Patch Occupancy Research Articles

Abundance, density and activity ofSalvator merianae(Reptilia: Teiidae) and the effect of poaching on the site occupancy by the lizard in an Atlantic Forest Reserve, Brazil

AbstractWe aimed to estimate the density, occupancy and detectability ofSalvator merianae(Tegu) in one of the largest Atlantic rainforest remnants in Espírito Santo, Brazil, theVNR. Species patch occupancy was modelled and used to predict the response direction of six covariates based on prior knowledge of the Tegu's ecology.A priori, we expected that the covariates measured should represent key habitat features for the species (i.e. temperature, forest edge, open habitats) or elements possibly avoided by the species, based on the hypothesis that poaching would have a negative effect on patch occupancy. We used line‐transect surveys to estimate density and abundance. Camera‐traps were used to estimate patch occupancy by the Tegu. Estimated density forS. merianaewas 0.21 ± 0.02 Tegus/ha and estimated population size was 4990 ± 521 individuals. Patch occupancy was best described by two covariates: poaching intensity and distance to the forest edge. Detectability was affected by three covariates: poaching intensity, tree density and temperature. Our study presents robust information on abundance and density, habitat use, and activity ofS. merianaein theVNRand is the first study providing data on the effects that poaching has on patch occupancy of this lizard. The data indicated that the occupancy and detectability of this species were influenced by a set of factors, providing information that can be useful in management plans in areas where this species can potentially decline and in areas where it may be introduced.

Habitat effects on golden‐cheeked warbler productivity in an urban landscape

ABSTRACTHabitat fragmentation and isolation can result in decreased occupancy and reproductive success within songbirds, particularly for species inhabiting urban environments where available habitat may be limited. The golden‐cheeked warbler (Setophaga chrysoparia) is a federally endangered songbird that inhabits oak–juniper (Quercus spp.–Juniperus spp.) woodlands across central Texas, USA. Past research has indicated decreased patch occupancy and productivity near urban areas. We monitored patch occupancy, territory establishment, pairing success, and fledging success of warblers in an urban environment. Warblers occupied 24% (n = 63) of patches surveyed; 10% (n = 63) of habitat patches had ≥1 established territory. Warblers successfully paired in 4 patches and fledged young in 3 patches. We found an increasing probability of occupancy at approximately 65–70% canopy cover, and an added effect of distance to the nearest habitat patch. We found that distance to and size of the nearest habitat patch best predicted territory establishment. Patch size and size of the nearest habitat patch best predicted pairing success. Although our results were inconclusive for fledging success, a review of available data suggests patch size, size of, and distance to the nearest habitat patch all affect warbler reproductive activity. We recommend to manage for oak–juniper woodland patches with >70% canopy cover that are >26 ha in size, in close proximity to other oak–juniper woodland patches with equal or greater canopy cover and patch size when managing for golden‐cheeked warblers within an urban matrix. © 2018 The Wildlife Society.

Patch dynamics of various plant-animal interactions in fragmented landscapes

Habitat destruction, characterized by patch loss and patch fragmentation, has been recognized as one of leading factors driving species loss. Although some studies have already explored how patch loss affects metacommunity dynamics, the effect of patch configurational fragmentation remains vaguely understood. Here we construct a patch-dynamic model for various plant-animal interactions in fragmented landscapes, including neutralism (0, 0), poison (0, −), competition (−, −), predation (−, +), fruitivory (0, +) and mutualism (+, +). Counter-intuitively, negative plant-animal interactions (harmful for one or both species) show stronger tolerance to habitat destruction (i.e., higher species persistence) than positive interactions (beneficial to one or both species), in spite of lower patch occupancy. This is because animal species survival in positive interactions largely depends on plant species abundance. Furthermore, neutralism displays most robust to both patch loss and fragmentation while mutualism showing most vulnerability. Essentially, neutral interaction leads to more patches available for both plant and animal species, while in mutualistic interaction (e.g., pollination), both plant and animal species can only persist when they co-occur at the same patches. Compared to other interactions, predation (−, +) results in lowest patch occupancy, but such trophic interaction does not exhibit highest sensitivity to habitat destruction. Overall, our modelling framework provides new insights into how different plant-animal interactions respond to landscape fragmentation.

How to preserve a butterfly species within an urbanising settlement and its surroundings: a study of the scarce copper (Lycaena virgaureae L.) in southern Sweden

Urbanisation is a rapidly ongoing process worldwide with profound consequences for wildlife in urban and peri-urban areas. Species are affected by habitat loss, habitat alternation and degradation, fragmentation and increased human population and activity. Habitat loss can occur due to construction of housing and infrastructure in peri-urban areas and within urban areas due to compaction. Undeveloped areas can also be changed from ruderal land, wilderness areas or leftover green space to more formal and more intensively used urban green space. This study investigated a butterfly species, the scarce copper (Lycaena virgaureae L.), in an urbanising and expanding settlement in a rural location in southern Sweden. The scarce copper is still relatively common in Sweden, but has experienced severe decline in certain areas and in other parts of Europe. Patch occupancy and abundance of the species were investigated in 44 patches ranging from urban and peri-urban to rural locations. Habitats investigated were parks, urban grasslands managed for biodiversity by the local authority, unmanaged abandoned arable sites, road verges, meadows and pastures. In total, 624 sightings of scarce coppers were recorded. The highest abundances were observed in larger unmanaged patches and in meadows in peri-urban areas, while pastures had low abundances. In urban parks, no coppers were found. The smaller sites managed for biodiversity by the local authority within the settlement were often occupied by the scarce copper, although abundances were low (mean number of individuals 3 ± 1.2). In patches which were cut, copper numbers dropped in almost all cases to zero after cutting. Patch occupancy was affected by habitat characteristics such vegetation height, tree succession, abundance of Rumex acetosella (sheep’s sorrel), as well as landscape features such as length of forest edge. Factors identified as influencing abundance were the same, but additionally also flower abundance. The current high abundances of the scarce copper in the area will not be ensured in the longer term when all building plans are implemented and no other measures are taken. Recommendations are made on management and planning to preserve the species in the study area.

Habitat use, but not gene flow, is influenced by human activities in two ecotypes of Egyptian fruit bat (Rousettus aegyptiacus).

Understanding the ecological, behavioural and evolutionary response of organisms to changing environments is of primary importance in a human-altered world. It is crucial to elucidate how human activities alter gene flow and what are the consequences for the genetic structure of a species. We studied two lineages of the Egyptian fruit bat (Rousettus aegyptiacus) throughout the contact zone between mesic and arid Ecozones in the Middle East to evaluate the species' response to the growing proportion of human-altered habitats in the desert. We integrated population genetics, morphometrics and movement ecology to analyse population structure, morphological variation and habitat use from GPS- or radio-tagged individuals from both desert and Mediterranean areas. We classified the spatial distribution and environmental stratification by describing physical-geographical conditions and land cover. We analysed this information to estimate patch occupancy and used an isolation-by-resistance approach to model gene flow patterns. Our results suggest that lineages from desert and Mediterranean habitats, despite their admixture, are isolated by environment and by adaptation supporting their classification as ecotypes. We found a positive effect of human-altered habitats on patch occupancy and habitat use of fruit bats by increasing the availability of roosting and foraging areas. While this commensalism promotes the distribution of fruit bats throughout the Middle East, gene flow between colonies has not been altered by human activities. This discrepancy between habitat use and gene flow patterns may, therefore, be explained by the breeding system of the species and modifications of natal dispersal patterns.

Modelling the effects of spatial heterogeneity and temporal variation in extinction probability on mosquito populations.

Spatial synchrony plays an important role in dictating the dynamics of spatial and stage-structured populations. Here we argue that, unlike the Moran effect where spatial synchrony is driven by exogenous factors, spatial correlation in intrinsic/local-scale processes can affect the level of spatial synchrony among distinct sub-populations, and therefore the persistence of the entire population. To explore this mechanism, we modelled the consequences of spatial heterogeneity in aquatic habitat quality, and that of temporal variation in local extinction probability, on the persistence of stage-structured mosquito populations. As a model system, we used two widely distributed mosquito species, Aedes albopictus and Culex pipiens, both key vectors of a range of infectious diseases. Spatial heterogeneity in aquatic habitat quality led to increased population persistence, and this pattern was more pronounced at intermediate dispersal rates, and in the long-dispersing species (C.pipiens). The highest regional persistence was obtained at high dispersal rates. This is probably because dispersal, in our model, did not carry any additional costs. Population persistence of both species was negatively correlated with increased temporal variation in local extinction probability. These differences were stronger in the short-dispersing species (A.albopictus), especially at intermediate dispersal rates. The dispersal of A.albopictus adults in each time step was limited to the nearest habitat patches, weakening the positive effect of spatial heterogeneity in aquatic habitat quality on population persistence. In contrast, C.pipiens adults could disperse into more remote sub-populations, resulting in much higher recolonization rates. Hence, the negative effect of temporal variation in local extinction probability on patch occupancy disappeared at intermediate dispersal rates. We suggest that effectively controlling these two mosquito species requires making few spatially synchronized control efforts (i.e., generating high temporal variation in local extinction probability), rather than many asynchronized local control efforts. Finally, our model can be easily fitted to other organisms characterized by complex life cycles, and it can be also used to examine alternative scenarios, including the effect of spatial configuration of local habitat patches and dispersal kernel shape on population persistence.

Apparent climate-mediated loss and fragmentation of core habitat of the American pika in the Northern Sierra Nevada, California, USA.

Contemporary climate change has been widely documented as the apparent cause of range contraction at the edge of many species distributions but documentation of climate change as a cause of extirpation and fragmentation of the interior of a species’ core habitat has been lacking. Here, we report the extirpation of the American pika (Ochotona princeps), a temperature-sensitive small mammal, from a 165-km2 area located within its core habitat in California’s Sierra Nevada mountains. While sites surrounding the area still maintain pikas, radiocarbon analyses of pika fecal pellets recovered within this area indicate that former patch occupancy ranges from before 1955, the beginning of the atmospheric spike in radiocarbon associated with above ground atomic bomb testing, to c. 1991. Despite an abundance of suitable rocky habitat climate warming appears to have precipitated their demise. Weather station data reveal a 1.9°C rise in local temperature and a significant decline in snowpack over the period of record, 1910–2015, pushing pika habitat into increasingly tenuous climate conditions during the period of extirpation. This is among the first accounts of an apparently climate-mediated, modern extirpation of a species from an interior portion of its geographic distribution, resulting in habitat fragmentation, and is the largest area yet reported for a modern-era pika extirpation. Our finding provides empirical support to model projections, indicating that even core areas of species habitat are vulnerable to climate change within a timeframe of decades.

Spatial effects in meta-foodwebs

In ecology it is widely recognised that many landscapes comprise a network of discrete patches of habitat. The species that inhabit the patches interact with each other through a foodweb, the network of feeding interactions. The meta-foodweb model proposed by Pillai et al. combines the feeding relationships at each patch with the dispersal of species between patches, such that the whole system is represented by a network of networks. Previous work on meta-foodwebs has focussed on landscape networks that do not have an explicit spatial embedding, but in real landscapes the patches are usually distributed in space. Here we compare the dispersal of a meta-foodweb on Erdős-Rényi networks, that do not have a spatial embedding, and random geometric networks, that do have a spatial embedding. We found that local structure and large network distances in spatially embedded networks, lead to meso-scale patterns of patch occupation by both specialist and omnivorous species. In particular, we found that spatial separations make the coexistence of competing species more likely. Our results highlight the effects of spatial embeddings for meta-foodweb models, and the need for new analytical approaches to them.

Disentangling the role of seed bank and dispersal in plant metapopulation dynamics using patch occupancy surveys

In plants, the presence of a seed bank challenges the application of classical metapopulation models to aboveground presence surveys; ignoring seed bank leads to overestimated extinction and colonization rates. In this article, we explore the possibility to detect seed bank using hidden Markov models in the analysis of aboveground patch occupancy surveys of an annual plant with limited dispersal. Patch occupancy data were generated by simulation under two metapopulation sizes (N=200 and N=1,000 patches) and different metapopulation scenarios, each scenario being a combination of the presence/absence of a 1-yr seed bank and the presence/absence of limited dispersal in a circular 1-dimension configuration of patches. In addition, because local conditions often vary among patches in natural metapopulations, we simulated patch occupancy data with heterogeneous germination rate and patch disturbance. Seed bank is not observable from aboveground patch occupancy surveys, hence hidden Markov models were designed to account for uncertainty in patch occupancy. We explored their ability to retrieve the correct scenario. For 10yr surveys and metapopulation sizes of N=200 or 1,000 patches, the correct metapopulation scenario was detected at a rate close to 100%, whatever the underlying scenario considered. For smaller, more realistic, survey duration, the length for a reliable detection of the correct scenario depends on the metapopulation size: 3yr for N=1,000 and 6yr for N=200 are enough. Our method remained powerful to disentangle seed bank from dispersal in the presence of patch heterogeneity affecting either seed germination or patch extinction. Our work shows that seed bank and limited dispersal generate different signatures on aboveground patch occupancy surveys. Therefore, our method provides a powerful tool to infer metapopulation dynamics in a wide range of species with an undetectable life form.

A spatially structured metapopulation model within a stochastic environment

Populations often exist, either by choice or by external pressure, in a fragmented way, referred to as a metapopulation. Typically, the dynamics accounted for within metapopulation models are assumed to be static. For example, patch occupancy models often assume that the colonisation and extinction rates do not change, while spatially structured models often assume that the rates of births, deaths and migrations do not depend on time. While some progress has been made when these dynamics are changing deterministically, less is known when the changes are stochastic. It can be quite common that the environment a population inhabits determines how these dynamics change over time. Changes to this environment can have a large impact on the survival probability of a population and such changes will often be stochastic. The typical metapopulation model allows for catastrophes that could eradicate most, if not all, individuals on an entire patch. It is this type of phenomenon that this article addresses. A Markov process is developed that models the number of individuals on each patch within a metapopulation. An approximation for the original model is presented in the form of a piecewise-deterministic Markov process and the approximation is analysed to present conditions for extinction.

Area requirements and landscape‐level factors influencing shrubland birds

ABSTRACTDeclines in populations of birds that breed in disturbance‐dependent early‐successional forest have largely been ascribed to habitat loss. Clearcutting is an efficient and effective means for creating early‐successional vegetation; however, negative public perceptions of clearcutting and the small parcel size typical of private forested land in much of the eastern United States make this practice impractical in many situations. Group selection harvests, where groups of adjacent trees are removed from a mature forest matrix, may be more acceptable to the public and could provide habitat for shrubland birds. Although some shrubland bird species that occupy clearcuts are scarce or absent from smaller patches created by group selection, some of these smaller patches support shrubland species of conservation concern. The specific factors affecting shrubland bird occupancy of these smaller patches, such as habitat structure, patch area, and landscape context, are poorly understood. We sampled birds in forest openings ranging 0.02–1.29 ha to identify species‐specific minimum‐area habitat requirements and other factors affecting shrubland birds. We modeled bird occurrence in relation to microhabitat‐, patch‐, and landscape‐level variables using occupancy models. The minimum‐area requirements for black‐and‐white warblers (Mniotilta varia), common yellowthroats (Geothlypis trichas), chestnut‐sided warblers (Setophaga pensylvanica), eastern towhees (Pipilo erythrophthalmus), and gray catbirds (Dumetella carolinensis) were ≤0.23 ha, whereas indigo buntings (Passerina cyanea) and prairie warblers (S. discolor) required openings of 0.56 ha and 1.11 ha, respectively. Notably, prairie warblers were more likely to occur in openings closer to large patches of habitat such as powerline corridors, even if those openings were small in size. We concluded that, despite their inability to support the entire suite of shrubland species, small forest openings can provide habitat for several species of conservation concern if proper attention is given to promoting suitable microhabitat, patch, and landscape characteristics. © 2017 The Wildlife Society.

Integrating disparate occurrence reports to map data-poor species ranges and occupancy: a case study of the Vulnerable bearded pigSus barbatus

AbstractMonitoring species ranges and suitable and occupied habitat are core components of biogeography, ecology and conservation biology, but it is difficult to do for rare, cryptic, wide-ranging, migratory or nomadic species. We present a transparent and objective process to combine multiple types of locality data (peer-reviewed and grey literature, museum collections, camera-trap inventories, and citizen science reports). We illustrate the advantages of this pooled approach by assessing change in range and patch occupancy for a data-poor and threatened nomadic keystone species, the bearded pigSus barbatus, in Borneo, Sumatra and Peninsular Malaysia. We used a collated set of all occurrence observations (n = 240) to create minimum convex polygons for forested habitats for two time periods. We evaluated confidence that a patch was truly occupied by the overlap among data types. We found that 62% of the forest habitat of the Sumatran bearded pigS. barbatus oiwas lost during 1990–2010 and that its range contracted by 76%; the Bornean bearded pigS.barbatus barbatuslost 23 and 24% of its forest habitat and range, respectively, and in Peninsular Malaysia the 93% range collapse of this subspecies during 1985–2010 is more severe than the 33% habitat loss alone would suggest. We conclude that integrating data types can improve mapping of the ranges of many data-poor species.

Screening allergic reactions to resol resin based on phenol and formaldehyde in a clinic of occupational dermatology.

Allergic reactions to resol-type phenol formaldehyde resin [phenol formaldehyde resin 2 (PFR2)] are relatively common. It has been suggested that PFR2 should be included in baseline series. However, a recent international study found clinical relevance in only 25% of patients. To report the results of screening with PFR2 over a 5-year period (2012-2016), and to study the clinical relevance of allergic reactions to PFR2 over a 15-year period (2002-2016). At the Finnish Institute of Occupational Health, PFR2 was added to the baseline series in 2012. We had previously tested PFR2 in the plastic and glue series. We searched the patch test files for patients with allergic reactions to PFR2, and analysed their patch test results, occupation, exposure, and diagnosis. During the screening period of 5 years, a total of 10 (1.6%) patients reacted positively to PFR2. Seven of these had occupational allergic contact dermatitis caused by phenol formaldehyde resin (PFR). In 3 patients, we found no exposure to PFR. Over the preceding 10 years, the clinical relevance of 10 additional allergic reactions to PFR2 was similarly high. In an occupational dermatology clinic, 70% of PFR2 reactions were clinically relevant. Further studies in general dermatology clinics are needed.

Exploring uncertainty in population viability analysis and its implications for the conservation of a freshwater fish

Abstract A spatially explicit metapopulation viability model was created within RAMAS‐GIS to address questions related to the conservation and management of a freshwater species at risk (Notropis anogenus). Population viability analysis was conducted to evaluate extinction risk and sensitivity analyses were undertaken to identify the most important spatial and non‐spatial parameters influencing extinction and decline. As biodiversity offsets are increasingly used to compensate for habitat loss, the population model was also used to explore the effectiveness of four potential offsetting mechanisms. In particular, this study addressed whether the impact of habitat loss on a species at risk could be compensated by: (i) increasing habitat elsewhere; (ii) increasing vital rates; (iii) increasing abundance; and (iv) increasing connectivity. Results suggest that extinction risk is low for this metapopulation and that the risk of extinction was most sensitive to vital rates. Compensating habitat loss with habitat gain, the most straightforward approach explored, was by far the most effective type of compensation. Increasing vital rates was the second most promising approach. Although increasing abundance and increasing connectivity could not be categorically ruled out, their effectiveness was much more limited. Overall, this study provided insight into the influence of spatial and non‐spatial parameters on abundance, patch occupancy, and extinction risk of an aquatic species. This approach can be applied to a wide variety of species to evaluate the effect of ecosystem perturbations and inform management options.

Environmental flow assessment in estuaries taking into consideration species dispersal in fragmented potential habitats

Here, we propose an approach to environmental flow assessment that pays attention to species dispersal among fragmented potential habitat patches affected by river inflow and tidal currents in estuaries. The approach consists of three steps. In step one, potential suitable habitats were mapped and the Habitat Aggregation Index (HAI) was determined to understand the fragmentation of potential suitable habitats by integrating the requirements for critical environmental factors that have temporal and spatial variability. In the second step, an individual-based model was developed to simulate the dispersal of target species among potential habitat patches. The model provided the species distributions for altered hydrological processes. In the third step, environmental flows were defined by comparing the occupancy of suitable habitat patches by individual organisms and habitat aggregation for varying freshwater inflows. This approach was tested using a case study in the Yangtze River Estuary. We stressed the ecological importance of flood pulse, rather than average discharge, and recommend a Gaussian-type flood pulse, as provides a win–win point for both the numbers of individuals that could occupy suitable habitat and the HAI. We also demonstrated the importance of the peak flow and flood pulse duration in terms of affecting species distribution. Based on the results presented here, the proposed approach offers a flexible assessment of environmental flow for aquatic ecosystems.

When Group Dispersal and Allee Effect Shape Metapopulation Dynamics

The dispersal ability of a species will be critical for how population dynamics are realized in spatially structured systems. To date, the effect of group dispersal on metapopulation dynamics is poorly understood. Here, we investigate how group dispersal and Allee effects shape metapopulation dynamics identifying conditions in which group dispersal can be an advantage over independent dispersal. We approach this question by building and analysing a Markovian random walk for metapopulation dynamics including group dispersal and Allee effect. This Markovian random walk is analogous to the discrete-time Stochastic Patch Occupancy Model (SPOM). We find that intermediate group sizes may lead to larger and more sustainable metapopulations in the presence of an Allee effect. Hence, understanding how group size variation and realized (meta)population dynamics are linked offers an exciting future venue for research that is expected to yield key insights into the ecology and evolution of populations occupying spati...

Grassland songbird occurrence on remnant prairie patches is primarily determined by landscape characteristics

North American grassland songbird populations have declined significantly due to habitat loss and fragmentation. Understanding the influence of the surrounding landscape on prairie fragment occupancy is vital for predicting the fate of grassland birds in these heavily altered landscapes. We examined the relative importance of local and landscape variables on grassland bird occupancy of prairie fragments using a focal-patch study. We also investigated the spatial scale at which landscape variables were most influential. We surveyed birds on 29 unplowed prairie fragments in western Minnesota and eastern North and South Dakota. We quantified local habitat on the fragment using vegetation surveys and aerial photographs and the landscape surrounding the fragment out to 4 km using aerial photographs. We analyzed occupancy using multi-model approaches applied to multiple logistic regression. Of 38 species encountered, nine were neither too rare nor too abundant to be analyzed. Predictors of patch occupancy were unique for each bird species, yet general patterns emerged. For eight species, landscape variables were more important than local variables. Mostly, those landscape variables measured configuration (e.g., edge density) and not composition (e.g., percent cover of a particular matrix element). Landscape effects were mostly from variables measured at the greatest extents from the prairie fragment. Using a focal-patch study design we demonstrated the importance of the surrounding landscape, often out to 4 km from the fragment edge, on prairie occupancy by grassland birds. Effective management of grassland songbirds will require attention to the landscape context of prairie fragments.

Host-plant patch qualities and presence of a likely competitor species affect the distribution and abundance of a rare British moth, Cucullia lychnitis

Understanding the environmental factors that affect the distribution and abundance of rare and threatened species can help identify priority sites for conservation action such as habitat management. The moth Cucullia lychnitis is identified in UK legislation as a priority species for conservation. Its conspicuous larvae feed on a patchily distributed host plant Verbascum nigrum, but are entirely absent from some host plant patches within the species’ range. Environmental variability among patches was investigated to understand factors affecting (i) patch occupancy by C. lychnitis and (ii) abundance of C. lychnitis, where present. Occupancy of individual V. nigrum plants within occupied patches was also investigated. The likelihood of patch occupancy increased with patch size, and decreased with patch isolation. Abundance of C. lychnitis was negatively correlated with patch isolation and with abundance of the weevil Cionus nigritarsis, which exploits the same host plant and may be a competitor. Within occupied patches, larvae of C. lychnitis were significantly more likely to be found on taller plants with more flower spikes; such plants are typical of established rather than newly-created patches. These results may help to guide efforts to conserve C. lychnitis, highlighting the importance of habitat connectivity and indicating potential management actions to promote features positively associated with larval incidence and abundance.

Metapopulation models predict the temporal response of two macrophytes to drought in a subtropical water reservoir

Water level fluctuations are among the main drivers of the temporal dynamics of aquatic species, and droughts represent a major disturbance that can affect aquatic populations. We applied a metapopulation perspective to model the temporal variation in the patch occupancy of local populations of two species of submerged macrophytes (Egeria densa and E. najas) that colonise a large reservoir (Itaipu, Paraguay/Brazil border) and suffered an intense drought disturbance. The severe water drawdown caused a decrease in the numbers of patches that were colonised by both macrophyte species. This disturbance decreased the fractions of patches occupied by E. densa and E. najas from 13% and 38% to 0.9% and 8.5%, respectively. The recovery of the fraction of patches colonised by populations of these two species had similar responses to the disturbance: a time lag phase, followed by an exponential increase and finally stabilization of the number of occupied patches. Recovery of the fractions of patches that were colonised by E. densa and by E. najas took 80 and 38 months, respectively. A time lag in the temporal metapopulation, followed by an exponential increase in patch occupancy, strongly indicates that both populations recovered by passive dispersal of fragments between patches. Indeed, a metapopulation model that accounts for the fraction occupied and the water level (as an indication of disturbance) explained the temporal dynamics of both species (coefficients of determination=78% for E. densa and 43% for E. najas) relatively well. Our results indicate that aquatic species that follow a metapopulation dynamic and depend on dispersal among sites to recover may be severely affected in a future climate change scenario, in which extreme events (including droughts) will tend to be more frequent.

Host plant density and patch isolation drive occupancy and abundance at a butterfly's northern range margin.

Marginal populations are usually small, fragmented, and vulnerable to extinction, which makes them particularly interesting from a conservation point of view. They are also the starting point of range shifts that result from climate change, through a process involving colonization of newly suitable sites at the cool margin of species distributions. Hence, understanding the processes that drive demography and distribution at high‐latitude populations is essential to forecast the response of species to global changes. We investigated the relative importance of solar irradiance (as a proxy for microclimate), habitat quality, and connectivity on occupancy, abundance, and population stability at the northern range margin of the Oberthür's grizzled skipper butterfly Pyrgus armoricanus. For this purpose, butterfly abundance was surveyed in a habitat network consisting of 50 habitat patches over 12 years. We found that occupancy and abundance (average and variability) were mostly influenced by the density of host plants and the spatial isolation of patches, while solar irradiance and grazing frequency had only an effect on patch occupancy. Knowing that the distribution of host plants extends further north, we hypothesize that the actual variable limiting the northern distribution of P. armoricanus might be its dispersal capacity that prevents it from reaching more northern habitat patches. The persistence of this metapopulation in the face of global changes will thus be fundamentally linked to the maintenance of an efficient network of habitats.