Date Thesis Awarded


Access Type

Honors Thesis -- Access Restricted On-Campus Only

Degree Name

Bachelors of Science (BS)




James Skelton

Committee Members

Randolph Chambers

James Kaste


Generalist consumers often are assumed to fill similar or redundant ecological niches by eating indiscriminately. As populations decline for many consumers, including generalists, the potential effects that losing or replacing generalist species may have on the surrounding ecosystem should be determined. This evaluation is especially necessary for generalists with considerable impact other species and the surrounding habitat, i.e., keystone species and ecosystem engineers. As abundant and often dominant omnivores, crayfish (Decapoda: Astacoidea and Parasticoidea) exert strong influence on aquatic ecosystems through predation, herbivory, and detritivory and are therefore often considered keystone species and ecosystem engineers. Recent work has suggested that crayfish species may be functionally redundant, and that invasive crayfish species are thought by some researchers to fill a similar ecological role as the natives they displace. However, despite their ecological importance, we have virtually no species-specific data on crayfish diet in-situ. In Virginia, for example, stream-dwelling Faxonius (formerly Orconectes) crayfish that are native from Missouri to the Great Lakes, recently have expanded to eastern Virginia where they are displacing native crayfish in the genus Cambarus. To assess the potential impacts of this invasion on aquatic invertebrate communities, the gut contents of both native Cambarus crayfish and the invasive Faxonius to were collected and analyzed via DNA metabarcoding with plant-targeting (TRNL) and arthropod-targeting (ANML) primers to compare their diets. We also compared the gut contents of native burrowing crayfish to native non-borrowing crayfish to determine whether ecologically distinct native species compete for food resources where they co-occur. We found that both plant and animal components of crayfish diets significantly differed between native and non-native species as well as stream-dwelling versus burrowing species. Our results indicate that crayfish species may be 5 functionally distinct, so that a displacement of native species by non-native species is likely to have broad ecological impacts. Our study also demonstrates the great utility of DNA metabarcoding to determine plant detrital and animal components of crayfish diet. Knowledge of the different trophic roles of generalists will inform ecosystem restoration by encouraging efforts to maintain native generalist species.

On-Campus Access Only