These talks, held both days of the Spring Symposium, provide an opportunity for ecology-focused graduate and undergraduate students and postdoctoral scientists to share their research.
Diel Variation of Carbon Dioxide and Methane from a Temperate Wetland Stream
Adam Rexroade, Emily Stanley
2:35-2:55 p.m. May 2
Streams are an important conduit for carbon transport to downstream environments and the atmosphere. Drivers, magnitude, and variability of carbon dioxide (CO2) emissions from streams are well understood. However, streams also emit significant amounts of methane, a greenhouse gas 28 times more potent than CO2. Yet, the magnitude, drivers and temporal variation of methane is not understood. Using measurements of gas concentration and gas evasion to the atmosphere, we captured temporal variation in gas flux to the atmosphere. Gas data combined with other environmental information, we identified key drivers of gas evasion. We found that CO2 emissions are significantly higher at night while methane emissions do not statistically differ from those during the day. Dissolved oxygen concentrations and groundwater sources were identified as drivers of both gases. These results highlight the need for further exploration of drivers of greenhouse gas fluxes from aquatic ecosystems, especially methane.
Nutrient Analysis and Biological Indicators Near Green Lake, Wisconsin
Laura Bates, Anita Thompson
2:55-3:15 p.m. May 2
Green Lake, Wisconsin’s deepest inland lake, is threatened by excessive nutrient loading from the surrounding agricultural landscapes. The Green Lake Watershed does not currently have an assessment of the biological conditions of its eight tributaries using aquatic taxa, particularly diatoms, which indicate the water quality flowing into Green Lake. Many efforts to mitigate negative effects of nutrient transport into Green Lake include the implementation of restoration projects, however such projects are very expensive and complex. Understanding the local relationship between natural and anthropogenic stressors influencing in-stream biological conditions and stream eutrophication in the Green Lake Watershed would make the restoration project implementation process more efficient and effective.
The purpose of this research is to assess the water quality of Green Lake’s tributaries using biological indicators, and to understand the interconnectedness of local anthropogenic and natural stressors that affect aquatic ecosystem conditions and nutrient pollution in the watershed. Stream and biological conditions will be assessed using taxa assemblages and biotic indices of diatoms and macroinvertebrates. Evaluations of natural and anthropogenic stressors influencing the stream physiochemical environment will be conducted using land use and water quality data from each sample site. This research will help watershed managers understand how nutrient pollution and other anthropogenic activities are influencing biological assemblages in Green Lake’s tributaries and help contribute to the establishment of nutrient thresholds specific to the Green Lake watershed.
Outcomes of Soil Mixing Disturbances on the Microbial Community
Jaimie West, Thea Whitman
3:15-3:35 p.m. May 2
Soil is a complex and heterogeneous web of disconnected microhabitats that harbors vastly diverse microbial communities that drive crucial soil functions such as biogeochemical cycling, organic matter decomposition, and plant productivity. The spatial heterogeneity of soil’s microhabitats warrants the study of ecological patterns and community assembly in the context of community coalescence, or the combining and restructuring of communities along with their environment. By mixing soil at various frequencies in a 16-week lab incubation and using 16S rRNA gene sequencing, we explored the effects of mixing disturbances on soil bacterial richness, community composition, community assembly processes, and co-occurrence networks.
We hypothesized that well-mixed soil would harbor less rich communities and demonstrate homogenizing processes. Findings supported our hypotheses, with a > 20% decrease in soil bacterial richness in well-mixed soil, and increasingly self-similar communities structured by homogenizing selection and dispersal. Our results imply that the vast microbial diversity in soil may be underpinned by the unmixed and spatially heterogeneous nature of soil. We will also take a preliminary look at the effects of disturbance via soil mixing in the context of agricultural tillage in southern WI and the invasive Amynthas spp. (jumping worm) activity at the UW Arboretum. By better understanding the importance of spatial heterogeneity and physical disturbance for soil microbial communities, we may better extrapolate how anthropogenic disturbances, such as climate change or land use change, may affect broad soil functions.
Peeking Under the Canopy: Effects of Short Fire-Return Intervals on Herbaceous Understories in Greater Yellowstone
Nathan G. Kiel, Kristin H. Braziunas, Monica G. Turner
3:35-3:55 p.m. May 2
Throughout western North America, anomalously short fire-return intervals (FRI) are becoming more common, reducing postfire tree establishment and eroding forest resilience. However, potential effects on understory plant communities, the most diverse floral stratum in temperate forests, remain less well understood. In Greater Yellowstone, forests adapted to historical FRI of 100-300yrs have recently reburned at <30yr FRI.
To elucidate the effects of short- (<30yr) v. long- (>125yr) interval fire, we quantified plant community composition in 31 paired 0.25-ha plots across a range of FRI, time since fire (TSF), and climatic conditions. In each plot, percent cover by species was measured in 25 0.25-m2 quadrats and plot richness determined. Paired t-tests were used to quantify differences in species and functional group cover. Pairwise compositional differences were assessed using dissimilarity indices, and multiple regression was used to explain dissimilarity over environmental and climatic variables.
Richness and diversity did not differ, and understory cover was marginally higher following short- v. long-interval fire (~32% v. ~28%). Graminoid (~14% v. ~11%) and non-native (1.1% v. 0.8%) cover were slightly greater following short-interval fire, and plots following short-interval fire shifted to proportionally more annual and less perennial cover. Paired communities differed substantially (mean ± SE; Jaccard’s dissimilarity = 0.77±0.015), with TSF and multiple climate variables important in explaining pairwise plot dissimilarity (R2adj = 0.62). With continued changes to climate and fire expected through the end of this century, current plant community responses may signal the beginning of fundamental shifts to Greater Yellowstone plant communities.
Long Term Body Condition Reveals Strong Species Coupling
Ben Martin, Jake Vander Zanden
2:30-2:50 p.m. May 3
Predator-prey coupling can result in oscillations of predator-prey abundances. Strong predator-prey coupling can trigger entire ecosystem trophic cascades where the shifts in predator and prey abundances has a rippling impact on lower trophic levels. Here, we investigated how the body condition (body weight relative to body length) of a strongly coupled predator and prey changes as their respective population densities shifted due to cascading interactions.
We found that predator and prey body condition was strongly influenced by their respective population densities, which signifies strong population density dependence. Further, we found predator and prey body conditions were inversely related, which highlights strong predator-prey coupling. We further note that in cases where coupled predator-prey have inverse body condition relationships, we can use historical length/weight data to illuminate past ecological conditions. Here, we were able to suggest whether the food web was historically three or four-tiered based on historical predator body condition. Overall, this study highlights strong predator-prey coupling as indicated by inverse body condition, and highlights the application of synthesizing long-term trends in body condition.
How Should We Evaluate Grassland Restoration? A Review of Metrics Used and What They Tell Us
Stephanie L. McFarlane, Laura M. Ladwig, Quinn M. Sorenson, Ellen I. Damschen
2:50-3:10 p.m. May 3
Grassland habitat restoration is critical for preventing continued loss of plant diversity. As we enter the United Nations Decade on Restoration, restoration ecologists are actively monitoring restoration outcomes so that we can understand the mechanisms responsible for failure or success. However, there is no scientific consensus on how to determine if restoration efforts are successful or which metrics best measure outcomes. This leads us to a clear question: how do we define and measure restoration success? To answer this, we used the PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) review process to summarize how restoration outcomes are measured. In our review, we ask the following questions:
- How many different metrics are used to evaluate restoration outcomes?
- Which metrics are the most common?
- Which are most useful for assessing restoration outcomes?
We identified >500 peer-reviewed articles discussing outcomes of grassland restoration worldwide. Target organisms ranged widely from soil microbes to plants to songbirds, which, when paired with more than 100 ecological metrics led to 600 unique metrics for reporting restoration outcomes. Quantitative metrics, including plant diversity and abundance, were the most common while metrics with an assigned value, such as floristic quality index and coefficient of conservatism, were infrequent. Which metric is appropriate often depends on the amount of degradation and the restoration goals. It is essential to set intentional goals when restoring grassland ecosystems and to continue refining the most appropriate metrics to use when assessing restoration success.
These can be viewed from 3:10 to 4:10 p.m. Tuesday, May 3.
Genetic Dispersal of Spiroplasma in the Alpine Ground Beetle Nebria Ingens Species Complex and Sympatric Neighbors
Robert Hall, Yi-Ming Weng, Sean Schoville
Insect endosymbionts have been found in more than half of insect species. The roles these microorganisms play in their host could vary from parasitism to mutualism but have not been well explored due to the high diversity of insects and their extremely heterogeneous life histories. In this study, we aim to understand the role of Spiroplasma sp. NR in their host — the Nebria ingens species complex — by scanning the prevalence of infection, genetic diversity, geographic distribution, and associating the infection rate with environmental factors as well as the physiological, morphological, and molecular characteristics of the beetles.
Initial results show a relatively high (57%) and geographically widespread infection rate of Spiroplasma throughout the Nebria ingens species complex. Both host and microbe populations show a similar trend of gradual genetic divergence across geographical space, but Spiroplasma appears to have longer dispersal distance. Also, findings show Spiroplasma in sympatric species of Nebria at different altitudes. Our ongoing research utilizes population genomic variation of both species, including the beetle mitochondrial DNA, to identify inheritance patterns and assess the beneficial or detrimental ecological role of Spiroplasma in this insect host.
Defense at What Cost? Quantifying the Cost of Inflammation Impact of Fire on Native Orthopteran Species
Trey Sasser, Jesse Weber
The threespine stickleback (G. aculeatus) is a small species of fish that provides an ideal suite of traits for studying the evolution of immune function. Stickleback populations vary in a number of immune phenotypes, including peritoneal fibrosis: an inflammatory response that allows fish to stunt parasite growth. One potential explanation for this variation is that the costs of mounting a fibrotic response may be untenable in some environments. To quantify the energetic cost of fibrosing, we measured the standard metabolic rate (SMR) and mass of stickleback before and after inducing fibrosis using a pro-inflammatory immune stimulant. We found that fish that were injected with the immune stimulant had significantly higher metabolic rates 10 days post-injection and lost significantly more mass than fish injected with our control. Our work suggests that fibrosing entails significant energetic costs.
Environmental Predictors of Electroactive Bacterioplankton in Small Boreal Lakes
Charles Olmsted, Rogert Ort, Patricia Tran, Elizabeth McDaniel, Eric Roden, Shaomei He, Katherine McMahon
Extracellular electron transfer (EET) by electroactive bacteria in anoxic soils and sediments is an intensively researched subject, but EET’s function in planktonic ecology has been less considered. Following the discovery of an unexpectedly high prevalence of EET proteins in a bog lake’s bacterioplankton, we hypothesized that the redox capacities of dissolved organic matter (DOM) enrich for electroactive bacteria by mediating redox chemistry. We developed the bioinformatics pipeline FEET (Find EET) to identify and summarize EET proteins from metagenomics data. We then applied FEET to several bog and thermokarst lakes and correlated EET protein occurrence values with environmental data to test our predictions.
Our results provide evidence that DOM participates in EET by bacterioplankton. We found a similarly high prevalence of EET proteins in most of these lakes, where oxidative EET strongly correlated with DOM. Numerous novel clusters of multiheme cytochromes that may enable EET were identified. Taxa previously not considered EET-capable were found to carry EET proteins. We conclude that EET and DOM interactions are of major ecological importance to bacterioplankton in small boreal lakes, and that EET, particularly by methylotrophs and phototrophs, should be further studied and incorporated into both conceptual and quantitative methane emission models of melting permafrost.
Stem Density of Invasive Shrubs Facilitate Increased Winter Seed Removal by Small Mammals
Mark Fuka, John Orrock
Exotic plants can lead to significant changes in native habitats they invade. A growing body of evidence suggests that many ways exotic shrubs impact native plants is through indirect effects that may be of critical importance. For example, exotic shrubs may modify the structural complexity of invaded habitats, leading to increased activity of rodents and consumer pressure on seeds. This change in rodent granivory is important to understand because it can generate significant increases in seed consumption. While invasive plant modified granivory can be significant, it can also be highly variable among seasons and may coincide with when native seeds are most vulnerable. We manipulated the presence of a common, widespread invasive species, Rhamnus cathartica, to examine seasonal effects of invasive shrubs on rodent seed removal. We used seed removal depots in summer, autumn, and winter to quantify seasonal trends in rodent granivory of three native tree species, Tilia americana, Prunus serotina, and Acer saccharum, and the invasive shrub, Rhamnus cathartica.
Our results reveal a significant interaction of season and invasive shrubs: in summer and autumn, there was no effect of invasive shrubs on seed removal, but removal was 21% greater in invaded habitat in winter that varied by seed species. Habitat characteristics, like stem density, could be an important driver in seasonal seed removal within invaded habitats when vegetative cover is no longer present. Because the effects of invasive shrubs were greatest in the winter, understanding when seeds are most vulnerable may have important implications for overwinter seed survival.
METABOLIC – A Scalable High-Throughput Metabolic and Biogeochemical Functional Trait Profiler
Zhichao Zhou, Patricia Q. Tran, and Karthik Anantharaman
METABOLIC (METabolic And BiogeOchemistry anaLyses In miCrobes) is a scalable software to study microbial metabolic traits and biogeochemical functional profiles based on microbial genomes. METABOLIC can help to annotate and organize the genome annotation result. It can also visualize the biogeochemical cycles. Furthermore, if the metagenomic reads are provided, further analyses can be conducted to study genome abundance, sequential metabolic transformations, metabolic energy flow pattern, and metabolic networking pattern at community scale. It provides user-friendly results with curated tables and diagrams. It integrates genome-informed metabolism into biogeochemical models to study microbial community to improve current situation that many community-based biogeochemical studies rely primarily on physicochemical data and treat microorganisms as blackbox.
The Effects of Prairie Restoration on Wisconsin Orthopteran Species
MaryBeth Barker, Matthew Fox, Stephanie L. Mcfarlane, Gus Brunette, Lydia Dean, Jade Kochanski, Grant Witynski, Claudio Gratton, Ellen I. Damschen
Grassland ecosystems have been reduced to a fraction of their historic extent and rely extensively on habitat restoration. The impacts of restoration methods, such as seeding and fire, on insect populations is often overlooked. This research analyzes how restoration practices impact the abundance and species diversity of grasshopper and katydid species in tallgrass prairies. Previous studies determined species diversity per Wisconsin county, but further research is needed to determine the prairie type preferences. Orthopterans are a common inhabitant of grasslands making it important to compare the impacts between restored and remnant prairie sites. The restored sites were categorized as seeded, seeded and burned, or non-seeded. We ask the following: How effective are restoration practices at promoting Orthopteran species diversity when compared to remnant prairies? We predict that there will be greater diversity at the seeded or seeded and burned sites.
We visited 32 restored prairies and 7 remnant prairies during the summer of 2019 and 2020. At each site, 25 sweeps were done at three transects. Samples were frozen until they could be counted and identified in the lab. Immature individuals were identified to family and adults were identified to species. The average Orthopterans abundance was 13.1 individuals per seeded sites, 11 per seeded and burned sites, 62.6 individuals per non-seeded sites, and 16.7 individuals at remnant sites. Preliminary data suggests that non-seeded sites had the greatest abundance. We believe this is likely due to Orthopterans’ tendency to be generalists and therefore commonly found in tallgrass prairies.
Pollen quality as a potential driver for bumble bee diversity and abundance in restored prairies
Michelle Chung, Stephanie L. McFarlane, Jade Kochanski, Claudio Gratton, Ellen I. Damschen
Many bee populations are declining globally, in large part due to habitat loss and the resulting nutritional shortages. Restored prairies have a greater abundance and diversity of bumble bees than non-restored agricultural fields. However, the nutritional quality of the floral resources in these restored prairies is largely unknown. Given bumble bees’ development and survival depends upon pollen with a high nutritional value (i.e., a high protein:lipid ratio), understanding the nutritional quality of the floral resources found in these prairies would aid our understanding of the potential mechanisms for variation in local bumble bee abundance and diversity in restored prairies. Pollen from herbaceous species commonly found in restored prairies across southern Wisconsin was collected in the summer of 2021.
I am currently completing pollen assays to determine protein and lipid content. Using flowering species and bumble bee data already collected from the Damschen and Gratton Labs, I expect to find a positive correlation between the pollen quality of the floral resources of these sites and their bumble bee diversity and abundance. This knowledge can be used to select optimal plant species for future restoration efforts to ensure that restored prairies are providing adequate nutrition to support bumble bee populations in Wisconsin.
Species-Specific Effects of Elevated Atmospheric Carbon Dioxide on Pollen Macronutrients
Anupreksha Jain, Olivia Bernauer, James Crall
The concentration of CO2 in the atmosphere has increased from 280 parts per million (ppm) before the Industrial Revolution to 412.5 ppm in 2020, and is projected to keep rising with global emissions. Elevated atmospheric CO2 is known to alter the nutritional and biochemical makeup of plants, with dire consequences for their interactions with insects. However, the changes in pollen composition, essential for pollinator health and fidelity, are largely unexplored. We ran a glasshouse experiment to investigate the effects of elevated CO2 on pollen protein and metabolomic concentrations.
We grew seven species of plants under either ambient (~450 ppm) or elevated (650 ppm) CO2 conditions. We collected pollen or anther samples from each plant for several weeks and pooled them across days. Using an elemental analyzer, we measured C:N ratio, and used a conversion factor to determine protein concentrations. We observed species-specific alterations in pollen nutritional quality.
Influence of Landscape Cover Types on Body Size Variation Across Bumble Bee Species in Illinois
Yichen Li, Jade Kochanski, Jeremy Hemberger, Claudio Gratton
Bumble bees are an important primary pollinator. Understanding how they respond to environmental disturbances like human land use is critical for conservation efforts. Body size is widely used to evaluate fitness of bumble bees as it has been shown to correlate with colony performance (e.g., fecundity and foraging distance). Bee populations with large variation in body size across individuals may be more resilient to land use change. However, these landscape-level effects on body size of bumble bees have not been investigated.
In this study, I measured body size of Illinois bumble bees using intertegular distance (ITD) and we compared them across counties with contrasting landscape composition. We also compared body size across common and declining species since they should have differing responses to land use change. We hypothesize that the average body size would be greater for bee populations in counties with lower percentage of developed land. Additionally, there would be smaller body size variation in species that are declining or in human-dominated landscapes since they are less able to adapt to change.
Taxonomic, Phylogenetic, and Functional Change of North American Grasslands Following Woody Encroachment
Hannah Davidson, Katherine T. Charton, Ellen I. Damschen
Woody encroachment is the increase of woody species in open-canopied, herbaceous communities and is widespread throughout grasslands and savannas. Previous studies have reported losses in taxonomic diversity with woody encroachment, but few have looked at changes in phylogenetic and functional diversity. As opposed to taxonomic diversity, which illustrates the variety of species present, phylogenetic diversity highlights the variation in evolutionary histories and relatedness among a population. Functional diversity examines the variety of morphologies and physiologies within a plant community.
To understand the impact of woody encroachment on phylogenetic and functional diversity of existing herbaceous communities, we conducted a meta-analysis of 32 studies in North America. We extracted relevant data on low and high measures of woody vegetation and corresponding measures of herbaceous vegetation. When reported, we recorded the identity of herbaceous species that either significantly increased or decreased under encroachment. To investigate phylogenetic and functional changes, we will use existing regional phylogenies and plant trait data for the species reported.
We hypothesize that phylogenetic and functional diversity of herbaceous communities will decrease with woody encroachment more so than taxonomic diversity due to certain evolutionary histories and/or functional traits being particularly vulnerable to selective pressures of encroachment. These results will allow us to predict species that may be lost in the future, even if they are not currently declining, as these more specific measures of diversity indicate how plants are responding to changing environmental conditions.