Assessing Variation In Stress Among and Within American Pika (Ochotona princeps) Territories

As climate change alters ecosystems, how wild animals respond to changes in their habitats will determine their ability to persist into the future. By monitoring stress levels of individuals, we can concentrate conservation efforts on populations at most risk of decline before population loss is apparent. I used the American pika (Ochotona princeps), a highly territorial small mammal, to investigate the stress response to habitat quality. First, I investigated individual level differences in stress among territories of pika through time. Second, I investigated population level differences in mean stress of pika occupying two types of habitats. Observed patterns in stress across landscapes in our study suggest that stress could be used to evaluate seasonal variation in habitat quality. Our approach could be used in other wildlife studies to refine our understanding of habitat quality and its effect on individual stress levels as a driver of population decline.</p

Gene Expression during Survival of Escherichia coli O157:H7 in Soil and Water

The in vitro survival of Escherichia coli O157:H7 at 15°C under two experimental conditions (sterile soil and sterile natural water) was examined. DNA microarrays of the entire set of E. coli O157:H7 genes were used to measure the genomic expression patterns after 14 days. Although the populations declined, some E. coli O157:H7 cells survived in sterile stream water up to 234 days and in sterile soil for up to 179 days. Cells incubated in soil microcosms for 14 days expressed genes for antibiotic resistance, biosynthesis, DNA replication and modification, metabolism, phages, transposons, plasmids, pathogenesis and virulence, antibiotic resistance, ribosomal proteins, the stress response, transcription, translation, and transport and binding proteins at significantly higher levels than cells grown in Luria broth. These results suggest that E. coli O157:H7 may develop a different phenotype during transport through the environment. Furthermore, this pathogen may become more resistant to antibiotics making subsequent infections more difficult to treat

The Behavior of Novae Light Curves Before Eruption

In 1975, E. R. Robinson conducted the hallmark study of the behavior of classical nova light curves before eruption, and this work has now become part of the standard knowledge of novae. He made three points; that 5 out of 11 novae showed pre-eruption rises in the years before eruption, that one nova (V446 Her) showed drastic changes in the variability across eruptions, and that all but one of the novae (excepting BT Mon) have the same quiescent magnitudes before and after the outburst. This work has not been tested since it came out. We have now tested these results by going back to the original archival photographic plates and measuring large numbers of pre-eruption magnitudes for many novae using comparison stars on a modern magnitude scale. We find in particular that four out of five claimed pre-eruption rises are due to simple mistakes in the old literature, that V446 Her has the same amplitude of variations across its 1960 eruption, and that BT Mon has essentially unchanged brightness across its 1939 eruption. Out of 22 nova eruptions, we find two confirmed cases of significant pre-eruption rises (for V533 Her and V1500 Cyg), while T CrB has a deep pre-eruption dip. These events are a challenge to theorists. We find no significant cases of changes in variability across 27 nova eruptions beyond what is expected due to the usual fluctuations seen in novae away from eruptions. For 30 classical novae plus 19 eruptions from 6 recurrent novae, we find that the average change in magnitude from before the eruption to long after the eruption is 0.0 mag. However, we do find five novae (V723 Cas, V1500 Cyg, V1974 Cyg, V4633 Sgr, and RW UMi) that have significantly large changes, in that the post-eruption quiescent brightness level is over ten times brighter than the pre-eruption level.Comment: 91 pages (preprint), AJ accepte

Temporal vs. spatial variation in stress-associated metabolites within a population of climate-sensitive small mammals

Temporal variation in stress might signify changes in an animal&rsquo;s internal or external environment, while spatial variation instress might signify variation in the quality of the habitats that individual animals experience. Habitat-induced variationsin stress might be easiest to detect in highly territorial animals, and especially in species that do not take advantage ofcommon strategies for modulating habitat-induced stress, such as migration (escape in space) or hibernation (escape intime). Spatial and temporal variation in response to potential stressors has received little study in wild animals, especiallyat scales appropriate for relating stress to specific habitat characteristics. Here, we use the American pika (Ochotona princeps),a territorial small mammal, to investigate stress response within and among territories. For individually territorial animalssuch as pikas, differences in habitat quality should lead to differences in stress exhibited by territory owners. We indexedstress using stress-associated hormone metabolites in feces collected non-invasively from pika territories every 2 weeks fromJune to September 2018.We hypothesized that differences in territory qualitywould lead to spatial differences in mean stressand that seasonal variation in physiology or the physical environment would lead to synchronous variation across territoriesthrough time.We used linear mixed-effects models to explore spatiotemporal variation in stress using fixed effects of day-ofyearand broad habitat characteristics (elevation, aspect, site), aswell as local variation in habitat characteristics hypothesizedto affect territory quality for this saxicolous species (talus depth, clast size, available forage types). We found that temporalvariation within territories was greater than spatial variation among territories, suggesting that shared seasonal stressors aremore influential than differences in individual habitat quality. This approach could be used in other wildlife studies to refineour understanding of habitat quality and its effect on individual stress levels as a driver of population decline.</p

PMB Panel : Carving My Own Bench by the Road: Examining the Seats of Power for Black Women Educators through Playwriting

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Spatial scale selection for informing species conservation in a changing landscape

Abstract Identifying the relevant spatial scale at which species respond to features in a landscape (scale of effect) is a pressing research need as managers work to reduce biodiversity loss amid a variety of environmental challenges. Until recently, researchers often evaluated a subset of potential scales of effect inferred from previous studies in other locations, often based on different biological responses and environmental variables. These approaches, however, can create uncertainty as to whether relevant spatial scales were identified, and whether the effects of environmental variables at scale were accurately estimated. Identifying scales of effect is particularly relevant for the greater sage‐grouse (Centrocercus urophasianus), a sagebrush‐obligate species of conservation concern requiring large areas of intact sagebrush cover (Artemisia spp.) for habitat. We demonstrate the application of a scale selection approach that jointly estimates the scale of effect and the effect of sagebrush cover on trends in population size using counts from 584 sage‐grouse leks in southwestern Wyoming (2003–2019) and annual estimates of sagebrush cover from a remote sensing product. From this approach, we estimated a positive effect of mean sagebrush cover with a 95% probability that the scale of effect occurred within 5.02 km of leks. In an average year, we found that lower levels of sagebrush cover within these estimated scales could support increasing trends in sage‐grouse population size when populations were small, but higher levels of sagebrush cover were needed to sustain growing populations when populations were larger. With standardized monitoring and annual estimates of vegetation from remote sensing, this scale selection approach can be applied to identify relevant scales for other populations, species, and biological responses such as demography and movement

The Impact of Stimulus Presentation and Size On Preference

The impact of stimulus size and presentation on choice during a preference assessment was investigated using a modified multiple-stimulus without replacement (MSWO) technique. Stimuli were either presented with a uniform magnitude, as determined by mass, or in a manner consistent with caregiver report of reinforcer consumption. While both assessment procedures identified the same top three preferred items in three out of five cases, greater variability in the preference rank of less preferred items was observed between assessments