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At least 307 records · Page 17Linked to original sources

USGS2015

Mountain pine beetle host selection between lodgepole and ponderosa pines in the southern Rocky Mountains

Recent evidence of range expansion and host transition by mountain pine beetle ( Dendroctonus ponderosae Hopkins; MPB) has suggested that MPB may not primarily breed in their natal host, but will switch hosts to an alternate tree species. As MPB populations expanded in lodgepole pine forests in the southern Rocky Mountains, we investigated the potential for movement into adjacent ponderosa pine forests. We conducted field and laboratory experiments to evaluate four aspects of MPB population dynamics and host selection behavior in the two hosts: emergence timing, sex ratios, host choice, and reproductive success. We found that peak MPB emergence from both hosts occurred simultaneously between late July and early August, and the sex ratio of emerging beetles did not differ between hosts. In two direct tests of MPB host selection, we identified a strong preference by MPB for ponderosa versus lodgepole pine. At field sites, we captured naturally emerging beetles from both natal hosts in choice arenas containing logs of both species. In the laboratory, we offered sections of bark and phloem from both species to individual insects in bioassays. In both tests, insects infested ponderosa over lodgepole pine at a ratio of almost 2:1, regardless of natal host species. Reproductive success (offspring/female) was similar in colonized logs of both hosts. Overall, our findings suggest that MPB may exhibit equally high rates of infestation and fecundity in an alternate host under favorable conditions.

Rocky Mountains↗

USGS2025

Elevated mercury concentrations in riparian predators unaccounted for by trophic magnification

Riparian predators integrate both nutrients and contaminants from neighboring aquatic systems through their predation of emerging aquatic insects. The reliance of some riparian taxa on aquatic subsidies has led to them to being utilized as biosentinels of aquatic contamination, often justified through stable isotope studies (δ 13 C, δ 15 N) and trophic magnification models. However, evidence suggests that both isotopic signatures and contaminant burdens can be altered during insect metamorphosis, which could propagate to riparian predators. Here, we measured total mercury and δ 15 N in riparian and aquatic organisms in the headwater streams of southern Appalachia to compare biomagnification in both systems. We found that biomagnification rates were similar, but that mercury concentrations in riparian organism were approximately six times higher than neighboring aquatic organisms. We propose possible ecological mechanisms, occurring separately or simultaneously, that might explain these surprising observations: (1) metamorphosis bioamplifies mercury, (2) metamorphosis enriches δ 15 N values, and/or (3) the fractionation of δ 15 N that occurs during predation is less for the observed riparian predators than for the aquatic organisms. Further study is needed to elucidate the exact mechanism driving elevated mercury concentrations in riparian predators.

Environmental Science & Technology↗

USGS2019

Perspectives and challenges for the use of radar in biological conservation

Radar is at the forefront for the study of broad‐scale aerial movements of birds, bats and insects and related issues in biological conservation. Radar techniques are especially useful for investigating species which fly at high altitudes, in darkness, or which are too small for applying electronic tags. Here, we present an overview of radar applications in biological conservation and highlight its future possibilities. Depending on the type of radar, information can be gathered on local‐ to continental‐scale movements of airborne organisms and their behaviour. Such data can quantify flyway usage, biomass and nutrient transport (bioflow), population sizes, dynamics and distributions, times and dimensions of movements, areas and times of mass emergence and swarming, habitat use and activity ranges. Radar also captures behavioural responses to anthropogenic disturbances, artificial light and man‐made structures. Weather surveillance and other long‐range radar networks allow spatially broad overviews of important stopover areas, songbird mass roosts and emergences from bat caves. Mobile radars, including repurposed marine radars and commercially dedicated ‘bird radars’, offer the ability to track and monitor the local movements of individuals or groups of flying animals. Harmonic radar techniques have been used for tracking short‐range movements of insects and other small animals of conservation interest. However, a major challenge in aeroecology is determining the taxonomic identity of the targets, which often requires ancillary data obtained from other methods. Radar data have become a global source of information on ecosystem structure, composition, services and function and will play an increasing role in the monitoring and conservation of flying animals and threatened habitats worldwide.

Ecography↗

USGS2012

Optimal temperature for malaria transmission is dramaticallylower than previously predicted

The ecology of mosquito vectors and malaria parasites affect the incidence, seasonal transmission and geographical range of malaria. Most malaria models to date assume constant or linear responses of mosquito and parasite life-history traits to temperature, predicting optimal transmission at 31 °C. These models are at odds with field observations of transmission dating back nearly a century. We build a model with more realistic ecological assumptions about the thermal physiology of insects. Our model, which includes empirically derived nonlinear thermal responses, predicts optimal malaria transmission at 25 °C (6 °C lower than previous models). Moreover, the model predicts that transmission decreases dramatically at temperatures > 28 °C, altering predictions about how climate change will affect malaria. A large data set on malaria transmission risk in Africa validates both the 25 °C optimum and the decline above 28 °C. Using these more accurate nonlinear thermal-response models will aid in understanding the effects of current and future temperature regimes on disease transmission.

Ecology Letters↗

USGS2020

Mountain stoneflies may tolerate warming streams: Evidence from organismal physiology and gene expression

Rapid glacier recession is altering the physical conditions of headwater streams. Stream temperatures are predicted to rise and become increasingly variable, putting entire meltwater-associated biological communities at risk of extinction. Thus, there is a pressing need to understand how thermal stress affects mountain stream insects, particularly where glaciers are likely to vanish on contemporary timescales. In this study, we measured the critical thermal maximum (CT MAX ) of stonefly nymphs representing multiple species and a range of thermal regimes in the high Rocky Mountains, USA. We then collected RNA-sequencing data to assess how organismal thermal stress translated to the cellular level. Our focal species included the meltwater stonefly, Lednia tumana , which was recently listed under the U.S. Endangered Species Act due to climate-induced habitat loss. For all study species, critical thermal maxima (CT MAX > 20°C) far exceeded the stream temperatures mountain stoneflies experience (<10°C). Moreover, while evidence for a cellular stress response was present, we also observed constitutive expression of genes encoding proteins known to underlie thermal stress (i.e., heat shock proteins) even at low temperatures that reflected natural conditions. We show that high-elevation aquatic insects may not be physiologically threatened by short-term exposure to warm temperatures and that longer-term physiological responses or biotic factors (e.g., competition) may better explain their extreme distributions.

Global Change Biology↗

USGS2008

Assessing streamflow characteristics as limiting factors on benthic invertebrate assemblages in streams across the western United States

1. Human use of land and water resources modifies many streamflow characteristics, which can have significant ecological consequences. Streamflow and invertebrate data collected at 111 sites in the western U.S.A. were analysed to identify streamflow characteristics (magnitude, frequency, duration, timing and variation) that are probably to limit characteristics of benthic invertebrate assemblages (abundance, richness, diversity and evenness, functional feeding groups and individual taxa) and, thus, would be important for freshwater conservation and restoration. Our analysis investigated multiple metrics for each biological and hydrological characteristic, but focuses on 14 invertebrate metrics and 13 streamflow metrics representing the key associations between streamflow and invertebrates. 2. Streamflow is only one of many environmental and biotic factors that influence the characteristics of invertebrate assemblages. Although the central tendency of invertebrate assemblage characteristics may not respond to any one factor across a large region like the western U.S.A., we postulate that streamflow may limit some invertebrates. To assess streamflow characteristics as limiting factors on invertebrate assemblages, we developed a nonparametric screening procedure to identify upper (ceilings) or lower (floors) limits on invertebrate metrics associated with streamflow metrics. Ceilings and floors for selected metrics were then quantified using quantile regression. 3. Invertebrate assemblages had limits associated with all streamflow characteristics that we analysed. Metrics of streamflow variation at daily to inter-annual scales were among the most common characteristics associated with limits on invertebrate assemblages. Baseflow recession, daily variation and monthly variation, in streamflow were associated with the largest number of invertebrate metrics. Since changes in streamflow variation are often a consequence of hydrologic alteration, they may serve as useful indicators of ecologically significant changes in streamflow and as benchmarks for managing streamflow for ecological objectives. 4. Relative abundance of Plecoptera, richness of non-insect taxa and relative abundance of intolerant taxa were associated with multiple streamflow metrics. Metrics of sensitive taxa (Ephemeroptera, Plecoptera and Trichoptera), and intolerant taxa generally had ceilings associated with flow metrics while metrics of tolerant taxa, non-insects, dominance and chironomids generally had floors. Broader characteristics of invertebrate assemblages such as abundance and richness had fewer limits, but these limits were nonetheless associated with a broad range of streamflow characteristics.

Freshwater Biology↗

USGS2011

Diet composition and feeding patterns of adult shovelnose sturgeon (Scaphirhynchus platorynchus) in the lower Platte River, Nebraska, USA

Two-hundred and seven adult shovelnose sturgeon ranging from 450 to 718 mm in length were sampled from June to October 2001 and May to July 2002 to determine diet composition and feeding patterns in the lower Platte River. Shovelnose sturgeon fed primarily upon aquatic insect larvae and nymphs (>99% composition by number). Diptera of the family Chironomidae were the dominant prey items in both years and composed 98.1% of the shovelnose sturgeon diet in 2001 and 96.8% in 2002. Chironomidae were primarily represented by the four genera Paracladopelma , Chernovskiia , Saetheria and Robackia accounting for 90.2% of the ingested prey items in 2001 and 83.6% in 2002. In addition, shovelnose sturgeon showed in both years a generalized feeding pattern towards Ephemeroptera of the families Isonychiidae and Caenidae, as well as Trichoptera of the family Hydropsychidae. Other aquatic insects, terrestrial invertebrates and fishes were found infrequently and in low numbers in shovelnose sturgeon diets. The four most abundant Chironomidae genera are often found on sand and the high abundance of these taxa in the diet suggests that shovelnose sturgeon feed primarily near or on this substrate type. This highlights the importance of habitats that provide sand substrate for shovelnose sturgeon foraging in the lower Platte River.

Nebraska↗

USGS2015

Temperate forest health in an era of emerging megadisturbance

Although disturbances such as fire and native insects can contribute to natural dynamics of forest health, exceptional droughts, directly and in combination with other disturbance factors, are pushing some temperate forests beyond thresholds of sustainability. Interactions from increasing temperatures, drought, native insects and pathogens, and uncharacteristically severe wildfire are resulting in forest mortality beyond the levels of 20th-century experience. Additional anthropogenic stressors, such as atmospheric pollution and invasive species, further weaken trees in some regions. Although continuing climate change will likely drive many areas of temperate forest toward large-scale transformations, management actions can help ease transitions and minimize losses of socially valued ecosystem services.

Science↗

USGS2025

Rapid butterfly declines across the United States during the 21st century

Reports of declining insect populations have received widespread media attention, but evidence for declines has been variable across regions and taxonomic groups. Edwards et al . examined trends in the most surveyed taxon: butterflies (see the Perspective by Inouye). Combining data from 35 citizen science programs across the continental US, the authors found declines in overall butterfly abundance over the past 20 years across almost all major regions. Two-thirds of studied species showed declines of more than 10%. Many insects have the potential for rapid population growth and recovery, but habitat restoration, species-specific interventions, and reducing pesticide use are all likely needed to curb population declines.

contiguous United States↗

USGS2000

Trophic ecology of largemouth bass and northern pike in allopatric and sympatric assemblages in northern boreal lakes

Largemouth bass ( Micropterus salmoides ) and northern pike ( Esox lucius ) are top predators in the food chain in most aquatic environments that they occupy; however, limited information exists on species interactions in the northern reaches of largemouth bass distribution. We investigated the seasonal food habits of allopatric and sympatric assemblages of largemouth bass and northern pike in six interior lakes within Voyageurs National Park, Minnesota. Percentages of empty stomachs were variable for largemouth bass (38-54%) and northern pike (34.7-66.7%). Fishes (mainly yellow perch, Perca flavescens ) comprised greater than 60% (mean percent mass, MPM) of the northern pike diet during all seasons in both allopatric and sympatric assemblages. Aquatic insects (primarily Odonata and Hemiptera) were important in the diets of largemouth bass in all communities (0.0-79.7 MPM). Although largemouth bass were observed in the diet of northern pike, largemouth bass apparently did not prey on northern pike. Seasonal differences were observed in the proportion of aquatic insects ( P = 0.010) and fishes ( P = 0.023) in the diets of northern pike and largemouth bass. Based on three food categories, jackknifed classifications correctly classified 77 and 92% of northern pike and largemouth bass values, respectively. Percent resource overlap values were biologically significant (greater than 60%) during at least one season in each sympatric assemblage, suggesting some diet overlap.

Minnesota↗

USGS2010

Central Arctic caribou and petroleum development: Distributional, nutritional, and reproductive implications

We synthesize findings from cooperative research on effects of petroleum development on caribou ( Rangifer tarandus granti ) of the Central Arctic Herd (CAH). The CAH increased from about 6000 animals in 1978 to 23000 in 1992, declined to 18 000 by 1995, and again increased to 27 000 by 2000. Net calf production was consistent with changes in herd size. In the Kuparuk Development Area (KDA), west of Prudhoe Bay, abundance of calving caribou was less than expected within 4 km of roads and declined exponentially with road density. With increasing infrastructure, high-density calving shifted from the KDA to inland areas with lower forage biomass. During July and early August, caribou were relatively unsuccessful in crossing road/pipeline corridors in the KDA, particularly when in large, insect-harassed aggregations; and both abundance and movements of females were lower in the oil field complex at Prudhoe Bay than in other areas along the Arctic coast. Female caribou exposed to petroleum development west of the Sagavanirktok River may have consumed less forage during the calving period and experienced lower energy balance during the midsummer insect season than those under disturbance-free conditions east of the river. The probable consequences were poorer body condition at breeding and lower parturition rates for western females than for eastern females (e.g., 1988–94: 64% vs. 83% parturient, respectively; p = 0.003), which depressed the productivity of the herd. Assessments of cumulative effects of petroleum development on caribou must incorporate the complex interactions with a variable natural environment.

Arctic↗

USGS1997

Habitat use and feeding ecology of riverine juvenile American shad

We examined premigratory populations of American shad Alosa sapidissima in the upper Delaware River to determine habitat and microhabitat use, differential prey use among habitat types, and habitat suitability indices for this previously unmodeled life stage. Both seining and diving techniques were used to quantify juveniles in six habitat types with six physical habitat covariables. Plankton and drift samples also were compared with stomach contents within habitats. We found no relation between relative abundance of juveniles and habitat type, which suggests general use of most riverine habitats. Physical habitat variables likewise did not affect use of habitat within ranges recorded, with two exceptions: (1) a positive relationship between abundance and water temperature in riffles and (2) a positive relationship between abundance and percent submerged aquatic vegetation (SAV) cover in SAV habitats. Opportunistic use of prey items was apparent; however, juveniles selected chironomid larvae and pupae and adult terrestrial insects and avoided ephemeropterans. Overlap between diets and available prey was high for most habitat types ( C λ mean = 0.71), especially for riffles ( C λ = 0.91). However, overlap for juveniles foraging at tributary mouths, where they strongly selected adult terrestrial insects, was low ( C λ = 0.49).

Pennsylvania↗

USGS2002

Potential nontarget effects of Metarhizium anisopliae (Deuteromycetes) used for biological control of ticks (Acari: Ixodidae)

The potential for nontarget effects of the entomopathogenic fungus Metarhizium anisopliae (Metschnikoff) Sorokin, when used for biological control of ticks, was assessed in laboratory trials. Fungal pathogenicity was studied against convergent ladybird beetles, Hippodamia convergens Guérin-Méneville, house crickets, Acheta domesticus (L.), and the milkweed bugs Oncopeltus fasciatus (Dallas). Fungal spores applied with a spray tower produced significant mortality in H. convergens and A. domesticus , but effects on O. fasciatus were marginal. Placing treated insects with untreated individuals resulted in mortality from horizontal transmission to untreated beetles and crickets, but not milkweed bugs. Spread of fungal infection in the beetles resulted in mortality on days 4–10 after treatment, while in crickets mortality was on day 2 after treatment, suggesting different levels of pathogenicity and possibly different modes of transmission. Therefore, M. anisopliae varies in pathogenicity to different insects. Inundative applications can potentially affect nontarget species, but M. anisopliae is already widely distributed in North America, so applications for tick control generally would not introduce a novel pathogen into the environment. Pathogenicity in lab trials does not, by itself, demonstrate activity under natural conditions, so field trials are needed to confirm these results and to assess methods to minimize nontarget exposure.

Environmental Entomology↗

USGS2007

Testing tail-mounted transmitters with Myocastor coypus (nutria)

We developed a tail-mounted radio-transmitter for Myocastor coypus (nutria) that offers a practical and efficient alternative to collar or implant methods. The mean retention time was 96 d (range 57-147 d, n = 7), making this a practical method for short-term studies. The tail-mounts were less injurious to animals than collars and easier for field researchers to implement than either collars or surgically implanted transmitters.

Southeastern Naturalist↗

USGS2004

Characterization of the habitat of Lythrum salicaria L. in floodplain forests in western Turkey—Effects on stem height and seed production

Lythrum salicaria (purple loosestrife) is an invasive wetland perennial in North America native to Eurasia. Because light environment may limit the species’ distribution, information on the relationship of forest canopy coverage to relative height and seed set in its native environment could give insight into its control in North America. This study examined the effect of various light environments related to forest canopy structure on seed set and stem height in L. salicaria in three biogeographical regions of Turkey spanning latitudes from 36 to 39° N. In Turkey, Lythrum salicaria grows in discrete patches in the canopy gaps of riverine forests, which often are dominated by Populus alba . The mean number of seeds per individual and stem height increased with decreasing canopy coverage (10437±284 to 20652±664 seeds individual −1 and 116±2 to 173±2 cm, respectively). A number of insect seed herbivores were noted on these Turkish populations, most notably a seed predator ( Nanophyes marmoratus ), which destroyed all seeds in infested capsules. Our study suggested that the light characteristics associated with canopy gaps influenced the seed set and height of L. salicaria . Other factors likely played a role, such as insect herbivores, soil fertility, and competition with other species, which may also be affected by the light levels provided at various levels of canopy coverage.

Wetlands↗

USGS1999

Foods of American badgers in west-central Minnesota and southeastern North Dakota during the duck nesting season

Although the American badger (Taxidea taxus) is common in grasslands and preys on a wide diversity of foods including birds, little is known about badger diet in areas where nesting ducks are common. Small mammals, primarily Muridae and Geomyidae, were the most common food items in the diet of badgers collected from west-central Minnesota and southeastern North Dakota during April-July 1987 through 1990, based on analysis of gastrointestinal tracts of 47 adult ( 1/4 -y-old) and 5 juvenile (<6-mo-old) badgers. Remains of mammals occurred in 98% of samples from adult badgers. Small quantities of insects were found in 40% of adult samples. Bird remains were in 32% of adult samples, most birds identified as Anatidae; ducks or ducklings occurred in 27% and duck eggs in 60% of those samples. Remains of reptiles, amphibians and mollusks were present, but were less common than other foods. Insects and bird eggs were more common during spring (April-May) than summer (June-July). Birds were more frequent in diets of adults than juvenile badgers.

American Midland Naturalist↗

USGS2019

First examination of diet items consumed by wild-caught black carp (Mylopharyngodon piceus) in the U.S.

Black carp ( Mylopharyngodon piceus ) were imported to the U.S. in the 1970s to control snails in aquaculture ponds and have since escaped from captivity. The increase in captures of wild fish has raised concerns of risk to native and imperiled unionid mussels given previous literature classified this species a molluscivore. We acquired black carp from commercial fishers and biologists, and examined digestive contents of 109 fish captured over 8 y from lentic and lotic habitats in the central and southern U.S.A. Digestive tract contents were preserved, and diet items inventoried. We identified 59 aquatic animal taxa (21 mollusks, 27 insects, and 11 other invertebrates) and various plant material including nuts and seeds; no fish were found. Approximately 45% of stomachs examined were empty or only contained flukes (Trematoda) that had infected mollusks before they were ingested. Nonempty stomachs contained snails (16.5%), bivalve mussels (22.8%), and insect larvae (net-spinning caddisflies, 15.6%; burrowing mayflies, 6.4%; and midges, 13.7%). Fish also consumed freshwater sponges (Porifera), moss animals (Bryozoa), crustaceans (Ostracoda and Decapoda), water mites (Acarina), and three worm phyla (Nematoda, Nemertea, Annelida). Seven taxa of unionid mussels were identified from shell fragments among the fish we examined, all of which are found in habitats with soft mud or sand/silt substrates. Diet of fish captured in lentic environments contained significantly higher richness than those captured in lotic environments. Individual black carp often contained large numbers of only one or two diet items that were assumed locally abundant and did not always crush the shells of mollusks. Most fish we examined consumed benthic prey, which supports the classification of black carp as a benthic foraging species. However, the presence of other aquatic taxa associated with pelagic or subsurface zones suggests black carp are opportunistic in their consumption of diet items and flexible in their feeding modes.

The American Midland Naturalist↗

USGS2012

Comparing modern and presettlement forest dynamics of a subboreal wilderness: Does spruce budworm enhance fire risk?

Insect disturbance is often thought to increase fire risk through enhanced fuel loadings, particularly in coniferous forest ecosystems. Yet insect disturbances also affect successional pathways and landscape structure that interact with fire disturbances (and vice-versa) over longer time scales. We applied a landscape succession and disturbance model (LANDIS-II) to evaluate the relative strength of interactions between spruce budworm ( Choristoneura fumiferana ) outbreaks and fire disturbances in the Boundary Waters Canoe Area (BWCA) in northern Minnesota (USA). Disturbance interactions were evaluated for two different scenarios: presettlement forests and fire regimes vs. contemporary forests and fire regimes. Forest composition under the contemporary scenario trended toward mixtures of deciduous species (primarily Betula papyrifera and Populus spp.) and shade-tolerant conifers ( Picea mariana, Abies balsamea, Thuja occidentalis ), with disturbances dominated by a combination of budworm defoliation and high-severity fires. The presettlement scenario retained comparatively more “big pines” (i.e., Pinus strobus, P. resinosa ) and tamarack ( L. laricina ), and experienced less budworm disturbance and a comparatively less-severe fire regime. Spruce budworm disturbance decreased area burned and fire severity under both scenarios when averaged across the entire 300-year simulations. Contrary to past research, area burned and fire severity during outbreak decades were each similar to that observed in non-outbreak decades. Our analyses suggest budworm disturbances within forests of the BWCA have a comparatively weak effect on long-term forest composition due to a combination of characteristics. These include strict host specificity, fine-scaled patchiness created by defoliation damage, and advance regeneration of its primary host, balsam fir ( A. balsamea ) that allows its host to persist despite repeated disturbances. Understanding the nature of the three-way interaction between budworm, fire, and composition has important ramifications for both fire mitigation strategies and ecosystem restoration initiatives. We conclude that budworm disturbance can partially mitigate long-term future fire risk by periodically reducing live ladder fuel within the mixed forest types of the BWCA but will do little to reverse the compositional trends caused in part by reduced fire rotations.

Minnesota↗