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in category ecology

2,725 results found. For more information, click each entry to expand.

2621: Spatial variability in pollen and resource limitation for fruit production of two species in Interior Alaska: Vaccinium uliginosum and V. vitis-idaea
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Posted to bioRxiv 08 Oct 2019

Spatial variability in pollen and resource limitation for fruit production of two species in Interior Alaska: Vaccinium uliginosum and V. vitis-idaea
62 downloads ecology

Lindsey Viann Parkinson, Christa PH Mulder

Many recent studies assessing fruit productivity of plants in the boreal forest focus on interannual variability across a forested region, rather than on environmental variability within the forest. Frequency and severity of wildfires in the boreal forest affect soil moisture, canopy, and community structure at the landscape level, all of which may influence overall fruit production at a site directly (through resource availability) or indirectly (through impacts on pollinators) . We evaluated how fruit production in two boreal shrubs, Vaccinium uliginosum (blueberry) and V. vitis-idaea (lingonberry) , was explained by factors associated with resource availability (such as canopy cover and soil conditions) and pollen limitation (such as floral resources for pollinators and pollen deposition) across boreal forest sites of Interior Alaska . We classified our study sites into upland and lowland sites, which differed in elevation, soil moisture (lower in upland sites), and active layer (deeper in upland sites). We found that resource and pollen limitation differed between the two species and between uplands and lowlands. L ingonberry was more pollen limited than blueberry, and plants in lowland sites were more pollen limited relative to other sites while plants in upland sites were relatively more resource limited. Additionally, canopy cover had a significant negative effect in upland sites on a ramet’s investment in reproductive tissues and leaves versus structural growth, but little effect in lowland sites. These results point to importance of including pollinator abundance as well as resource availability in predictions for changes in berry abundance.

2622: Influence of human population density on spatial distribution patterns of environmental suitability for triatomine vectors of Chagas disease
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Posted to bioRxiv 28 Jul 2019

Influence of human population density on spatial distribution patterns of environmental suitability for triatomine vectors of Chagas disease
62 downloads ecology

Anderson A. Eduardo, Lucas A. B. O. Santos, Monica C. Reboucas, Pablo A. Martinez

Previous work on Chagas Disease disease at large spatial scales has not explored how interaction with humans can affect projections for geographical distribution of environmental suitability of vector species. Here, we compare niche-based species distribution models with climatic variables as predictors (SDM clim) and with climatic variables + human population density (SDM Human). Our results show that accounting for human population density helps refine the models to finer geographical scales. Also, different spatial patterns of accumulated environmental suitability were obtained by SDM clim and SDM Human. Moreover, projections were more accurate for SDM Human than for SDM clim. Our results show that considering human populations in SDMs for epidemiologically relevant triatomiane species can improve our understanding of macroecology and biogeography of environmental suitability for vectors of Chagas disease.

2623: Genotypic Variation in Below- to Aboveground Systemic Induction of Glucosinolates Mediates Plant Fitness Consequences under Herbivore Attack
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Posted to bioRxiv 18 Oct 2019

Genotypic Variation in Below- to Aboveground Systemic Induction of Glucosinolates Mediates Plant Fitness Consequences under Herbivore Attack
62 downloads ecology

Moe BAKHTIARI, Sergio Rasmann

Plants defend themselves against herbivore attack by constitutively producing toxic secondary metabolites, as well as by inducing them during herbivore feeding. Induction of secondary metabolites can cross plant tissue boundaries, such as from root to shoot. However, whether the potential for plants to systemically induce secondary metabolites from roots to shoots shows genetic variability, and thus, potentially, is under selection conferring fitness benefits to the plants is an open question. To address this question, we induced 26 maternal plant families of the wild species Cardamine hirsuta belowground (BG) using the wound-mimicking phytohormone jasmonic acid (JA). We measured resistance against a generalist (Spodoptera littoralis) and a specialist (Pieris brassicae) herbivore species, as well as the production of glucosinolates (GSLs) in plants. We showed that BG induction increased AG resistance against the generalist but not against the specialist, and found substantial plant family-level variation for resistance and GSL induction. We further found that the systemic induction of several GSLs tempered the negative effects of herbivory on total seed set production. Using a widespread natural system, we thus confirm that BG to AG induction has a strong genetic component, and it can be under positive selection by increasing plant fitness. We suggest that natural variation in systemic induction is in part dictated by allocation trade-offs between constitutive and inducible GSL production, as well as natural variation in AG and BG herbivore attack in nature.

2624: No division of labour, and subfertile foundresses, in a phyllode-gluing Acacia thrips
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Posted to bioRxiv 05 Sep 2019

No division of labour, and subfertile foundresses, in a phyllode-gluing Acacia thrips
62 downloads ecology

James DJ Gilbert

Behavioural variation is a hallmark of animal societies, which commonly contain breeders and nonbreeders, and helpers and nonhelpers. In some cases labour is divided with nonbreeders 'helping' - gaining indirectly, via genetic benefits, or directly, e.g. by augmenting group size. Conversely, they may benefit by not helping, conserving energy for breeding later. However, subordinate behaviour after inheriting a breeding position is rarely evaluated. In the Australian interior, Acacia thrips Dunatothrips aneurae (Thysanoptera) glue Acacia phyllodes together into 'domiciles'. Foundresses, usually sisters, build domiciles singly or communally. Some co-foundresses are nonreproductive, and their role is currently unknown. I experimentally rejected the idea that they substantially 'help' by contributing to domicile repair. Nonreproductives were less likely to repair damage than reproductives. Alternatively, they may be waiting to inherit the domicile, or simply of too poor quality to reproduce or help. To test these alternatives, in the field, I allowed repairer or nonrepairer females to 'inherit' a domicile by removing their nestmate(s). Thus isolated, 'nonrepairer' females took much longer to repair domiciles than 'repairers', control singletons or pairs. Although ovarian condition was equivalent across groups, after 21 days nonrepairers actually laid fewer eggs compared to other groups. Thus, labour was not divided: instead reproduction and helping covaried, probably depending on female quality and the outcome of intra-domicile competition. Nonreproductive nonhelpers were not waiting to breed. Their role, and their net effect on colony productivity, remains to be shown. They are likely subfertile, and may make the 'best of a bad job' by gaining indirect benefits to the best of their limited ability.

2625: Errors associated with compound specific δ15N analysis of amino acids in preserved fish samples purified by high pressure liquid chromatography
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Posted to bioRxiv 21 Oct 2019

Errors associated with compound specific δ15N analysis of amino acids in preserved fish samples purified by high pressure liquid chromatography
61 downloads ecology

Rasmus Swalethorp, Lihini Aluwihare, Andrew R. Thompson, Mark D Ohman, Michael R Landry

During the past decade compound specific nitrogen (N) isotopic analysis of amino acids (CSIA−AA) has become an increasingly used method for tracking the origin and fate of N in ecological and biogeochemical studies. CSIA−AA has the potential for resolving finer scale trophic dynamics than previously possible with bulk stable isotope analysis (SIA) and for reconstructing past food webs using historical archives of organismal samples. However, there is little information on the effects of chemical preservation used in historical archives on δ15NAA values, and conventional CSIA conducted on derivatized AAs using gas chromatography − combustion − isotope ratio mass spectrometry (GC−C−IRMS) has analytical errors in the range of what may be expected from chemical preservation. Here we present analytical errors across 11 underivatized AA standards analyzed by high pressure liquid chromatography followed by offline elemental analysis − IRMS (HPLC/EA−IRMS) an approach originally developed by Broek and McCarthy (2014). Using this method, we test the effects of ethanol and formaldehyde preservation (1½ and 27 years) on δ15NAA in Northern Anchovy ( Engraulis mordax ). We found minimal isotopic fractionation from the HPLC/EA-IRMS approach in 8 AAs and more than twice the precision (0.15 ± 0.08 ‰) typically reported for GC-C-IRMS. Preservation effects on δ15NAA were similar regardless of duration and type of preservative used. Although several AAs differed significantly from frozen control samples (average +1.0 ± 0.8 ‰), changes in trophic position (TP) estimates were insignificant. These results are encouraging for resolving the fine-scale natural variability expected in most low TP organisms via high precision HPLC/EA−IRMS and for the use of chemically preserved sample archives in reconstructing biogeochemical records and trophic dynamics over long time scales.

2626: Limited selection on leaf traits in Danish grasslands
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Posted to bioRxiv 15 Aug 2019

Limited selection on leaf traits in Danish grasslands
61 downloads ecology

Christian Damgaard

Only limited trait selection was observed on leaf traits (SLA and LDMC) in a study of an extensive ten-year Danish grassland vegetation dataset. The negative result of this study may partly be due to the relatively conservative analysis, where the continuous plant trait variables are used for grouping plant species into functional types, which are then treated as dependent variables. This procedure is in contrast to most other analyses of trait selection, where it is the community weighted mean of the traits that are used as the dependent variable. However, it is not the traits, but rather individual plants that are sampled and, consequently, it is important to consider the sampling of species abundance in the statistical modelling of plant traits. This misapprehension has not received sufficient proper attention in the plant trait literature.

2627: Diversity of responses of soil saprobic fungi to recurring heat events
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Posted to bioRxiv 14 Aug 2019

Diversity of responses of soil saprobic fungi to recurring heat events
61 downloads ecology

Aleksandra Szymczak, Masahiro Ryo, Matthias C Rillig

As a consequence of ongoing climate change, the frequency of extreme heat events is expected to increase. Recurring heat pulses may disrupt functions supported by soil microorganisms, thus affecting the entire ecosystem. However, most perturbation experiments only test effects of single heat events, and therefore it remains largely unknown how soil microorganisms react to repeated pulse events. Here we present data from a lab experiment exposing 32 filamentous fungi, originally isolated from the same soil, to sequential heat perturbations. Soil saprobic fungi isolates were exposed to one or two heat pulses: mild (35oC/2h), strong (45oC/1h), or both in sequence (35oC/2h+45oC/1h), and we assessed growth rate. Out of the 32 isolates 13 isolates showed an antagonistic response, 3 isolates a synergistic response and 16 isolates responded in an additive manner. These differences in species responses to the thermal environment may contribute to species coexistence, and such dissimilarities in thermal perturbation responses may be a key aspect influencing ecosystem services that soil saprobic fungi support.

2628: Physiological and Molecular Responses Suggest Local Adaptation of the Lobe Coral Porites lobata to the Nearshore Environment
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Posted to bioRxiv 30 Sep 2019

Physiological and Molecular Responses Suggest Local Adaptation of the Lobe Coral Porites lobata to the Nearshore Environment
61 downloads ecology

Kaho H Tisthammer, Emma Timmins-Schiffman, Francois Seneca, Brook Nunn, Robert Richmond

Corals in nearshore marine environments are increasingly exposed to reduced water quality, which is the major local threat to coral reefs in Hawaii. Corals surviving in such conditions may have acclimatized and/or adapted to withstand sedimentation, pollutants, and other environmental stressors. Lobe coral ( Porites lobata ) populations from Maunalua Bay, Hawaii showed clear genetic differentiation along with distinct cellular protein expressions between the 'polluted, high-stress' nearshore site and the 'low-stress' offshore site. To understand the driving force of the observed genetic partitioning, reciprocal transplant and common-garden experiments were conducted using the nearshore and offshore colonies of P. lobata from Maunalua Bay to assess phenotypic differences of stress-related physiological and molecular responses between the two coral populations. Physiological responses (tissue layer thickness, tissue lipid content, and short-term growth rates) all showed differences between the populations, revealing more stress resilient traits in the nearshore corals. Proteomic responses highlighted the inherent differences in the cellular metabolic state and activities between the two populations under the same environmental conditions; nearshore corals did not significantly alter their proteome between the sites, while offshore corals responded to the nearshore transplantation with increased abundances of proteins associated with detoxification, antioxidant, and various metabolic processes. The response differences across multiple phenotypes suggest that the observed genetic partitioning was likely due to local adaptation of nearshore corals to the nearshore environmental conditions.

2629: Trophic complexity alters the diversity-multifunctionality relationship in experimental grassland mesocosms
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Posted to bioRxiv 23 Jan 2019

Trophic complexity alters the diversity-multifunctionality relationship in experimental grassland mesocosms
61 downloads ecology

Krishna Anujan, Sebastian A Heilpern, Case M Prager, Brian C Weeks, Shahid Naeem

Diversity within trophic levels influences the number of ecosystem functions maintained simultaneously by a community, or multifunctionality. Depending on threshold cutoffs applied to measuring these functions, the diversity-multifunctionality relationship changes from positive until intermediate thresholds to negative effect at high function thresholds. Although the presence of multiple trophic levels or trophic complexity affects levels of functions, its effect on the diversity-multifunctionality relationship has not been experimentally tested. We simultaneously manipulated plant diversity and trophic complexity in a multifactorial tall-grass prairie mesocosm experiment at Cedar Creek, Minnesota, USA and measured multiple ecosystem functions. Trophic complexity altered the diversity-multifunctionality relationship in two key ways: it lowered the maximum strength of the diversity-multifunctionality effect and it resulted in a switch from positive to negative relationship between increasing diversity and multifunctionality at lower function thresholds. Our findings suggest that global declines in trophic complexity will exacerbate the reduction in ecosystem multifunctionality as a result of widespread declines in biodiversity.

2630: Insights from two decades of the Student Conference on Conservation Science
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Posted to bioRxiv 29 Oct 2019

Insights from two decades of the Student Conference on Conservation Science
61 downloads ecology

Jonas Geldmann, Helena Alves-Pinto, Tatsuya Amano, Harriet Bartlett, Alec P Christie, Lydia Collas, Sophia C Cooke, Roberto Correa, Imogen Cripps, Anya Doherty, Tom Finch, Emma E Garnett, Fangyuan Hua, Julia Patricia Gordon Jones, Tim Kasoar, Douglas MacFarlane, Philip A Martin, Nibu Mukherjee, Hannah S. Mumby, Charlotte Payne, Silviu O Petrovan, Ricardo Rocha, Kirsten Russell, Benno I Simmons, Hannah Wauchope, Thomas A Worthington, Rosie Trevelyan, Rhys Green, Andrew Balmford

Conservation science is a crisis-oriented discipline focused on delivering robust answers to reducing human impacts on nature. To explore how the field might have changed during the past two decades, we analyzed 3,245 applications for oral presentations submitted to the Student Conference on Conservation Science (SCCS) in Cambridge, UK. SCCS has been running every year since 2000, aims for global representation by providing bursaries to early-career conservationists from lower-income countries, and has never had a thematic focus, beyond conservation in the broadest sense. We found that the majority of submissions to SCCS were based on primary biological data collection from local scale field studies in the tropics, contrary to established literature which highlights gaps in tropical research. Our results showed a small increase over time in submissions framed around how nature benefits people as well as a small increase in submissions integrating social science. Our findings also suggest that students and early-career conservationists could provide pathways to increased availability of data from the tropics and for addressing well-known biases in the published literature towards wealthier countries. We hope this research will motivate efforts to support student projects, ensuring data and results are published and made publicly available.

2631: The concerted emergence of well-known spatial and temporal ecological patterns in an evolutionary food web model in space
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Posted to bioRxiv 18 Oct 2019

The concerted emergence of well-known spatial and temporal ecological patterns in an evolutionary food web model in space
60 downloads ecology

Michaela Hamm, Barbara Drossel

Ecological systems show a variety of characteristic patterns of biodiversity in space and time. It is a challenge for theory to find models that can reproduce and explain the observed patterns. Since the advent of island biogeography these models revolve around speciation, dispersal, and extinction, but they usually neglect trophic structure. Here, we propose and study a spatially extended evolutionary food web model that allows us to study large spatial systems with several trophic layers. Our computer simulations show that the model gives rise simultaneously to several biodiversity patterns in space and time, from species abundance distributions to the waxing and waning of geographic ranges. We find that trophic position in the network plays a crucial role when it comes to the time evolution of range sizes, because the trophic context restricts the occurrence and survival of species especially on higher trophic levels.

2632: Drivers of plant traits and forest functional composition in coastal plant communities of the Atlantic Forest
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Posted to bioRxiv 21 Oct 2019

Drivers of plant traits and forest functional composition in coastal plant communities of the Atlantic Forest
60 downloads ecology

Jehová Lourenço, Erica A Newman, Jose A. Ventura, Camilla Rozindo Dias Milanez, Luciana Dias Thomaz, Douglas Tinoco Wandekoken, Brian J Enquist

The severe deforestation of Brazil's Atlantic Forest and increasing effects of climate change underscore the need to understand how tree species respond to climate and soil drivers. We studied 42 plots of coastal restinga forest, which is highly diverse and spans strong environmental gradients. We determined the forest physiognomy and functional composition, which are physical properties of a community that respond to climate and soil properties, to elucidate which factors drive community-level traits. To identify the most important environmental drivers of coastal Atlantic forest functional composition, we performed a forest inventory of all plants of diameter 5 cm and above. We collected wood samples and leaves from ~85% of the most abundant plant species and estimated height, aboveground biomass (AGB), and basal area of individual plants, and the community-weighted specific leaf area (SLA). In addition to plant traits, we measured water table depth and 25 physicochemical soil parameters. We then parameterized several models for different hypotheses relating the roles of nutrients and soil to tropical forest diversity and functioning, as represented by plant traits. Hypotheses were formalized via generalized additive models and piecewise structural equation models. Water table depth, soil coarseness, potential acidity, sodium saturation index (SSI) and aluminum concentration were all components of the best models for AGB, height, basal area, and trait composition. Among the 25 environmental parameters measured, those related to water availability (water table depth and coarse sand), followed by potential acidity, SSI, and aluminum consistently emerged as the most important drivers of forest physiognomy and functional composition. Increases in water table depth, coarse sand, and soil concentration of aluminum negatively impacted all the measured functional traits, whereas SSI had a positive effect on AGB and plant height. These results suggest that sodium is not merely tolerated by Atlantic Forest restinga plant communities, but is important to their structure and functioning. Presence of aluminum in the soil had a complex relationship to overall basal area, possibly mediated by soil organic matter.

2633: Complex multi-trait responses to multivariate environmental cues in a seasonal butterfly
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Posted to bioRxiv 18 Sep 2019

Complex multi-trait responses to multivariate environmental cues in a seasonal butterfly
60 downloads ecology

Pragya Singh, Erik van Bergen, Oskar Brattström, Dave Osbaldeston, Paul M Brakefield, Vicencio Oostra

Developmental plasticity in a seasonal environment allows an organism to optimally match its life-history traits with the fluctuating conditions. This critically relies on abiotic and biotic factors, such as temperature or food quality, that act as environmental cues and predict seasonal transitions. In most seasonal environments, multiple factors vary together, making it crucial to understand their combined effects on an organisms phenotype. Here, we study plasticity in a multivariate environment in the butterfly Bicyclus anynana that exhibits two distinct seasonal phenotypes. Temperature is an important cue mediating plasticity in this species, but other environmental cues such as larval host plant quality could also be informative since plant quality deteriorates during the transition from wet to dry season in the field. We examine how temperature and host plant quality interact to affect life-history traits. Using a full-factorial design, we expose cohorts of larvae to either poor (old plants) or high (young plants) quality plants at different temperatures. Our results show that plant quality had a temperature and sex-dependent effect on life-history traits. At lower and intermediate temperatures, it decreased body mass and prolonged development time, indicating that poor plant quality acted as a stressor. However, metabolic rates in adults were not affected, indicating that individuals could, at least in part, compensate for stressful juvenile conditions. In contrast, at higher temperatures poor plant quality induced a partial dry-season phenotype, indicating that it may have acted as an environmental cue. Moreover, poor plant quality, particularly in males, also decreased the correlation between life history traits, signifying disrupted phenotypic integration. Our study reveals complex interactive effects of two environmental variables on seasonal plasticity, reflecting differences in their reliability as seasonal cues. This highlights the importance of studying the combined effects of multiple environmental factors to better understand the regulation of phenotypic plasticity in wild.

2634: Thermal sensitivity of lizard embryos indicates a mismatch between oxygen supply and demand at near-lethal temperatures
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Posted to bioRxiv 30 Sep 2019

Thermal sensitivity of lizard embryos indicates a mismatch between oxygen supply and demand at near-lethal temperatures
60 downloads ecology

Joshua Matthew Hall, Daniel A Warner

Aspects of global change (e.g. urbanization, climate change) result in novel, stressful thermal environments that threaten biodiversity. Though much research quantifies the thermal sensitivity of adult organisms, effects of global change on developing offspring (e.g. embryos) are also important. Oviparous, non-avian reptiles have received considerable attention because eggs are left to develop under prevailing environmental conditions, making them vulnerable to increases in ambient temperature. Though many studies assess embryo thermal tolerance and physiology in response to long-term (i.e. chronic), constant incubation temperatures, fewer assess responses to acute exposures which are more ecologically relevant for many species. We subjected eggs of the brown anole lizard ( Anolis sagrei ) to heat shocks, thermal ramps, and extreme diurnal fluctuations to determine the lethal temperature of embryos, measure the thermal sensitivity of embryo heart rate and metabolism, and quantify the effects of sub-lethal but stressful temperatures on embryo development and hatchling phenotypes and survival. Most embryos died at heat shocks of 45 or 46 °C, which is ~12 °C warmer than the highest constant temperatures suitable for development. Heart rate and O2 consumption increased with temperature; however, as embryos approached the lethal temperature, heart rate and CO2 production continued rising while O2 consumption plateaued. These data indicate a mismatch between oxygen supply and demand at high temperatures. Exposure to extreme, diurnal temperature fluctuations depressed embryo developmental rates and heart rates, and resulted in hatchlings with smaller body size, reduced growth rates, and lower survival in the laboratory. Thus, even brief exposure to extreme temperatures can have important effects on embryo development, and our study highlights the role of both immediate and cumulative effects of high temperatures on egg survival. Such effects must be considered to predict how populations will respond to global change.

2635: Geographical origin determines responses to salinity of Mediterranean caddisflies
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Posted to bioRxiv 15 Jul 2019

Geographical origin determines responses to salinity of Mediterranean caddisflies
59 downloads ecology

Mauricio J. Carter, Matías Flores, Rodrigo Ramos-Jiliberto

Many freshwater ecosystems worldwide, and particularly Mediterranean ones, show increasing levels of salinity. This changes in water conditions could affect abundance and distribution of inhabiting species as well as the provision of ecosystem services. In this study we conduct laboratory experiments using the macroinvertebrate Smicridea annulicornis as a model organism. Our factorial experiments were designed to evaluate the effects of geographical origin on organisms and salinity levels on survival and behavioral responses of caddisflies. The experimental organisms were captured from rivers belonging to three hydrological basins along a 450 Km latitudinal gradient in the Mediterranean region of Chile. Animals were exposed to three conductivity levels, from 180 to 1400 u S/cm, close to the historical averages of the source rivers. We measured the behavioral responses to experimental stimulii and the survival time. Our results showed that geography origin shaped the behavioral and survival responses to salinity. In particular, survival and activity decreased more strongly with increasing salinity in organisms coming from more dilute waters. This suggests local adaptation to be determinant for salinity responses in this species of benthic invertebrate. In the current scenario of fast temporal and spatial changes in water levels and salt concentration, the conservation of geographic intra-specific variation of aquatic species is crucial for lowering the risk of salinity-driven biodiversity loss.

2636: Switchgrass Rhizosphere Metabolite Chemistry Driven by Nitrogen Availability
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Posted to bioRxiv 16 Oct 2019

Switchgrass Rhizosphere Metabolite Chemistry Driven by Nitrogen Availability
59 downloads ecology

Darian Smercina, Alan W. Bowsher, Sarah E Evans, Maren L. Friesen, Elizabeth K Eder, David W Hoyt, Lisa K Tiemann

Plants and soil microorganisms interact closely in the rhizosphere where plants may exchange carbon (C) for functional benefits from the microbial community. For example, the bioenergy crop, switchgrass (Panicum virgatum) is thought to exchange root-exuded C for nitrogen (N) fixed by diazotrophs (free-living N-fixers). However, this interaction is not well characterized and it is not known how or if switchgrass responds to diazotrophs or their activity. To explore this question, we assessed rhizosphere metabolite chemistry of switchgrass grown in a hydroponic system under two N levels and under inoculated or uninoculated conditions. We found switchgrass root exudate chemistry to be more responsive to N availability than to diazotroph presence. Total metabolite concentrations were generally greater under high N versus low N and unaffected by inoculation. Examination of rhizosphere chemical fingerprints indicates metabolite chemistry was also driven strongly by N availability with a greater relative abundance of carbohydrates under high N and greater relative abundance of organic acids under low N. We also found evidence of changes in rhizosphere chemical fingerprints by inoculation treatment suggesting a potential for switchgrass to respond or even recruit diazotrophs. However, we found little evidence of N treatment and inoculation interaction effects which suggests switchgrass response to diazotroph presence is not mediated by N availability.

2637: Distinctive tasks of different cyanobacteria and associated bacteria in carbon as well as nitrogen fixation and cycling in a late stage Baltic Sea bloom
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Posted to bioRxiv 19 Sep 2019

Distinctive tasks of different cyanobacteria and associated bacteria in carbon as well as nitrogen fixation and cycling in a late stage Baltic Sea bloom
59 downloads ecology

Falk Eigemann, Angela Vogts, Maren Voss, Luca Zoccarato, Heide Schulz-Vogt

Cyanobacteria and associated heterotrophic bacteria hold key roles in carbon as well as nitrogen fixation and cycling in the Baltic Sea due to massive cyanobacterial blooms each summer. The species specific activities of different cyanobacterial species as well as the N- and C-exchange of associated heterotrophic bacteria in these processes, however, are widely unknown. Within one time series experiment we tested the cycling in a natural, late stage cyanobacterial bloom by adding 13C bi-carbonate and 15N2, and performed sampling after 10 min, 30 min, 1 h, 6 h and 24 h in order to determine the fixing species as well as the fate of the fixed carbon and nitrogen in the associations. Uptake of 15N and 13C isotopes by the most abundant cyanobacterial species as well as the most abundant associated heterotrophic bacterial groups was then analysed with a NanoSIMS. Overall, the filamentous, heterocystous species Dolichospermum sp., Nodularia sp., and Aphanizomenon sp. revealed no or erratic uptake of carbon and nitrogen, indicating mostly inactive cells. In contrary, non-heterocystous Pseudanabaena sp. dominated the nitrogen and carbon fixation, with uptake rates up to 1.49 ± 0.47 nmol N h-1 l-1 and 2.55 ± 0.91 nmol C h-1 l-1. Associated heterotrophic bacteria dominated the subsequent nitrogen cycling with uptake rates up to 1.2 ± 1.93 fmol N h-1 cell -1, but were also indicative for fixation of di-nitrogen.

2638: Shifting transmission risk for malaria in Africa with climate change: a framework for planning and intervention
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Posted to bioRxiv 08 Oct 2019

Shifting transmission risk for malaria in Africa with climate change: a framework for planning and intervention
59 downloads ecology

Sadie J. Ryan, Catherine A Lippi, Fernanda Zermoglio

Background: Malaria continues to be a disease of massive burden in Africa, and the public health resources targeted at surveillance, prevention, control, and intervention comprise large outlays of expense. Malaria transmission is largely constrained by the suitability of the climate for Anopheles mosquitoes and Plasmodium parasite development. Thus, as climate changes, we will see shifts in geographic locations suitable for transmission, and differing lengths of seasons of suitability, which will require changes in the types and amounts of resources. Methods: We mapped the shifting geographic risk of malaria transmission, in context of changing seasonality (i.e. endemic to epidemic, and vice-versa), and the number of people affected. We applied a temperature-dependent model of malaria transmission suitability to continental gridded climate data for multiple future climate model projections. We aligned the resulting outcomes with programmatic needs to provide summaries at national and regional scales for the African continent. Model outcomes were combined with population projections to estimate the population at risk at three points in the future, 2030, 2050, and 2080, under two scenarios of greenhouse gas emissions (RCP4.5 and RCP8.5). Results: Geographic shifts in endemic and seasonal suitability for malaria transmission were observed across all future scenarios of climate change. The worst-case regional scenario (RCP8.5) of climate change places an additional 75.9 million people at risk from endemic (10-12 months) exposure to malaria transmission in Eastern and Southern Africa by the year 2080, with the greatest population at risk in Eastern Africa. Despite a predominance of reduction in season length, a net gain of 51.3 million additional people will be put at some level of risk in Western Africa by midcentury. Conclusions: This study provides an updated view of potential malaria geographic shifts in Africa under climate change for the more recent climate model projections (AR5), and a tool for aligning findings with programmatic needs at key scales for decision makers. In describing shifting seasonality, we can capture transitions between endemic and epidemic risk areas, to facilitate the planning for interventions aimed at year-round risk versus anticipatory surveillance and rapid response to potential outbreak locations.

2639: Breeding at higher latitude as measured by stable isotope is associated with higher photoperiod threshold and delayed reproductive development in a songbird
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Posted to bioRxiv 01 Oct 2019

Breeding at higher latitude as measured by stable isotope is associated with higher photoperiod threshold and delayed reproductive development in a songbird
59 downloads ecology

Devraj Singh, S.R. Reed, A.A. Kimmitt, K. A. Alford, E.D. Ketterson

Many organisms time reproduction to photoperiod, a constant from year to year. Predicting how anthropogenic change will influence future timing demands greater knowledge of the current role of photoperiod. We held two closely related bird populations in a common environment. One population is resident; the other winters in sympatry with the resident population but migrates north prior to reproducing. We increased photoperiod gradually and measured preparation for migration and reproduction, using feather stable isotopes to estimate breeding latitude. We predicted population differences in the minimum stimulatory day length to elicit a response (CPP, critical photoperiod) and co-variation between CPP and distance migrated. We found clear population differences in CPP and greater CPP in longer distance migrants. We conclude that current geographic variation in reproductive timing has a genetic or early developmental basis and recommend that future research focus on how anthropogenic changes will interact with CPP to adjust timing of reproduction and migration.

2640: Differential lipid dynamics in stocked and wild juvenile lake trout
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Posted to bioRxiv 30 Jul 2019

Differential lipid dynamics in stocked and wild juvenile lake trout
59 downloads ecology

Madelyn G. Sorrentino, Taylor R. Stewart, J. Ellen Marsden, Jason D. Stockwell

After more than 40 years of stocking, lake trout (Salvelinus namaycush) in Lake Champlain have started to exhibit strong, natural recruitment. The abrupt surge in recruitment suggests a change in limiting factors such as prey availability or overwinter survival. The distribution of juvenile wild lake trout varies in relative abundance among regions of Lake Champlain. The differences suggest the prey base, or foraging success, may vary geographically within the lake. Stocked and wild lake trout may differ in their ability to use resources and in overwinter survival. One metric that can indicate differences in resources across regions is lake trout lipid content, which reflects the quality of available food and serves as an important energy reserve for overwinter survival. We quantified total lipid content of stocked and wild juvenile lake trout across spatial (lake regions) and temporal (seasonal) scales. No spatial differences in lipid content were apparent. Wild fish had greater lipid content than stocked fish. Seasonally, stocked fish showed a continuous drop in lipid content from pre-winter levels at stocking to the following autumn. Wild fish showed a cyclical summer increase in lipids following winter depletion, which plateaued by autumn. The high lipid content of hatchery lake trout may be necessary as they acclimate to foraging in the wild. Hatcheries would benefit from evaluating whether post-stocking survival could be improved by altering feeding or rearing regimes.

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