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At least 1,153 records · Page 64Linked to original sources

USGS2021

Pollinator communities vary with vegetation structure and time since management within regenerating timber harvests of the Central Appalachian Mountains

Native pollinator populations across the United States are increasingly threatened by a multitude of ecological stressors. Although the drivers behind pollinator population declines are varied, habitat loss/degradation remains one of the most important threats. Forested landscapes, where the impacts of habitat loss/degradation are minimized, are known to support robust pollinator populations in eastern North America. Within heavily forested landscapes, timber management is already implemented as a means for improving forest health and enhancing wildlife habitat, however, little is known regarding the characteristics within regenerating timber harvests that affect forest pollinator populations. In 2018-19, we monitored insect pollinators in 143 regenerating (≤ 9 growing seasons post-harvest) timber harvest sites across Pennsylvania. During 1,129 survey events, we observed over 9,100 bees and butterflies, 220 blooming plant taxa, and collected over 2,200 pollinator specimens. Bee and butterfly abundance were positively associated with season-wide floral abundance and negatively associated with dense vegetation that inhibits the growth of understory floral resources. Particularly in late summer, few pollinators were observed in stands > 6 years post-harvest, with models predicting five times more bees in 1-year-old harvests than in 9-year-old harvests. Pollinator species diversity was positively associated with floral diversity and percent forb cover, and negatively associated with percent tall (>1m) sapling cover. These results suggest that regenerating timber harvests promote abundant and diverse pollinator communities in the Appalachian Mountains, though pollinator abundance declined quickly as woody stems regenerated. Ultimately, our findings contribute to a growing body of literature suggesting that dynamic forest management producing an even mix of age classes would benefit forest pollinator populations in the Central Appalachian Mountains.

Pennsylvania↗

USGS2019

Field-level characteristics influence wild bee functional guilds on public lands managed for conservation

Throughout the Midwestern US, many public lands set aside for conservation engage in management activities (e.g., agriculture) that may act as stressors on wild bee populations. Several studies have investigated how wild bees respond to large-scale agriculture production; however, there has been limited assessment of how wild bees may be impacted by agricultural activity on public lands or how local variables may influence bee communities in these same areas. In this study, we assessed the abundance and richness of wild bee floral and nesting guilds at 30 agricultural field margins located on five Conservation Areas in Missouri. Generally, regardless of guild, bee abundance and richness was greater in field margins with more floral diversity and taller vegetation. Bee guilds responded negatively to agricultural production in Conservation Areas with fewer soil- and cavity-nesting bees collected in margins adjacent to annually cropped fields. Although fewer diet specialists were collected, specialist bee abundance and richness was greater in margins near fields that were uncropped (i.e., vegetated, but not row-cropped) during the previous year. Overall, the percentage of trees and shrubs within 800 m of study fields (i.e., “woodland”) was negatively associated with abundance and richness of bees, but specifically, reduced richness of soil-nesters and diet specialists. Our findings indicate agricultural management activities on public lands may lead to decreased abundance and richness of wild bee guilds. If public lands are to be managed for species diversity, including wild bees, maintaining diverse plant communities with taller vegetation (>100 cm) near cultivated fields and/or modifying agricultural production practices on public lands may greatly improve the conservation of local bee communities.

Global Ecology and Conservation↗

USGS2017

Chemistry of diagenetic features analyzed by ChemCam at Pahrump Hills, Gale crater, Mars

The Curiosity rover's campaign at Pahrump Hills provides the first analyses of lower Mount Sharp strata. Here we report ChemCam elemental composition of a diverse assemblage of post-depositional features embedded in, or cross-cutting, the host rock. ChemCam results demonstrate their compositional diversity, especially compared to the surrounding host rock: (i) Dendritic aggregates and relief enhanced features, characterized by a magnesium enhancement and sulfur detection, and interpreted as Mg-sulfates; (ii) A localized observation that displays iron enrichment associated with sulfur, interpreted as Fe-sulfate; (iii) Dark raised ridges with varying Mg- and Ca-enriched compositions compared to host rock; (iv) Several dark-toned veins with calcium enhancement associated with fluorine detection, interpreted as fluorite veins. (v) Light-toned veins with enhanced calcium associated with sulfur detection, and interpreted as Ca-sulfates. The diversity of the Pahrump Hills diagenetic assemblage suggests a complex post-depositional history for fine-grained sediments for which the origin has been interpreted as fluvial and lacustrine. Assessment of the spatial and relative temporal distribution of these features shows that the Mg-sulfate features are predominant in the lower part of the section, suggesting local modification of the sediments by early diagenetic fluids. In contrast, light-toned Ca-sulfate veins occur in the whole section and cross-cut all other features. A relatively late stage shift in geochemical conditions could explain this observation. The Pahrump Hills diagenetic features have no equivalent compared to targets analyzed in other locations at Gale crater. Only the light-toned Ca-sulfate veins are present elsewhere, along Curiosity's path, suggesting they formed through a common late-stage process that occurred at over a broad area.

Icarus↗

USGS2011

Genetic characterisation of Toxoplasma gondii in wildlife from North America revealed widespread and high prevalence of the fourth clonal type

Little is known of the genetic diversity of Toxoplasma gondii circulating in wildlife. In the present study wild animals, from the USA were examined for T. gondii infection. Tissues of naturally exposed animals were bioassayed in mice for isolation of viable parasites. Viable T. gondii was isolated from 31 animals including, to our knowledge for the first time, from a bald eagle ( Haliaeetus leucocephalus ), five gray wolves ( Canis lupus ), a woodrat ( Neotoma micropus) , and five Arctic foxes (Alopex lagopus) . Additionally, 66 T. gondii isolates obtained previously, but not genetically characterised, were revived in mice. Toxoplasma gondii DNA isolated from these 97 samples (31 + 66) was characterised using 11 PCR-restriction fragment length polymorphism (RFLP) markers (SAG1, 5′- and 3′-SAG2, alt.SAG2, SAG3, BTUB, GRA6, c22–8, c29–2, L358, PK1 and Apico). A total of 95 isolates were successfully genotyped. In addition to clonal Types II, and III, 12 different genotypes were found. These genotype data were combined with 74 T. gondii isolates previously characterised from wildlife from North America and a composite data set of 169 isolates comprised 22 genotypes, including clonal Types II, III and 20 atypical genotypes. Phylogenetic network analysis showed limited diversity with dominance of a recently designated fourth clonal type (Type 12) in North America, followed by the Type II and III lineages. These three major lineages together accounted for 85% of strains in North America. The Type 12 lineage includes previously identified Type A and X strains from sea otters. This study revealed that the Type 12 lineage accounts for 46.7% (79/169) of isolates and is dominant in wildlife of North America. No clonal Type I strain was identified among these wildlife isolates. These results suggest that T. gondii strains in wildlife from North America have limited diversity, with the occurrence of only a few major clonal types.

International Journal for Parasitology↗

USGS2016

Ectoparasitism on deep-sea fishes in the western North Atlantic: In situ observations from ROV surveys

A complete understanding of how parasites influence marine ecosystem functioning requires characterizing a broad range of parasite-host interactions while determining the effects of parasitism in a variety of habitats. In deep-sea fishes, the prevalence of parasitism remains poorly understood. Knowledge of ectoparasitism, in particular, is limited because collection methods often cause dislodgment of ectoparasites from their hosts. High-definition video collected during 43 remotely operated vehicle surveys (2013–2014) provided the opportunity to examine ectoparasitism on fishes across habitats (open slope, canyon, seamount, cold seep) and depths (494–4689 m) off the northeastern U.S., while providing high-resolution images and valuable observations of fish behavior. Only 9% (n = 125 individuals) of all observed fishes (25 species) were confirmed with ectoparasites, but higher percentages (&sim;33%) were observed for some of the most abundant fish species (e.g., Antimora rostrata) . Ectoparasites included two copepod families (Lernaeopodidae, Sphyriidae) that infected four host species, two isopod families (Cymothoidae, Aegidae) that infected three host species, and one isopod family (Gnathiidae) that infected 19 host species. Hyperparasitism was also observed. As host diversity declined with depth, ectoparasite diversity declined; only gnathiids were observed at depths down to 3260 m. Thus, gnathiids appear to be the most successful group to infect a diversity of fishes across a broad depth range in the deep sea. For three dominant fishes ( A. rostrata , Nezumia bairdii , Synaphobranchus spp.), the abundance and intensity of ectoparasitism peaked in different depths and habitats depending on the host species examined. Notably, gnathiid infections were most intense on A. rostrata , particularly in submarine canyons, suggesting that these habitats may increase ectoparasite infections. Although ectoparasitism is often overlooked in deep-sea benthic communities, our results demonstrate that it occurs widely across a variety of habitats, depths, and locations and is a significant component of deep-sea biodiversity.

New England Seamount Chain↗

USGS2008

Temporal variation in the arthropod community of desert riparian habitats with varying amounts of saltcedar (Tamarix ramosissima)

We used Malaise traps to examine the aerial arthropod community in riparian habitats dominated by native willow, exotic saltcedar, or a mixture of these two tree species in central Arizona, USA. Over the course of three sampling periods per year in 2003 and 2004, native habitats had significantly greater diversity (Shannon-Wiener) and supported different arthropod communities compared to exotic habitats, while mixed habitats were intermediate in terms of diversity and supported an arthropod community statistically indistinguishable from the exotic site. The composition of arthropod communities varied significantly between the two years, and there was an approximately two-fold difference in richness and diversity. Overall, we documented complex interactions indicating that differences among the arthropod communities of riparian habitats may be driven not only by the composition of native and exotic tree species making up these habitats, but also by year and season of arthropod sampling.

Journal of Arid Environments↗

USGS2024

Strategic restoration planning for land birds in the Colorado River Delta, Mexico

Ecological restoration is an essential strategy for mitigating the current biodiversity crisis, yet restoration actions are costly. We used systematic conservation planning principles to design an approach that prioritizes restoration sites for birds and tested it in a riparian forest restoration program in the Colorado River Delta. Restoration goals were to maximize the abundance and diversity of 15 priority birds with a variety of habitat preferences. We built abundance models for priority birds based on the current landscape, and predicted bird distributions and relative abundances under a scenario of complete riparian forest restoration throughout our study area. Then, we used Zonation conservation planning software to rank this restored landscape based on core areas for all priority birds. The locations with the highest ranks represented the highest priorities for restoration and were located throughout the river reach. We optimized how much of the available landscape to restore by simulating restoration of the top 10–90% of ranked sites in 10% intervals. We found that total diversity was maximized when 40% of the landscape was restored, and mean relative abundance was maximized when 80% of the landscape was restored. The results suggest that complete restoration is not optimal for this community of priority birds and restoration of approximately 60% of the landscape would provide a balance between maximum relative abundance and diversity. Subsequent planning efforts will combine our results with an assessment of restoration costs to provide further decision support for the restoration-siting process. Our approach can be applied to any landscape-scale restoration program to improve the return on investment of limited economic resources for restoration.

Colorado River Delta↗

USGS2017

Community stability within the St. Marys River fish community: Evidence from trawl surveys

A trawl survey was conducted in the Saint Marys River during 2010–2011 and we compared our results to a prior trawl survey conducted during 1979–1983 to look for long-term changes in the fish community, especially in terms of changes induced by invasive species. We found no substantive temporal differences in fish density, fish biomass, or fish diversity; lower trawl biomass during 2010–2011 was likely a result of day versus night trawling. The Saint Marys River remains a center of high fish diversity, invasive species remain rare, and the system continues to exhibit overall long-term stability. Trawling captured a wide range of fish species, but was likely not an effective stock assessment tool for managed game fish because catch rates were low or variable for all game species except yellow perch. Trawling appeared to be an effective tool for sampling connecting channel diversity, especially when large numbers of individuals are needed for directed studies, but annual sampling would be needed to use data to assess recruitment.

St. Marys River↗

USGS2017

Genetic structure of muskellunge in the Great Lakes region and the effects of supplementation on genetic integrity of wild populations

Muskellunge ( Esox masquinongy ) are important apex predators that support numerous recreational fisheries throughout the Great Lakes region. Declines in muskellunge abundance from historical overharvest and environmental degradation have threatened the viability of many populations and prompted significant restoration efforts that often include stocking. The goal of our study was to investigate contemporary population structure and genetic diversity in 42 populations of muskellunge sampled across the Great Lakes region to inform future management and supplementation practices. We genotyped 1896 muskellunge ( N = 10–123/population) at 13 microsatellite loci. The greatest genetic variation was between populations of Great Lakes origin and populations of Northern (inland) origin, with both groups also exhibiting significant substructure (overall F ST = 0.23). Genetic structure was generally correlated with geography; however, we only found marginal evidence of isolation by distance, likely due to high genetic differentiation among proximate populations. Measures of genetic diversity were moderate across most populations, but some populations displayed low diversity consistent with small population sizes or historical bottlenecks. Many of the populations studied displayed evidence of historic introductions and supplemental stocking, including the presence of individuals with primarily non-native ancestry as well as interlineage hybrids. Our results suggest that the historic population structure of muskellunge is largely intact across the Great Lakes region, but also that stocking practices have altered this structure to some degree. We suggest that future supplementation practices use local sources where possible, and incorporate genetic tools including broodstock screening to ensure that non-native muskellunge are not used to supplement wild populations.

Great Lakes↗

USGS2021

Towards improving an Area of Concern: Main-channel habitat rehabilitation priorities for the Maumee River

The Maumee River watershed in the Laurentian Great Lakes Basin has been impacted by decades of pollution and habitat modification due to human settlement and development. As such, the lower 35 km of the Maumee River and several smaller adjacent watersheds comprising over 2000 km 2 were designated the Maumee Area of Concern (AOC) under the revised Great Lakes Water Quality Agreement in 1987. As part of pre-rehabilitation assessments in the Maumee AOC, we assessed fish and invertebrate communities in river km 24–11 of the Maumee River to identify: 1) areas that exhibit the highest biodiversity, 2) habitat characteristics associated with high biodiversity areas, 3) areas in need of protection from further degradation, and 4) areas that could feasibly be rehabilitated to increase biodiversity. Based on benthic trawl data, shallow water habitats surrounding large island complexes had the highest fish diversity and catch per unit effort (CPUE). Electrofishing displayed similar fish diversity and CPUE patterns across habitat types early in the study but yielded no discernable fish diversity or CPUE patterns towards the end of our study. Although highly variable among study sites, macroinvertebrate density was greatest in shallow water habitats <2.5 m and around large island complexes. Our results provide valuable baseline data that could act as a foundation for developing rehabilitation strategies in the lower Maumee River and for assessing the effectiveness of future aquatic habitat rehabilitation projects. In addition to increasing in-channel habitat, watershed-scale improvements of water quality might be necessary to ensure rehabilitation strategies are successful.

Ohio↗

USGS2004

Overland flow generation in two lithologically distinct rainforest catchments

Streams on uniformly rainforest-covered, but lithologically very diverse Barro Colorado Island in central Panama?? show remarkable differences in their runoff response to rainfall. This lithological diversity is reflected in equally diverse soilscapes, and our objective was to test the hypothesis that contrasting runoff responses derive from soilscape features that control the generation of overland flow. We determined the soil saturated hydraulic conductivity (Ks) of two neighboring, but hydrologically contrasting catchments (Lutz Creek with a flashy and Conrad Trail with a delayed response to rainfall), and quantified the spatial and temporal frequency of overland flow occurrence. The median Ks values at a depth of 12.5 cm are large enough to rule out Hortonian overland flow, but a marked decrease in K s in Lutz Creek catchment at 30 cm suggests the formation of a perched water table and the generation saturation overland flow; the decrease in Ks in the Conrad Trail catchment is more gradual, and a perched water table is expected to form only at depths below 50 cm. In Lutz Creek, overland flow was generated frequently in time and space and regardless of topographic position, including near the interfluve, with very low thresholds of storm magnitude, duration, intensity and antecedent wetness, whereas in Conrad Trail, overland flow was generated much less frequently and then only locally. We conclude that soilscape features and microtopography are important controls of overland flow generation in these catchments. Our results contribute to the growing evidence that overland flow and forests are not a priori a contradiction in terms. ?? 2004 Elsevier B.V. All rights reserved.

Journal of Hydrology↗

USGS2026

Exploring trip preference heterogeneity in away-from-home birdwatchers using a discrete choice experiment

Birdwatching has grown in popularity worldwide and birdwatchers have emerged as an important constituency for wildlife and habitat conservation. To help promote wetland conservation, agencies and managers need to understand birdwatchers' desired trip experiences. We conducted national web-based surveys of American and Canadian birdwatchers by employing a discrete choice experiment to explore birdwatching trip preferences. We also collected information about participation in birdwatching and recreation specialization. We used latent class analysis to identify groups of birdwatchers with similar preferences. Our analysis indicated that birdwatchers were not homogeneous in their preferences. The seven attributes and associated attribute levels that were presented to participants (travel distance, site naturalness, bird rarity, the presence of waterfowl and wetlands, ease of access, species diversity and the number of birds seen) were all relevant, to varying degrees, in decisions about whether to take a birdwatching trip. We identified five latent classes of birdwatchers in the United States and Canada. ‘Nature seekers’ prioritised setting naturalness; ‘local birdwatchers’ strongly preferred shorter travel distances; ‘list-focused birdwatchers’ prioritised bird rarity and diversity; whereas ‘site-focused birdwatchers’ prioritised on-site characteristics above bird-related characteristics; and ‘casual birdwatchers’ were most likely to opt out of taking a trip. We found variation in recreation specialization and avidity levels across all the classes. Some classes ( e.g. list-focused birdwatchers) tend to be more specialised and more avid than others ( e.g. casual and local birdwatchers). Recognising the diversity of birdwatcher trip preferences can help outdoor recreation and wildlife managers provide a variety of suitable settings, services, and experiences.

Journal of Outdoor Recreation and Tourism↗

USGS2011

Mechanical analysis of fault slip data: Implications for paleostress analysis

Stress inversions are a useful and popular tool for structural geologist and seismologist alike. These methods were first introduced by Wallace (1951) and Bott (1959) and subsequent studies continue to be based on their assumptions: the remote stress tensor is spatially uniform for the rock mass containing the faults and temporally constant over the history of faulting in that region, and the slip on each fault surface has the same direction and sense as the maximum shear stress resolved on that surface from the remote stress tensor. Furthermore, successful implementation requires that slip accumulates on faults of diverse orientation. Many studies employ these methods on isolated faults or on fault systems with limited ranges of orientations, which can lead to erroneous results. We propose a new method that incorporates the effects of mechanical interaction of the entire fault or fault system, and solves the complete mechanical problem rather than employing empirical relationships between slip and stress or strain (or strain rate). The method requires knowledge of the fault geometry and information on at least one slip vector component along portions of the known fault geometry. For example, if throw is known, the strike-slip component can be solved for. We test the method using a single synthetic fault with anisotropic roughness similar to that measured at fault outcrops. While the orientation of remote stress may be determined precisely, the lack of diverse fault orientations introduces a systematic error in the remote stress ratio. We further test the effect of diversity of fault orientations and find that Wallace–Bott type inversions do not perform as well for limited ranges of orientations when compared to the proposed method. Finally, we use published data from the 1999 Chi-Chi, Taiwan, earthquake, and find that the method using surface data only, and surface data with subsurface focal mechanisms, produce similar results. The resulting stress orientations are in good agreement with results from Wallace–Bott inversions. Furthermore, the slip distribution is in general agreement with kinematic slip inversions using coseismic surface deformation. Stress inversion methods using fault slip data can thus be improved upon, significantly in some cases, by solving a mechanical boundary value problem that takes into account the geometry of faults or fault systems. As a bonus, the solution provides the stress, strain, and displacement fields throughout the region and the slip distributions on the faults.

Journal of Structural Geology↗

USGS2009

Foraminiferal assemblages in Biscayne Bay, Florida, USA: Responses to urban and agricultural influence in a subtropical estuary

This study assessed foraminiferal assemblages in Biscayne Bay, Florida, a heavily utilized estuary, interpreting changes over the past 65 years and providing a baseline for future comparisons. Analyses of foraminiferal data at the genus level revealed three distinct biotopes. The assemblage from the northern bay was characterized by stress-tolerant taxa, especially Ammonia , present in low abundances (∼2.0 × 10 3 foraminifers/gram) though relatively high diversity (∼19 genera/sample). The southwestern margin of the bay was dominated by Ammonia and Quinqueloculina , an assemblage characterized by the lowest diversities (∼12 genera/sample) and highest abundances (∼1.1 × 10 4 foraminifers/gram), influenced by both reduced salinity and elevated organic-carbon concentrations. A diverse assemblage of smaller miliolids and rotaliids (∼26 genera/sample) characterized the open-bay assemblage, which also had a significant component (∼10%) of taxa that host algal endosymbionts. In the past 65 years, populations of symbiont-bearing taxa, which are indicators of normal-marine conditions, have decreased while stress-tolerant taxa, especially Ammonia spp., have increased in predominance.

Florida↗

USGS2016

Temporal, geographic, and host distribution of avian paramyxovirus 1 (Newcastle disease virus)

Newcastle disease is caused by virulent forms of avian paramyxovirus of serotype 1 (APMV-1) and has global economic importance. The disease reached panzootic proportions within two decades after first being identified in 1926 in the United Kingdom and Indonesia and still remains endemic in many countries across the world. Here we review information on the host, temporal, and geographic distribution of APMV-1 genetic diversity based on the evolutionary systematics of the complete coding region of the fusion gene. Strains of APMV-1 are phylogenetically separated into two classes (class I and class II) and further classified into genotypes based on genetic differences. Class I viruses are genetically less diverse, generally present in wild waterfowl, and are of low virulence. Class II viruses are genetically and phenotypically more diverse, frequently isolated from poultry with occasional spillovers into wild birds, and exhibit a wider range of virulence. Waterfowl, cormorants, and pigeons are natural reservoirs of all APMV-1 pathotypes, except viscerotropic velogenic viruses for which natural reservoirs have not been identified. Genotypes I and II within class II include isolates of high and low virulence, the latter often being used as vaccines. Viruses of genotypes III and IX that emerged decades ago are now isolated rarely, but may be found in domestic and wild birds in China. Containing only virulent viruses and responsible for the majority of recent outbreaks in poultry and wild birds, viruses from genotypes V, VI, and VII, are highly mobile and have been isolated on different continents. Conversely, virulent viruses of genotypes XI (Madagascar), XIII (mainly Southwest Asia), XVI (North America) and XIV, XVII and XVIII (Africa) appear to have a more limited geographic distribution and have been isolated predominantly from poultry.

Infection, Genetics and Evolution↗

USGS2017

Evaluating the impact of irrigation on surface water – groundwater interaction and stream temperature in an agricultural watershed

Changes in groundwater discharge to streams caused by irrigation practices can influence stream temperature. Observations along two currently flood-irrigated reaches in the 640-square-kilometer upper Smith River watershed, an important agricultural and recreational fishing area in west-central Montana, showed a downstream temperature decrease resulting from groundwater discharge to the stream. A watershed-scale coupled surface water and groundwater flow model was used to examine changes in streamflow, groundwater discharge to the stream and stream temperature resulting from irrigation practices. The upper Smith River watershed was used to develop the model framework including watershed climate, topography, hydrography, vegetation, soil properties and current irrigation practices. Model results were used to compare watershed streamflow, groundwater recharge, and groundwater discharge to the stream for three scenarios: natural, pre-irrigation conditions (PreIrr); current irrigation practices involving mainly stream diversion for flood and sprinkler irrigation (IrrCurrent); and a hypothetical scenario with only groundwater supplying sprinkler irrigation (IrrGW). Irrigation increased groundwater recharge relative to natural PreIrr conditions because not all applied water was removed by crop evapotranspiration. Groundwater storage and groundwater discharge to the stream increased relative to natural PreIrr conditions when the source of irrigation water was mainly stream diversion as in the IrrCurrent scenario. The hypothetical IrrGW scenario, in which groundwater withdrawals were the sole source of irrigation water, resulted in widespread lowering of the water table and associated decreases in groundwater storage and groundwater discharge to the stream. A mixing analysis using model predicted groundwater discharge along the reaches suggests that stream diversion and flood irrigation, represented in the IrrCurrent scenario, has led to cooling of stream temperatures relative to natural PreIrr conditions improving fish thermal habitat. However, the decrease in groundwater discharge in the IrrGW scenario resulting from large-scale groundwater withdrawal for irrigation led to warmer than natural stream temperatures and possible degradation of fish habitat.

Montana↗

USGS2021

Impacts of neonicotinoid seed treatments on the wild bee community in agricultural field margins

Wild bees support global agroecosystems via pollination of agricultural crops and maintaining diverse plant communities. However, with an increased reliance on pesticides to enhance crop production, wild bee communities may inadvertently be affected through exposure to chemical residues. Laboratory and semi-field studies have demonstrated lethal and sublethal effects of neonicotinoids on limited genera (e.g., Apis , Bombus , Megachile ), yet full field studies evaluating impacts to wild bee communities remain limited. Here, we conducted a two-year field study to assess whether neonicotinoid seed treatment and presence in environmental media (e.g., soil, flowers) influenced bee nest and diet guild abundance and richness. In 2017 and 2018, we planted 23 Missouri agricultural fields to soybeans ( Glycine max) using one of three seed treatments: untreated (no insecticide), treated (imidacloprid), or previously-treated (untreated, but neonicotinoid use prior to 2017). During both years, wild bees were collected in study field margins monthly (May to September) in tandem with soil and flowers from fields and field margins that were analyzed for neonicotinoid residues. Insecticide presence in soils and flowers varied over the study with neonicotinoids infrequently detected in both years within margin flowers (0%), soybean flowers (<1%), margin soils (<8%), and field soils (~39%). Wild bee abundance and species richness were not significantly different among field treatments. In contrast, neonicotinoid presence in field soils was associated with significantly lower richness (ground- and aboveground-nesting, diet generalists) of wild bee guilds. Our findings support that soil remains an underexplored route of exposure and long-term persistence of neonicotinoids in field soils may lead to reduced diversity in regional bee communities. Future reduction or elimination of neonicotinoid seed treatment use on areas managed for wildlife may facilitate conservation goals to sustain viable, diverse wild bee populations.

Missouri↗

USGS2023

Understanding ecological response to physical characteristics in side channels of a large floodplain-river ecosystem

Side channels in large floodplain rivers serve a variety of important ecological roles, particularly in reaches where habitat conditions have been degraded or diminished. We developed hypotheses regarding side channel ecological structure whereby we expected species richness of young-of-year fishes to generally be higher in shallower, more physically heterogeneous side channels with lower velocities, with differences based on reproductive guild. We also hypothesized species richness of adult fishes to be higher in side channels with greater heterogeneity that could support diverse foraging resources and provide refugia during extreme flow conditions. To test these hypotheses, we used a 28-year fish community dataset from the Upper Mississippi and Illinois Rivers. Across six study reaches, we assessed metrics of side channel physical size, heterogeneity, and connectivity that were hypothesized to explain variance of fish community response, while accounting for site-level factors across 52 side channels using multilevel models. We then used these side channel-level characteristics in a K-means cluster analysis to classify 1126 side channels across 32 reaches of the river system. Our results indicated that the relative explanatory contributions of physical metrics varied by response variable, providing varying evidence in support of our hypotheses, and indicating that different forms of heterogeneity matter in different ways. Side channel-level factors were more explanatory of fish community responses in side channels of upstream reaches compared to downstream reaches and percent wet forest was the most explanatory side channel-level factor of fish community responses across all models. Our classification of side channels indicated strong spatial contrasts in the abundance and diversity of side channels across reaches. Scaling up to understand how the diversity and abundance of different types of side channels contributes to landscape-scale ecological functions and processes would be useful for establishing targets for reach-scale physical heterogeneity.

Upper Mississippi River and Illinois River↗