Integrative Taxonomy of the Criconematidae

Our overall goal is to describe and map nematode biodiversity in North America. Specifically we will concentrate on Criconematina, a suborder of plant parasitic, soil-dwelling nematodes. Criconematina, commonly referred to as ring-nematodes, are distributed globally and associated with a wide range of hosts and habitats. In native grasslands and forests, they may constitute as much as 30% of the below-ground nematode community. Their abundance often approaches 500 individuals per 100cc of soil with as many as a dozen species recorded from a single habitat. Host associations may be broad, covering entire plant families, or they may specialize in feeding on a few closely related plant species. Several are known agronomic pest species, but the vast majority is known only from native habitats and responds negatively to soil disturbance. Due to their sensitivity to disturbance and associations with a range of plant species, some ecologists have suggested that ring nematodes could serve as a below-ground biological indicator of habitat quality. Before this application is possible taxonomic boundaries need to be evaluated and a reference database needs to be established.
Our approach to constructing the nematode reference database is based on sampling soil from plant communities characteristic of major ecoregions of North America as defined by Olson et al., (2001). Within each ecoregion sampling sites will be selected to reflect areas of high plant diversity, endemicity, or varying levels of disturbance. At each sampling site a single 40x40m plot will be established with the corners marked by GPS coordinates. At a predetermined point along one border, the plot will be entered and traversed by the collector with an Oakfield tube soil corer of 2cm diameter. Every 6 meters a core will be extracted to a depth of approximately 20 cm, until 500cc of soil is accumulated. The soil is then placed into a plastic collection bag and stored for analysis. Images of the study site and notes on the plant community will be recorded. Each site will be sampled at least once, preferably in the spring or fall depending on root growth. In some cases, nematode analysis may suggest a second sampling of the site will be productive. The discovery of new species or the observation of unusual nematode assemblages or stages could initiate a second sampling session.
In the laboratory nematodes will be isolated from the soil sample by a process of floatation and sieving followed by sugar centrifugation. Members of the suborder Criconematina will be measured, photographed and then stored for PCR/DNA sequencing analysis. A critical component of this analysis is the linkage of nematode morphology from individual specimens with their corresponding DNA haplotype. All images and DNA sequences will be deposited in public access data repositories.