Habitat use by the southern red-backed vole (Clethrionomys gapperi) : response of an old-growth associated species to succession

I examined populations of the southern red-backed vole ( Clethrionomys gappen) and deer mouse (Peromyscus maniculatus) in 4 successional stages (65, 138, 256, 457 Y) in cedar-hemlock (Thuja plicata-Tsuga heterophylla) forests of Glacier National Park to determine macrohabitat selection among stands and microhabitat selection within stands. Abundance of Clethrionomys gapperi and Peromyscus maniculatus increased with increasing stand age. Microhabitat use differed from available habitat for both species within most age classes, but was not consistent for either species among age classes. The inconsistency in microhabitat use among successional stages and lack of correspondence between micro- and macrohabitat variables selected leads to the conclusion that macrohabitat associations determine microhabitat selection. In order to properly assess habitat use at either scale the difference between scales must be addressed in the design and analysis of habitat studies. Peromyscus maniculatus behaved as a generalist at the macrohabitat scale, but exhibited stronger microhabitat selection than did C. gapperi. I suggest that P. maniculatus may exhibit habitat switching and respond to local site conditions by developing search images that manifest themselves as distinctive foraging patterns at the microhabitat scale. Such behavior would render P. maniculatus a potentially formidable competitor for resources and explain its tenacity for a wide variety of habitats. Clethrionomys gapperi exhibits a strong positive linear relationship with stand age and old-growth conditions near the forest floor. If monitored in conjunction with other species such as the pine marten (Martes americana), pileated woodpecker (Dryocopus pileatus) and barred owl (Strix asio), C. gapperi could contribute significantly to an indicator guild for identifying and monitoring the old-growth condition. I also compared fluorescent pigment tracking and live trapping to determine microhabitat use by Clethrionomys gapperi. The two methods generally agreed, but fluorescent pigment tracking may allow more sensitive analyses of microhabitat use

Weed-Biocontrol Insects Reduce Native-Plant Recruitment Through Second-Order Apparent Competition

Small-mammal seed predation is an important force structuring native-plant communities that may also influence exotic-plant invasions. In the intermountain West, deer mice (Peromyscus maniculatus) are prominent predators of native-plant seeds, but they avoid consuming seeds of certain widespread invasives like spotted knapweed (Centaurea maculosa). These mice also consume the biological-control insects Urophora spp. introduced to control C. maculosa, and this food resource substantially increases deer mouse populations. Thus, mice may play an important role in the invasion and management of C. maculosa through food-web interactions. We examined deer mouse seed predation and its effects on seedling emergence and establishment of a dominant native grass, Pseudoroegneria spicata, and forb, Balsamorhiza sagittata, in C. maculosa-invaded grasslands that were treated with herbicide to suppress C. maculosa or left untreated as controls. Deer mice readily took seeds of both native plants but removed 2–20 times more of the larger B. sagittata seeds than the smaller P. spicata seeds. Seed predation reduced emergence and establishment of both species but had greater impacts on B. sagittata. The intensity of seed predation corresponded with annual and seasonal changes in deer mouse abundance, suggesting that abundance largely determined mouse impacts on native-plant seeds. Accordingly, herbicide treatments that reduced mouse abundance by suppressing C. maculosa and its associated biocontrol food subsidies to mice also reduced seed predation and decreased the impact of deer mice on B. sagittata establishment. These results provide evidence that Urophora biocontrol agents may exacerbate the negative effects of C. maculosa on native plants through a form of second-order apparent competition—a biocontrol indirect effect that has not been previously documented. Herbicide suppressed C. maculosa and Urophora, reducing mouse populations and moderating seed predation on native plants, but the herbicide\u27s direct negative effects on native forb seedlings overwhelmed the indirect positive effect of reducing deer mouse seed predation. By manipulating this four-level food chain, we illustrate that host-specific biological control agents may impact nontarget plant species through food-web interactions, and herbicides may influence management outcomes through indirect trophic interactions in addition to their direct effects on plants. Read More: http://www.esajournals.org/doi/abs/10.1890/07-1789.1?journalCode=eca

Biotic Resistance Via Granivory: Establishment by Invasive, Naturalized, and Native Asters Reflects Generalist Preference

Escape from specialist natural enemies is frequently invoked to explain exotic plant invasions, but little attention has been paid to how generalist consumers in the recipient range may influence invasion. We examined how seed preferences of the widespread generalist granivore Peromyscus maniculatus related to recruitment of the strongly invasive exotic Centaurea stoebe and several weakly invasive exotics and natives by conducting laboratory feeding trials and seed addition experiments in the field. Laboratory feeding trials showed that P. maniculatus avoided consuming seeds of C. stoebe relative to the 12 other species tested, even when seeds of alternative species were 53–94% smaller than those of C. stoebe. Seed addition experiments conducted in and out of rodent exclosures revealed that weakly invasive exotics experienced relatively greater release from seed predation than C. stoebe, although this was not the case for natives. Seed mass explained 81% of the variation in recruitment associated with rodent exclusion for natives and weak invaders, with larger-seeded species benefiting most from protection from granivores. However, recruitment of C. stoebe was unaffected by rodent exclusion, even though the regression model predicted seeds of correspondingly large mass should experience substantial predation. These combined laboratory and field results suggest that generalist granivores can be an important biological filter in plant communities and that species-specific seed attributes that determine seed predation may help to explain variation in native plant recruitment and the success of exotic species invasions

Effects of water availability on the germination of native and exotic forbs

Native and Exotic Forbes Germination Response to Drought Stress Beau R. Jennings, Mandy L. Slate, Dean E. Pearson Abstract The shifting climate of the western North American grasslands is forecasted to continue the trend of decreased annual rainfall and longer phases of rain-free windows in times where rainfall has been previously abundant. This understanding has inspired many studies on how ecosystems will respond to these changes. One of the key factors in the shaping of the ecosystem is the availability of precipitation in the spring, which will limit plant recruitment and seedling survival for the dryland ecosystem. Furthermore, seedling’s ability to establish themselves prior to hot dry summers is a key attribute to ensuring success in survival and reproduction. Yet, the expansion of exotic over native species in dryland ecosystems suggests that some exotic plants have traits that allow them to succeed at a higher success rate than native plants. Specifically, understanding the germination tendencies of exotic and native forbes will allow better predictions to be made on the future shaping of these ecosystems. We conducted an experiment in a lab comparing germination percentages and rates of germination for multiple species of native and exotic grassland forbs under different levels of water availability. The experiment was conducted in a growth chamber where temperature, lighting, and humidity were kept as constant variables. The specimens were placed in petri dishes on top of filter paper, and each petri dish lid had three ⅛” holes to allow some evaporation. We hydrated seeds with either 2ml and 3ml daily or every other day. Specimens were examined daily in order to record germination promptly. We will present a comparison of Germination synchrony, germinability, time to germination, germination t50, and germination range between native and exotic forbes species, and discuss how these findings may be used to better understand the processes in which exotic plants are able to overtake plants in their native habitats

Counterintuitive Effects of Large-Scale Predator Removal on a Midlatitude Rodent Community

Historically, small mammals have been focal organisms for studying predator–prey dynamics, principally because of interest in explaining the drivers of the cyclical dynamics exhibited by northern vole, lemming, and hare populations. However, many small-mammal species occur at relatively low and fairly stable densities at temperate latitudes, and our understanding of how complex predator assemblages influence the abundance and dynamics of these species is surprisingly limited. In an intact grassland ecosystem in western Montana, USA, we examined the abundance and dynamics of Columbian ground squirrels (Spermophilus columbianus), deer mice (Peromyscus maniculatus), and montane voles (Microtus montanus) on 1-ha plots where we excluded mammalian and avian predators and ungulates, excluded ungulates alone, or allowed predators and ungulates full access. Our goal was to determine whether the relatively low population abundance and moderate population fluctuations of these rodents were due to population suppression by predators. Our predator-exclusion treatment was divided into two phases: a phase where we excluded all predators except weasels (Mustela spp.; 2002–2005), and a phase where all predators including weasels were excluded (2006–2009). Across the entire duration of the experiment, predator and/or ungulate exclusion had no effect on the abundance or overall dynamics of ground squirrels and deer mice. Ground squirrel survival (the only species abundant enough to accurately estimate survival) was also unaffected by our experimental treatments. Prior to weasel exclusion, predators also had no impacts on montane vole abundance or dynamics. However, after weasel exclusion, vole populations reached greater population peaks, and there was greater recruitment of young animals on predator-exclusion plots compared to plots open to predators during peak years. These results suggest that the impacts of predators cannot be generalized across all rodents in an assemblage. Furthermore, they suggest that specialist predators can play an important role in suppressing vole abundance even in lower-latitude vole populations that occur at relatively low densities

Population-Level Compensation Impedes Biological Control of an Invasive Forb and Indirect Release of a Native Grass

The intentional introduction of specialist insect herbivores for biological control of exotic weeds provides ideal but understudied systems for evaluating important ecological concepts related to top-down control, plant compensatory responses, indirect effects, and the influence of environmental context on these processes. Centaurea stoebe (spotted knapweed) is a notorious rangeland weed that exhibited regional declines in the early 2000s, attributed to drought by some and to successful biocontrol by others. We initiated an experiment to quantify the effects of the biocontrol agent, Cyphocleonus achates, on Ce. stoebe and its interaction with a dominant native grass competitor, Pseudoroegneria spicata, under contrasting precipitation conditions. Plots containing monocultures of each plant species or equal mixtures of the two received factorial combinations of Cy. achates herbivory (exclusion or addition) and precipitation (May–June drought or “normal,” defined by the 50-year average) for three years. Cy. achates herbivory reduced survival of adult Ce. stoebe plants by 9% overall, but this effect was stronger under normal precipitation compared to drought conditions, and stronger in mixed-species plots compared to monocultures. Herbivory had no effect on Ce. stoebe per capita seed production or on recruitment of seedlings or juveniles. In normal-precipitation plots of mixed composition, greater adult mortality due to Cy. achates herbivory resulted in increased recruitment of new adult Ce. stoebe. Due to this compensatory response to adult mortality, final Ce. stoebe densities did not differ between herbivory treatments regardless of context. Experimental drought reduced adult Ce. stoebe survival in mixed-species plots but did not impede recruitment of new adults or reduce final Ce. stoebe densities, perhaps due to the limited duration of the treatment. Ce. stoebe strongly depressed P. spicata reproduction and recruitment, but these impacts were not substantively alleviated by herbivory on Ce. stoebe. Population-level compensation by dominant plants may be an important factor inhibiting top-down effects in herbivore-driven and predator-driven cascades

Soft Robotics: Cerebellar Inspired Control of Artificial Muscles

Soft robots have the potential to greatly improve human-robot interaction via intrinsically safe, compliant designs. However, new compliant materials used in soft robotics – artificial muscles – are fabricated with poor tolerances and have time-varying dynamics. Therefore, a key technical challenge is to develop adaptive control algorithms for these materials. Here, we take a novel bio-inspired approach to artificial muscle control using the adaptive filter model of the cerebellum. The cerebellum is a brain structure essential for fine-tuning human performance in a diverse range of sensory and motor tasks. Its ability to automatically calibrate and adapt to changes in a wide variety of systems using a homogenous, repeating structure suggests that cerebellar-inspired models are highly suited to controlling artificial muscles in a range of tasks. We investigate the performance of the cerebellar adaptive filter algorithm in the displacement control of a soft actuator. Experimental results demonstrate that the cerebellar algorithm is successful and learns to accurately control the time-varying dynamics of the soft actuator in real-time

Implementing pelvic floor muscle training in women's childbearing years: A critical interpretive synthesis of individual, professional, and service issues

Antenatal pelvic floor muscle training (PFMT) may be effective for the prevention and treatment of urinary and fecal incontinence both in pregnancy and postnatally, but it is not routinely implemented in practice despite guideline recommendations. This review synthesizes evidence that exposes challenges, opportunities, and concerns regarding the implementation of PFMT during the childbearing years, from the perspective of individuals, healthcare professionals (HCPs), and organizations.MethodsCritical interpretive synthesis of systematically identified primary quantitative or qualitative studies or research syntheses of women's and HCPs attitudes, beliefs, or experiences of implementing PFMT.ResultsFifty sources were included. These focused on experiences of postnatal urinary incontinence (UI) and perspectives of individual postnatal women, with limited evidence exploring the views of antenatal women and HCP or wider organizational and environmental issues. The concept of agency (people's ability to effect change through their interaction with other people, processes, and systems) provides an over?arching explanation of how PFMT can be implemented during childbearing years. This requires both individual and collective action of women, HCPs, maternity services and organizations, funders and policymakers.ConclusionNumerous factors constrain women's and HCPs capacity to implement PFMT. It is unrealistic to expect women and HCPs to implement PFMT without reforming policy and service delivery. The implementation of PFMT during pregnancy, as recommended by antenatal care and UI management guidelines, requires policymakers, organizations, HCPs, and women to value the prevention of incontinence throughout women's lives by using low?risk, low?cost, and proven strategies as part of women's reproductive health