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Chronic wasting disease (CWD) is a fatal transmissible spongiform encephalopathy affecting white-tailed deer (Odocoileus virginianus), mule deer (Odocoileus hemionus), Rocky Mountain elk (Cervus elaphus nelsoni), and moose (Alces alces shirasi) in North America. In southeastern Wyoming average annual CWD prevalence in mule deer exceeds 20% and appears to contribute to regional population declines. We determined the effect of CWD on mule deer demography using age-specific, female-only, CWD transition matrix models to estimate the population growth rate (λ). Mule deer were captured from 2010-2014 in southern Converse County Wyoming, USA. Captured adult (≥ 1.5 years old) deer were tested ante-mortem for CWD using tonsil biopsies and monitored using radio telemetry. Mean annual survival rates of CWD-negative and CWD-positive deer were 0.76 and 0.32, respectively. Pregnancy and fawn recruitment were not observed to be influenced by CWD. We estimated λ = 0.79, indicating an annual population decline of 21% under current CWD prevalence levels. A model derived from the demography of only CWD-negative individuals yielded; λ = 1.00, indicating a stable population if CWD were absent. These findings support CWD as a significant contributor to mule deer population decline. Chronic wasting disease is difficult or impossible to eradicate with current tools, given significant environmental contamination, and at present our best recommendation for control of this disease is to minimize spread to new areas and naïve cervid populations.

Plants of Purshia tridentata and Purshia stansburyana, 2 shrub species from the western United States, naturally display eccentric stem growth. The purpose of this study was to quantitatively document stem eccentricity for these 2 species. Stem segments were obtained from 3 different plants of each species at locations in central Utah. Each stem was sawed into 8-mm sections and photographed for analysis. Every stem section was then marked at a 36° interval to produce 10 wedge-shaped sectors. The areas of each sector were determined and analyzed. Stem segment areas were about 40, 60, and 100 mm2 for stem diameters of 6, 8, and 11 mm, respectively, for both species. Consecutive 8-mm segments were compared at 6 and 11 mm for both species. Absolute differences between paired segments ranged between 0.0 and 12.0. On average, 43% of all pairs had absolute differences above 0.40. These results suggest marked differences between consecutive segments. The eccentric growth percentages were also the same for both species. Mean eccentric percentages for 6-mm-diameter segments were 43.4% and 49.6% for the 2 species. Moreover, 11-mm-diameter segments of P. tridentata and P. stansburyana had mean eccentric percentages of 36.4% and 34.0%, respectively. Overall, 81% of all stem segments showed eccentricity. Many long-lived desert shrubs of the western United States exhibit a wide range of wood anomalies. These wood anomalies may be endemic in these species.

There is increasing recognition that overall interactions among plant species are often the net result of both positive and negative effects. However, the positive influence of other plants has rarely been examined using detailed demographic methods, which are useful for partitioning net effects at the population level into positive and/or negative effects on individual vital rates. This study examines the influence of microhabitats created by the native shrubs Artemisia tridentata and Purshia tridentata on the demography of the invasive annual grass Bromus tectorum in the Great Basin Desert, California, USA. Shrub understory environments differed significantly from intershrub space and were characterized by higher soil fertility and less extreme microclimates. There existed a strong spatial association between B. tectorum and the shrubs across four years, with more than double the density of B. tectorum in shrub microhabitats compared to intershrub space. Periodic matrix models were used to calculate population growth (λ) and reproductive potential (RP, expected lifetime fecundity of seedlings) of B. tectorum in different microhabitats over two years. Modeled population growth was significantly increased in shrub microhabitats in the first of two years. This was primarily due to increased seedling establishment in Artemisia microhabitats, rather than effects during the growing season. In the following year, B. tectorum individuals in shrub microhabitats had a significantly greater reproductive potential than those in intershrub microhabitats, indicating shrub facilitation during the growing season. Loop analysis revealed an interacting effect of year and microhabitat on B. tectorum life history pathway elasticity values, demonstrating a fundamental influence of spatiotemporal factors on which life history pathways are important and/or possible. Life table response experiment (LTRE) analysis showed that increased survival and growth rates positively contributed to population growth in both years under Purshia, but only in the second year under Artemisia. This research provides evidence that the positive effects of native shrubs on B. tectorum can be strong enough to produce net positive effects at the population level, although positive effects were variable. In this study, a rigorous demographic approach was particularly useful in partitioning overall interactions into positive and negative components.

The four-subfamily subdivision of Rosaceae has been recently replaced by a three-subfamily scheme. The re-circumscribed Rosoideae lacks a solid and well-resolved phylogeny on which a classification can be based. In this study, we sampled 56 genera presumably belonging to Rosoideae and 10 genera belonging to other subfamilies or families and used 12 chloroplast regions ( mat K, rbc L, trn L, trn L–F, ndh F, ycf 1, trn C– ycf 6, trn S–G, trn S, psb A– trn H, rpo C1 and trn S– ycf 9) to reconstruct their phylogeny. Our results confirmed (1) the exclusion of Rhodotypos and Kerria from Rosoideae and their inclusion in the subfamily Amygdaloideae and (2) the exclusion of Chamaebatia , Cercocarpus , Dryas and Purshia (including Cowania ) from Rosoideae and their inclusion in Dryadoideae, the sister subfamily of Rosoideae. Within Rosoideae, there are six strongly supported lineages that correspond to six tribes: Ulmarieae, Colurieae, Rubeae, Roseae, Agrimonieae and Potentilleae. We dated the divergence of Rosoideae back to approximately 69.77 million years ago (Mya; 95% HPD = 61.28–78.33 Mya) and that of the tribes within Rosoideae to from 10.42 to 40.02 million years ago (Mya; 95% HPD = 4.73–59.08 Mya). The subfamily is probably of North American and Asian origin and thrives in the northern hemisphere, especially in Asia. After re-circumscriptions of several genera, there are 36 genera recognized in Rosoideae.

The threat of global warming to rare species is a growing concern, yet few studies have predicted its effects on rare populations. Using demographic data gathered in both drought and nondrought years between 1996-2003 in central Arizona upper Sonoran Desert, we modeled population viability for the federally endangered Purshia subintegra (Kearney) Henrickson (Arizona cliffrose). We used deterministic matrix projection models and stochastic models simulating weather conditions during our study, given historical weather variation and under scenarios of increased aridity. Our models suggest that the P. subintegra population in Verde Valley is slowly declining and will be at greater risk of extinction with increased aridity. Across patches at a fine spatial scale, demographic performance was associated with environmental factors. Moist sites (patches with the highest soil moisture, lowest sand content, and most northern aspects) had the highest densities, highest seedling recruitment, and highest risk of extinction over the shortest time span. Extinction risk in moist sites was exacerbated by higher variance in recruitment and mortality. Dry sites had higher cumulative adult survival and lower extinction risk but negative growth rates. Steps necessary for the conservation of the species include introductions at more northern latitudes and in situ manipulations to enhance seedling recruitment and plant survival. We demonstrate that fine spatial-scale modeling is necessary to predict where patches with highest extinction risk or potential refugia for rare species may occur. Because current climate projections for the 21st century imply range shifts at rates of 300 to 500 km-century, which are beyond even exceptional examples of shifts in the fossil record of 100-150 km, it is likely that preservation of many rare species will require human intervention and a long-term commitment. Global warming conditions are likely to reduce the carrying capacity of many rare species' habitats.Original Abstract: La amenaza del calentamiento global a las especies raras es una preocupacion creciente, a pesar de ello pocos estudios han predicho sus efectos sobre poblaciones raras. Utilizando datos demograficos obtenidos en anos con y sin sequia entre 1996 y 2003 en el centro de Arizona en el desierto de Sonora, modelamos la viabilidad poblacional de Purshia subintegra (Kearney) Henrickson, federalmente en peligro. Utilizamos modelos deterministicos de proyeccion matricial y modelos estocasticos que simularon las condiciones del tiempo durante nuestro estudio, considerando la variacion climatologica historica y bajo escenarios de aridez creciente. Nuestros modelos sugieren que la poblacion de P. subintegra en Valle Verde esta declinando lentamente y estara en mayor riesgo de extincion con la aridez creciente. En una escala espacial fina, el funcionamiento poblacional se asocio con factores ambientales. Los sitios humedos (parches con la mayor humedad del suelo, menor contenido de arena y con los aspectos mas nortenos) tuvieron las densidades mas altas, el mayor reclutamiento de plantulas y el mayor riesgo de extincion en el plazo mas corto. El riesgo de extincion en los sitios humedos fue exacerbado por la mayor variacion en el reclutamiento y la mortalidad. Los sitios secos tuvieron mayor supervivencia acumulativa de adultos y menor riesgo de extincion pero tasas negativas de crecimiento. Los pasos necesarios para la conservacion de las especies incluyen introducciones en latitudes mas al norte y manipulaciones in situ para reforzar el reclutamiento de plantulas y la supervivencia de plantas. Demostramos que el modelado a escala espacial fina es necesario para predecir donde pueden ocurrir parches con mayor riesgo de extincion o como refugios para especies raras. Debido a que las actuales proyecciones climaticas para el siglo veintiuno implican cambios en los rangos de distribucion a una tasa de 300 a500 km-siglo, que exceden aun a los ejemplos de cambios excepcionales de 100-150 km en el registro fosil, es probable que la preservacion de muchas especies raras requiera de la intervencion humana con un compromiso a largo plazo. Las condiciones del calentamiento global probablemente reduciran la capacidad de carga de los habitats de muchas especies raras.

Seed-caching rodents store large quantities of seeds during the summer and autumn but the number of stored seeds has rarely been estimated. Understanding how many seeds each individual stores has implications for energetics during the period of food scarcity, and the number of seeds scatter hoarded has implications for how well animals disperse the seed of plants and thereby effect ecological processes. The number of seeds of antelope bitterbrush (Purshia tridentata) and Jeffrey pine (Pinus jeffreyi) scatter hoarded by yellow pine chipmunks (Tamias amoenus) was estimated in a year of good seed production. Both of these plant species are adapted for seed dispersal by scatter-hoarding animals. Individual chipmunks scatter hoarded an estimated 29,629 bitterbrush seeds and 5,945 Jeffrey pine seeds each year. These estimates are likely underestimates and do not include the many thousands of seeds eaten during the harvest period. Combined, the number of seeds of these two species that chipmunks scatter hoard in soil provided 2.8 times more energy than required to survive the autumn and winter. Populations of yellow pine chipmunks have the potential to scatter hoard nearly a million seeds per hectare in good seed years.

Shrub volume is used to calculate numerous, essential ecological indicators in rangeland ecosystems such as biomass, fuel loading, wildlife habitat, site productivity, and ecosystem structure. Field techniques for biomass estimation, including destructive sampling, ocular estimates, and allometric techniques, use shrub height and canopy widths to estimate volume and translate it to biomass with species‐specific allometric equations. These techniques are time‐consuming and pose challenges, including removal of plant material and training of observers. We compared canopy volume estimates from field‐based measurements with drone‐collected canopy volume estimates for seven dominant shrub species within mountain big sagebrush (Artemisia tridentata subsp. vaseyana) plant communities in southern Idaho, USA. Canopy height and two perpendicular width measurements were taken from 103 shrubs of varying sizes, and volume was estimated using a traditional allometric equation. Overlapping aerial images captured with a DJI Mavic 2 Professional drone were used to create a 3D representation of the study area using structure‐from‐motion photogrammetry. Each shrub was extracted from the point cloud, and volume was estimated using allometric and volumetric methods. The volumetric method, which involved converting point clouds to raster canopy height models with 2.5‐ and 5‐cm grid cells, outperformed the allometric method (R2 > 0.7) and was more reproducible and robust to user‐related variability. Drone‐estimated volume best‐matched field‐estimated volume (R2 > 0.9) for three larger species: A. tridentata subsp. tridentata, A. tridentata subsp. vaseyana, and Purshia tridentata. The volume of smaller shrubs (canopy widths <1 m) was slightly overestimated from drone‐based models. We argue that drone‐based models provide a suitable alternative to field methods, while having the added benefit of being less time‐consuming, with fewer limitations, and more easily scaled to larger study areas than traditional field techniques. Finally, we demonstrate a proof of concept for automating canopy volume estimates using point‐cloud‐based automatic shrub detection algorithms. These findings demonstrate that drone‐collected images can be used to assess shrub canopy volume for at least five upland sagebrush steppe shrub species and support the integration of drone data collection into rangeland vegetation monitoring.

Shrub canopy cover can take between 10 and >50 years to recover to predisturbance levels following fire in sagebrush communities. The high degree of unpredictability of shrub recovery following prescribed fires and wildfires makes it difficult to prioritize restoration efforts and develop long-term plans for restoring or maintaining the integrity of sagebrush communities. Our overall goal was to develop a hypothesis based on descriptive data that describes the temporal pattern of recruitment for 2 important shrubs, Artemisia tridentata Nutt. ssp. vaseyana (Rydb.) Beetle and Purshia tridentata (Pursh) DC., in the interiors of large burns where little seed input from surviving shrubs occurs. We had 2 primary questions: (1) are there distinct temporal patterns of recruitment in the interiors of large burns that determine the recovery rate of the shrub canopy layer for species largely dependent on seedlings for reestablishment and (2) can we generate hypotheses that explain this variation in shrub recovery rates? To address the question of recruitment, we measured shrub density and age for A. tridentata ssp. vaseyana and P. tridentata in the interiors of 4 large (>400-ha) burns. Time since fire varied from 6 to 41 years. All 4 fires burned in August and were relatively complete with few to no unburned patches. Our data indicate that (1) A. tridentata ssp. vaseyana and P. tridentata seed remained viable up to 4 years postfire and that (2) the rate of shrub recovery is largely determined by the success or failure of seedling establishment in the first 2–3 years following disturbance. From these data we generated a hypothesis describing 2 scenarios of postfire shrub recovery.

The study was conducted within a well-managed beef cattle operation in northeastern Mexico. Each nest was weighed and dissected to obtain the plant and animal material used to build the nests. The number of materials present per nest and relative frequency were determined. Twenty-one building materials were used. Over the years, Muhlenbergia torreyi represented 85.5% of the total biomass of the nests, and Aristida longiseta, Bouteloua gracilis, Brickellia canescens, Purshia mexicana and Cirsium ehrenbergii constituted 2.45, 2.80, 2.44, 1.34 and 1.11% of the total biomass, respectively. The above-mentioned grasses represented 95.62% of the total biomass. Material of animal origin was horse and cow hair, which represented 0.84 and 0.58% of the total biomass, respectively. It was concluded that, at the study site, Muhlenbergia torreyi was a key nest-building material for the Worthen sparrow nest.

The aim of this study was to identify wild plant species with potential for remediation of As and Pb and to measure the 40K activity on soil mine tailings in Sombrerete, Zacatecas (North Central Mexico). The analysis of As and Pb was performed by atomic absorption spectrometry, while the concentration of 40K was carried out by low-resolution gamma-ray spectrometry. Plants growing on two mine tailings show ability to accumulate or tolerate heavy metals. Major family represented in the area was Asteraceae. Arsenic showed the highest concentrations, in soils, of 2004 and 1101 mg/kg, respectively, while Pb at 132 and 113 mg/kg, respectively. These results evidence that the tailings are highly contaminated and represent a potential risk for population and the environment. Wild plants that showed maximum values of As in their shoots were Asphodelus fistulosus (447 mg/kg), Pennisetum villosum (342 mg/kg) and Purshia mexicana (268 mg/kg). Presence of P. mexicana shrub is reported for the first time as accumulator of As in semi-arid region of Mexico. The concentration of 40K in soil samples from the mine tailings reported for the first time is in agreement with the mean values reported for the world. The wild plant species identified could be used for re-vegetation and stabilization of the mining wastes and contribute to decrease As bioavailability in arid and semi-arid regions.