Marginal Habitats Research Articles

Enhancing the conservation status and resilience of a narrowly distributed forest: A challenge to effectively support ecosystem services in practice

The conservation and sustainable management of forests has become an important issue, especially in ecosystems where keystone species form unique and marginal forest habitats with narrow distribution. With increasing pressures and threats to nature, the establishment of Protected Areas has been recognized as a major tool for maintaining well-functioning forest ecosystems and their associated ecosystem services (ES). This study aims at assessing the changes in the status of a narrowly distributed Mediterranean forest through the perspective of land cover dynamics and the ES framework. Using the priority habitat of Cedrus brevifolia forest as a case study, the distribution of land use and land cover (LULC) was mapped and simulated, together with the supply of multiple ES before and after the implementation of conservation measures. The results prior applying the management actions revealed a general pattern of forest densification that did not act fully in favor of C. brevifolia due to competitions among forest species. From an ES viewpoint, forest densification led to landscape homogenization affecting important ES such as the increase in the supply of regulating services, and the decrease in the ability to support nursery populations and habitats. By contrast, the future simulation of LULC integrated with afforestation and thinning measures showed an expected increase in both high-density vegetation and cedar trees, benefiting multiple ES. The current findings highlight the importance of sustainable forest management in enhancing the co-occurrence of several ES and supporting the overall multi-functionality of ecosystems. The holistic approach presented in this study can offer new insights into the relation between ES and natural ecosystem and/or habitats’ management while avoiding potential negative impacts on human well-being and ecosystem resilience.

Unraveling a paradox of habitat relationships: scale-dependent drivers of temporal occupancy-abundance relationships in a cooperatively breeding bird

ContextSpatial occupancy and local abundance of species often positively covary, but the mechanisms driving this widespread relationship are poorly understood. Resource dynamics and habitat changes have been suggested as potential drivers, but long-term studies relating them to abundance and occupancy are rare. In this 34-year study of acorn woodpeckers (Melanerpes formicivorus), a cooperatively breeding species, we observed a paradoxical response to changes in habitat composition: despite a reduction in the availability of high-quality breeding habitat, the population increased considerably.ObjectivesWe investigated the role of annual variation in food availability and long-term changes in habitat composition as predictors of population dynamics.MethodsUsing model selection, we contrasted competing hypotheses on the effects of changing resource availability on occupancy and social group size across three spatial scales: territory, neighborhood, and landscape.ResultsThe increase in abundance was largely determined by the formation of new social groups, driven by a landscape-level expansion of canopy cover and its interaction with neighborhood-level acorn abundance, indicative of long-term increases in overall acorn productivity. Group size increased with neighborhood acorn crop two years earlier but groups were smaller in territories with more canopy cover.ConclusionsOur results indicate that scale-dependent processes can result in paradoxical relationships in systems with spatial and temporal resource heterogeneity. Moreover, the findings support the role of resources in driving changes in abundance and occupancy at a landscape scale, suggesting that colonization of marginal habitat drives the positive occupancy-abundance relationship in this cooperatively breeding species.

Effects of heat and hyposalinity on the gene expression in Acropora pruinosa larvae

IntroductionClimate change has resulted in elevated sea surface temperature as well as increased frequency of extreme weather events, e.g. cyclones and rainstorms, which could lead to reduced seawater salinity. While temperature effects on corals have been widely examined, the combined effects of both temperature and salinity on corals, especially their early stages, remain poorly known. This study aimed to examine how the larvae of Acropora pruinosa in a marginal coral habitat, Hong Kong, respond to high temperature (+5°C ambient, HT), low salinity (26 psu, LS), and the combined effects of both stressors (HTLS).MethodsWe recorded larval survival and settlement success under different experimental treatments, and used RNA-Seq technique to compare the gene expression patterns of these larvae to understand the underlying molecular mechanism of stress responses.ResultsOur results showed that the survivorship of coral larvae was not affected in all experimental treatments, with all larvae surviving through the 72-hour period of the experiment. Yet, larval settlement was compromised under all stress treatments. The settlement rates were 39.3%, 12%, and 0% for the elevated temperature, reduced salinity, and the combined treatment, respectively, which were all significantly lower than that under the control treatment (78%). We demonstrated that low salinity (LS) triggered responsive gene sets with functions in ATP production, protein translation, and receptor for neuroactive ligands. In addition, high temperature (HT) treatment also triggered MAPK and NF-kB signaling and apoptosis in these coral larvae. The combined stressor treatment (HTLS) acted synergistically, resulting in the up-regulation of intracellular transducers that could trigger the intrinsic apoptosis pathway. This may explain the total failure in larval settlement under HTLS that could further increase larval vulnerability in the natural environment.DiscussionOur results provide new insights into the molecular responses of coral larvae and represent an essential first step in expanding ourunderstanding of the mechanisms of tolerance that may be exhibited by coral larvae exposed to multiple stressors.

Forest conversion into pasture selects dung beetle traits at different biological scales depending on species pool composition.

The conversion of forests into open areas has large effects on the diversity and structure of native communities. The intensity of these effects may vary between regions, depending on the existence of native species adapted to open habitats in the regional pool or the time since habitat change.We assess the differences in species richness and functional diversity of dung beetle communities (Coleoptera: Scarabaeinae) between native forests and novel pasturelands of the Atlantic Forest and the Cerrado, two biomes with contrasting histories of human occupation in Brazil. We conducted standardized surveys in seven forest fragments and adjacent pastures in each region and measured 14 traits in individuals collected in each type of habitat at each particular site. We calculated functional richness, functional evenness, functional divergence, and community-weighted mean of traits for each area, and analyzed individual variation through nested variance decomposition and Trait Statistics.Communities were richer and more numerous at the Cerrado. We did not find any consistent relationship between functional diversity and forest conversion beyond the changes in species diversity. Although landscape changes were more recent at the Cerrado, the colonization of the new habitat by native species already adapted to open habitats lessens the functional loss in this biome. This indicates that habitat change's effects on trait diversity depend on the regional species pool rather than on time since land conversion.Forest conversion effects were primarily due to internal filtering. The effects of external filtering only appear at the intraspecific variance level, with contrasting differences between the Cerrado, where traits related to relocation behavior and size are selected, and the Atlantic Forest, where selection operates for traits related to relocation behavior and flight. These results evidence the importance of considering individual variance to address the responses of dung beetle communities to forest conversion.

Demographics of Gray Wolf (Canis lupus) Packs Recolonizing Variable Habitats in Central Wisconsin

Some Canis lupus (Gray Wolf, hereafter Wolf) live in disjunct populations including Wisconsin's Central Forest Region (CFR), recolonizing there in the early 1990s. We examined how habitat factors and period of initial recolonization facilitated successful re-establishment of Wolves to this region. We divided this event into 3 periods: early (1994–1999), middle (2000–2005), and late (2006–2012). We defined habitat classes of individual pack territories as optimal, mixed, and marginal, based on: (1) percent public land, (2) percent agricultural land, and (3) road density. We analyzed the influence of time and habitat classes on pack territory size, winter pack size, pup presence, Wolf–human conflicts, human-caused Wolf mortalities, territory persistence, and reproductive performance. Pack demographics were similar across time, except pup presence was slightly lower during the middle period. Wolf–human conflicts increased over time and were correlated with population growth. Packs in marginal habitat were smaller in winter, exhibited lower reproductive performance, had more conflicts with humans, and experienced human-caused mortalities at rates 4 and 7 times higher than mixed and optimal habitats, respectively. We demonstrate that Gray Wolves tolerate some level of human-altered landscapes and identify demographic parameters that impact the Wolves' ability to survive in human-dominated landscapes.

Fishing for hosts: Larval spurting by the endangered thick-shelled river mussel, Unio crassus.

Fishing for hosts: Larval spurting by the endangered thick-shelled river mussel, Unio crassus.

Immigration drives ship rat population irruptions in marginal high‐elevation habitat in response to pulsed resources

AbstractPest animal populations, such as rodents, often irrupt in response to pulsed resources. However, few studies have considered how understanding the propagation of irruptions across landscapes could lead to more efficient pest suppression. Resource pulses might create temporary source–sink dynamics in heterogeneous environments, whereby reservoirs of animals living in high‐quality habitat increase and spill over into more marginal habitat. Low‐density populations in marginal habitat could also increase through in situ breeding by residents in response to increased food availability. Understanding the relative importance of these two nonmutually exclusive processes is important as pest outbreaks could potentially be more efficiently controlled by targeting source populations early in an outbreak. We used a Bayesian hierarchical model to estimate the importance of density‐dependent emigration from lower elevation habitats versus in situ breeding by resident animals to the population growth of invasive ship rats (Rattus rattus) in marginal, high elevation habitats during a pulsed resource event (beech seed mast). We found that emigration from lower elevations was important for facilitating rapid population growth at high elevations, enabling rats to reach peak densities of 10.6 rats ha−1. Without immigration, rats were predicted to reach peak densities of only 1.8 rats ha−1 at high elevation, given their densities in that habitat when we started monitoring (0.6 rats ha−1). This result suggests that rat control that targets low and mid‐elevations only may be sufficient to suppress irruptions in high‐elevation habitat if control effectively prevents immigration. Our study suggests spillover from higher quality habitats may enable outbreaks to rapidly propagate over landscapes. However, for r‐selected taxa such as rodents, even very low densities of animals living in marginal habitats can increase significantly when resource pulses occur, albeit at lower densities than for populations in higher quality habitat.

Habitat selection of a migratory freshwater fish in response to seasonal hypoxia as revealed by acoustic telemetry

Adaptive efforts to achieve water quality objectives by modifying nutrient loading can have attendant impacts on fish habitats and fisheries. Thus, coordinating fishery and water quality management depends on knowledge of fish behavioral responses to habitat change. This study combined acoustic telemetry of fish with water quality modelingto understand how water quality management might impact fishery management. We examined habitat use of a native demersal fish, lake whitefishCoregonus clupeaformis, in Lake Erie. We focused on the summer stratified period when habitat was expected to be most limiting and used a forecast model to predict temperature and oxygen in the hypolimnion when fish were detected. As hypothesized, lake whitefish occupied a subset of available conditions with occupied habitats characterized by a cool, normoxic, hypolimnion. On some occasions fish were detected when the hypolimnion was predicted to be hypoxic, suggesting that fish were either displaced vertically or horizontally into marginal habitats or uncertainty in model predictions was high. Still, when hypolimnetic conditions were hypoxic, fish tended to move toward normoxia as expected, but when initial conditions were cold with high dissolved oxygen, fish movements were toward lower oxygen (but still normoxic) conditions. We also observed a high affinity for fish to remain near the southern shore in eastern Ohio, Pennsylvania, and New York. If current nutrient reduction objectives are achieved and the extent and severity of hypoxia is reduced, an expansion of lake whitefish habitat and distribution may have significance to the spatial regulation of fishing effort in Lake Erie.

DNA barcodes for Great Salt Lake brine flies establish a baseline for monitoring changes in biodiversity

ABSTRACT Great Salt Lake (GSL) is the center of a valuable wetland ecosystem in the Great Basin of North America. The lake is an important site for millions of migratory birds that feed on 2 principal invertebrates, brine shrimp and brine flies (Diptera: Ephydridae). Despite their ecological and economic importance, no genetic studies have been published for either resident GSL invertebrate. The family Ephydridae (shore flies and brine flies) is one of the largest in the order Diptera, with nearly 2000 described species. Members of this family are prominent in a variety of aquatic environments and are particularly interesting because of their adaptation to several marginal habitats, including hot springs, oil ponds, highly saline lakes, and inland alkaline pools and marshes. This report provides cytochrome c oxidase I (COI) DNA barcodes for 5 species of GSL shore flies, distributed among 5 genera and 3 subfamilies. The phylogenetic content of these DNA sequences is explored by comparing a molecular phylogeny to those based on morphological features. Over the past decade, urbanization and inflow diversion have reduced the surface area of GSL by nearly 50%, with unknown consequences for the ecosystem. This study establishes a genetic framework to assess changes in GSL invertebrate diversity important in monitoring the effects of anthropogenic and climate pressures on this important natural resource.

Phylogeny of Saxifraga section Saxifraga subsection Arachnoideae (Saxifragaceae) and the origin of low elevation shade-dwelling species.

Saxifraga section Saxifraga subsection Arachnoideae is a lineage of 12 species distributed mainly in the European Alps. It is unusual in terms of ecological diversification by containing both high elevation species from exposed alpine habitats and low elevation species from shady habitats such as overhanging rocks and cave entrances. Our aims are to explore which of these habitat types is ancestral, and to identify the possible drivers of this remarkable ecological diversification. Using a Hybseq DNA-sequencing approach and a complete species sample we reconstructed and dated the phylogeny of subsection Arachnoideae. Using Landolt indicator values, this phylogenetic tree was used for the reconstruction of the evolution of temperature, light and soil pH requirements in this lineage. Diversification of subsection Arachnoideae started in the late Pliocene and continued through the Pleistocene. Both diversification among and within clades was largely allopatric, and species from shady habitats with low light requirements are distributed in well-known refugia. We hypothesize that low light requirements evolved when species persisting in cold-stage refugia were forced into marginal habitats by more competitive warm-stage vegetation. While we do not claim that such competition resulted in speciation, it very likely resulted in adaptive evolution.

Fish functional trophic groups in headwater karst streams from the Upper Paraguay River basin

Abstract Data obtained by direct observation of organisms in their natural habitats can provide valuable contributions regarding intra- and inter-specific interactions, as well as spatial distribution and trophic relationships. However, relatively few such data are available for the Neotropical ichthyofauna relative to the great species diversity of this region. We present data on the ichthyofauna in karst environments of the Serra da Bodoquena, Upper Paraguay River basin regarding their categorization into functional trophic groups. We used direct observations that focused on the most frequent feeding tactics and their spatial (vertical and horizontal) distribution in the channel. We observed 83 fish species in 17 functional trophic groups. The greatest species richness was concentrated in the Characidae and Loricariidae in the categories Diurnal Backwater Drift Feeders and Grazers, respectively. Regarding horizontal depth stratification, we found a positive relationship between the association of small fish with the shallow marginal habitats. This work represents a contribution to a region known for its high tourist potential and to the important diversity of the entire ichthyofauna of the Upper Paraguay basin region that requires proper conservation strategies for sustaining these species.

Responses of avian assemblages to spatiotemporal landscape dynamics in urban ecosystems

ContextUrbanization and its associated impacts on biodiversity are increasing globally. There is a need to enhance our understanding of species responses to inform strategies for sustainable urbanization.ObjectivesThree extensive bird monitoring campaigns took place over the last three decades in the city of Naples, Italy, providing a comprehensive longitudinal dataset to analyse occurrence trends of urban birds. We aimed to assess both species-specific and assemblage-level changes in urban birds according to land cover dynamics.MethodsWe extracted bird data for the periods 1990–95, 2000–05, and 2014–18, and explored the spatial and temporal relationships between bird presence/avian assemblage composition, and land cover variation.ResultsThe species richness of breeding birds remained stable over time, despite a notable species turnover, influenced by changes in the species’ key land cover classes. Species associated with forest and urban land cover tended to colonise the area, while those dependent on abandoned and cultivated areas decreased or went locally extinct. Birds changed their degree of dependence upon their key habitat type over time, as species from marginal and open habitat types needed larger amounts of habitat to persist within the area, while forest species showed an opposite trend.ConclusionsHabitat-driven changes in avian assemblages within the urban landscape led to an increase in forest-associated species, and a decrease in birds associated with declining habitat types. Our findings may inform urban planning to promote more wildlife-friendly cities, which for our study area should prioritise open and marginal habitats.

Revision of the Semicytherura henryhowei group (Crustacea, Ostracoda) with the new records from Korea

The genus Semicytherura Wagner, 1957 has nearly 300 species, is common in shallow and marginal marine habitats, and has a worldwide distribution. It is divided into several species groups, of which the Semicytherura henryhowei Hanai & Ikeya, 1977 group is one of the most frequently recorded in temperate Asia. A previous study indicated that many of its members are actually species complexes, and that several morphotypes could be distinguished by carapace shape and ornamentation. We review these complexes and conclude that the henryhowei group currently contains 29 species, nine of which are undescribed. We also provide an illustrated guide and a key to species, based on newly standardized carapace ridge terminology. This enabled us to describe one new species from the extant (i.e., present-day) sediments in Jeju Island, Korea, S. kiostisp. nov. We also found one juvenile valve of S. kazahana Yamada, Tsukagoshi & Ikeya, 2005, the first official illustrated record of this species from Korean waters. Our revised spatial and temporal distributions of fossil and extant records from this group provide new insights into trans-Arctic interchange of ostracod fauna from the Late Miocene onwards.

Living on the edge: morphological and behavioral adaptations to a marginal high-elevation habitat in an arboreal mammal.

Habitats are characterized by different local environmental conditions that influence both behavior and morphology of species, which can result in habitat-dependent phenotypic differences among animals living in heterogeneous environments. We studied 3 alpine populations of Eurasian red squirrels (Sciurus vulgaris), 1 living in a marginal high-elevation habitat at the edge of the species' altitudinal distribution, and 2 occurring in higher-quality habitats. Here, we investigated whether squirrels living in the marginal area differed in 2 morphological parameters (body size and body mass) and/or in the expression of 4 personality traits estimated with an open field test and a mirror image stimulation test (activity, exploration, activity-exploration, and social tendency). Furthermore, we tested whether within-individual variance of the traits (behavioral plasticity) was higher in the edge habitat. Male squirrels in the edge habitat were smaller and weighed less than in the other study areas, while among females, size-habitat relationships were less marked. These sex-specific patterns were explained by a strong association between body mass and reproductive success in female squirrels. Squirrels in the marginal habitat were more active, explorative, and had a more social personality than in the other habitats. However, in contrast to our predictions, behavioral plasticity was smaller in the marginal habitat, but only for the trait exploration. Our results suggest that animals choose the habitat that best fits their personality, and that habitat-related differences in selective pressures may shape animals' morphology.

Evolutionary history of marginal habitats regulates the diversity of tree communities in the Atlantic Forest.

The Atlantic Forest biodiversity hotspot is a complex mosaic of habitat types. However, the diversity of the rain forest at the core of this complex has received far more attention than that of its marginal habitats, such as cloud forest, semi-deciduous forest or restinga. Here, we investigate broad-scale angiosperm tree diversity patterns along elevation gradients in the south-east Atlantic Forest and test if the diversity of marginal habitats is shaped from the neighbouring rain forest, as commonly thought. We calculated phylogenetic indices that capture basal [mean pairwise phylogenetic distance (MPD)] and terminal [mean nearest taxon distance (MNTD)] phylogenetic variation, phylogenetic endemism (PE) and taxonomic and phylogenetic beta diversity (BD and PBD) for 2074 angiosperm tree species distributed in 108 circular sites of 10 km diameter across four habitat types i.e. rain forest, cloud forest, semi-deciduous forest and coastal vegetation known as restinga. We then related these metrics to elevation and environmental variables. Communities in wetter and colder forests show basal phylogenetic overdispersion and short phylogenetic distances towards the tips, respectively. In contrast, communities associated with water deficit and salinity show basal phylogenetic clustering and no phylogenetic structure toward the tips. Unexpectedly, rain forest shows low PE given its species richness, whereas cloud and semi-deciduous forests show unusually high PE. The BD and PBD between most habitat types are driven by the turnover of species and lineages, except for restinga. Our results contradict the idea that all marginal habitat types of the Atlantic Forest are sub-sets of the rain forest. We show that marginal habitat types have different evolutionary histories and may act as 'equilibrium zones for biodiversity' in the Atlantic Forest, generating new species or conserving others. Overall, our results add evolutionary insights that reinforce the urgency of encompassing all habitat types in the Atlantic Forest concept.

Reef on the edge: resilience failure of marginal patch coral reefs in Eastern Arabian Sea under recurrent coral bleaching, coral diseases, and local stressors.

Marked by strong El Niño-Southern Oscillation (ENSO) effects during 2014-2016, global coral reefs underwent mass bleaching. Here, we conducted a comprehensive (2014-2019) study, coinciding with the 2014-16 ENSO, to investigate the response and resilience potential of marginal coral communities to the combined impact of recurrent thermal anomalies and multiple anthropogenic stressors before, during, and after the mass bleaching episodes. Our result unveiled that thermal-stress-driven back-to-back annual coral bleaching episodes caused coral mortality and significantly decimated coral cover, primarily in 2015 and 2016. Subsequent benthic regime shifts toward macroalgal and algal turf colonization, followed by an increase in coral disease prevalence and recruitment failure wasobserved after the recurrent bleaching episodes. Algal cover increased from 21% in 2014 to 52.90% in 2019, and a subsequent increase in coral disease occurrence was observed from 16% in 2015 to 29% in 2019. The cascading negative effect of multiple stressors magnified coral loss and decreased the coral cover significantly from 45% in 2014 to 20% in 2019. The corals in the intensive recreational diving activity sites showed higher disease prevalence, concurring with high mechanical coral damage. The present study demonstrates that consecutive thermal bleaching episodes combined with local stressors can cause declines in coral cover and promote an undesirable regime shift to algal dominance in marginal coral reef habitats within a short duration. These results are of particular interest given that marginal reefs were traditionally perceived as resilient reef habitats due to their higher survival threshold to environmental changes. The present study indicates that mitigation of local stressors by effective management strategies, in conjunction with globally coordinated efforts to ameliorate climate change, can protect these unique coral reefs.

Tick range expansion to higher elevations: does Borrelia burgdorferi sensu lato facilitate the colonisation of marginal habitats?

BackgroundParasites can alter host and vector phenotype and thereby affect ecological processes in natural populations. Laboratory studies have suggested that Borrelia burgdorferi sensu lato, the causative agent of human Lyme borreliosis, may induce physiological and behavioural alterations in its main tick vector in Europe, Ixodes ricinus, which increase the tick’s mobility and survival under challenging conditions. These phenotypic alterations may allow I. ricinus to colonise marginal habitats (‘facilitation hypothesis’), thereby fuelling the ongoing range expansion of I. ricinus towards higher elevations and latitudes induced by climate change. To explore the potential for such an effect under natural conditions, we studied the prevalence of B. burgdorferi s.l. in questing I. ricinus and its variation with elevation in the Swiss Alps.ResultsWe screened for B. burgdorferi s.l. infection in questing nymphs of I. ricinus (N = 411) from 15 sites between 528 and 1774 m.a.s.l to test if B. burgdorferi s.l. prevalence is higher at high elevations (i.e. in marginal habitats). Opposite of what is predicted under the facilitation hypothesis, we found that B. burgdorferi s.l. prevalence in I. ricinus nymphs decreased with increasing elevation and that Borrelia prevalence was 12.6% lower in I. ricinus nymphs collected at the range margin compared to nymphs in the core range. But there was no association between Borrelia prevalence and elevation within the core range of I. ricinus. Therefore the observed pattern was more consistent with a sudden decrease in Borrelia prevalence above a certain elevation, rather than a gradual decline with increasing elevation across the entire tick range.ConclusionsIn conclusion, we found no evidence that B. burgdorferi s.l.-induced alterations of I. ricinus phenotype observed in laboratory studies facilitate the colonisation of marginal habitats in the wild. Rather, ticks in marginal habitats are substantially less likely to harbour the pathogen. These findings have implications for a better understanding of eco-evolutionary processes in natural host-parasite systems, as well as the assessment of Lyme borreliosis risk in regions where I. ricinus is newly emerging.

Greater sage‐grouse habitat selection varies across the marginal habitat of its lagging range margin

AbstractStudying wildlife–habitat relationships at the edges of their range can provide valuable insights into the environmental factors limiting wildlife distributions and most likely to drive extirpations and range shifts in response to landscape change. Yet the relative impact of those factors is likely different along the range margin, so it is important to identify the limitations to suitable habitat at both regional and local scales. Some of the most drastic impacts of large‐scale landscape changes in North America have occurred and are forecasted in the sagebrush steppe ecosystems, where species unable to seek new habitat in the fragmented landscape will be vulnerable to climatic extremes, vegetation community shifts, and anthropogenic land use change. One of the species likely under major threat from landscape changes is the greater sage‐grouse (Centrocercus urophasianus), a sagebrush obligate with habitat constraints that make it susceptible to habitat loss impacts as sagebrush systems contract and fragment at their southern range margin, already naturally fragmented. In this study, we evaluated factors of topography and land cover directly impacting habitat selection by sage‐grouse in four study areas along their lagging range edge. We used >116,000 GPS locations from >90 grouse across four study areas in southern Utah and Nevada from 2014 to 2020 in habitat selection analyses using random forest models. Our results showed that sage‐grouse exploit topography and sagebrush cover, possibly to break predator sight lines and moderate the risk posed by avian predators using tree perches, complicating the effects of tree cover and conifer encroachment into sagebrush habitat. We found similar trends across all four study areas, suggesting sage‐grouse along the southern range margin face similar limitations. However, the effects were nonlinear and varied—models trained in one study area were only moderately successful at predicting selection in others. The local idiosyncrasies along this southern range margin indicate a need for place‐based conservation for sage‐grouse and other potentially imperiled species. Incorporating new understandings of local impacts will refine regional and range‐wide models and support efforts to effectively create habitat and plan for range shifts by vulnerable species in response to environmental change.

Greater sage‐grouse habitat selection varies across the marginal habitat of its lagging range margin

Greater sage‐grouse habitat selection varies across the marginal habitat of its lagging range margin

Reducing Fish Losses to Great Cormorants Using Artificial Fish Refuges: Refining Refuge Deployment Strategies

A series of paired-pond trials were completed during the winters of 2005 to 2008 to examine the effect of introducing artificial fish refuges on Great Cormorant Phalacrocorax carbo foraging behaviour, prey capture rates and fish losses in trial ponds, and to help refine their potential use as a tool in addressing cormorant-fisheries conflicts. Investigations comparing refuge volumes within a year provided clear evidence that larger refuges offered fish better protection than smaller ones. When compared across years, there was no clear relationship between refuge volume and prey consumption rate by Cormorants. There was, however, a very large difference in the consumption rate when ponds with no refuge were compared with any of the refuge volumes tested, suggesting that, in the absence of any other cover, the addition of even very small fish refuges can markedly reduce the quantity of fish eaten by Cormorants. Further trials indicated that introducing refuges as a single larger structure was more effective at reducing fish losses than an equivalent volume of refuge arranged as a number of smaller, widely-spaced, discrete units (>50% reduction in prey consumed per Cormorant visit). Trials further confirmed that the beneficial effects of fish refuges were not compromised by the presence of marginal habitat; indeed, prey consumption rates were >30% lower in the pond with additional simulated reed beds. The impact of refuge presence on fish loss rates varied between species, with Roach Rutilus rutilus benefitting in particular. The results are discussed in the wider context of interactions between Cormorants and their prey and with regard to the potential use of fish refuges as a management tool.