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Jannell Earle

1996 Research

Abstract: A Comparison of the Expression of a Chaoborus-Induced Phenotypic Plasticity in Daphnia Among Ten Natural Populations
Mentor: Dr. Ross Black, Department of Biology


A comparison of the expression of Chaoborus-induced neckteenth among ten natural pond populations of Daphnia was conducted to better understand the ecology of predator-induced phenotypic plasticities. Pond water was collected from each of the ten ponds to test the inducibility of the water on a single D. pulex clone using a reaction norm bioassay. Quantitative analysis of the ten pond populations suggests that the expression of neckteenth in Daphnia is an adaptive response to the predator: prey ratio. The expression of Chaoborius-induced phenotypic plasticity in first and second instar Daphnia in nature increases with Chaoborus density, and decreases with increased Daphnia density. This observation is further supported by several predators to prey ratios that were positively and significantly correlated with the proportion of first and second instar Daphnia possessing neckteenth. Interestingly, there was no significant correlation in the expression of neckteenth between the natural Daphnia populations and the Daphnia under pond water bioassay conditions suggesting the environment provides a significant source of variation influencing induction among first and second instar Daphnia.

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