Modeling ecological minimum requirements for distribution of greater sage‐grouse leks: implications for population connectivity across their western range,U.S.A

Greater sage‐grouse Centrocercus urophasianus (Bonaparte) currently occupy approximately half of their historical distribution across western North America. Sage‐grouse are a candidate for endangered species listing due to habitat and population fragmentation coupled with inadequate regulation to control development in critical areas. Conservation planning would benefit from accurate maps delineating required habitats and movement corridors. However, developing a species distribution model that incorporates the diversity of habitats used by sage‐grouse across their widespread distribution has statistical and logistical challenges. We first identified the ecological minimums limiting sage‐grouse, mapped similarity to the multivariate set of minimums, and delineated connectivity across a 920,000 km² region. We partitioned a Mahalanobis D² model of habitat use into k separate additive components each representing independent combinations of species–habitat relationships to identify the ecological minimums required by sage‐grouse. We constructed the model from abiotic, land cover, and anthropogenic variables measured at leks (breeding) and surrounding areas within 5 km. We evaluated model partitions using a random subset of leks and historic locations and selected D² (k = 10) for mapping a habitat similarity index (HSI). Finally, we delineated connectivity by converting the mapped HSI to a resistance surface. Sage‐grouse required sagebrush‐dominated landscapes containing minimal levels of human land use. Sage‐grouse used relatively arid regions characterized by shallow slopes, even terrain, and low amounts of forest, grassland, and agriculture in the surrounding landscape. Most populations were interconnected although several outlying populations were isolated because of distance or lack of habitat corridors for exchange. Land management agencies currently are revising land‐use plans and designating critical habitat to conserve sage‐grouse and avoid endangered species listing. Our results identifying attributes important for delineating habitats or modeling connectivity will facilitate conservation and management of landscapes important for supporting current and future sage‐grouse populations.     

Sagebrush treatments influence annual population change for greater sage‐grouse

Vegetation management practices have been applied worldwide to enhance habitats for a variety of wildlife species. Big sagebrush (Artemisia tridentata spp.) communities, iconic to western North America, have been treated to restore herbaceous understories through chemical, mechanical, and prescribed burning practices thought to improve habitat conditions for greater sage‐grouse (Centrocercus urophasianus) and other species. Although the response of structural attributes of sagebrush communities to treatments is well understood, there is a need to identify how treatments influence wildlife population dynamics. We investigated the influence of vegetation treatments occurring in Wyoming, United States, from 1994 to 2012 on annual sage‐grouse population change using yearly male sage‐grouse lek counts. We investigated this response across 1, 3, 5, and 10‐year post‐treatment lags to evaluate how the amount of treated sagebrush communities and time since treatment influenced population change, while accounting for climate, wildfire, and anthropogenic factors. With the exception of chemical treatments exhibiting a positive association with sage‐grouse population change 11 years after implementation, population response to treatments was either neutral or negative for at least 11 years following treatments. Our work supports a growing body of research advocating against treating big sagebrush habitats for sage‐grouse, particularly in Wyoming big sagebrush (A. t. wyomingensis). Loss and fragmentation of sagebrush habitats has been identified as a significant threat for remaining sage‐grouse populations. Because sagebrush may take decades to recover following treatments, we recommend practitioners use caution when designing projects to alter remaining habitats, especially when focused on habitat requirements for one life stage and a single species.     

Restoring Sage‐grouse nesting habitat through removal of early successional conifer

Conifer woodlands have expanded into sagebrush (Artemisia spp.) ecosystems and degrade habitat for sagebrush obligate species such as the Greater Sage‐grouse (Centrocercus urophasianus). Conifer management is increasing despite a lack of empirical evidence assessing outcomes to grouse and their habitat. Although assessments of vegetation recovery after conifer removal are common, comparisons of successional trends with habitat guidelines or actual data on habitat used by sage‐grouse is lacking. We assessed impacts of conifer encroachment on vegetation characteristics known to be important for sage‐grouse nesting. Using a controlled repeated measures design, we then evaluated vegetation changes for 3 years after conifer removal. We compared these results to data from 356 local sage‐grouse nests, rangewide nesting habitat estimates, and published habitat guidelines. We measured negative effects of conifer cover on many characteristics important for sage‐grouse nesting habitat including percent cover of forbs, grasses, and shrubs, and species richness of forbs and shrubs. In untreated habitat, herbaceous vegetation cover was slightly below the cover at local nest sites, while shrub cover and sagebrush cover were well below cover at the nest sites. Following conifer removal, we measured increases in herbaceous vegetation, primarily grasses, and sagebrush height. Our results indicate that conifer abundance can decrease habitat suitability for nesting sage‐grouse. Additionally, conifer removal can improve habitat suitability for nesting sage‐grouse within 3 years, and trajectories indicate that the habitat may continue to improve in the near future.     

Spatially explicit models of seasonal habitat for greater sage‐grouse at broad spatial scales: Informing areas for management in Nevada and northeastern California

Defining boundaries of species' habitat across broad spatial scales is often necessary for management decisions, and yet challenging for species that demonstrate differential variation in seasonal habitat use. Spatially explicit indices that incorporate temporal shifts in selection can help overcome such challenges, especially for species of high conservation concern. Greater sage‐grouse Centrocercus urophasianus (hereafter, sage‐grouse), a sagebrush obligate species inhabiting the American West, represents an important case study because sage‐grouse exhibit seasonal habitat patterns, populations are declining in most portions of their range and are central to contemporary national land use policies. Here, we modeled spatiotemporal selection patterns for telemetered sage‐grouse across multiple study sites (1,084 sage‐grouse; 30,690 locations) in the Great Basin. We developed broad‐scale spatially explicit habitat indices that elucidated space use patterns (spring, summer/fall, and winter) and accounted for regional climatic variation using previously published hydrographic boundaries. We then evaluated differences in selection/avoidance of each habitat characteristic between seasons and hydrographic regions. Most notably, sage‐grouse consistently selected areas dominated by sagebrush with few or no conifers but varied in type of sagebrush selected by season and region. Spatiotemporal variation was most apparent based on availability of water resources and herbaceous cover, where sage‐grouse strongly selected upland natural springs in xeric regions but selected larger wet meadows in mesic regions. Additionally, during the breeding period in spring, herbaceous cover was selected strongly in the mesic regions. Lastly, we expanded upon an existing joint–index framework by combining seasonal habitat indices with a probabilistic index of sage‐grouse abundance and space use to produce habitat maps useful for sage‐grouse management. These products can serve as conservation planning tools that help predict expected benefits of restoration activities, while highlighting areas most critical to sustaining sage‐grouse populations. Our joint–index framework can be applied to other species that exhibit seasonal shifts in habitat requirements to help better guide conservation actions.     

Range‐wide patterns of greater sage‐grouse persistence

Aim Greater sage‐grouse (Centrocercus urophasianus), a shrub‐steppe obligate species of western North America, currently occupies only half its historical range. Here we examine how broad‐scale, long‐term trends in landscape condition have affected range contraction. Location Sagebrush biome of the western USA. Methods Logistic regression was used to assess persistence and extirpation of greater sage‐grouse range based on landscape conditions measured by human population (density and population change), vegetation (percentage of sagebrush habitat), roads (density of and distance to roads), agriculture (cropland, farmland and cattle density), climate (number of severe and extreme droughts) and range periphery. Model predictions were used to identify areas where future extirpations can be expected, while also explaining possible causes of past extirpations. Results Greater sage‐grouse persistence and extirpation were significantly related to sagebrush habitat, cultivated cropland, human population density in 1950, prevalence of severe droughts and historical range periphery. Extirpation of sage‐grouse was most likely in areas having at least four persons per square kilometre in 1950, 25% cultivated cropland in 2002 or the presence of three or more severe droughts per decade. In contrast, persistence of sage‐grouse was expected when at least 30 km from historical range edge and in habitats containing at least 25% sagebrush cover within 30 km. Extirpation was most often explained (35%) by the combined effects of peripherality (within 30 km of range edge) and lack of sagebrush cover (less than 25% within 30 km). Based on patterns of prior extirpation and model predictions, we predict that 29% of remaining range may be at risk. Main Conclusions Spatial patterns in greater sage‐grouse range contraction can be explained by widely available landscape variables that describe patterns of remaining sagebrush habitat and loss due to cultivation, climatic trends, human population growth and peripherality of populations. However, future range loss may relate less to historical mechanisms and more to recent changes in land use and habitat condition, including energy developments and invasions by non‐native species such as cheatgrass (Bromus tectorum) and West Nile virus. In conjunction with local measures of population performance, landscape‐scale predictions of future range loss may be useful for prioritizing management and protection. Our results suggest that initial conservation efforts should focus on maintaining large expanses of sagebrush habitat, enhancing quality of existing habitats, and increasing habitat connectivity.     

Survival of Gunnison sage‐grouse Centrocercus minimus in Colorado,USA

Gunnison sage‐grouse Centrocercus minimus has declined from their historic range and recent monitoring has provided evidence that some populations are continuing to decline. The evaluation of long‐term, population‐specific survival rates is important to assess population stability, and is necessary for conservation of this species of concern. We evaluated adult and yearling survival in two dynamically different populations of Gunnison sage‐grouse (a relatively large, more stable population and a small, declining population). Our goal was to examine the relationship between annual survival and population, and test hypotheses with regards to temporal effects (across years and within year) and individual effects (sex and age). We also evaluated the effects of snow depth on sage‐grouse survival. We tracked 214 radiomarked birds in the large population from 2005–2010 and 25 birds in the small population from 2007–2010. We found no evidence for a difference in survival between yearlings and adults nor did we find an influence of snow depth on survival. Males had the lowest survival during the lekking season (March–April); females had lower survival during the nesting and chick rearing season (May–July) and late‐summer and fall (August–October). The annual survival rate was 0.61 (SE 0.06) for females and 0.39 (SE 0.08) for males. Survival was constant across years and between the populations suggesting observed population changes during this time period are not a result of changes in adult survival.     

Phenology largely explains taller grass at successful nests in greater sage‐grouse

Much interest lies in the identification of manageable habitat variables that affect key vital rates for species of concern. For ground‐nesting birds, vegetation surrounding the nest may play an important role in mediating nest success by providing concealment from predators. Height of grasses surrounding the nest is thought to be a driver of nest survival in greater sage‐grouse (Centrocercus urophasianus; sage‐grouse), a species that has experienced widespread population declines throughout their range. However, a growing body of the literature has found that widely used field methods can produce misleading inference on the relationship between grass height and nest success. Specifically, it has been demonstrated that measuring concealment following nest fate (failure or hatch) introduces a temporal bias whereby successful nests are measured later in the season, on average, than failed nests. This sampling bias can produce inference suggesting a positive effect of grass height on nest survival, though the relationship arises due to the confounding effect of plant phenology, not an effect on predation risk. To test the generality of this finding for sage‐grouse, we reanalyzed existing datasets comprising >800 sage‐grouse nests from three independent studies across the range where there was a positive relationship found between grass height and nest survival, including two using methods now known to be biased. Correcting for phenology produced equivocal relationships between grass height and sage‐grouse nest survival. Viewed in total, evidence for a ubiquitous biological effect of grass height on sage‐grouse nest success across time and space is lacking. In light of these findings, a reevaluation of land management guidelines emphasizing specific grass height targets to promote nest success may be merited.     

Restoring Forbs for Sage Grouse Habitat: Fire, Microsites, and Establishment Methods

Abstract The decline and range reduction of sage grouse populations are primarily due to permanent loss and degradation of sagebrush–grassland habitat. Several studies have shown that sage grouse productivity may be limited by the availability of certain preferred highly nutritious forb species that have also declined within sagebrush ecosystems of the Intermountain West, U.S.A. The purpose of this study was to determine the suitability of three species of forbs for revegetation projects where improving sage grouse habitat is a goal. Species suitability was determined by evaluating the emergence, survival, and reproduction of Crepis modocensis, C. occidentalis, and Astragalus purshii in response to method of establishment (seeding or transplanting), site preparation treatment (burned or unburned), and microsite (mound or interspace) in an Artemisia tridentata ssp. wyomingensis vegetation association in south central Oregon. For seeded plants A. purshii had the lowest emergence (8%) of all three species. Both seeded Crepis species had similar overall emergence (38%). Significantly more Crepis seedlings emerged from shrub mounds in unburned areas (50%) than in any other fire‐by‐microsite treatment (33 to 36%). Approximately 10% more Crepis seedlings survived in mounds compared with interspaces. Nearly twice as many emerging Crepis seedlings survived in the burned areas as opposed to unburned areas (p < 0.01). This resulted in more plant establishment in burned mounds despite higher emergence in unburned mounds. Astragalus purshii seedlings also survived better in burned areas (p = 0.06) but had no differential response to microsite. Fire enhanced survival of both Crepis and A. purshii transplants (p = 0.08 and p = 0.001). We believe additional research is needed to improve A. purshii emergence before it will become an effective plant for restoring sage grouse habitat. Conversely, we conclude that these Crepis species provide a viable revegetation option for improving sage grouse habitat in south central Oregon.     

An integrated modeling approach to estimating Gunnison sage‐grouse population dynamics: combining index and demographic data

Evaluation of population dynamics for rare and declining species is often limited to data that are sparse and/or of poor quality. Frequently, the best data available for rare bird species are based on large‐scale, population count data. These data are commonly based on sampling methods that lack consistent sampling effort, do not account for detectability, and are complicated by observer bias. For some species, short‐term studies of demographic rates have been conducted as well, but the data from such studies are typically analyzed separately. To utilize the strengths and minimize the weaknesses of these two data types, we developed a novel Bayesian integrated model that links population count data and population demographic data through population growth rate (λ) for Gunnison sage‐grouse (Centrocercus minimus). The long‐term population index data available for Gunnison sage‐grouse are annual (years 1953–2012) male lek counts. An intensive demographic study was also conducted from years 2005 to 2010. We were able to reduce the variability in expected population growth rates across time, while correcting for potential small sample size bias in the demographic data. We found the population of Gunnison sage‐grouse to be variable and slightly declining over the past 16 years.     

Age‐dependence and individual heterogeneity in reproductive success of greater sage‐grouse

Research on iteroparous species has shown that reproductive success may increase with age until the onset of senescence. However, from the population perspective, increased reproductive success with age could be a consequence of within‐individual variation (e.g. ageing, breeding experience, foraging ability hypotheses), between‐individual variation (e.g. individual heterogeneity, frailty, selection, delayed breeding hypotheses), or a combination thereof. We evaluated within‐ and between‐individual variation in reproductive success of greater sage‐grouse (Centrocercus urophasianus; sage‐grouse), a galliforme of conservation concern throughout western North America. We monitored female reproductive activity from 1998–2010 and used generalized linear mixed models incorporating within‐subject centering to evaluate and separate within‐ and between‐individual effects. We detected positive effects of within‐individual variation on nest initiation and success where ageing increased the likelihood of both parameters, which appears to support the breeding experience and/or foraging ability hypotheses. However, nest initiation was also affected by between‐individual variation whereby the likelihood of initiation was higher for individuals with higher mean age (i.e. survived longer), as is predicted by the frailty and selection hypotheses. Our results indicate both within‐ and between‐individual variation affect reproductive output of sage‐grouse, but the effects of each varied by measure of reproductive output. Our results corroborate previous findings that suggest population age parameters (i.e. cross‐sectional) should be interpreted with caution due to potential entanglement of within‐ and between‐individual processes. Moreover, the relative role and strength of within‐ and between‐individual processes appeared to vary by measure of reproductive output in our results, which further emphasizes the need for longitudinal analysis of age effects, even in relatively short‐lived iteroparous animals, to adequately interpret biological processes.     

A method for estimating population sex ratio for sage‐grouse using noninvasive genetic samples

Population sex ratio is an important metric for wildlife management and conservation, but estimates can be difficult to obtain, particularly for sexually monomorphic species or for species that differ in detection probability between the sexes. Noninvasive genetic sampling (NGS) using polymerase chain reaction (PCR) has become a common method for identifying sex from sources such as hair, feathers or faeces, and is a potential source for estimating sex ratio. If, however, PCR success is sex‐biased, naively using NGS could lead to a biased sex ratio estimator. We measured PCR success rates and error rates for amplifying the W and Z chromosomes from greater sage‐grouse (Centrocercus urophasianus) faecal samples, examined how success and error rates for sex identification changed in response to faecal sample exposure time, and used simulation models to evaluate precision and bias of three sex assignment criteria for estimating population sex ratio with variable sample sizes and levels of PCR replication. We found PCR success rates were higher for females than males and that choice of sex assignment criteria influenced the bias and precision of corresponding sex ratio estimates. Our simulations demonstrate the importance of considering the interplay between the sex bias of PCR success, number of genotyping replicates, sample size, true population sex ratio and accuracy of assignment rules for designing future studies. Our results suggest that using faecal DNA for estimating the sex ratio of sage‐grouse populations has great potential and, with minor adaptations and similar marker evaluations, should be applicable to numerous species.     

A population genetic comparison of large- and small-bodied sage grouse in colorado using microsatellite and mitochondrial DNA markers

Sage grouse (Centrocercus urophasianus) from southwestern Colorado and southeastern Utah (United States) are 33% smaller than all other sage grouse and have obvious plumage and behavioural differences. Because of these differences, they have been tentatively recog-nized as a separate 'small-bodied' species. We collected genetic evidence to further test this proposal, using mitochondrial sequence data and microsatellite markers to determine whether there was gene flow between the two proposed species. Significant differences in the distribution of alleles between the large- and small-bodied birds were found in both data sets. Analysis of molecular variance (AMOVA) revealed that 65% of the variation in mitochondrial DNA (mtDNA) haplotypes could be explained by the large- vs. small-bodied distinction. Genetic distances and neighbour-joining trees based on allelic frequency data showed a distinct separation between the proposed species, although cladistic analysis of the phylogenetic history of the mitochondrial sequence haplotypes has shown a lack of reciprocal monophyly. These results further support the recognition of the small-bodied sage grouse as a distinct species based on the biological species concept, providing additional genetic evidence to augment the morphological and behavioural data. Furthermore, small-bodied sage grouse had much less genetic variation than large-bodied sage grouse, which may have implications for conservation issues.     

Carryover effects and climatic conditions influence the postfledging survival of greater sage‐grouse

Prebreeding survival is an important life history component that affects both parental fitness and population persistence. In birds, prebreeding can be separated into pre‐ and postfledging periods; carryover effects from the prefledging period may influence postfledging survival. We investigated effects of body condition at fledging, and climatic variation, on postfledging survival of radio‐marked greater sage‐grouse (Centrocercus urophasianus) in the Great Basin Desert of the western United States. We hypothesized that body condition would influence postfledging survival as a carryover effect from the prefledging period, and we predicted that climatic variation may mediate this carryover effect or, alternatively, would act directly on survival during the postfledging period. Individual body condition had a strong positive effect on postfledging survival of juvenile females, suggesting carryover effects from the prefledging period. Females in the upper 25th percentile of body condition scores had a postfledging survival probability more than twice that (Φ = 0.51 ± 0.06 SE) of females in the bottom 25th percentile (Φ = 0.21 ± 0.05 SE). A similar effect could not be detected for males. We also found evidence for temperature and precipitation effects on monthly survival rates of both sexes. After controlling for site‐level variation, postfledging survival was nearly twice as great following the coolest and wettest growing season (Φ = 0.77 ± 0.05 SE) compared with the hottest and driest growing season (Φ = 0.39 ± 0.05 SE). We found no relationships between individual body condition and temperature or precipitation, suggesting that carryover effects operated independently of background climatic variation. The temperature and precipitation effects we observed likely produced a direct effect on mortality risk during the postfledging period. Conservation actions that focus on improving prefledging habitat for sage‐grouse may have indirect benefits to survival during postfledging, due to carryover effects between the two life phases.     

The potential importance of unburned islands as refugia for the persistence of wildlife species in fire‐prone ecosystems

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Killing of raptors on grouse moors: evidence and effects

Owing to the intensity of game management in Britain, managers of grouse moors have illegally killed raptors to increase the numbers of Red Grouse Lagopus l. scotica available for shooting. This paper summarizes evidence for the recent scale of illegal raptor killing on grouse moors and its effects on populations. It provides insights into how raptors themselves respond demographically to different levels of killing. Over Britain as a whole, most raptors have increased and expanded considerably since the 1970s, in response to reduced killing and nest destruction, and the diminished impacts of organo‐chlorine pesticides; however, in recent decades the populations of some species have declined on and around grouse moors. This is widely evident in Hen Harrier Circus cyaneus, Peregrine Falcon Falco peregrinus and Golden Eagle Aquila chrysaetos populations and in more restricted areas also in Northern Goshawk Accipiter gentilis and Red Kite Milvus milvus populations, in all of which illegal killing has been sufficient to affect numbers over wider areas. The evidence consists mainly of: (1) greater disappearance of nesting pairs, lower breeding densities or reduced occupancy of apparently suitable traditional territories on grouse moors compared with other areas; (2) reduced nest success compared with other areas; (3) reduced adult survival compared with other areas; (4) reduced age of first breeding, reflecting the removal of adults from nesting territories and their replacement by birds in immature plumage; (5) greater levels of disappearance of satellite‐tracked birds on grouse moors than elsewhere; and (6) the finding of poisoned baits and traps, and shot or poisoned carcasses of raptors. Not all these types of evidence are available for every species, and other types of evidence are available for some. The Common Buzzard Buteo buteo is currently the most numerous raptor in Britain and also seems to be killed in the greatest numbers. Other raptor species, including Merlin Falco columbarius, Common Kestrel Falco tinnunculus and Eurasian Sparrowhawk Accipiter nisus which nest on or near grouse moors, have little or no significant impact on grouse and are killed less often or not at all. In the absence of illegal killing, some raptor species breed as well or better on grouse moors than in other habitats. Merlins, in particular, seem to thrive on grouse moors, benefiting from the management involved (including predator control). Other aspects of illegal raptor killing are discussed, including suggestions for ways in which it might be reduced.     

Seasonal reproductive costs contribute to reduced survival of female greater sage‐grouse

Tradeoffs among demographic traits are a central component of life history theory. We investigated tradeoffs between reproductive effort and survival in female greater sage‐grouse breeding in the American Great Basin, while also considering reproductive heterogeneity by examining covariance among current and future reproductive success. We analyzed survival and reproductive histories from 328 individual female greater sage‐grouse captured between 2003 and 2011, and examined the effect of reproductive effort on survival and future reproduction. Monthly survival of females was variable within years, and this within‐year variation was associated with distinct biological seasons. Monthly survival was greatest during the winter (November–March; Φ_W= 0.99 ± 0.001 SE), and summer (June–July; Φ_S= 0.98 ± 0.01 SE), and lower during nesting (April–May; Φ_N= 0.93 ± 0.02 SE) and fall (August–October; Φ_F= 0.92 ± 0.02 SE). Successful reproduction was associated with reduced monthly survival during summer and fall, and this effect was greatest during fall. Females that successfully fledged chicks had lower annual survival (0.47 ± 0.05 SE) than females who were not successful (0.64 ± 0.04 SE). Annual survival did not vary across years, consistent with a slow‐paced life history strategy in greater sage‐grouse. In contrast, reproductive success varied widely, and was positively correlated with annual rainfall. We found evidence for heterogeneity among females with respect to reproductive success; compared with unsuccessful females, females that raised a brood successfully in year t were more than twice as likely to be successful in year t+ 1. Female greater sage‐grouse incur costs to survival associated with reproduction, however, variation in quality among females may override costs to subsequent reproductive output.     

Management of Non‐Native Annual Plants to Support Recovery of an Endangered Perennial Forb,Ambrosia pumila

Invasive non‐native plants pose a ubiquitous threat to native plant communities and have been blamed for the decline of many endangered species. Endangered species legislation provides legal instruments for protection, but identifying a general method for protecting endangered species by managing non‐natives is confounded by multiple factors. We compared non‐native management methods aimed at increasing populations of an endangered forb, Ambrosia pumila, and associated native plants. We compared the effects of a grass‐specific herbicide (Fusilade II), hand‐pulling, and mowing in two degraded coastal sage scrub sites in southern California, U.S.A. At both sites, hand‐pulling had the greatest effect on non‐native cover, and correspondingly resulted in the greatest increase in A. pumila stems. Fusilade II application also led to an increase in A. pumila, but was not as effective in controlling non‐native plants as hand‐pulling and its effect varied with the dominant non‐native species. Mowing was not effective at promoting A. pumila, and its effect on non‐native cover seemed to be related to rainfall patterns. Although some methods increased A. pumila, none of our treatments simultaneously increased cover of other native plants. Hand‐pulling, the most effective treatment, is labor intensive and thus only feasible at small spatial scales. At larger scales, managers should take an experimental approach to identifying the most appropriate method because this can vary depending on the specific management objective (endangered species or whole native community), the dominant non‐natives, yearly variation in weather, and the timing of treatment application.     

Fine‐scale genetic structure in an eastern Alpine black grouse Tetrao tetrix metapopulation

Understanding genetic consequences of habitat fragmentation is crucial for the management and conservation of wildlife populations, especially in case of species sensitive to environmental changes and landscape alteration. In central Europe, the Alps are the core area of black grouse Tetrao tetrix distribution. There, black grouse dispersal is limited by high altitude mountain ridges and recent black grouse habitats are known to show some degree of natural fragmentation. Additionally, substantial anthropogenic fragmentation has occurred within the past ninety years. Facing losses of peripheral subpopulations and ongoing range contractions, we explored genetic variability and the fine‐scale genetic structure of the Alpine black grouse metapopulation at the easternmost fringe of the species’ Alpine range. Two hundred and fifty tissue samples and non‐invasive faecal and feather samples of eleven a priori defined subpopulations were used for genetic analysis based on nine microsatellite loci. Overall, eastern Alpine black grouse show similar amounts of genetic variation (H_O = 0.65, H_E = 0.66) to those found in more continuous populations like in Scandinavia. Despite of naturally and anthropogenically fragmented landscapes, genetic structuring was weak (global F_ST < 0.05), suggesting that the actual intensity of habitat fragmentation does not completely hamper dispersal, but probably restricts it to some extent. The most peripheral subpopulations at the edge of the species range show signs of genetic differentiation. The present study gives new insights into the population genetic structure of black grouse in the eastern Alps and provides a more fine‐scale view of genetic structure than previously available. Our findings will contribute to monitor the current and future status of the population under human pressures and to support supra‐regional land use planning as well as decision making processes in responsibilities of public administration.     

The absence of genotypic diversity in a successful parthenogenetic invader

Invasiveness might depend on the ability of genetically diverse populations of exotic species to adapt to novel environments, which suggests a paradox since exotic species are expected to lose genetic diversity when introduced. The apparent need for genetic diversity is particularly important for exotic species that lack bi-parental reproduction and genetic recombination. We used genetic marker studies to determine the genotypic diversity of invasive US populations of the clonal New Zealand mudsnail (Potamopyrgus antipodarum). We report here on a three-pronged survey of allozyme, microsatellite DNA, and mitochondrial DNA genetic markers of invasive populations with a focus on the western US. Combining the three types of genetic markers, we discovered four distinct genotypes of P. antipodarum. These results show that only one genotype (US 1) occupied the vast majority of the western US range, and a second occurred in the Great Lakes in the eastern US (US 2). Two other genotypes occurred in the western US (US 1a and US 3), but were restricted to populations near the presumed source of invasion in the middle Snake River, ID. These results suggest that P. antipodarum spread across a broad geographic range in the western US from a single introduced source population, and that the populations are comprised of a single clonal lineage.     

Effects of livestock grazing on rangeland biodiversity: A meta‐analysis of grouse populations

Livestock grazing affects over 60% of the world's agricultural lands and can influence rangeland ecosystem services and the quantity and quality of wildlife habitat, resulting in changes in biodiversity. Concomitantly, livestock grazing has the potential to be detrimental to some wildlife species while benefiting other rangeland organisms. Many imperiled grouse species require rangeland landscapes that exhibit diverse vegetation structure and composition to complete their life cycle. However, because of declining populations and reduced distributions, grouse are increasingly becoming a worldwide conservation concern. Grouse, as a suite of upland gamebirds, are often considered an umbrella species for other wildlife and thus used as indicators of rangeland health. With a projected increase in demand for livestock products, better information will be required to mitigate the anthropogenic effects of livestock grazing on rangeland biodiversity. To address this need, we completed a data‐driven and systematic review of the peer‐reviewed literature to determine the current knowledge of the effects of livestock grazing on grouse populations (i.e., chick production and population indices) worldwide. Our meta‐analysis revealed an overall negative effect of livestock grazing on grouse populations. Perhaps more importantly, we identified an information void regarding the effects of livestock grazing on the majority of grouse species. Additionally, the reported indirect effects of livestock grazing on grouse species were inconclusive and more reflective of differences in the experimental design of the available studies. Future studies designed to evaluate the direct and indirect effects of livestock grazing on wildlife should document (i) livestock type, (ii) timing and frequency of grazing, (iii) duration, and (iv) stocking rate. Much of this information was lacking in the available published studies we reviewed, but is essential when making comparisons between different livestock grazing management practices and their potential impacts on rangeland biodiversity.