range boundaries northward. We show that, for Boreal Lepidoptera, a combination of phenology and range shifts is the most viable strategy under a changing climate. Effectively, this may divide species into winners and losers based on their propensity to capitalize on this combination, with potentially large consequences on future community composition.

Ecological intensification has been proposed as a strategy to mitigate the impacts of conventional intensive land use on pollinators and insect pollination. However, research has concentrated on the effects of land management on pollinator abundance and diversity, while studies directly measuring pollination services are still lacking for many crops and regions. This study examines the effects of landscape heterogeneity, pesticide use intensity and flowering time on insect pollination of turnip rape Brassica rapa ssp. oleifera, a major oil crop at high latitudes. The field experiment included monitoring pollinator visits on turnip rape flowers and measuring yield in 34 spring-sown turnip rape fields in Southern Finland. The fields were situated in two landscape types that differed in the cover of arable land and represented independent gradients of pesticide use intensity and flowering time. Based on flower visits and number of seeds per silique, turnip rape was best pollinated in fields with late flowering time. The result suggests a temporal mismatch between crop flowering and the availability of pollination service in early sown fields. The increase in flower visits during summer was steeper among fields with low than high pesticide use, possibly due to a faster colony growth of important bee pollinators. Pollinator community in turnip rape fields was more diverse in heterogeneous landscapes with less arable land than in homogeneous field-dominated landscapes, suggesting higher stability of pollination services in diverse landscapes. Total yield per plant was positively related to pesticide use intensity. The relationship between insect pollination and total yield was weakened by high compensation capacity of turnip rape, the plants producing more flowers under poor pollination.Synthesis and applications. Crop pollination can be enhanced by shifting sowing time to better match crop flowering to the peak availability of the most important pollinators. Reduced pesticide use may also enhance pollination services but can lead to the total yield reduction due to pests. This highlights the need for pollinator-friendly pest control methods to maintain turnip rape yields while conserving pollination services. Foreign Language AbstractTiivistelma Maatalouden ekologista tehostamista on esitetty strategiaksi, jonka avulla intensiivisen maankayton kielteisia vaikutuksia polyttajiin ja hyonteispolytykseen voidaan hillita. Tutkimukset maankayton vaikutuksista viljelykasvien hyonteispolytykseen kuitenkin puuttuvat yha monilta viljelykasveilta ja alueilta. Tama tutkimus tarkasteli maiseman monimuotoisuuden, torjunta-aineiden kayton ja kukinta-ajan vaikutusta rypsin hyonteispolytykseen. Peltokokeessa seurattiin polyttajien vierailuja rypsin kukilla ja mitattiin satoa 34 kevatrypsipellolla Uudellamaalla. Pellot sijaitsivat kahdessa maisematyypissa, joista toinen oli peltovaltainen ja toinen monimuotoisempi ja vahemman peltoa sisaltava. Lisaksi pellot erosivat toisistaan torjunta-aineiden kayton ja kukinta-ajan suhteen. Polyttajien kukkavierailut ja siementen maara per litu olivat korkeimmillaan myohaan kukkineilla rypsipelloilla, mika kertoo hyvasta polytyksesta. Tuloksen perusteella aikaisin kylvetyt rypsipellot saattavat kukkia liian aikaisin polyttajien saatavuuden nakokulmasta. Voimakkaimmin polyttajien maara lisaantyi kesan aikana niiden peltojen joukossa, joilla ei kaytetty torjunta-aineita. Mahdollinen selitys on, etta tarhamehilaisten ja kimalaisten yhdyskunnat kasvoivat nopeimmin naiden peltojen laheisyydessa. Polyttajien monimuotoisuus oli suurempi monimuotoisessa kuin peltovaltaisessa maisemassa, mika parantaa polytyspalvelun vakautta muuttuvissa olosuhteissa. Kokonaissato per kasvi nousi torjunta-aineiden kayton lisaantyessa. Hyonteispolytyksen ja sadon valista yhteytta heikensi rypsin hyva kompensaatiokyky, jonka ansiosta heikosti polyttyneet kasvit tuottivat enemman kukkia.Yhteenveto ja sovellukset. Viljelykasvin polytysta voi parantaa saatamalla kylvoaikaa siten, etta kasvin kukinta ajoittuu tarkeimpien polyttajien runsaushuippuun. Torjunta-aineiden kayton vahentaminen voi parantaa polytysta mutta laskea samaan aikaan satoa tuholaisten ja rikkakasvien lisaantymisen takia. Polyttajaystavallisten kasvinsuojelukeinojen kehittaminen on tarkeaa korkeiden rypsisatojen ja polytyspalveluiden sailymisen kannalta. Crop pollination can be enhanced by shifting sowing time to better match crop flowering to the peak availability of the most important pollinators. Reduced pesticide use may also enhance pollination services but can lead to the total yield reduction due to pests. This highlights the need for pollinator-friendly pest control methods to maintain turnip rape yields while conserving pollination services. peerReviewed

Aim Nitrogen deposition is a major global driver of change in plant communities, but its impacts on higher trophic levels are insufficiently understood. Here, we introduce and test a novel conceptual trait-based model describing how the effects of soil eutrophication cascade to higher trophic levels across differential plant–herbivore interactions. Location Northern Europe. Methods We synthesize previous literature on the effects of nitrogen on plants and herbivorous insects as well as relevant multispecies patterns of insect communities concerning species dietary breadth, body size, dispersal propensity and voltinism in order to derive the model. We empirically evaluate the proposed, hitherto untested, four main model pathways using statistical modelling and data on 1064 northern European butterfly and moth species, their life-history traits, phylogeny and population trends. Results We show that across all species: (1) larval dietary breadth and host plant foliar nitrogen content are positively and equally strongly related to insect body size, and that (2) multivoltinism, host plant preferences for soil nitrogen, body size and larval dietary breadth are positively related to population trends of butterflies and moths as predicted by the model. Positive relationships between plant foliar nitrogen content and body size as well as multivoltinism and population trends are the first multispecies demonstrations for these patterns. Main conclusions Soil nitrogen enrichment amplifies the diverging trends of herbivorous insects feeding on nitrophilous versus nitrophobous plants through differential plant–herbivore interactions, causing predictable changes in community composition at higher trophic levels. A positive foliar nitrogen–insect body size relationship, now empirically supported, is the integrating link within this cascade. As nitrogen deposition is a global driver, our model suggests that a major future trend may be an increased dominance of insects that are large, dispersive, multivoltine, dietary generalists or specialized on nitrophilous plant species at the expense of species preferring oligotrophic environments.

Mobility is a key factor determining lepidopteran species responses to environmental change. However, direct multispecies comparisons of mobility are rare and empirical comparisons between butterflies and moths have not been previously conducted. Here, we compared mobility between butterflies and diurnal moths and studied species traits affecting butterfly mobility. We experimentally marked and released 2011 butterfly and 2367 moth individuals belonging to 32 and 28 species, respectively, in a 25 m × 25 m release area within an 11-ha, 8-year-old set-aside field. Distance moved and emigration rate from the release habitat were recorded by species. The release experiment produced directly comparable mobility data in 18 butterfly and 9 moth species with almost 500 individuals recaptured. Butterflies were found more mobile than geometroid moths in terms of both distance moved (mean 315 m vs. 63 m, respectively) and emigration rate (mean 54% vs. 17%, respectively). Release habitat suitability had a strong effect on emigration rate and distance moved, because butterflies tended to leave the set-aside, if it was not suitable for breeding. In addition, emigration rate and distance moved increased significantly with increasing body size. When phylogenetic relatedness among species was included in the analyses, the significant effect of body size disappeared, but habitat suitability remained significant for distance moved. The higher mobility of butterflies than geometroid moths can largely be explained by morphological differences, as butterflies are more robust fliers. The important role of release habitat suitability in butterfly mobility was expected, but seems not to have been empirically documented before. The observed positive correlation between butterfly size and mobility is in agreement with our previous findings on butterfly colonization speed in a long-term set-aside experiment and recent meta-analyses on butterfly mobility.

Aim We test the prediction that beta diversity (species turnover) and the decay of community similarity with distance depend on spatial resolution (grain). We also study whether patterns of beta diversity are related to variability in climate, land cover or geographic distance and how the independent effects of these variables depend on the spatial grain of the data. Location Europe, Great Britain, Finland and Catalonia. Methods We used data on European birds, plants, butterflies, amphibians and reptiles, and data on British plants, Catalonian birds and Finnish butterflies. We fitted two or three nested grids of varying resolutions to each of these datasets. For each grid we calculated differences in climate, differences in land-cover composition (CORINE) and beta diversity (bsim, bJaccard) between all pairs of grid cells. In a separate analysis we looked specifically at pairs of adjacent grid cells (the first distance class). We then used variation partitioning to identify the magnitude of independent statistical associations (i.e. independent effects in the statistical sense) of climate, land cover and geographic distance with spatial patterns of beta

Local species richness of butterflies can be expected to benefit from both local habitat properties as well as the availability of suitable habitats and source populations in the surrounding landscape. Whether local species richness is dependent on local or landscape factors can be assessed by examining the relationship between local and landscape species richness. Here we studied how local species richness is related to landscape-level species richness in landscapes differing in agricultural intensity. The relationship was linear for field boundaries in intensively cultivated landscapes and non-linear in less-intensively cultivated landscapes. In landscapes containing semi-natural grasslands (on average 4% of overall land-use), the relationship was non-linear for field boundaries, but linear when considering local species richness of the grasslands themselves. These results show that local factors are more important than landscape factors in determining local species richness in landscapes which contained semi-natural grasslands. Local species richness was limited by landscape factors in intensively cultivated landscapes. This interpretation was supported by the relationship between local species richness and landscape-scale average mobility and generalist percentage of butterfly assemblages. We conclude that the management of field boundary habitat quality for butterflies is expected to be most effective in landscapes with semi-natural grasslands, the species composition of which in turn is dependent on the regional occurrence of grasslands. Based on our results, managing non-crop habitats for the conservation of habitat specialists and species with poor mobility will be most efficient in regions where patches of semi-natural grasslands occur.

Summary 1. Establishing temporal habitat patches, such as long-term set-aside, is potentially a valuable approach to support pollinator populations in intensively cultivated landscapes. The benefits of this approach are expected to differ between pollinator groups, because of fundamental differences in their ecology. 2. We studied the responses of two pollinator groups, bumblebees and diurnal Lepidoptera (butterflies and diurnal moths), to the vegetation succession in experimental set-aside during six consecutive years. The pollinators were monitored in 24 large treatment plots (50 · 50 m), sown with three different seed mixtures (competitive and two alternatives) and unmanaged or managed by mowing, and on 10 surrounding field margins. 3. The responses of the two pollinator groups to vegetation succession were distinctly different. Bumblebees showed a very strong positive response to the diverse seed mixture with abundant floral resources, and their abundance peaked in the first year. The species richness and abundance of Lepidoptera were increased gradually, suggesting differential colonization speeds of species and a gradual establishment of populations. Lepidopteran abundance reached the level of the field margins in 3 years, whereas the corresponding species richness level was not reached. The benefits of the alternative seed mixtures were less pronounced in Lepidoptera than in bumblebees. No effects of the mowing treatment on either species group were detected. 4. Within both pollinator groups, the response to vegetation succession was associated with species traits. In bumblebees, long-tongued species (indicating specialization) were increased during succession. In butterflies and diurnal moths, colonization success of species was strongly correlated with their wing span (indicating mobility). The most successful colonizers in butterflies were grass feeders and in diurnal moths the species feeding on leguminous plants at the larval stage. 5. Synthesis and applications. The ecological requirements of different pollinator groups should be taken into account when establishing set-aside. Supporting bumblebees is possible even on shortterm set-aside, assuming nectar and pollen sources are made available. The occurrence of butterflies and diurnal moths is strongly driven by additional factors, such as the availability of larval host plants as well as adult mobility, which calls for set-aside management regimes to be in place for several years.

Species are differentially affected by habitat fragmentation as a consequence of differences in mobility, area requirements, use of the matrix, and responses to edges. A quantitative understanding of these differences is essential not only for conservation biology but also for basic ecological theory. Here, we examine density responses by butterflies to patch size and use a quantitative theory on the scaling of population density with patch size to interpret results. Theory suggests that the density distribution of mobile species along a patch size gradient should depend on the scaling of net migration rates, whereas the density distribution of less mobile species should depend more on local growth. Using data from 11 localities in three European countries, we calculated the slope in the relationship between patch size and population density. These slopes were evaluated in relation to butterfly traits and matrix composition. As estimates of butterfly mobility we used both wing span and expert mobility rankings. The slope of the density–area relationship changed as predicted with wing span and the association of species to grasslands. Large and highly mobile species had a negative slope, similarly for grassland specialists and generalist species, and the slope matched quantitative predictions based on the scaling of net migration rates. Small and less mobile grassland specialists had a slope that was less negative than the slope of large and mobile grassland specialists, whereas the slope did not change with size for generalist species. These analyses suggest that the variability in response among butterfly species to patch size could be explained by accounting for body size/mobility and habitat associations among species. A caveat is that edge effects are not explicitly included in the model analysis, and future research should aim to combine area and edge effects in a common theoretical framework.

Intensification or abandonment of agricultural land use has led to a severe decline of semi-natural habitats across Europe. This can cause immediate loss of species but also time-delayed extinctions, known as the extinction debt. In a pan-European study of 147 fragmented grassland remnants, we found differences in the extinction debt of species from different trophic levels. Present-day species richness of long-lived vascular plant specialists was better explained by past than current landscape patterns, indicating an extinction debt. In contrast, short-lived butterfly specialists showed no evidence for an extinction debt at a time scale of c. 40 years. Our results indicate that management strategies maintaining the status quo of fragmented habitats are insufficient, as time-delayed extinctions and associated co-extinctions will lead to further biodiversity loss in the future.

Landscape simplification and habitat fragmentation may cause severe declines of less mobile and habitat specialist species and lead to biotic homogenization of species communities, but large-scale empirical evidence on biotic homogenization remains sparse. We sampled butterfly and day-active geometrid moth communities within 134 differently fragmented landscapes in Finland situated in five geographical regions. Overall species richness was partitioned into alpha and beta diversity and butterflies were assigned a species-specific mobility rank and habitat specificity score based on published ecological trait classifications. Alpha and beta diversity of butterflies and geometrid moths decreased with increasing agricultural intensity, independently of geographical position. The responses were either linear or nonlinear with accelerating decrease of diversity when arable field cover exceeded 60%. Mobility rank and percentage generalists of butterfly communities increased linearly with increasing field cover. In landscapes with high agricultural intensity (>60% field coverage), the decrease in beta diversity of butterflies was strongly associated with an increasing proportion of habitat generalists and increasing average mobility in the butterfly communities. However, there was no such relationship in landscapes with low or moderate agricultural intensity. Synthesis and applications. We demonstrate that biotic homogenization caused by land-use change arises as a consequence of the loss of habitat specialists and poor dispersers in intensively cultivated landscapes with simplified landscape structure. Agri-environment schemes will therefore be inefficient in protecting high beta diversity unless they explicitly increase habitat availability and connectivity for habitat specialists and poor dispersers. © 2010 The Authors. Journal compilation © 2010 British Ecological Society. (Less)

This study provides a novel systematic comparative analysis of the species characteristics affecting the range margin shifts in butterflies towards higher latitudes, while taking phylogenetic relatedness among species into account. We related observed changes in the northern range margins of 48 butterfly species in Finland between two time periods (1992–1996 and 2000–2004) to 11 species traits. Species with positive records in at least ten 10 km × 10 km grid squares (in the Finnish National Butterfly Recording Scheme, NAFI) in both periods were included in the study. When corrected for range size change, the 48 butterfly species had shifted their range margins northwards on average by 59.9 km between the study periods, with maximum shifts of over 300 km for three species. This rate of range shifts exceeds all previously reported records worldwide. Our findings may be explained by two factors: the study region is situated in higher latitudes than in most previous studies and it focuses on the period of most prominent warming during the last 10–15 years. Several species traits exhibited a significant univariate relationship with the range margin shift according to generalized estimation equations (GEE) taking into account the phylogenetic relatedness among species. Nonthreatened butterflies had on average expanded their ranges strongly northwards (84.5 km), whereas the distributions of threatened species were stationary (−2.1 km). Hierarchical partitioning (HP) analysis indicated that mobile butterflies living in forest edges and using woody plants as their larval hosts exhibited largest range shifts towards the north. Thus, habitat availability and dispersal capacity of butterfly species are likely to determine whether they will be successful in shifting their ranges in response to the warming climate.

Empirical studies have suggested that species richness of grassland insects usually decreases under grazing management. By contrast, grazing has been shown to increase the species density and richness of vascular plants, especially on productive soils. In order to test the suggested differences in response to management between plants and insects, we simultaneously studied species richness of vascular plants and their insect herbivores, butterflies and moths, in 68 semi-natural grasslands with varying grazing intensity and frequency in SW Finland. Species richness of plants and insects was for the first time related to a quantitative measure of disturbance intensity and successional age, mean vegetation height, by using generalized additive models (GAM). The effects of soil nutrients on vegetation height were accounted for by using phosphorus concentration as a productivity surrogate. The results showed that species richness of butterflies and moths peaked in taller vegetation compared with vascular plants, corresponding to a lower disturbance intensity and increasing time since abandonment. These patterns are discussed in the light of two hypotheses, the ‘‘structural diversity hypothesis’’ and ‘‘dynamic equilibrium model’’ of Huston, both suggesting a weaker disturbance tolerance of insects compared with plants. Butterflies and moths which are specialists in their larval host-plant use (monophagous and oligophagous species) preferred lower vegetation (higher disturbances) compared with generalists (polyphagous species), as predicted by Huston’s model. This difference indicates a stronger relationship with plant species richness for specialist than for generalist butterflies and moths. Our results support the application of regionally and temporally varying grazing intensities in grassland conservation management.

Aim To assess the relative importance of climate, biotope and soil variables as well as geographical location for the species richness of plants, butterflies, day-active macromoths and wild bees in boreal agricultural landscapes. Location A total of 68 agricultural landscapes located in southern Finland. Methods Generalized linear mixed models were used to analyse the effects of environmental (climate, biotope and soil) and spatial (latitude and longitude) variables on species richness of four taxa in 136 study squares of 0.25 km2. Using partial regression, the variation in species richness was decomposed into the purely environmental fraction; the spatially structured environmental fraction; and the purely spatial fraction, including variables retained in cubic trend surface regression. Results Species richness of all taxa was positively correlated with temperature. Species richness of plants and butterflies was also positively correlated with the heterogeneity of landscape. The extent of low-intensity agricultural land and forest had a positive effect, and the extent of cultivated field a negative effect on the species richness of these taxa. The effect of soil characteristics on the number of observed species was negligible for all taxa. The greatest part of the explained variation for all taxa was accounted for by the pure effect of geographical location. To a somewhat lesser extent, the species richness of plants, butterflies and bees was also related to the effects of spatially structured environmental variables, and the species richness of macromoths to the effects of environmental variables. Main conclusions Multi-species richness of boreal agricultural landscapes at the scale of 0.25 km2 was associated with the heterogeneity of the local landscape. However, large-scale geographical variation in species richness was also observed, which indicates the importance of climate and geographical location for the taxa studied. These results highlight the fact that, even on a landscape scale, geographical factors should be taken into account in biodiversity studies. Heterogeneous agricultural landscapes, including forest and non-crop biotopes, should be preserved or restored to maintain biodiversity.

Aim We tested the usefulness of satellite based remote sensing data and geographical information system (GIS) techniques (1) in explaining the observed distribution of the threatened clouded apollo butterfly (Parnassius mnemosyne) and (2) in predicting the occurrence of the butterfly in two independent test areas with different landscape structure. Location The three study areas are located along the rivers Rekijoki and Halikonjoki in a boreal agricultural landscape in south-western Finland (60°40′ N; 23°20′ E). Methods Landsat satellite images were used to generate habitat maps of the three study areas. Topographical variables were calculated from a digital elevation model. These data were used to construct a multiple logistic regression model fitted with the observed occurrence of clouded apollo in 126 grid squares of 0.25 km2 within an area of 31.5 km2 (model building area). The parameterized model was used to predict the occurrence of the butterfly in an adjacent test area with a similar landscape structure as in the model building area, as well as in a more distant test area with a more fragmented pattern of semi-natural grassland. Results In the model building area probability of clouded apollo occurrence increased with connectivity of semi-natural grassland, cover of deciduous forest, cover of semi-natural slope grassland and topographical heterogeneity. The model accuracy was high, the correct classification rate being 98.4% overall and 95.0% for the butterfly presence squares. In both test areas the overall correct classification of the model prediction was high (c. 92%). However, in predicting the actual butterfly presence squares the model succeeded substantially better in the adjacent than in the distant test area (correct classification rates 91.3% and 66.7%, respectively). Main conclusions The results showed that the distribution of a habitat specialized butterfly may be quite successfully explained and predicted based on pure satellite imagery and topographical data. Nevertheless, the decrease of accuracy of the model prediction when applied to a different landscape structure than the one in which the model was parameterized suggests that the useful application of such models is limited by the environmental variability of the original model building data.

Recent studies on the determinants of distribution and abundance of animals at landscape level have emphasized the usefulness of the metapopulation approach, in which patch area and habitat connectivity have often proved to explain satisfactorily existing patch occupancy patterns. A different approach is needed to study the common situation in which suitable habitat is difficult to determine or does not occur in well-defined habitat patches. We applied a landscape ecological approach to study the determinants of distribution and abundance of the threatened clouded apollo Parnassius mnemosyne butterfly within an area of 6 km2 of agricultural landscape in south-western Finland. The relative role of 24 environmental variables potentially affecting the distribution and abundance of the butterfly was studied using a spatial grid system with 2408 grid squares of 0.25 ha, of which 349 were occupied by the clouded apollo. Both the probability of butterfly presence and abundance in a 0.25 ha square increased with the presence of the larval host plant Corydalis solida, the cover of semi-natural grassland, the amount of solar radiation and spatial autocorrelation in butterfly occurrence. Additionally, butterfly abundance increased with overall mean patch size and decreased with maximum slope angle and wind speed. Two advantages of the employment of a spatial grid system included the avoidance of a subjective definition of suitable habitat patches and an evaluation of the relative significance of different components of habitat quality at the same time with habitat availability and connectivity. The large variation in habitat quality was influenced by the abundance of the larval host plant and adult nectar sources but also by climatological, topographical and structural factors. The application of a spatial grid system as used here has potential for a wide use in studies on landscape-level distribution and abundance patterns in species with complex habitat requirements

We studied host plant abundance, host use, and oviposition preference in metapopulations of the butterfly Melitaea cinxia within an area of 3500 km2 in the Aland islands, southwestern Finland. In the study area, M. cinxia has -400 small local populations on dry meadows with the larval host plants, Plantago lanceolata and Veronica spicata. Plantago lanceolata occurs in practically all meadows otherwise suitable for the butterfly, whereas the distribution of V. spicata is largely restricted to the northwestern part of the study area. Based on observations of 6500 prediapause larval groups during 1993-1996, we document spatial variation in host plant use in relation to their abundance (electivity). The fraction of larval groups found on V. spicata increased disproportionally with the relative cover of V. spicata in the habitat patches. Additionally, the probability of Veronica use in a population increased with increasing number of larval groups found on Veronica in the surrounding populations but decreased with increasing use of Plantago in the neigh- borhood. This regional effect on host use at the scale of migrating butterflies could be caused either by spatial variation in the insect (in either preference or performance) or by spatial variation in plants (in resistance to attack by the butterflies). To study the first possibility, we conducted oviposition preference experiments using butterflies from five metapopulations located 2-55 km from each other and characterized by differences in host plant availability and host use. We found clear genetic differences in oviposition preference between the five metapopulations consistent with the observed host use patterns in the field. We conclude that the spatial host use patterns of M. cinxia in the study area are driven both by direct effects of local host abundance and by indirect effects mediated through metapopulation-level adaptation to the regionally more abundant host plant.

The incidence function model is derived from a linear first-order Markov chain of the presence or absence of a species in a habitat patch. The model can be parameterized with “snapshot” presence/absence data from a patch network. Using the estimated parameter values the Markov chain can be iterated in the same or in some other patch network to generate quantitative predictions about transient metapopulation dynamics and the stochastic steady state. We tested the ability of the incidence function model to predict patch occupancy using extensive data on an endangered butterfly, the Glanville fritillary (Melitaea cinxia) Parameter values were estimated with data collected from a 50-patch network in 1991. In 1993 we surveyed the entire geographic range of the species in Finland, within an area of 50 × 70 km2, with 1502 habitat patches (dry meadows) of which 536 were occupied. Model predictions were generated for the 1502 patches and were compared with the observed pattern of occupancy in 1993. The model predicted patch occupancy well in more than half of the study area, but prediction was poor for one quarter of the area, probably because of regional variation in habitat quality and because metapopulations may have been perturbed away from the steady state. The incidence function model provides a practical tool for making quantitative predictions about metapopulation dynamics of species living in fragmented landscapes.

There is a lack of quantitative syntheses of fragmentation effects across species and biogeographic regions, especially with respect to species life-history traits. We used data from 24 independent studies of butterflies and moths from a wide range of habitats and landscapes in Europe and North America to test whether traits associated with dispersal capacity, niche breadth and reproductive rate modify the effect of habitat fragmentation on species richness. Overall, species richness increased with habitat patch area and connectivity. Life-history traits improved the explanatory power of the statistical models considerably and modified the butterfly species-area relationship. Species with low mobility, a narrow feeding niche and low reproduction were most strongly affected by habitat loss. This demonstrates the importance of considering life-history traits in fragmentation studies and implies that both species richness and composition change in a predictable manner with habitat loss and fragmentation.