Community Ecology and Evolutionary Ecology
In collaboration with a great team of social scientists and natural scientists, the Lau lab is investigating how farmer decisions affect the capacity of soil microbes to protect plants from drought stress. This collaboration investigates feedbacks between humans and microbes, linking the social and natural sciences in new ways.
The next phase of the Kellogg Biological Station Long-term Ecological Research, the KBS LTER, is investigating how resources, diversity, and adaptation might promote resilience to drought. We are investigating whether microbial diversity can promote plant drought resilience and how plant species and functional diversity promote resilience.
Global warming is often hypothesized to facilitate biological invasions. We tested this hypothesis by planting phylogenetically paired invasive, non-invasive exotic, and native species into an experimental field heating array at KBS. Preliminary results suggest that although species vary in warming response, native and invasive species on average respond similarly. Interestingly, invasive species differ dramatically from non-invasive exotic and native species in phenological response to warming. Invasive species substantially advance flowering under warmer conditions, but native and non-invasive exotic species do not. Additional analyses measure herbivory to test how global warming influences the strength of enemy release, building on previous work testing the enemy release hypothesis by former student Liz Schultheis.
The legume-rhizobium symbiosis is a classic example of mutualism. Leguminous host plants trade carbohydrates for the nitrogen fixed by their rhizobium symbionts. In collaboration with Katy Heath (U. of Illinois), we are investigating how long-term nitrogen addition treatments at the KBS LTER have influenced the ecology and evolution of rhizobium populations and their Trifolium host plants. Nitrogen-rich environments have been hypothesized to shift the legume-rhizobium mutualism towards parasitism because plants can obtain nitrogen more efficiently from the abiotic environment than from their rhizobium symbionts. We find that long-term nitrogen addition experiments have caused the evolution of less mutualistic rhizobia (Weese et al. 2015), that horizontal gene transfer has contributed to the evolution of less cooperative rhizobia (Gordon et al. 2016), and have identified the genes underlying these evolutionary responses (Klinger et al. 2016). Our current work investigates the ecological consequences of these evolutionary changes and how the evolution of reduced cooperation influences pollinators, herbivores, and soil nitrogen availability.
Intraspecific genetic variation can have large effects on ecological processes; however, effects may be underestimated because most studies to date are on small spatial-scales and short time-scales. In collaboration with Lars Brudvig (MSU) and Emily Grman (Eastern Michigan University), we are manipulating both plant genetic diversity and plant species richness at the field scale. Our experiment opens up new research possibilities, such as studies investigating the effects of genetic diversity on population demography and plant evolution. We have established permanent sampling transects within each site and are working with students and citizen scientists to monitor these treatments over the coming decades. Shorter-term manipulations explored the effects of climate warming, herbivory by insects and mollusks, seed consumption, soil microbes, and invasive species on native species establishment. Results from these studies document that warming changes which seed sources establish best in prairie restorations; that arthropods are voracious seed predators and potentially more important to prairie establishment than previously thought, and that patterns of prairie plant species establishment are impacted by vertebrate (mammals and birds) consumers and proximity to the restoration site’s edge.