Date of this Version
A thesis presented to the faculty of the Graduate College at the University of Nebraska in partial fulfillment of requirements for the degree of Master of Science
Major: Plant Pathology
Under the supervision of Professor Thomas O. Powers
Lincoln, Nebraska, August 2021
The tallgrass prairie was once one of the most diverse grasslands on the planet, however over 95% has been converted to agriculture in the past 150 years. The remaining prairie is still host to a wide variety of plants, insects, mammals, and soil-dwelling microorganisms, creating an incredibly complex ecosystem. The first aim of this study is to compare three approaches for the measurement of nematode diversity within a 10-mile-long protected prairie habitat corridor near Lincoln, Nebraska. The methods are 1) a traditional morphological analysis of 150 nematodes per study site, 2) a metabarcoding analysis using the 18S genetic marker of the nematode community from 100cc of soil collected at each site, and 3) a Sanger Sequencing DNA barcode analysis of selected nematodes from each site using COI and 18S genetic markers. The three nematode diversity assessments differed in the type of information produced. Nematode genus richness based on morphology produced a range of 19 to 38 genera per site, and 80 different genera across the 15 sites. The metabarcoding analysis resulted in 171 unique Molecular Operational Taxonomic Units (MOTUs). However, only 45 genera of the 80 genera identified via morphology were specifically represented in the taxonomic assignments of the metabarcoding MOTUs. The DNA barcode approach using the COI genetic marker revealed greater taxonomic resolution and more diversity within certain genera, but non-amplification events with some taxa reduced overall assessment of taxonomic diversity by COI alone. The second aim of the study was to compare the plant diversity within the fifteen remnant tallgrass prairie sites and the nematode diversity. The nematode diversity assessment revealed a core set of taxa that make up the tallgrass prairie nematode community, which is distinct from cultivated land. Within the remnant tallgrass prairies, increased plant diversity was positively correlated with increased nematode metabarcoding MOTU richness. The remnant tallgrass prairies in this study contain a unique nematode community that is changed in response to the degree of plant diversity.
Advisor: Thomas O. Powers
Metabarcoding V9 MOTUs
Supplementary_Table2.xlsx (52 kB)
Metabarcoding NF1 MOTUs
Supplementary_Figure1 _Mesocriconema_COI_NJTree.pdf (50 kB)
Neighbor-joining phylogenetic tree of COI sequences of Mesocriconema sp.