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Direct and indirect effects of the invasive Orconectes rusticus on native O. sanbornii in Ohio streams

Johnson, Christopher A.
http://rave.ohiolink.edu/etdc/view?acc_num=osu1471626347

Abstract Details

2016, Master of Science, Ohio State University, Environment and Natural Resources.
While the direct effects of non-native species as predators and competitors have been widely studied, the indirect effects of invasive species as novel prey are relatively unexplored. Yet, these novel energetic pathways are of great importance to long-term community response to biological invasions. Novel prey, as supplemental resources for native predators, can positively influence predator abundances. These changes in predator populations, and the associated shifts in predation risk, may result in concomitant effects upon native prey. These indirect effects may impose significant consequences on native prey populations. Aquatic systems are among the most impacted by biological invasions. Globally, freshwater crayfish are among the taxa most at risk to the effects of invasive species. In Ohio, the invasive rusty crayfish (Orconectes rusticus) has been implicated in the decline of a native congener, O. sanbornii. This research aimed to evaluate the influence of indirect effects of invasive O. rusticus on patterns of replacement of the native O. sanbornii in Ohio streams. I used a combination of field observations and experimental manipulations to fulfill three objectives. First, I quantified population demographics of O. sanbornii from streams invaded and not yet invaded by O. rusticus. I also measured and compared the body size of O. rusticus in streams where they currently co-occur with O. sanbornii or have replaced the native species. Second, I conducted a within stream tethering experiment to test for differences in predation risk between these two species. Finally, I used a laboratory experiment to explore the effect of predation risk, competitor identity, and the interaction of the two factors on the behavior of both O. sanbornii and O. rusticus. Results of field surveys indicated a significantly smaller average O. sanbornii body size in streams where they are found co-occurring with O. rusticus. However, there was no detectable difference in O. rusticus body size between streams where they currently co-occur versus streams which they have displaced O. sanbornii. There were no detectable differences in sex ratios or risk of predation across populations of either species. Results of the laboratory experiment indicated that both species respond to increased risk of predation with increased refuge use and reduced measures of activity. However, risk effects depended upon competitor identity. When competing with conspecifics, O. sanbornii significantly increased its use of refuge with elevated predation risk, while decreasing measures of activity. However, when competing against invasive O. rusticus, O. sanbornii only increased refuge use at high predation risk and demonstrated increased activity at zero and low risk. In contrast, O. rusticus decreased activity with elevated risk, an effect which was heightened when facing a heterospecific competitor. Native O. sanbornii suffers a tradeoff between managing the risk of predation versus cost of competing with a novel competitor. However, O. rusticus responds to competition from O. sanbornii in ways which are advantageous in risky environments. These results suggest that the behaviors of O. rusticus may allow the species to minimize the trade-off between finding food and avoiding predators and out-compete native O. sanbornii.
Lauren Pintor (Advisor)
Suzanne Gray (Committee Member)
Stephen Matthews (Committee Member)
121 p.
Ecology; Environmental Science
biological invasions; competition; indirect effects; Orconectes rusticus

Recommended Citations

Citations

  • Johnson, C. A. (2016). Direct and indirect effects of the invasive Orconectes rusticus on native O. sanbornii in Ohio streams [Master's thesis, Ohio State University]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=osu1471626347

    APA Style (7th edition)

  • Johnson, Christopher. Direct and indirect effects of the invasive Orconectes rusticus on native O. sanbornii in Ohio streams. 2016. Ohio State University, Master's thesis. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=osu1471626347.

    MLA Style (8th edition)

  • Johnson, Christopher. "Direct and indirect effects of the invasive Orconectes rusticus on native O. sanbornii in Ohio streams." Master's thesis, Ohio State University, 2016. http://rave.ohiolink.edu/etdc/view?acc_num=osu1471626347

    Chicago Manual of Style (17th edition)

osu1471626347
301
© 2016, all rights reserved.
This open access ETD is published by The Ohio State University and OhioLINK.