bluuebunny/crossref_metadata_2025_split huggingface dataset:
Plant preferential allocation and fungal reward decline with soil phosphorus: implications for mycorrhizal mutualism
Authors: Ji Baoming , Bever James D. 
Published: June 2016

AbstractExplaining the persistence of mutualism remains a challenge in ecology and evolutionary biology. The evolutionary stability of arbuscular mycorrhiza, a most widespread and ancient mutualistic association, is particularly intriguing because plants lack apparent mechanisms to prevent cheaters from gaining competitive advantages over cooperators. We developed a triple isotopic labeling method (14C, 32P, and 33P) within a split‐root design to measure the exchange of carbon (C) and phosphorus (P) between the host plant and two mycorrhizal partners across a soil P gradient. Host plant preferentially allocated more C to the roots associated with the fungus delivering higher P per unit plant C, and the strength of preferential allocation decreased with increasing soil P availability. The host plant received more P per unit of allocated C from the better fungus and this advantageous exchange rate did not depend upon P availability. As a result, the level of preferential allocation was correlated with the differential delivery of P from the two fungi. Our findings suggest that plant preferential allocation to better mutualists can stabilize mutualisms in environments limiting in the traded resource, but as the availability of this resource increases, plant preferential allocation declines. This environmental dependence of preferential allocation generates predictions of declining levels in relative abundance of mutualistic fungi in high‐resource environments.
Larval long‐toed salamanders incur nonconsumptive effects in the presence of nonnative trout
Authors: Kenison Erin K. , Litt Andrea R. , Pilliod David S. , McMahon Thomas E. 
Published: June 2016

AbstractPredators can influence prey directly through consumption or indirectly through nonconsumptive effects (NCEs) by altering prey behavior, morphology, and life history. We investigated whether predator‐avoidance behaviors by larval long‐toed salamanders (Ambystoma macrodactylum) in lakes with nonnative trout result in NCEs on morphology and development. Field studies in lakes with and without trout were corroborated by experimental enclosures, where prey were exposed only to visual and chemical cues of predators. We found that salamanders in lakes with trout were consistently smaller than in lakes without trout: 38% lower weight, 24% shorter body length, and 29% shorter tail length. Similarly, salamanders in protective enclosures grew 2.9 times slower when exposed to visual and olfactory trout cues than when no trout cues were present. Salamanders in trout‐free lakes and enclosures were 22.7 times and 1.48 times, respectively, more likely to metamorphose during the summer season than those exposed to trout in lakes and/or their cues. Observed changes in larval growth rate and development likely resulted from a facultative response to predator‐avoidance behavior and demonstrate NCEs occurred even when predation risk was only perceived. Reduced body size and growth, as well as delayed metamorphosis, could have ecological consequences for salamander populations existing with fish if those effects carry‐over into lower recruitment, survival, and fecundity.
Nonsystemic fungal endophytes increase survival but reduce tolerance to simulated herbivory in subarcticFestuca rubra
Authors: Santangelo James S. , Kotanen Peter M. 
Published: June 2016

AbstractPlant–microbial symbioses are widespread in nature and can shape the ecology and evolution of hosts and interacting symbionts. Fungal endophytes—fungi that live asymptomatically within plant tissues—are a pervasive group of symbionts well known for their role in mediating host‐responses to biotic and abiotic stresses. However, they also may become pathogenic and often impose metabolic costs on hosts. Here, we examine the role of fungal endophytes in mediating responses of the host grass red fescue (Festuca rubra) to salt and herbivore stress. We collected 38 red fescue genotypes from within its native range on Akimiski Island, Nunavut, Canada, where it occurs in the supratidal region on the northern part of the island and is heavily grazed by nesting and brood‐rearing snow geese (Chen caerulescens caerulescens) and Canada geese (Branta canadensis). We screened all plants for the presence of the systemic endophyteEpichloë festucaeand sequenced the nonsystemic endophytic community on a subset of these plants. While we did not detectE. festucae, our plants instead were host to a diverse array of nonsystemic fungal endophytes. We then conducted a fully factorial greenhouse experiment where we crossed plant genotype (4 levels) with simulated grazing (clipped or unclipped), endophyte status (present or absent) and salinity (0, 32 or 64 ppt) to examine the ecological role of this endophytic community. Overall, the presence of nonsystemic endophytes increased plant survival, but only in the absence of salt or clipping. On the other hand, these endophytes reduced plant tolerance to simulated herbivory by 69% but had no effect on aboveground plant growth. Thus, our results identify a potential nonsystemic endophyte‐mediated trade‐off in host plant survival and tolerance to herbivory and suggest this trade‐off may be altered by stressful abiotic conditions.
Tick‐, mosquito‐, and rodent‐borne parasite sampling designs for the National Ecological Observatory Network
Authors: Springer Yuri P. , Hoekman David , Johnson Pieter T. J. , Duffy Paul A. , Hufft Rebecca A. , Barnett David T. , Allan Brian F. , Amman Brian R. , Barker Christopher M. , Barrera Roberto , Beard Charles B. , Beati Lorenza , Begon Mike , Blackmore Mark S. , Bradshaw William E. , Brisson Dustin , Calisher Charles H. , Childs James E. , Diuk‐Wasser Maria A. , Douglass Richard J. , Eisen Rebecca J. , Foley Desmond H. , Foley Janet E. , Gaff Holly D. , Gardner Scott L. , Ginsberg Howard S. , Glass Gregory E. , Hamer Sarah A. , Hayden Mary H. , Hjelle Brian , Holzapfel Christina M. , Juliano Steven A. , Kramer Laura D. , Kuenzi Amy J. , LaDeau Shannon L. , Livdahl Todd P. , Mills James N. , Moore Chester G. , Morand Serge , Nasci Roger S. , Ogden Nicholas H. , Ostfeld Richard S. , Parmenter Robert R. , Piesman Joseph , Reisen William K. , Savage Harry M. , Sonenshine Daniel E. , Swei Andrea , Yabsley Michael J. 
Published: June 2016

AbstractParasites and pathogens are increasingly recognized as significant drivers of ecological and evolutionary change in natural ecosystems. Concurrently, transmission of infectious agents among human, livestock, and wildlife populations represents a growing threat to veterinary and human health. In light of these trends and the scarcity of long‐term time series data on infection rates among vectors and reservoirs, the National Ecological Observatory Network (NEON) will collect measurements and samples of a suite of tick‐, mosquito‐, and rodent‐borne parasites through a continental‐scale surveillance program. Here, we describe the sampling designs for these efforts, highlighting sampling priorities, field and analytical methods, and the data as well as archived samples to be made available to the research community. Insights generated by this sampling will advance current understanding of and ability to predict changes in infection and disease dynamics in novel, interdisciplinary, and collaborative ways.
Biocontrol insect impacts population growth of its target plant species but not an incidentally used nontarget
Authors: Catton Haley A. , Lalonde Robert G. , Buckley Yvonne M. , De Clerck‐Floate Rosemarie A. 
Published: June 2016

AbstractUnderstanding the impact of herbivory on plant populations is a fundamental goal of ecology. Damage to individual plants can be visually striking and affect the fates of individuals, but these impacts do not necessarily translate into population‐level differences in vital rates (survival, growth, or fecundity) or population growth rates. In biological control of weeds, quantitative assessments of population‐level impacts of released agents on both target invasive plants and native, nontarget plants are needed to inform evaluations of the benefits and risks of releasing agents into new regions. Here we present a 3‐yr experimental demographic field study using the European root‐feeding biocontrol weevil, Mogulones crucifer, first released in Canada in 1997 to control the invasive weed Cynoglossum officinale (Boraginaceae). Mogulones crucifer is an effective “search and destroy” agent in Canada, but sporadically feeds, oviposits, and develops on native nontarget Boraginaceae. We investigated the population‐level impacts of this biocontrol insect on its target weed and a native nontarget plant, Hackelia micrantha (Boraginaceae), by releasing large numbers of weevils into naturally occurring patches of H. micrantha growing isolated from or interspersed with C. officinale. We followed the fates of individual plants on release and nonrelease (control) sites for two transition years, developed matrix models to project population growth rates (λ) for each plant species, and examined the contributions from differences in vital rates to changes in λ using life table response experiments (LTRE). In contrast to studies of the insect–plant interaction in its native range, as a biocontrol agent, M. crucifer increased mortality of C. officinale rosettes in the year immediately following release, depressing the weed's λ to below the population replacement level. However, λ for H. micrantha was never depressed below the replacement level, and any differences between release and nonrelease sites in the nontarget could not be explained by significant contributions from vital rates in the LTRE. This study is the first to simultaneously and experimentally examine target and nontarget population‐level impacts of a weed biocontrol insect in the field, and supports the theoretical prediction that plant life history characteristics and uneven herbivore host preferences can interact to produce differences in population‐level impacts between target and nontarget plant species.
Visualizing land‐use and management complexity within biogeochemical cycles of an agricultural landscape
Authors: Nitzsche Kai Nils , Verch Gernot , Premke Katrin , Gessler Arthur , Kayler Zachary E. 
Published: June 2016

AbstractCrop fields are cultivated across continuities of soil, topography, and local climate that drive biological processes and nutrient cycling at the landscape scale; yet land management and agricultural research are often performed at the field scale, potentially neglecting the context of the surrounding landscape. Adding to this complexity is the overlap of ecosystems and their biogeochemical legacies, as a patchwork of crops fields, natural grasslands, and forests develops across the landscape. Furthermore, as new technologies and policies are introduced, management practices change, including fertilization strategies, which further alter biological productivity and nutrient cycling. All of these environmental, biological, and historical legacies are potentially recorded in the isotopic signal of plant, soil, and sediment organic matter across the landscape. We mapped over 1500 plant, soil, and sediment isotopic values and generated an isotopic landscape (isoscape) over a 40‐km2 agricultural site in NE Germany. We observed distinct patterns in the isotopic composition of organic matter sampled from the landscape that clearly reflect the landscape complexity. C3 crop intrinsic water‐use efficiency reflected a precipitation gradient, while native forest and grassland plant species did not, suggesting that native plants are more adapted to predominant climatic conditions. δ13Csoil patterns reflected both the long‐term input of plant organic matter, which was affected by the local climate conditions, and the repeated cultivation of corn. Soil organic matter 15N isotopic values also revealed spatial differences in fertilization regimes. Forest fragments, in which the nitrogen cycle was relatively open, were more water‐use efficient. Sediments from small water bodies received substantial inputs from surrounding field vegetation but were also affected by seasonal drying. These isotopic maps can be used to visualize large spatial heterogeneity and complexity, and they are a powerful means to interpret past and current trends in agricultural landscapes.
Thermal environment and maternal effects shape egg size in a freshwater fish
Authors: Feiner Zachary S. , Wang Hui‐Yu , Einhouse Donald W. , Jackson James. R. , Rutherford Edward S. , Schelb Chris , Vandergoot Christopher S. , Zorn Troy G. , Höök Tomas O. 
Published: June 2016

AbstractOffspring size determines offspring survival rates; thus, understanding factors influencing offspring size variability could elucidate variation in population dynamics. Offspring size variation is influenced through multigenerational adaptation to local environments and within‐lifetime plastic responses to environmental variability and maternal effects among individuals. Moreover, offspring size variation may represent trade‐offs in energy allocation within individuals that influence lifetime reproductive success. However, the mechanisms whereby environmental conditions influence offspring size, e.g., via inducing adaptive and plastic variation in population‐scale maternal effects, remain poorly understood. We evaluated intra‐specific variation in maternal effects, egg size, and intra‐individual egg size variation in six populations of walleye (Sander vitreus) and related among‐ and within‐population patterns to thermal conditions. Egg size was conserved within populations and negatively related to long‐term thermal conditions among populations, while maternal effect strengths were positively related to thermal conditions, suggesting that populations inhabiting warmer environments adapted to produce smaller eggs but stronger maternal effects. Within a population, egg size was positively related to colder winters, suggesting cold winters may alter egg size through effects on maternal condition or as an adaptive maternal effect to improve offspring survival. Intra‐individual egg size variation varied little among populations or with female size, but declined with increasing summer and decreasing winter temperatures. Our result suggests that environmental conditions could impact not only short‐term offspring production but also spur adaptive changes in offspring phenotypes. Thus, it is necessary to account for adaptive responses to predict population dynamics under environmental changes.
Conceptual guidelines for the implementation of the ecosystem approach in biodiversity monitoring
Authors: Mueller Melanie , Geist Juergen 
Published: June 2016

AbstractThe theoretical concept of the ecosystem approach (EA) aims at assessing ecosystem function based on integrative assessments of multiple levels of biological organization. Since the United Nations Convention on Biological Diversity in 1992, the EA has been increasingly integrated into environmental policy and legislation, but to date, its practical implementation remains vague with a lack of universal guidelines and concrete recommendations for its use across ecosystem boundaries. On the basis of a review of scientific literature, worldwide environmental legislation and existing monitoring approaches, we identified the most important factors which hamper the feasibility of the EA. We propose a generally applicable methodology for implementing the EA in ecological and environmental monitoring across different ecosystems and habitat types. Successful application of the EA largely depends on adequately standardized and synchronized sampling designs for all abiotic and biotic components, appropriate depth of taxonomic identification, and sufficient spatial and temporal replication. The proposed step‐by‐step guidelines for using the EA are valid across ecosystem types, geographic regions, and for a variety of data types, making them promising tools for ecological monitoring.
Release date influences first‐year site fidelity and survival in captive‐bred Vancouver Island marmots
Authors: Jackson Cheyney L. , Schuster Richard , Arcese Peter 
Published: June 2016

AbstractMaximizing survival in reintroduced, captive‐bred animals requires evaluation to identify best practices. This is particularly true for critically endangered species like the Vancouver Island marmot, endemic to British Columbia, Canada. From 2003 to 2010, 301 captive‐bred marmots were implanted with transmitters and released at extinct colony locations and other potentially preferred sites to bolster wild populations and establish new colonies. We evaluated release success based on three criteria: (1) site fidelity in the first summer, (2) survival to hibernation in fall, and (3) survival through winter. We used generalized linear mixed models and information theory to estimate the influence on release success of sex, age, and release practices, as well as local and landscape‐level habitat attributes. Our results suggest that overwinter survival most limited release success in the first‐year postrelease. In all years, overwinter survival was lower for newly released captive‐bred marmots than for wild or previously released marmots. Release date best predicted overall success, and was positively related to site fidelity and survival to hibernation but negatively related to overwinter survival. Our findings suggest that focused attempts to optimize release dates are likely to maximize long‐term reintroduction success.
Habitat requirements and ecological niche of two cryptic amphipod species at landscape and local scales
Authors: Eisenring Michael , Altermatt Florian , Westram Anja Marie , Jokela Jukka 
Published: June 2016

AbstractCryptic species are phylogenetically diverged taxa that are morphologically indistinguishable and may differ in their ecological and behavioral requirements. This may have important implications for ecosystem services and conservation of biodiversity. We investigated whether two ecologically important cryptic species of the freshwater amphipod Gammarus fossarum (types A and B) are associated with different habitats. We collected data on their occurrence at both the landscape scale (large watersheds) and at the local scale (river reach) to compare macro‐ and microscale environmental parameters associated with their presence. Analysis of the landscape scale data showed that occurrence of types A and B differ with respect to watershed and river size and, interestingly, human impact on river ecomorphology. Whereas type B was mainly found in less forested areas with higher human impact, type A showed the opposite occurrence pattern. Analyses of the local scale data suggested that habitats occupied by type A were characterized by larger gravel, larger stones and less macrophytes than habitats occupied by type B. The landscape and local data set showed contradicting patterns with regard to stream size. Overall, the observed differences between the two types of G. fossarum most likely reflect ecological differences between them, but alternative explanations (e.g., historical colonization processes) cannot be completely ruled out. Our study underlines that common cryptic species can differ in their ecology and response to anthropogenic influence. Such differences in habitat requirements among difficult‐to‐identify taxa present a challenge for biodiversity and ecosystem management. Our results emphasize the importance of conservative and precautionary approaches in maintenance of habitat diversity and environmental heterogeneity.
Latrine marking patterns of badgers (Meles meles) with respect to population density and range size
Authors: Buesching Christina D. , Newman Chris , Service Katrina , Macdonald David W. , Riordan Philip 
Published: June 2016

AbstractEuropean badgers (Meles meles) use shared defecation sites, termed latrines, to demarcate group ranges. While some latrines are small, comprising few pits with few fresh scats spread over a small area, others are large, comprising many pits with many fresh droppings and extending over a large area. Although many studies have investigated badger latrine usage patterns, and speculated on latrine function, this variation in relative latrine size remains unexplained. Using nearest neighbor analyses, we analyzed the latrine positioning, use, and inter‐latrine distances from four study areas with different population densities. We found that latrines were spaced regularly throughout the range, and border marking was prioritized, increasing the chances of traversing badgers intercepting a latrine. While the numbers of latrines increased with group range size, the number of fresh feces per latrine decreased, suggesting that fresh feces may be a limiting resource in the maintenance of latrines, and that maintaining latrine spacing pattern is more important than the actual number of fresh feces in each latrine. We thus posited that, where territories are small and groups large, the capacity to produce feces exceeds the minimum need for perimeter marking, resulting in fecal redundancy and large latrines. In contrast, in larger territories, especially when occupied by smaller groups, badgers may experience fecal constraint, thus maintaining smaller latrines. We concluded that latrine maintenance and fecal scent‐marking activity in badgers involves a trade‐off between group size and group range area, leading to different degrees of fecal constraint, while energetic costs of signaling are minimized.