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Michael S. Robeson

Interspecific plant interactions reflected in soil bacterial community structure and nitrogen cycling in primary succession.

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Front. Microbiology, in the press, January 2018  | doi: 10.3389/fmicb.2018.00128

Joseph E. Knelman, Emily B. Graham, Janet S. Prevéy, Michael S. Robeson, Patrick Kelly, Eran Hood and Steve K. Schmidt

Past research demonstrating the importance plant-microbe interactions as drivers of ecosystem succession has focused on how plants condition soil microbial communities, impacting subsequent plant performance and plant community assembly. These studies, however, largely treat microbial communities as a black box. In this study we sought to examine how emblematic shifts from early-successional Alnus sinuata (alder) to late successional Picea sitchensis (spruce) in primary succession may be reflected in specific belowground changes in bacterial community structure and nitrogen cycling related to the interaction of these two plants. We examined early successional alder-conditioned soils in a glacial forefield to delineate how alders alter the soil microbial community with increasing dominance. Further, we assessed the impact of late-successional spruce plants on these early-successional alder-conditioned microbiomes and related nitrogen cycling through a leachate addition microcosm experiment. In total, we show how increasingly abundant alder select for particular bacterial taxa. Additionally, we found that spruce leachate significantly alters the composition of these microbial communities in large part by driving declines in taxa that are enriched by alder, including bacterial symbionts. We found these effects to be spruce-specific, beyond a general leachate effect. Our work also demonstrates a unique influence of spruce on ammonium availability. Such insights bolster theory relating the importance of plant-microbe interactions with late-successional plants and interspecific plant interactions more generally.

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Assessing the utility of metabarcoding for diet analyses of the omnivorous wild pig (Sus scrofa)

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Ecology and Evolution, (2018), 8:185-196. DOI: 10.1002/ece3.3638

Michael S. Robeson II, Kamil Khanipov, George Golovko, Samantha M. Wisely, Michael D. White, Michael Bodenchuck, Timothy J. Smyser, Yuriy Fofanov, Noah Fierer, Antoinette J. Piaggio


Wild pigs (Sus scrofa) are an invasive species descended from both domestic swine and Eurasian wild boar that was introduced to North America during the early 1500s. Wild pigs have since become the most abundant free-ranging exotic ungulate in the United States. Large and ever-increasing populations of wild pigs negatively impact agricul- ture, sport hunting, and native ecosystems with costs estimated to exceed $1.5 bil- lion/year within the United States. Wild pigs are recognized as generalist feeders, able to exploit a broad array of locally available food resources, yet their feeding behaviors remain poorly understood as partially digested material is often unidentifiable through traditional stomach content analyses. To overcome the limitation of stomach content analyses, we developed a DNA sequencing-based protocol to describe the plant and animal diet composition of wild pigs. Additionally, we developed and evaluated block- ing primers to reduce the amplification and sequencing of host DNA, thus providing greater returns of sequences from diet items. We demonstrate that the use of block- ing primers produces significantly more sequencing reads per sample from diet items, which increases the robustness of ascertaining animal diet composition with molecular tools. Further, we show that the overall plant and animal diet composition is signifi- cantly different between the three areas sampled, demonstrating this approach is suit- able for describing differences in diet composition among the locations.



blocking primer, CO1, diet, feral swine, metabarcoding, trnL