Thesis Title

Environmental Limits To Invasion Of Ponds By The Exotic Zooplankter Daphnia Lumholtzi Sars

Author

Tina Tamme

Date of Graduation

Summer 2002

Degree

Master of Science in Biology

Department

Biology

Committee Chair

John Havel

Subject Categories

Biology

Abstract

Within any given region, local environments include only a portion of the organisms found within that region, indicating that either dispersal is highly limited or that local biotic and abiotic factors limit what can live in local environments. The current study examined what limits an exotic zooplankter, Daphnia lumholtzi, from invading ponds in the region of Bull Shoals Lake, Taney County, Missouri. To investigate this question, I conducted surveys of the ponds and lake and coupled this information with data from a series of laboratory and field experiments. Species lists compiled from pond and lake zooplankton samples together with multivariate analyses indicated high variation in community composition in ponds, but substantial differences of those from the lake where D. lumholtzi is a resident. In a laboratory experment, I tested water chemistry tolerance and determined that D. lumholtzi was able to survive and reproduce in water collected from four different ponds and Bull Shoals Lake. In a second laboratory experiment, I compared susceptibility of D. lumholtzi to two different predators common in nearby ponds: larvae of the newt Notophthalmus v. louisianensis, and the dipteran insect Chaoborus americanus. Both predators were significantly able to suppress D. lumholtzi populations. In two field experiments, I introduced D. lumholtzi into 50L play pools, which contained different zooplankton community treatments (pond, lake, control). Based on weekly samples, zooplankton communities maintained high species diversity in these pools, and D. lumholtzi grew in all treatments. However, D. lumholtzi populations tended to be lower in the presence of a pond zooplankton community, suggesting suppression by competing pond zooplankton. Overall the experiments demonstrate that both predators and competitors may limit D. lumholtzi from invading pond environments.

Copyright

© Tina Tamme

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