Natural and sexual selection shape animal communication signals according to the demands of social context and the environment, which results in enormous variation in signal properties. My dissertation uses the electrocommunication signals of South American weakly electric knifefish to compare signal structure across several closely related species, with particular emphasis on signals that are extreme or unusual. Weakly electric fish continuously generate an electric field using an electric organ discharge (EOD). During short-range social interactions, fish produce chirps by rapidly and transiently increasing EOD frequency. I used recordings with playbacks of conspecific signals and hormone manipulation to characterize the sexually dimorphic chirp duration of Parapteronotus hasemani, a species of electric fish with high-frequency, long-duration chirps and huge variation in male morphology. I also described signaling behavior in Distocyclus conirostris , a species of electric fish with a low-frequency EOD and an unusual asymmetrical behavioral response to “jamming” created when EODs of similar frequencies interact. Next, I compared across species to examine how signal properties (EODs and chirping) interact to influence each other’s detection and evolution. Certain signal parameters such as chirp frequency modulation and EOD frequency difference have substantial effects on chirp conspicuousness. Contrary to expectations, there was little support for a strict co-evolution in which a species’ chirps are most conspicuous on their own EOD waveforms. Thus, although EOD properties influence chirp conspicuousness, other factors such as the social or physical environment also likely shape chirp structure. Additionally, I show that EOD waveform may differ in perceptibility based on the EOD waveform complexity of the interacting fish. I consider how chirp conspicuousness could drive the evolution of sexually dimorphic chirps (such as those produced by P. hasemani), and I raise questions about whether low-frequency EODs (such as those produced by D. conirostris) contain sufficient information for fish to detect conspecific EOD frequencies using the neural mechanisms described in fish with high-frequency EODs. Taken together, these results show how the properties of multi-component signals shape each other and impact signal detectability. Finally, my dissertation concludes with a description of an innovative approach to teaching scientific communication skills in a highly structured undergraduate introductory biology lab.
|Advisor:||Smith, G. Troy|
|Commitee:||Demas, Gregory, Hurley, Laura, Kearns, Katherine, Sengelaub, Dale|
|School Location:||United States -- Indiana|
|Source:||DAI-B 78/05(E), Dissertation Abstracts International|
|Subjects:||Biology, Aquatic sciences|
|Keywords:||Behavior, Communication, Conspicuousness, Sexual dimorphism, Signals, Weakly electric fish|
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