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theses

Several studies have established the existence of temperature-controlled physiological color change (PCC) in Odonata species. Individuals capable of this PCC darken to “dark-phase” (DP) coloration below a temperature threshold and return to “bright-phase” (BP) coloration once above it. The stimulus controlling PCC in Argia apicalis (Say) has been contentious since first studied in the 1960s, as BP and DP males are often present under seemingly identical conditions. In Chapter 1, my goal was to determine if the control of A. apicalis male PCC could be attributed to one specific variable or if it is dual-controlled. I first tested whether ambient temperature can be used to predict color phase and found that it is a significant predictor of DP coloration in solitary males only. I next looked for an association between DP coloration and mating status (mating or solitary) and found that DP is far more likely to be exhibited by mating males, thus PCC is also mating-controlled in A. apicalis males. Finally, I looked for a relationship between mating stage and color phase and established that matingcontrolled PCC is initiated during copulation, further supporting the link between mating and PCC. Additionally, males were darkest during oviposition—the mating stage when males may be most vulnerable to predation. My results indicate that A. apicalis males possess dual-controlled PCC. In Chapter 2, my objective was to establish whether DP coloration could be operating as an anti-predator defense strategy in A. apicalis males. I first measured the reflectance spectra of DP and BP males and found that BP males are approximately 4.8 times brighter than DP males. I subsequently performed a binary choice experiment to determine whether BP males suffer higher levels of predation than DP males. I tested two predator groups for their color phase preference: avians, Gallus gallus domesticus (Linnaeus), and anurans, Lithobates clamitans melanota (Rafinesque) and Lithobates catesbeianus (Shaw). I found that both groups attacked significantly more BP than DP models, so it is plausible that the mating-controlled PCC exhibited by A. apicalis males could be functioning as an anti-predator defense strategy during oviposition

ETD_7642

Ph.D.

Includes bibliographical references

by Amanda Marie Whispell

doi:10.7282/T3DR2XT3

ETD doctoral

The author owns the copyright to this work.