Biological Sciences, School of


Date of this Version



A THESIS Presented to the Faculty of The Graduate College at the University of Nebraska In Partial Fulfillment of Requirements For the Degree of Master of Science, Major: Biological Sciences, Under the Supervision of Professor Chad E. Brassil. Lincoln, Nebraska: November, 2010


Species interactions within a community are impacted by a variety of abiotic factors. Temperature is known to alter population dynamics such that direct and indirect interactions between populations within a community are affected. Here I investigate the effect of temperature change on species interactions within a duckweed-herbivore mesocosm. Multiple communities were constructed, from a single population of duckweed, to two populations of duckweed consumed by aphids. In the one-predator two-prey web we predicted mutually positive indirect effects between duckweed populations during the first generation of growth. As aphid populations respond numerically to more abundant prey, mutually negative and asymmetric indirect effects should occur due to interspecific variation in growth response to temperature. We found direct and indirect interactions varied across time and temperature. Notably, the effects of competition were often asymmetric between duckweed populations. The effects of herbivory were sometimes positive due to the effects of density dependent growth in duckweed populations grown without herbivory. There was also a transient mutually positive indirect effect between duckweed populations at 27°C that did not occur at 19°C. In general, indirect effects between duckweed populations were variable in sign and magnitude across time and temperature.