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All photos by A. Keeler. Top to bottom: L. argenteus & B. flavifrons; L. leucanthus; V. americana.
I'm interested in learning how prolonged seasonal drought will alter legume - N-fixing bacteria mutualisms and their associated ecosystem services.
The Rocky Mountain Biological Laboratory (RMBL, photo to the right) offers an excellent system to answer questions about phenology and drought. At RMBL, total June precipitation has decreased significantly since the 1980s, and the date of spring snowmelt has shifted earlier, extending the summer drought period. Lupinus argentues, Lathyrus lanszwertii var. leucanthus, and Vicia americana, three biologically important, rhizobia-hosting leguminous species found at RMBL are the focal species for this experiment (photos to the left). Dry soils may not contain active rhizobia at the time of Lupinus, Lathyrus, and Vicia germination or early growth which could impact germination success and phenology.
Drought-induced mutualism breakdown between legumes and N-fixing bacteriaUsing stable isotope analysis, we predict that legumes growing in dry conditions will have a positive d15N value, indicating a breakdown between legumes and rhizobia. Legumes interacting with rhizobia (more likely in wetter conditions) will have a negative d15N value. Additionally, as the duration and frequency of summer droughts at RMBL increases, we predict that the average d15N value of legumes will increase over time, indicating more regular short-term breakdowns today.
Legume early-life traits in the absence of mutualists: drought & upward range shiftsPreliminary results suggest that the onset of germination of L. leucanthus and V. americana in soils depleted of rhizobia is significantly delayed by two weeks compared to germination in natural soils and that legume germination success is halved when completely mismatched from rhizobial partners (unpublished data). This is similar in dry vs. well-watered soils, indicating that dry soils could be causing a breakdown. Additionally, rhizobia do not seem to be present beyond the current elevational range of these upward-expanding legumes, as germination success is reduced beyond the current range and germination phenology is delayed. The timing of plant germination is particularly important as it relates to seedling survival, downstream phenological patterns, and reproductive success.
The effect of drought-induced breakdown between legumes and rhizobia on floral traits and reproductive successNitrogen generally benefits plants, increasing their flower number and reward quality. A breakdown between legumes and rhizobia is then predicted to decrease plant N, thus alter floral functional traits. We find that, in conditions where rhizobia are weakly or not at all interacting with legumes, flowering duration is shorter, fewer flowers are produced, rewards are of lesser quality and quantity, and fewer seeds are set.
Bottom-up effects of mutualism breakdown between legumes and N-fixing bacteria on legume pollinators Reduced floral reward quality and fewer flowers may alter interactions between legumes and their pollinators. We are working in the lab and field to determine the effects of reduced reward amino acid diversity on bee feeding behavior, where preliminary results suggest that females prefer higher quality rewards while males are less choosy.
All of my work is done at the Rocky Mountain Biological Laboratory in Gothic, Colorado and at the University of California, Riverside.
The Rocky Mountain Biological Laboratory (RMBL, photo to the right) offers an excellent system to answer questions about phenology and drought. At RMBL, total June precipitation has decreased significantly since the 1980s, and the date of spring snowmelt has shifted earlier, extending the summer drought period. Lupinus argentues, Lathyrus lanszwertii var. leucanthus, and Vicia americana, three biologically important, rhizobia-hosting leguminous species found at RMBL are the focal species for this experiment (photos to the left). Dry soils may not contain active rhizobia at the time of Lupinus, Lathyrus, and Vicia germination or early growth which could impact germination success and phenology.
Drought-induced mutualism breakdown between legumes and N-fixing bacteriaUsing stable isotope analysis, we predict that legumes growing in dry conditions will have a positive d15N value, indicating a breakdown between legumes and rhizobia. Legumes interacting with rhizobia (more likely in wetter conditions) will have a negative d15N value. Additionally, as the duration and frequency of summer droughts at RMBL increases, we predict that the average d15N value of legumes will increase over time, indicating more regular short-term breakdowns today.
Legume early-life traits in the absence of mutualists: drought & upward range shiftsPreliminary results suggest that the onset of germination of L. leucanthus and V. americana in soils depleted of rhizobia is significantly delayed by two weeks compared to germination in natural soils and that legume germination success is halved when completely mismatched from rhizobial partners (unpublished data). This is similar in dry vs. well-watered soils, indicating that dry soils could be causing a breakdown. Additionally, rhizobia do not seem to be present beyond the current elevational range of these upward-expanding legumes, as germination success is reduced beyond the current range and germination phenology is delayed. The timing of plant germination is particularly important as it relates to seedling survival, downstream phenological patterns, and reproductive success.
The effect of drought-induced breakdown between legumes and rhizobia on floral traits and reproductive successNitrogen generally benefits plants, increasing their flower number and reward quality. A breakdown between legumes and rhizobia is then predicted to decrease plant N, thus alter floral functional traits. We find that, in conditions where rhizobia are weakly or not at all interacting with legumes, flowering duration is shorter, fewer flowers are produced, rewards are of lesser quality and quantity, and fewer seeds are set.
Bottom-up effects of mutualism breakdown between legumes and N-fixing bacteria on legume pollinators Reduced floral reward quality and fewer flowers may alter interactions between legumes and their pollinators. We are working in the lab and field to determine the effects of reduced reward amino acid diversity on bee feeding behavior, where preliminary results suggest that females prefer higher quality rewards while males are less choosy.
All of my work is done at the Rocky Mountain Biological Laboratory in Gothic, Colorado and at the University of California, Riverside.
All photos by A. Keeler. Top to bottom: a field site on Mt. Baldy with L. argenteus flowers; L. leucanthus seeds; the RMBL field station.
Photos from top to bottom: Toronto the Blue Jay from the Steven's Lab; sampling water from an urban day-lighted stream in Minneapolis in the winter for the Finlay Lab; sampling water from the Mississippi river in downtown Minneapolis for the Finlay Lab. All photos by A. Keeler
Previous research experience
2017 Junior Specialist, University of California, Riverside (EEOB)Manage common garden projects on seed germination and functional trait expression of six species collected from three distinct elevations at the Rocky Mountain Biological Lab, CO; manage undergraduate volunteers; conduct fieldwork at the Rocky Mountain Biological Lab. Advisor: Dr. Nicole Rafferty
2014 - 2015 Research Assistant, University of Minnesota, Twin Cities (EEB)Conduct research on urban and agriculturally influenced aquatic biogeochemistry and ecology; stable isotope mapping of food webs. Senior thesis: The effects of management regimes on nitrate assimilation in urban daylighted streams.Advisor: Dr. Jacques Finlay
2015 - 2016 Research Volunteer, University of Minnesota, Twin Cities (EEB)Assist with behavioral research on blue jays and starlings relating to the evolution of cognition, foraging, trade-offs, social vs. independent learning, and aposematism.Advisor: Dr. David Stephens
2013 Research Assistant, University of Minnesota, Twin Cities (Entomology)Assist with IPM research regarding plant herbivory by Western corn rootworms, Diabrotica virgifera virgifera. Advisor: Dr. Ken Ostlie
Photo below: The Finlay Lab research team sampling agriculturally influenced stream networks in Southeastern MN.
2017 Junior Specialist, University of California, Riverside (EEOB)Manage common garden projects on seed germination and functional trait expression of six species collected from three distinct elevations at the Rocky Mountain Biological Lab, CO; manage undergraduate volunteers; conduct fieldwork at the Rocky Mountain Biological Lab. Advisor: Dr. Nicole Rafferty
2014 - 2015 Research Assistant, University of Minnesota, Twin Cities (EEB)Conduct research on urban and agriculturally influenced aquatic biogeochemistry and ecology; stable isotope mapping of food webs. Senior thesis: The effects of management regimes on nitrate assimilation in urban daylighted streams.Advisor: Dr. Jacques Finlay
2015 - 2016 Research Volunteer, University of Minnesota, Twin Cities (EEB)Assist with behavioral research on blue jays and starlings relating to the evolution of cognition, foraging, trade-offs, social vs. independent learning, and aposematism.Advisor: Dr. David Stephens
2013 Research Assistant, University of Minnesota, Twin Cities (Entomology)Assist with IPM research regarding plant herbivory by Western corn rootworms, Diabrotica virgifera virgifera. Advisor: Dr. Ken Ostlie
Photo below: The Finlay Lab research team sampling agriculturally influenced stream networks in Southeastern MN.
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