Permeability of the urban matrix to arboreal gliding mammals: Sugar gliders in Melbourne,Australia

Habitat corridors that facilitate functional connectivity are a fundamental component of wildlife conservation in fragmented landscapes. However, the landscape matrix separating suitable habitat is not uniformly impermeable to movement and management to increase matrix permeability could be an alternative means to maintain connectivity. Gliding mammals are particularly sensitive to fragmentation because their movements are constrained by glide distance thresholds. Populations of gliders in cities are at risk of being isolated by increasing habitat loss and urban development, yet little is known about how the urban matrix affects glider movement. Here we investigate how the level of urbanization and tree cover in the matrix influence matrix permeability to sugar gliders (Petaurus breviceps) within suburban forest reserves. Twenty‐two sugar gliders were radio‐tracked over winter and summer at four reserves. Boundary crossing behaviour was measured as the number of times each glider crossed into the matrix, and matrix permeability was determined as the maximum distance travelled by gliders into the matrix. The majority of gliders (81%) were located in the matrix at least once, and rates of boundary crossing were consistent across urbanization and tree cover levels. Matrix permeability was negatively affected by matrix urbanization, but not by matrix tree cover, and no interaction effects were found. Although distances travelled by gliders into the matrix did not exceed 180 m, they were comparable with typical movement distances by gliders in reserves. Our results demonstrate that the urban matrix can provide suitable habitat for gliding mammals to move and forage, but that increased urbanization may inhibit glider use of the matrix irrespective of tree cover. This finding has implications for conservation planning and suggests that structurally connected areas may not be used if movement behaviour is inhibited. Conversely, management of matrix permeability could be used to maintain connectivity without needing to construct physical corridors.     

Barriers to dispersal of rain forest butterflies in tropical agricultural landscapes

Fragmentation of natural habitats can be detrimental for species if individuals fail to cross habitat boundaries to reach new locations, thereby reducing functional connectivity. Connectivity is crucial for species shifting their ranges under climate change, making it important to understand factors that might prevent movement through human‐modified landscapes. In tropical regions, rain forests are being fragmented by agricultural expansion, potentially isolating populations of highly diverse forest‐dependent species. The likelihood of crossing habitat boundaries is an important determinant of species dispersal through fragmented landscapes, and so we examined movement across rain forest‐oil palm plantation boundaries on Borneo by using relatively mobile nymphalid butterflies as our model study taxon. We marked 1666 individuals from 65 species, and 19 percent (100/527) of recaptured individuals crossed the boundary. Boundary crossing was relatively frequent in some species, and net movement of individuals was from forest into plantation. However, boundary crossing from forest into plantation was detected in less than 50 percent (12/28) of recaptured species and was dominated by small‐sized butterfly species whose larval host plants occurred within plantations. Thus, while oil palm plantations may be relatively permeable to some species, they may act as barriers to the movement of forest‐dependent species (i.e., species that require rain forest habitat to breed), highlighting the importance of maintaining forest connectivity for conserving rain forest species.     

The cost of dispersal: predation as a function of movement and site familiarity in ruffed grouse

Ecologists often assume that dispersing individuals experienceincreased predation risk owing to increased exposure to predatorswhile moving. To test the hypothesis that predation risk isa function of movement distance or rate of movement, we usedradio-telemetry data collected from 193 ruffed grouse (Bonasaumbellus) during 1996–1999 in southeastern Ohio. Cox'sproportional hazards model was used to examine whether the riskof predation was affected by the rate of movement and site familiarity.We found evidence indicating that increased movement rates mayincrease the risk of predation for adult birds but not juveniles.We also found juvenile and adult birds inhabiting unfamiliarspace were consistently at a much higher risk of predation (threeto 7.5 times greater) than those in familiar space. Our resultsindicate that although movement itself may have some effecton the risk of being preyed upon, moving through unfamiliarspace has a much greater effect on risk for ruffed grouse. Thissupports the hypothesis that increased predation risk may bean important cost of dispersal for birds.     

Disturbance induces the contrasting evolution of reinforcement and dispersiveness in directed and random movers

Spatial models commonly assume that dispersal rates are constant across individuals and environments and that movement directions are unbiased. These random-movement assumptions are inadequate to capture the range of dispersal behaviors revealed in diverse case studies. We examine an alternative assumption of directed movement, in which dispersal is a conditional and directional response by individuals to varying environmental conditions. Specifically, we assume individuals bias their movements to climb spatial fitness gradients. We compare the consequences of random and directed movement for local adaptation, the evolution of dispersal, and the reinforcement process. The implications of each movement strategy depend on the nature of environmental disturbance, and we examine the outcomes for undisturbed environments and with uncorrelated and autocorrelated disturbances. Both movement strategies offer advantages over sedentary life histories by allowing colonization of suitable habitats. However, random movement eventually becomes costly in stable environments because it inhibits local adaptation. In contrast, directed movement accelerates local adaptation. In disturbed environments, random movement offers bet-spreading advantages by distributing offspring across habitats. Despite being a more targeted strategy, an intermediate amount of directed movement provides similar bet-spreading benefits. These fitness consequences have implications for the evolution of dispersal. Dispersiveness is lost by random movers in undisturbed environments, is maintained in polymorphism with infrequent disturbances, and evolves when disturbances are uncorrelated. Directed movement becomes selectively neutral in the absence of disturbance, evolves when disturbances are autocorrelated, and is maintained in polymorphism with uncorrelated disturbances. Disturbance also determines the outcome of the reinforcement process for each strategy. For example, directed movers show no progress toward reinforcement in undisturbed environments, evolve random mating with uncorrelated disturbances, and can evolve assortative mating in infrequently disturbed environments.     

Interpopulation Differences in Shoaling Behaviour in Guppies (Poecilia reticulata): Roles of Social Environment and Population Origin

In Trinidad, guppies (Poecilia reticulata) in high‐predation localities show more cohesive shoaling behaviour than those living with less dangerous predators in low‐predation sites. We evaluated the relative contributions of population origin (i.e. genetic and/or maternal effects) and social environment on the expression of shoaling by assessing the behaviour of juveniles reared in a range of social conditions. Focal individuals, offspring of guppies from populations from high‐ or low‐predation localities, were reared in a multifactorial experiment; we created four different social conditions by manipulating the source and demography of the conspecific residents with whom focal individuals interacted. We found that high‐predation fish displayed a stronger propensity to shoal than low‐predation ones. Our results also suggest a role for interactions between the source of the focal individuals, the demography of the group in which they were reared and the origin of the guppies with whom they were reared. Depending on their origin (high‐ vs. low‐ predation) and rearing density, our focal fish were more likely to shoal if they were reared with high‐predation residents. Learning from high‐predation residents, aggressive interactions with low‐predation residents and/or phenotype matching could have played a role in driving this effect of social environment. This effect of the phenotype of conspecifics on shoaling development would enhance heritable differences in shoaling propensity such that both could contribute to the well‐documented difference in shoaling behaviour of high‐ and low‐predation guppies in natural populations.     

Body size and social dominance influence breeding dispersal in male Pachydiplax longipennis (Odonata)

1. Dispersal behaviour can be affected by an individual's phenotype, by the environmental or social context they experience, and by interactions between these factors. Differential dispersal propensities between individuals may also be an important modifier of functional connectivity between populations. To assess how a key trait, body size, affected both social interactions and dispersal behaviour, this study examined the relationship between body size, antagonistic interactions, and breeding dispersal in male dragonflies (Pachydiplax longipennis) across a seasonal decline in adult body size. 2. During a seasonal peak in male body size in this study, dispersers were smaller than non‐dispersers. Later in the season, the body size of dispersers and non‐dispersers did not differ. 3. Focal observations found that body size was related to competitive dominance, large males engaged in aggressive chases more often and smaller males were more frequently pursued. 4. These results indicate that when large males were present, small males were more likely to disperse suggesting that dispersal is a tactic adopted by social subordinates in this context. If breeding dispersal is typically undertaken by subordinate males, functional connectivity between populations may be less than estimated from absolute dispersal rates.     

What can genetics tell us about population connectivity?

Genetic data are often used to assess ‘population connectivity’ because it is difficult to measure dispersal directly at large spatial scales. Genetic connectivity, however, depends primarily on the absolute number of dispersers among populations, whereas demographic connectivity depends on the relative contributions to population growth rates of dispersal vs. local recruitment (i.e. survival and reproduction of residents). Although many questions are best answered with data on genetic connectivity, genetic data alone provide little information on demographic connectivity. The importance of demographic connectivity is clear when the elimination of immigration results in a shift from stable or positive population growth to negative population growth. Otherwise, the amount of dispersal required for demographic connectivity depends on the context (e.g. conservation or harvest management), and even high dispersal rates may not indicate demographic interdependence. Therefore, it is risky to infer the importance of demographic connectivity without information on local demographic rates and how those rates vary over time. Genetic methods can provide insight on demographic connectivity when combined with these local demographic rates, data on movement behaviour, or estimates of reproductive success of immigrants and residents. We also consider the strengths and limitations of genetic measures of connectivity and discuss three concepts of genetic connectivity that depend upon the evolutionary criteria of interest: inbreeding connectivity, drift connectivity, and adaptive connectivity. To conclude, we describe alternative approaches for assessing population connectivity, highlighting the value of combining genetic data with capture‐mark‐recapture methods or other direct measures of movement to elucidate the complex role of dispersal in natural populations.     

Conspecific and heterospecific attraction in assessments of functional connectivity

Functional connectivity is known to have an important, positive influence on species persistence. Measurements of functional connectivity traditionally focus on structural attributes of landscapes such as the distance and matrix type between habitat patches as well as on how species interact with those structural attributes. However, we propose that the social behavior of a species, through conspecific and heterospecific attraction, will also impact connectivity by changing how dispersers move with respect to each other and occupied patches. We analyzed functional connectivity patterns using circuit and graph theory for golden-headed lion tamarins (Leontopithecus chrysomelas) in Brazil under three scenarios. In the first scenario, we looked at connectivity without the effects of attraction under varying maximum dispersal distance and ecological movement cost thresholds. In the second scenario, we allowed dispersers to travel over more hostile matrix than they normally would to reach an occupied patch. In the final scenario, we allowed dispersers to move only to occupied patches. We found that, according to the first scenario, range-wide functional landscape connectivity for golden-headed lion tamarins is low at realistic maximum dispersal distance and movement cost thresholds. Incorporating the effects of conspecific or heterospecific attraction would increase functional connectivity, in the case of scenario two, or decrease functional connectivity, in the case of scenario three. Because conspecific/heterospecific attraction can have an impact on movement for some species, this factor should be incorporated in assessments of functional connectivity patterns for social species and others where patch occupancy is likely to influence the movements of dispersers.     

Inter‐individual variability in dispersal behaviours impacts connectivity estimates

The importance of landscape connectivity in determining biodiversity outcomes under environmental change has led to indices of connectivity becoming amongst the most widely used measures in conservation. Thus, it is vital that our understanding of connectivity and our use of indices describing it are reliable. Dispersal is the key ecological process involved in determining connectivity, and there is increasing evidence of substantial within‐population variability in dispersal behaviours. Here, we incorporate this inter‐individual variability into two approaches for estimating connectivity, least cost path analysis and stochastic movement simulation. Illustrative results demonstrate that including dispersal variability can yield substantially different estimates of connectivity. While connectivity is typically similar between nearby patches, the frequency of movements between patches further apart is often substantially increased when inter‐individual variability is included. Given the disproportionate role that unusual long‐distance dispersal events play in spatial dynamics, connectivity indices should seek to incorporate variability in dispersal behaviour.     

Interpatch movement and edge effects: the role of behavioral responses to the landscape matrix

Animal interpatch movement and spatial distribution are known to be influenced substantially by the composition of the landscape matrix, but little is known about the underlying mechanisms. In previous mark–recapture experiments we have found that the rates of emigration and immigration for the planthopper Prokelisia crocea are greater within a matrix composed of the introduced grass smooth brome (Bromus inermis) than a mudflat matrix. Additionally, census data indicated that individuals aggregate near the edge of host‐plant patches (prairie cordgrass; Spartina pectinata) bordered by mudflat, but not in patches bordered by nonhost grasses such as brome. Here, we investigate the mechanistic basis of these matrix effects by tracking the individual movements of planthoppers released at the edge of brome‐ and mudflat‐bordered cordgrass patches, and within homogeneous habitats of each type (cordgrass, brome, and mudflat). We found that patch edges bordered by brome were three times more permeable to emigration than mudflat‐bordered edges. Also, planthoppers exhibited no tendency to avoid edges by moving away (i.e. towards the patch interior). Within homogeneous habitats, comparison of the fractal dimension of movement paths revealed that movement was more linear in mudflat than in brome or cordgrass. In addition, planthoppers exhibited greater step lengths (distance moved per 10‐min interval), shorter residency times (duration of pauses between movements), and greater rates of net linear displacement in mudflat than brome and cordgrass. We attribute the planthopper's distributional patterns within patches to the lower permeability of mudflat than nonhost grass edges and the absence of edge–avoidance behavior. Contrary to conventional wisdom that low‐resistance matrix types (e.g. those that promote high displacement rates) enhance interpatch dispersal rates, dispersal success may be higher in brome matrix because tortuous movement through this matrix increases the planthopper's rate of encounter with cordgrass patches.     

Breaking functional connectivity into components: a novel approach using an individual-based model, and first outcomes

Landscape connectivity is a key factor determining the viability of populations in fragmented landscapes. Predicting 'functional connectivity', namely whether a patch or a landscape functions as connected from the perspective of a focal species, poses various challenges. First, empirical data on the movement behaviour of species is often scarce. Second, animal-landscape interactions are bound to yield complex patterns. Lastly, functional connectivity involves various components that are rarely assessed separately. We introduce the spatially explicit, individual-based model FunCon as means to distinguish between components of functional connectivity and to assess how each of them affects the sensitivity of species and communities to landscape structures. We then present the results of exploratory simulations over six landscapes of different fragmentation levels and across a range of hypothetical bird species that differ in their response to habitat edges. i) Our results demonstrate that estimations of functional connectivity depend not only on the response of species to edges (avoidance versus penetration into the matrix), the movement mode investigated (home range movements versus dispersal), and the way in which the matrix is being crossed (random walk versus gap crossing), but also on the choice of connectivity measure (in this case, the model output examined). ii) We further show a strong effect of the mortality scenario applied, indicating that movement decisions that do not fully match the mortality risks are likely to reduce connectivity and enhance sensitivity to fragmentation. iii) Despite these complexities, some consistent patterns emerged. For instance, the ranking order of landscapes in terms of functional connectivity was mostly consistent across the entire range of hypothetical species, indicating that simple landscape indices can potentially serve as valuable surrogates for functional connectivity. Yet such simplifications must be carefully evaluated in terms of the components of functional connectivity they actually predict.     

The impact of directed versus random movement on population dynamics and biodiversity patterns

An improved understanding of dispersal behavior is needed to predict how populations and communities respond to habitat fragmentation. Most spatial dynamic theory concentrates on random dispersal, in which movement rates depend neither on the state of an individual nor its environment and movement directions are unbiased. We examine the neglected dispersal component of directed movement in which dispersal is a conditional and directional response of individuals to varying environmental conditions. Specifically, we assume that individuals bias their movements along local gradients in fitness. Random movers, unable to track heterogeneous environmental conditions, face source-sink dynamics, which can result in deterministic extinction or increase their vulnerability to stochastic extinction. Directed movers track environmental conditions closely. In fluctuating environments, random movers "spread their bets" across patches, while directed movers invest offspring in habitats currently enjoying propitious conditions. The autocorrelation in the environment determines each strategy's success. Random movers permeate entire landscapes, but directed movers are more geographically constrained. Local information constraints limit the ranges of directed movers and introduce a role for historical contingency in determining their ultimate distribution. These geographic differences have implications for biodiversity. Random movement maintains biodiversity through local coexistence, but directed movement favors a spatial partitioning of species.     

Immune gene variability influences roe deer natal dispersal

Dispersal is a key life‐history trait governing the response of individuals, populations and species to changing environmental conditions. In the context of global change, it is therefore essential to better understand the respective role of condition‐, phenotype‐ and genetic‐dependent drivers of dispersal behaviour. Although the importance of immune function and pathogen infestation in determining patterns of dispersal is increasingly recognised, no study to our knowledge has yet investigated the influence of immune gene variability on dispersal behaviour. Here, we filled this knowledge gap by assessing whether individual heterozygosity at five immune gene loci (one from the Major histocompatibility complex and four from encoding Toll‐like receptors) influences roe deer natal dispersal. We found that dispersal propensity was affected by immune gene diversity, suggesting potential pathogen‐mediated selection through over‐dominance. However, the direction of this effect differed between high and low quality individuals, suggesting that dispersal propensity is driven by two different mechanisms. In support of the condition‐dependent dispersal hypothesis, dispersal propensity increased with increasing body mass and, among high quality individuals only (standardized body mass > 18 kg), with increasing immune gene diversity. However, among poor quality individuals, we observed the opposite pattern such that dispersal propensity was higher for individuals with lower immune gene diversity. We suggest that these poor quality individuals expressed an emergency dispersal tactic in an attempt to escape a heavily infested environment associated with poor fitness prospects. Our results have potentially important consequences in terms of population genetics and demography, as well as host–pathogen evolution.     

Predicting global population connectivity and targeting conservation action for snow leopard across its range

Movements of individuals within and among populations help to maintain genetic variability and population viability. Therefore, understanding landscape connectivity is vital for effective species conservation. The snow leopard is endemic to mountainous areas of central Asia and occurs within 12 countries. We assess potential connectivity across the species’ range to highlight corridors for dispersal and genetic flow between populations, prioritizing research and conservation action for this wide‐ranging, endangered top‐predator. We used resistant kernel modeling to assess snow leopard population connectivity across its global range. We developed an expert‐based resistance surface that predicted cost of movement as functions of topographical complexity and land cover. The distribution of individuals was simulated as a uniform density of points throughout the currently accepted global range. We modeled population connectivity from these source points across the resistance surface using three different dispersal scenarios that likely bracket the lifetime movements of individual snow leopard: 100 km, 500 km and 1000 km. The resistant kernel models produced predictive surfaces of dispersal frequency across the snow leopard range for each distance scenario. We evaluated the pattern of connectivity in each of these scenarios and identified potentially important movement corridors and areas where connectivity might be impeded. The models predicted two regional populations, in the north and south of the species range respectively, and revealed a number of potentially important connecting areas. Discrepancies between model outputs and observations highlight unsurveyed areas of connected habitat that urgently require surveying to improve understanding of the global distribution and ecology of snow leopard, and target land management actions to prevent population isolation. The connectivity maps provide a strong basis for directed research and conservation action, and usefully direct the attention of policy makers.     

Gene flow and functional connectivity in the natterjack toad

Functional connectivity is a key factor for the persistence of many specialist species in fragmented landscapes. However, connectivity estimates have rarely been validated by the observation of dispersal movements. In this study, we estimated functional connectivity of a real landscape by modelling dispersal for the endangered natterjack toad (Bufo calamita) using cost distance. Cost distance allows the evaluation of 'effective distances', which are distances corrected for the costs involved in moving between habitat patches in spatially explicit landscapes. We parameterized cost-distance models using the results of our previous experimental investigation of natterjack's movement behaviour. These model predictions (connectivity estimates from the GIS study) were then confronted to genetic-based dispersal rates between natterjack populations in the same landscape using Mantel tests. Dispersal rates between the populations were inferred from variation at six microsatellite loci. Based on these results, we conclude that matrix structure has a strong effect on dispersal rates. Moreover, we found that cost distances generated by habitat preferences explained dispersal rates better than did the Euclidian distances, or the connectivity estimate based on patch-specific resistances (patch viscosity). This study is a clear example of how landscape genetics can validate operational functional connectivity estimates.     

Movement Patterns of Frugivorous Birds Promote Functional Connectivity among Chaco Serrano Woodland Fragments in Argentina

Movement patterns of frugivorous birds may be altered in anthropogenically fragmented landscapes, with possible consequences for seed dispersal and plant recruitment. We studied the movement patterns and functional connectivity of six frugivorous bird species (Colaptes melanochloros, Thraupis bonariensis, Pitangus sulphuratus, Saltator aurantiirostris, Turdus amaurochalinus, and Elaenia spp.) in a fragmented Chaco‐woodland landscape in Argentina. We recorded the directions of bird movements (arrivals and departures) and whether their destination was oriented toward a specific neighboring fragment. We evaluated the movement rates, distance of interpatch movement, and functional connectivity within the landscape for the six bird species. We applied a novel approach, graph theory, to represent bird movement patterns in the landscape and the functional connections among fragments for each bird species. Bird movements were recorded at point‐count stations established along the edges of each fragment. The directions of arrival and departure movements from and to neighboring fragments revealed complex movement patterns. However, the destination of bird movements after leaving the focal fragments was usually concentrated on only a few neighboring fragments of different sizes. Pitangus sulphuratus and T. bonariensis showed larger movement rates and higher functional connectivity (number of graphs and functional area) than the other frugivorous species. The functional connectivity mediated by movement of frugivorous birds may promote seed dispersal of many bird‐dispersed plant species. As forest loss and fragmentation of Chaco subtropical forests increase, understanding the pivotal role of mobile links exerted by avian seed dispersers is vital to maintaining and conserving this unique ecosystem.     

Quantifying the activity levels and behavioural responses of butterfly species to habitat boundaries

1. The ability of species' to undergo climate‐driven range shifts across fragmented landscapes depends on their dispersal ability as well as the structure of the landscape. For species' range shifts to occur, individuals must first leave suitable habitat to seek new habitat; this is likely to depend on the rate of movement of individuals within habitat and the likelihood that a boundary is crossed, once it is encountered. For three species of butterfly with contrasting histories of recent range expansion, we examined the propensity of individuals to move within a habitat and their responses to habitat boundaries. 2. We quantified the extent to which Plebejus argus (Linnaeus) (a declining habitat specialist), Aricia agestis (Schiffermuller) (an expanding generalist) and Polymmatus icarus (Rottemburg) (a geographically ubiquitous generalist) crossed habitat boundaries into unsuitable habitat and moved within suitable habitat. The observed movement was then related to individual and environmental conditions. 3. Species differed in their activity levels in accordance within their recent distribution patterns (P. icarus > A. agestis > P. argus). Our results for P. argus suggest that movement may be motivated by nectar‐seeking, and that males generally move more than females. All three species tended to avoid crossing habitat boundaries; however the proportion of individuals crossing habitat boundaries did not differ significantly among species. 4. We conclude that levels of activity within a habitat, which will affect the frequency with which individuals encounter habitat boundaries, rather than behavioural responses to the boundaries, may be important drivers of distribution change.     

The integrative effects of behavior and morphology on amphibian movement

Animal movement and dispersal are key factors in population dynamics and support complex ecosystem processes like cross‐boundary subsidies. Juvenile dispersal is an important mechanism for many species and often involves navigation in unfamiliar habitats. For species that metamorphose, such as amphibians, this transition from aquatic to terrestrial environments involves the growth and use of new morphological traits (e.g., legs). These traits strongly impact the fundamental ability of an organism to move in novel landscapes, but innate behaviors can regulate choices that result in the realized movements expressed. By assessing the integrative role of morphology and behavior, we can improve our understanding of juvenile movement, particularly in understudied organisms like amphibians. We assessed the roles of morphological (snout‐vent length and relative leg length) and performance (maximal jump distance) traits in shaping the free movement paths, measured through fluorescent powder tracking, in three anuran species, Pacific treefrog (Hyliola regilla), Western toad (Anaxyrus boreas), and Cascades frog (Rana cascadae). We standardized the measurement of these traits to compare the relative role of species' innate differences versus physical traits in shaping movement. Innate differences, captured by species identity, were the most significant factor influencing movement paths via total movement distance and path sinuosity. Relative leg length was an important contributor but significantly interacted with species identity. Maximal jump performance, which was significantly predicted by morphological traits, was not an important factor in movement behavior relative to species identity. The importance of species identity and associated behavioral differences in realized movement provide evidence for inherent species differences being central to the dispersal and movement of these species. This behavior may stem from niche partitioning of these sympatric species, yet it also calls into question assumptions generalizing anuran movement behavior. These species‐level effects are important in framing differences as past research is applied in management planning.     

Butterfly abundance and movements among prairie patches: the roles of habitat quality, edge, and forest matrix permeability

The spatial distribution of patchy insect populations is partly caused by behavioral patterns of insect movement that are influenced by habitat quality, isolation, and the permeability of the surrounding matrix. We recorded insect movements, abundance, and edge behaviors in two species of butterflies, the great-spangled fritillary (Speyeria cybele F., Lepidoptera: Nymphalidae) and the pearl crescent (Phyciodes tharos Drury, Lepidoptera: Nymphalidae), inhabiting remnant prairies surrounded by a forest matrix in south-central Ohio. We also determined the number of forest matrix types present and recorded the permeability of the different types to butterfly movement. The great-spangled fritillary exhibited a relatively high number of interpatch movements, a higher abundance at patch edges, and a propensity to cross the prairie-forest edges, and the forest matrix had a high permeability to butterfly movement. The pearl crescent, in contrast, rarely crossed edge boundaries, moved infrequently among patches, and was more abundant within the patch interior and in patches with high host-plant and flower densities. There were three structurally different forest matrix types separating habitat patches, which in previous studies would have been classified as a single deciduous forest matrix. Butterfly movement and edge behaviors mechanistically interact with patch quality, isolation, and the matrix permeability to determine the spatial structure of these populations in fragmented habitats.     

Invasive plants in conservation linkages: a conceptual model that addresses an underappreciated conservation issue

Conservationists have frequently touted the merits of increased landscape connectivity, usually focusing on the efficacy of conservation linkages (corridors) for maintaining viable populations of target species. An often‐mentioned, but still greatly understudied, concern is that increased landscape connectivity via linkages may also aid the movement of undesired species. This paper provides conceptual guidance for research on one major aspect of this gap: invasive plants in conservation linkages. To guide research goals and methods, I develop a conceptual model describing eight interaction types between invasive plants and linkages, i.e. the ways that invasive plants can exist in and move into, through, and out of conservation linkages. Each interaction type within the model has three main components: linkage, matrix, and focal species. I discuss several aspects of these components, including a) differentiating among matrix types, b) understanding edge effects within the linkages, and c) incorporating relevant invasive species’ ecology (primarily dispersal ecology). Spatially‐explicit documentation of invasive plant distribution is essential to understanding these interactions. By focusing on landscape‐scale patterns in real‐world systems, this model will enhance landscape‐level knowledge of invasion ecology and aid land managers in identifying and prioritizing research and management decisions regarding invasive plants in conservation linkages.