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Bees require distinct foraging and nesting resources to occur in close proximity. However, spatial and temporal patterns in the availability and quantity of these resources can be affected by disturbances like wildfire. The potential for spatial or temporal separation of foraging and nesting resources is of particular concern for solitary wood‐cavity‐nesting bees as they are central‐place, short‐distance foragers once they have established their nest. Often the importance of nesting resources for bees have been tested by sampling foraging bees as a proxy, and nesting bees have rarely been studied in a community context, particularly postdisturbance. We tested how wood‐cavity‐nesting bee species richness, nesting success, and nesting and floral resources varied across gradients of wildfire severity and time‐since‐burn. We sampled nesting bees via nesting boxes within four wildfires in southwest Montana, USA, using a space‐for‐time substitution chronosequence approach spanning 3–25 years postburn and including an unburned control. We found that bee nesting success and species richness declined with increasing time postburn, with a complete lack of successful bee nesting in unburned areas. Nesting and floral resources were highly variable across both burn severity and time‐since‐burn, yet generally did not have strong effects on nesting success. Our results together suggest that burned areas may provide important habitat for wood‐cavity‐nesting bees in this system. Given ongoing fire regime shifts as well as other threats facing wild bee communities, this work helps provide essential information necessary for the management and conservation of wood‐cavity‐nesting bees. Bees require foraging and nesting resources which do not always co‐occur in space and time, and this can be exacerbated by disturbances like wildfire. We studied how wood‐cavity‐nesting bees respond to wildfire by looking at their nesting success across burn severity and time‐since‐burn. We observed nesting success to decline with greater time‐since‐burn, highlighting the importance of burned areas for wood‐cavity‐nesting bee habitat.

Intraoperative radiation therapy (IORT) delivers a single accelerated radiation dose to the breast tumor bed during breast-conserving surgery (BCS). The synergistic biologic effects of simultaneous surgery and radiation remain unclear. This study explores the cellular and molecular changes induced by IORT in the tumor microenvironment and its impact on the immune response modulation. Patients with hormone receptor (HR)-positive/HER2-negative, ductal carcinoma (DCIS), or early-stage invasive breast carcinoma undergoing BCS with margin re-excision were included. Histopathological evaluation and RNA-sequencing in the re-excision tissue were compared between patients with IORT (n=11) vs. non-IORT (n=11). Squamous metaplasia with atypia was exclusively identified in IORT specimens (63.6%, =0.004), mimicking DCIS. We then identified 1,662 differentially expressed genes (875 upregulated and 787 downregulated) between IORT and non-IORT samples. Gene ontology analyses showed that IORT was associated with the enrichment of several immune response pathways, such as inflammatory response, granulocyte activation, and T-cell activation ( <0.001). When only considering normal tissue from both cohorts, IORT was associated with intrinsic apoptotic signaling, response to gamma radiation, and positive regulation of programmed cell death ( <0.001). Using the xCell algorithm, we inferred a higher abundance of γδ T-cells, dendritic cells, and monocytes in the IORT samples. IORT induces histological changes, including squamous metaplasia with atypia, and elicits molecular alterations associated with immune response and intrinsic apoptotic pathways. The increased abundance of immune-related components in breast tissue exposed to IORT suggests a potential shift towards active immunogenicity, particularly immune-desert tumors like HR-positive/HER2-negative breast cancer.

The importance of microhabitat traits such as floral availability is well known; however, forest bee spatial dynamics have been variably studied across local to broad geographic scales. Past literature suggests that landscape factors from proximate to distal are important in determining forest bee community metrics, including richness, abundance, and taxonomic composition. Leveraging the interest and assistance of citizen science volunteers, we employed standard bee bowl trap transects across Maryland, Delaware, northern Virginia, and the District of Columbia and identified correlations between bee community composition, local and regional land cover, and broader geospatial patterns. We also identified the partial contributions of both specific species and sampling sites to total beta diversity. Various land cover metrics were significantly related to bee community structure, with bee abundance positively and negatively correlated with forest and wetland cover, respectively. In general, land cover metrics within 1000‐m buffer exhibited stronger correlations with bee communities; however, broader geographic variation, using Cartesian coordinates north and east as indices, was most significantly correlated with the bee community. Specifically, bee communities were less rich in the east and south of the study area. We also identified similar correlations with the bee community as categorized by both trophic and nesting behaviors, with both geographic northing and easting proving to be most strongly correlated with the forest bee community. Results of beta diversity and cluster analyses showed that the most species‐depauperate sites exhibited the highest contributions to beta diversity and that species‐poor sites consisted of a reduced subset of the greater community. Our results show that successful bee conservation must consider, beyond local‐scale resource availability, broad geospatial considerations and forest habitat connectivity across political and administrative boundaries.

High-severity wildfires, which can homogenize floral communities, are becoming more common relative to historic mixedseverity fire regimes in the Northern Rockies of the U.S. High-severity wildfire could negatively affect bumble bees, which are typically diet generalists, if floral species of inadequate pollen quality dominate the landscape post-burn. High-severity wildfires often require more time to return to pre-burn vegetation composition, and thus, effects of high-severity burns may persist past initial impacts. We investigated how wildfire severity (mixed-vs. high-severity) and time-since-burn affected available floral pollen quality, corbicular pollen quality, and bumble bee nutrition using percent nitrogen as a proxy for pollen quality and bumble bee nutrition. We found that community-weighted mean floral pollen nitrogen, corbicular pollen nitrogen, and bumble bee nitrogen were greater on average by 0.82%N, 0.60%N, and 1.16%N, respectively, in mixed-severity burns. This pattern of enhanced floral pollen nitrogen in mixed-severity burns was likely driven by the floral community, as community-weighted mean floral pollen percent nitrogen explained 87.4% of deviance in floral community composition. Only bee percent nitrogen varied with time-since-burn, increasing by 0.33%N per year. If these patterns persist across systems, our findings suggest that although wildfire is an essential ecosystem process, there are negative early successional impacts of high-severity wildfires on bumble bees and potentially on other pollen-dependent organisms via reductions in available pollen quality and nutrition. This work examines a previously unexplored pathway for how disturbances can influence native bee success via altering the nutritional landscape of pollen.

Across agricultural areas of the Prairie Pothole Region (PPR), floral resources are primarily found on public grasslands, roadsides, and private grasslands used as pasture or enrolled in federal conservation programs. Little research has characterized the availability of flowers across the region or identified the primary stakeholders managing lands supporting pollinators. We explored spatial and temporal variability in flower abundance and richness across multiple grassland categories (i.e. general grassland, conservation grassland, and engineered pollinator habitat) in the PPR from 2015 to 2018 and used these data to estimate the number of flowering stems present across the region on private and public land holdings. Both flowering plant abundance and richness were greatest on engineered pollinator habitat, but this land category encompassed < 0.01% of the total grassland area in the PPR. There was a steady decrease in flower abundance over the growing season across all land categories. We detected considerable variation in flower abundance and richness across grassland categories, indicating that not all natural or semi-natural covers provide similar value to pollinators. At a landscape scale, large land holdings such as privately-owned grasslands and Conservation Reserve Program lands contributed the greatest number of flowers by an order of magnitude, though these lands collectively did not support the greatest abundance of flowers per unit area. Our research depicts spatial and temporal variation in pollinator resources across the region. Further, our research will assist managers and policy makers in understanding the role of public and private lands and conservation programs in supporting pollinators.

Ecologists have taken two distinct approaches in studying the distribution and diversity of communities: a species-centric focus and an interaction-network based approach. A current frontier in community-level studies is the integration of these perspectives by investigating both simultaneously; one method for achieving this is evaluating the relative contributions of species turnover and host switching towards interaction turnover (i.e., the dissimilarity in interactions between two networks). We performed observations of plant-pollinator interactions to investigate (1) patterns in interaction turnover across spatial, temporal, and environmental gradients and (2) the relative contribution of pollinator species turnover, floral turnover, simultaneous pollinator & floral turnover, and host switching towards interaction turnover. Field work was conducted on the Beartooth Plateau, an alpine ecosystem in Montana and Wyoming, with weekly observations of plant-pollinator interactions across one growing season. Interaction turnover increased through time, with magnitudes consistently greater than 80%, even at time intervals as short as one week. Floral species turnover (41%) and simultaneous floral and pollinator species turnover (36%) accounted for almost all interaction turnover while host switching accounted for only 5%. Interaction turnover also significantly increased with spatial and elevational distance, albeit with lesser magnitudes than with temporal distance. The marginal spatial pattern was present for only some taxa ( Bombus spp. and solitary bee species), potentially indicating variable habitat use by pollinators across the landscape. Weak environmental trends may be a consequence of unmeasured environmental variables, yet our finding that environmental gradients structure plant-pollinator interaction partitions had not previously been tested with empirical data. Our observations suggest that host switching does not readily occur at the scales of alpine flowering phenology (i.e., ∼1 week); however, whether lack of host switching is indicative of inflexible pollinator foraging, or, more likely, a lack of opportunity or necessity to switch hosts, requires further investigation.

In 2017 the rusty patched bumble bee (Bombus affinis) became the first bee listed under the Endangered Species Act in the continental United States due to population declines and an 87% reduction in the species’ distribution. Bombus affinis decline began in the 1990s, predating modern bee surveying initiatives, and obfuscating drivers of decline. While understood to be a highly generalist forager, little is known about the role that resource limitation or shifting floral community composition could have played in B. affinis decline. Determining which floral species support B. affinis could assist conservation efforts where B. affinis persists and identify floral species for restoration efforts. We constructed a historical foraging profile of B. affinis via DNA sequencing of pollen from museum specimens spanning seven states collected from 1913 to 2013. Molecular analysis revealed no temporal changes in the floral richness or composition of B. affinis pollen samples across our sampling period. Likewise, we found no temporal changes in the presence or proportion of native vs. introduced species in pollen samples, though we observed much greater use of introduced floral species than previously determined for B. affinis. Floral community composition was regionally dissimilar, inconsistent with patterns of B. affinis decline by state. Our results suggest B. affinis decline was unlikely to have been driven by spatial or temporal limitations of specific floral species. This work greatly expands the known forage of B. affinis and will provide managers with insight to aid the conservation of B. affinis.

Aim Ecological theory predicts that invasive ecosystem engineers like the American beaver (Castor canadensis) in Tierra del Fuego (TDF) affect landscape-level biodiversity and ecosystem function (BEF) when engineered habitats are novel or extensive. We tested these hypotheses on freshwater BEF, sampling benthic habitat and macroinvertebrates in natural lotic (forest and grassland streams) and natural lentic habitats (bogs, lakes) and beaver-modified lentic ecosystems (active and abandoned ponds). Location Tierra del Fuego Archipelago (Chile and Argentina). Methods To determine effects on patch-scale BEF, we assessed two drivers: substrate diversity (H′) and benthic organic matter standing crop (BOM, g m -2 ). Extent of impact was estimated as relative stream length (%) for each patch type in four 1000 ha images. Results The freshwater landscape was 56% free-flowing streams (natural lotic), 13% bogs and lakes (natural lentic) and 31% active and abandoned beaver ponds (beaver lentic). While engineering significantly modified lotic habitats (converting them to ponds), the beaver ponds were largely similar to natural lentic systems, but engineered lentic patches retained more BOM. While benthic biodiversity in beaver ponds was less than streams, the assemblage contained no habitat-specific taxa and was a subset of the natural lentic community. Main conclusions Invasive beavers engineer habitats whose biodiversity is similar to the landscape's natural lentic habitats, but by increasing the surface area and unit area retention of BOM via its impoundments, this invasion augments carbon standing stock approximately 72% in watersheds. While this invasion is considered the largest alteration to TDF's forested biome in the Holocene, here we discover that its impact is to ecosystem function, rather than biodiversity in the aquatic landscape.

Fil: Anderson, Christopher Brian. Universidad Nacional de Tierra del Fuego. Instituto de Ciencias Polares, Recursos Naturales y Ambiente; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Austral de Investigaciones Científicas; Argentina. Omora Sub-Antarctic Research Alliance; Estados Unidos