EAGER-NEON: Earthworm Diversity at Multiple Scales: What can Genetics Tell us about the Distribution of these Important Soil Organisms?

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The proposed research will develop and apply methods (DNA metabarcoding) to examine and compare measures of earthworm diversity on a continental scale. These comparative studies of earthworm diversity provide a unique opportunity to evaluate several major environmental issues, such as soil ecosystem services and the existence and consequences of biodiversity loss and species invasion. About one fourth of all known species on Earth resides in the soil, but most of this biodiversity is hidden due to the amount of labor needed to sample, extract and identify soil organisms. DNA metabarcoding is a technique that targets extracellular DNA, that is DNA from lysed or degraded cells in the soil. Thus, it provides the opportunity to identify species that are not physically present in the soil at the time of sampling. The continental scale coverage of NEON data and archived soil samples provides a unique opportunity to examine patterns of earthworm species richness at different spatial scales.The first phase of the study will establish protocols tailored to soil samples collected and archived by NEON. Soils and earthworms collected at the Smithsonian Environmental Research Center (SERC) will be used for this phase. The main goal is to establish the minimum amount of soil needed for sequencing. The PIs will also sample soil within three different SERC habitats representing three distinct earthworm communities. Different species are active at different times of the year, thus they will conduct sampling both in spring and summer 2016. They plan to take composite samples mimicking the sampling that is currently used by the NEON network. In the next stage DNA from soil samples from the NEON archive will be extracted and sequenced. The species diversity data will then be correlated with environmental data, also collected by NEON. The environmental data includes: local climatic conditions, the amount and quality of leaf litter, and soil properties, particularly pH, organic matter content and texture. If available, data on soil microbe diversity will also be used as metadata to evaluate and interpret species richness patterns for earthworms. The PIs will publish papers focusing on the new methods, and on the results of the genetic analyses of earthworm biological diversity. Species new to science and/or significant new records will also be described in separate papers.