Explore the vast range of titles available.

The drivers of background tree mortality rates—the typical low rates of tree mortality found in forests in the absence of acute stresses like drought—are central to our understanding of forest dynamics, the effects of ongoing environmental changes on forests, and the causes and consequences of geographical gradients in the nature and strength of biotic interactions. To shed light on factors contributing to background tree mortality, we analyzed detailed pathological data from 200,668 tree-years of observation and 3,729 individual tree deaths, recorded over a 13-yr period in a network of old-growth forest plots in California's Sierra Nevada mountain range. We found that: (1) Biotic mortality factors (mostly insects and pathogens) dominated (58%), particularly in larger trees (86%). Bark beetles were the most prevalent (40%), even though there were no outbreaks during the study period; in contrast, the contribution of defoliators was negligible. (2) Relative occurrences of broad classes of mortality factors (biotic, 58%; suppression, 51%; and mechanical, 25%) are similar among tree taxa, but may vary with tree size and growth rate. (3) We found little evidence of distinct groups of mortality factors that predictably occur together on trees. Our results have at least three sets of implications. First, rather than being driven by abiotic factors such as lightning or windstorms, the \"ambient\" or \"random\" background mortality that many forest models presume to be independent of tree growth rate is instead dominated by biotic agents of tree mortality, with potentially critical implications for forecasting future mortality. Mechanistic models of background mortality, even for healthy, rapidly growing trees, must therefore include the insects and pathogens that kill trees. Second, the biotic agents of tree mortality, instead of occurring in a few predictable combinations, may generally act opportunistically and with a relatively large degree of independence from one another. Finally, beyond the current emphasis on folivory and leaf defenses, studies of broad-scale gradients in the nature and strength of biotic interactions should also include biotic attacks on, and defenses of, tree stems and roots.

Habitat exchange programs, a form of biodiversity offsetting, aim to compensate for negative impacts in one area by conservation in another. A newer subset of habitat exchange programs includes programs that have three distinct characteristics: they allow for temporary (as opposed to only permanent) credits; they are centralized and overseen by nonregulatory, independent administrators; and they exist in the absence of mandatory mitigation policy. As a result, these programs may be relatively flexible and practical in areas where environmental regulation is unpalatable politically. We synthesized gray and peer‐reviewed literature to evaluate these programs’ strengths and shortcomings. On the basis of our synthesis, we suggest that temporary conservation credits in habitat exchanges could encourage participation of landowners in conservation and enable programs to respond to environmental change. However, temporary credits can lead to trade‐offs between flexibility and uncertainty. Moreover, there is little evidence that these habitat exchange programs have benefited target species, and many challenges associated with offsetting programs persist. Newer forms of habitat exchange programs may have potential to achieve no net loss or net gains of biodiversity to a greater extent than other forms of offsetting, but this potential has not yet been realized.

Rangelands are temporally and spatially complex socioecological systems on which the predominant land use is livestock production. In North America, rangelands also contain approximately 80% of remaining habitat for grassland birds, a guild of species that has experienced precipitous declines since the 1970s. While livestock grazing management may benefit certain grassland bird species by generating the vegetation structure and density they prefer, these outcomes are poorly understood for avian species breeding in the shortgrass steppe. We evaluated how two grazing management systems, continuous, season-long grazing and adaptive, rest-rotational grazing, affected grassland bird abundance from 2013 to 2017 in Colorado’s shortgrass steppe. We examined grazing impacts in conjunction with ecological sites, which constitute unique soil and plant communities. When grazing management was evaluated in conjunction with spatial variation in ecological sites, we found three of our five focal bird species responded to grazing management. McCown’s Longspur abundance decreased in pastures rested from grazing the previous year. The effect of grazing on Horned Lark and Grasshopper Sparrow depended on ecological site: Horned Lark density was highest in pastures that were intensively grazed and Grasshopper Sparrow density was highest in pastures that were rested the previous year in the least productive ecological site. In addition, densities of all species varied across ecological sites. Our results suggest consideration of soil and vegetation characteristics can inform how adaptive management is applied on a landscape to benefit the full suite of breeding grassland birds, including species that have seemingly contrasting habitat needs. For example, a manager could target adaptive drought mitigation practices, such as resting pastures for 1 yr to generate grassbanks, in less productive soils to benefit grassland birds that prefer taller/denser vegetation structure, or could apply intensive, short-duration grazing on less productive soils to benefit species preferring shorter/sparser vegetation. A single year of intensive, short-duration grazing (i.e., one component of our rotational treatment) across the landscape, however, might not create sufficient habitat for species that prefer short/sparse vegetation in our system (e.g., McCown’s Longspur). Ultimately, our study indicates how cattle production on rangelands can congruently support grassland bird populations in the shortgrass steppe.

The habitat needs of common species can be understudied due to a focus on rarity and the prevention of extinction within traditional conservation policy and practice. Yet even common species are not immune to anthropogenic pressures on the environment, and understanding habitat needs for common species is critical information for management. This is the case for Eastern Screech-Owl (Megascops asio), a common species that is poorly studied in the west/northwest portion of its broad range across the central and eastern United States. Our objective was to explore environmental factors associated with Eastern Screech-Owl (M. a. maxwelliae subspecies) breeding season occupancy dynamics in this understudied region and to inform local land management efforts. To address this objective, we used 9 years of occupancy data (2013–2021) from a participatory science monitoring program in Fort Collins, CO, a mid-sized suburban city. We found that Eastern Screech-Owl persistence probability decreased while colonization probability increased with aggregation of tree cover and average breeding season temperature. We also found colonization probability increased with cumulative winter precipitation, and persistence probability decreased with average winter minimum temperature. Overall, our results suggest that this population of Eastern Screech-Owls responds to climate before and during the breeding season in complex ways, and that the species appears to experience high turnover in this study area along the western edge of its continental range. Our study highlights the importance of investigating how common species respond to their environment across the full extent of their distributions. En las políticas tradicionales y la práctica de la conservación, las necesidades de hábitat de las especies comunes pueden ser subestudiadas por el enfoque centrado en especies raras o para prevenir su extinción. Sin embargo, las especies comunes no son inmunes a las presiones antropogénicas en el medio ambiente y entender las necesidades de hábitat de éstas es información crítica para su manejo. Éste es el caso del búho Megascops asio, una especie común que ha sido escasamente estudiada en la porción oeste/noroeste de su amplio rango que cubre el centro y este de los Estados Unidos. Nuestro objetivo fue explorar los factores ambientales asociados con la dinámica de ocupación de la subespecie del este (M. a. maxwelliae) en esta región subestudiada e informar esfuerzos locales de manejo de la tierra. Para atender este objetivo, usamos 9 años de datos de ocupación (2013–2021) de un programa científico participativo de monitoreo en Fort Collins, Colorado, una ciudad suburbana de tamaño mediano. Encontramos que la probabilidad de persistencia de este búho decreció mientras la probabilidad aumentó con la agregación de cobertura arbórea y la temperatura media de la temporada reproductiva. También encontramos que la probabilidad de colonización se incrementó con la precipitación invernal cumulativa y la probabilidad de persistencia disminuyó con la temperatura media mínima invernal. En general, nuestros resultados sugieren que esta población de Megascops asio responde al clima antes y durante la estación reproductiva en formas complejas y que esta especie parece experimental un alto recambio en nuestra área de estudio en el margen oeste de su distribución continental. Nuestro estudio destaca la importancia de investigar cómo las especies comunes responden a su ambiente en todo su rango de distribución. PALABRAS CLAVE Ciencia ciudadana; ciencia comunitaria; ecología urbana; especies comunes; hábitat ripario; monitoreo participativo; ocupación

The frequency and magnitude of deluges (extremely large rain events) are increasing globally as the atmosphere warms. Small-scale experiments suggest that semiarid grasslands are particularly sensitive to both the timing and size of deluge events. However, the assumption that plot-scale results can be extrapolated across landscapes with variable soil textures, plant communities, and grazing regimes has seldom been tested, despite being key to forecasting regional consequences of precipitation extremes. We used precipitation data from an extensive rain gauge network to identify natural deluges (mean size = 60 ± 31 mm, 1984–2012) that occurred across a ∼60-km² heterogeneous native shortgrass steppe landscape in Colorado. We then related spatial variation in deluge precipitation to postdeluge responses in canopy greenness (normalized difference vegetation index, NDVI) via satellite imagery. Consistent with results from experiments, this semiarid grassland was most sensitive to mid–growing-season deluges, and postdeluge canopy greenness usually increased linearly (67% of the time) with increasing deluge size. This suggests that aboveground productivity in these semiarid systems will likely increase, rather than asymptote, with forecasted increases in deluge size. Importantly, differences in grazing regime did not significantly alter deluge responses, indicating that these patterns are robust to this widespread management practice.

Aim Human development and agriculture can have transformative and homogenizing effects on natural systems, shifting the composition of ecological communities towards non‐native and native species that tolerate or thrive under human‐dominated conditions. These impacts cannot be fully captured by summarizing species presence, as they include dramatic changes to patterns of species abundance. However, how human land use patterns and species invasions intersect to shape patterns of abundance and dominance within ecological communities is poorly understood even in well‐known taxa. Location Conterminous United States. Time period 2010–2012. Major taxa studied Passeriformes. Methods We analyse continental‐scale monitoring data to study the proportional abundance of non‐native and native synanthropic species within passerine bird communities. Synanthropic species are those that benefit from an association with humans. We estimate how the amount and configuration of human development and agriculture relate to the degree to which human‐associated species dominate passerine communities across the continent. Results Human‐associated species comprised the majority of detected passerine individuals across two‐thirds of bird surveys. Non‐native and synanthropic species responded differently to land cover and reached highest relative abundance in different portions of the continent. The proportional abundance of synanthropic birds increased rapidly with development, but was not related to the configuration of land cover. The proportion of non‐native individuals was higher when intensively‐used land cover was more aggregated. Main conclusions Even low amounts of intensively‐used lands were associated with a dramatic reshaping of passerine communities, with consequences for patterns of relative abundance across the continent.

Aim The degree to which species' niches remain stable over space and time–the niche conservatism hypothesis–is critical for predicting species' responses to environmental change. Tests of this hypothesis typically focus on changes in niche centroids and boundaries. An outstanding question is whether species' environmental associations differ within the interior of their niche space–that is, across the full range of occupied conditions–in original versus novel geographic space. Location Europe and North America. Time Period 1997–2018. Major Taxa Studied Birds. Methods We used over 400,000 observations collected over 22 years and across 28 countries to explore whether two common songbird species—European starling (Sturnus vulgaris) and house sparrow (Passer domesticus) – exhibit niche conservatism between their native European and non‐native North American ranges. We tested for niche conservatism via (1) an ordination approach that quantified change in niche shape and boundaries, and (2) generalised linear mixed effects models to quantify how abundance varied with the interaction between continent and climate or land cover variables. Results The ordination analysis indicated that both European starling and house sparrow exhibited niche conservatism between Europe and North America. However, abundance models revealed continental differences in how the species responded to temperature and land cover. The abundance models also revealed that areas with wetter conditions that were occupied by both species in their native European ranges were available but unoccupied in their non‐native North American ranges (i.e., niche unfilling). Main Conclusions Our work demonstrates that species can exhibit apparent consistency in niche boundaries but varied abundance responses to the environment within niche boundaries. Expanding the study of niche conservatism to explore changes both at the edge of and within niche boundaries would improve the ability to assess and predict species' invasion risk or sensitivity to ongoing global change.

The American kestrel ( Falco sparverius , hereafter referred to as kestrel) has declined across much of its North American range since at least the mid‐1960s. Kestrel population dynamics have been explored through a multitude of local studies and two broad reviews of available data. Across large geographic extents, however, the demographic cause(s) of kestrel population declines remain(s) largely unknown. As part of a collaborative effort to elucidate the drivers of kestrel population declines, we developed a continental‐scale integrated population model using band‐recovery data, productivity data, and Breeding Bird Survey indices from 1986 to 2019 to estimate indices of annual population sizes, survival, and productivity rates across the continental United States. We detected a decline in population size of ~1%–2% per year. Overall estimates of population growth from 1986 to 2019 suggest a 29% decline in population size (95% CI = −34% to −23%). There was little evidence of a trend in brood size. However, survival of juvenile birds (mean = −0.015, SD = 0.008 and mean = −0.024, SD = 0.010 for females and males, respectively) and adult males (mean = −0.016, SD = 0.010) in the summer declined, suggesting that these vital rates could be contributing to declines in populations over time. Winter adult survival rates (mean = −0.004, SD = 0.009 and mean = −0.009, SD = 0.010 for females and males, respectively) also declined but to a lesser extent than summer survival. For juvenile birds, winter survival increased (mean = 0.006, SD = 0.008 and mean = 0.002, SD = 0.009 for females and males, respectively); however, this was not enough to offset declines in summer survival and annual survival rates declined over the time series. Annual adult survival was also low relative to previous research on kestrel survival rates. Given the importance of survival to population trends, our findings provide support for several previously proposed broad classes of factors potentially contributing to observed population declines: declines in arthropod prey, second‐generation rodenticides, neonicotinoid insecticides, and predation.

An atypically large outbreak of Elizabethkingia anophelis infections occurred in Wisconsin. Here we show that it was caused by a single strain with thirteen characteristic genomic regions. Strikingly, the outbreak isolates show an accelerated evolutionary rate and an atypical mutational spectrum. Six phylogenetic sub-clusters with distinctive temporal and geographic dynamics are revealed, and their last common ancestor existed approximately one year before the first recognized human infection. Unlike other E. anophelis , the outbreak strain had a disrupted DNA repair mutY gene caused by insertion of an integrative and conjugative element. This genomic change probably contributed to the high evolutionary rate of the outbreak strain and may have increased its adaptability, as many mutations in protein-coding genes occurred during the outbreak. This unique discovery of an outbreak caused by a naturally occurring mutator bacterial pathogen provides a dramatic example of the potential impact of pathogen evolutionary dynamics on infectious disease epidemiology. Elizabethkingia anophelis is an emerging pathogen of high antimicrobial resistance. Perrin and colleagues sequenced isolates of a 2015/2016 E. anophelis outbreak in Wisconsin and found substantial genetic diversity, accelerated evolutionary rate and a disruptive mutation in the DNA repair gene mutY .

The microcirculation serves crucial functions in adult heart, distinct from those carried out by epicardial vessels. Microvessels are governed by unique regulatory mechanisms, impairment of which leads to microvessel-specific pathology. There are few treatment options for patients with microvascular heart disease, primarily due to limited understanding of underlying pathology. High throughput mRNA sequencing and protein expression profiling in specific cells can improve our understanding of microvessel biology and disease at the molecular level. Understanding responses of individual microvascular cells to the same physiological or pathophysiological stimuli requires the ability to isolate the specific cell types that comprise the functional units of the microcirculation in the heart, preferably from the same heart, to ensure that different cells have been exposed to the same in-vivo conditions. We developed an integrated process for simultaneous isolation and culture of the main cell types comprising the microcirculation in adult mouse heart: endothelial cells, pericytes, and vascular smooth muscle cells. These cell types were characterized with isobaric labeling quantitative proteomics and mRNA sequencing. We defined microvascular cell proteomes, identified novel protein markers, and confirmed established cell-specific markers. Our results allow identification of unique markers and regulatory proteins that govern microvascular physiology and pathology.