Cooperative Fish and Wildlife Research Units Program: Arkansas
Education, Research and Technical Assistance for Managing Our Natural Resources

Faxonius marchandi (Mammoth Spring Crayfish), is a narrow-ranged endemic occurring in the Ozark Highlands of northern Arkansas and southern Missouri and is under consideration by the U.S. Fish and Wildlife Service (USFWS) for listing under the Endangered Species Act (ESA). Populations of F. marchandi are limited to small streams on the eastern side of the Spring River drainage (Flinders and Magoulick 2005, DiStefano et al. 2017). Population genetics indicate two main clades of F. marchandi in the upper vs lower reaches of the Spring River drainage, suggesting these populations be given Evolutionary Significant Unit status (Yarra et al. 2018). The threat of an advancing invasive species that has displaced two native species, along with potential habitat loss and fragmentation, makes determining potential invasive species effects extremely important. Major questions that need to be addressed include “How will invasion of F. neglectus potentially affect F. marchandi populations?”, “Will drought and other disturbance influence the interaction between F. marchandi and F. neglectus?”, and “Do F. marchandi and F. neglectus have differing effects on stream ecosystem structure and function?”. Based on our previous research, we hypothesize that F. marchandi populations are at risk due to small geographic range and are susceptible to invasion by F. neglectus. We also hypothesize that drying and intermittent streams may act as refuges for F. marchandi. Finally, we hypothesize that F. marchandi and F. neglectus will not be ecologically redundant.
Objectives
Examine effects of invasive species (F. neglectus) and drought on survival and growth of F. marchandi. Examine differences in effects on stream structure and function among F. marchandi and invasive F. neglectus in the presence and absence of stream drying. Develop and improve models to examine potential effects of crayfish invasion and disturbance on extinction risk and population dynamics of both ESU’s of F. marchandi.