View Program - 2022 Population, Evolutionary, and Quantitative Genetics Conference

Generalists are species capable of surviving in a variety of niches and are present in most ecosystems. Despite their ubiquity, very little is known about how generalism evolves and is maintained. In this study, we will test two hypotheses for the maintenance of generalism using the obligate parasite and common crop pest, the root knot nematode Meloidogyne hapla. M. hapla has over 500 recorded host plants and the extant genetic variation for generalism across populations has yet to be described. We will test whether 1) Populations possess large amounts of standing genetic variation, maintained by spatial variation in in host species, that contributes to the expression of generalism at the species level (e.g. individuals and populations specialize on different host plant species) or 2) All individuals in the species possess a conserved set of “virulence” genes that allows individuals to infect most hosts they could potentially encounter. We predict that these two distinct mechanisms should give rise to unique population genetic signatures. For the first hypothesis, population genetic structure should be strongly associated with host plant use, while for hypothesis two, population genetic structure will not be associated with host plant use and instead be influenced by geographic distance. To test these hypotheses, we collected root knot nematodes from four host plant species at multiple locations across the Eastern United States. We sequenced individuals using a combined whole genome amplification and whole genome sequencing approach. To our knowledge this is the first population genetic study using individual root knot nematodes. In addition to exploring the evolutionary maintenance of generalism, our work will also quantify dispersal among populations. Dispersal distance is a central component to many models that predict the spread of root knot nematodes, but it has yet to be empirically estimated.

What makes a generalist? Using whole genome amplification with whole genome sequencing to quantify host-associated genetic structure in root knot nematodes