Coevolution Between Grasshopper mice (Onychomys spp.) and Bark and Striped Scorpions (Centruroides spp.)

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dc.contributor.advisor James Gilliam, Committee Member en_US
dc.contributor.advisor John Godwin, Committee Member en_US
dc.contributor.advisor Kenneth Pollock, Committee Member en_US
dc.contributor.advisor Harold Heatwole, Committee Chair en_US Rowe, Ashlee Hedgecock en_US 2010-04-02T19:09:17Z 2010-04-02T19:09:17Z 2004-11-29 en_US
dc.identifier.other etd-11292004-084002 en_US
dc.description.abstract Asymmetrical selection has been proposed as the strongest argument for rejecting hypotheses of coevolutionary arms races between predators and prey. In many cases there is evidence of increased investment by the prey in response to the predator, but no evidence of increased investment by the predator in response to the prey, thus producing asymmetry in selection. However, selection against a predator may be increased when the interaction is with a "dangerous" prey. Predators are most likely to respond evolutionarily to potentially lethal prey. This study employs grasshopper mice (Onychomys spp.) and bark and striped scorpions (Centruroides spp.) as a model to test the hypothesis that interspecific interaction between a predator and a potentially lethal prey will result in behavioral and physiological adaptations that reciprocally mediate their interaction (i.e., coevolution). Bark scorpions (Centruroides exilicauda) and striped scorpions (Centruroides vittatus) produce a potent venom containing neurotoxins that selectively bind to the ion-channels of vertebrates. Vertebrate-specific neurotoxins may produce lethal effects in mammals, especially small mammals. Southern grasshopper mice (Onychomys torridus) and Mearns' grasshopper mice (O. arenicola) are known to be voracious predators on scorpions. Southern grasshopper mice are broadly sympatric with bark scorpions in the Sonoran Desert, and Mearns' grasshopper mice are broadly sympatric with striped scorpions in the Chihuahuan Desert. The third species in this genus, the northern grasshopper mouse (O. leucogaster) is broadly allopatric with Centruroides spp. In a preliminary study, both southern and Mearns' grasshopper mice demonstrated resistance to bark and striped scorpion neurotoxins. The evolution of toxic venom and resistance to that venom strongly suggests a coevolutionary relationship between Onychomys spp. and Centruroides spp. To test this hypothesis, I evaluated the predator-prey relationship between grasshopper mice and their toxic scorpion prey during staged feeding trials. Additionally, I compared the geographic patterns of venom resistance in all three species of grasshopper mice with geographic patterns of venom toxicity in bark and striped scorpions. Results from the feeding study demonstrated that grasshopper mice do not distinguish between toxic and non-toxic species of scorpions; mice attacked, incapacitated, and consumed bark and striped scorpions without hesitation and as effectively as they attacked crickets and non-toxic scorpions in the genus Vaejovis. The feeding experiments indicate that grasshopper mice have the ability to prey on bark and striped scorpions in habitats where they co-occur. Venom resistance analyses demonstrated that all three species of grasshopper mice have evolved some resistance to the vertebrate-specific neurotoxins produced by Centruroides spp. The assays show that patterns of venom toxicity in Centruroides and venom resistance in Onychomys co-vary geographically, both within and among species; i.e., populations of Onychomys interacting with the most toxic populations of Centruroides were extremely resistant; populations of Onychomys interacting with only moderately toxic populations of Centruroides were only moderately resistant; and populations of Onychomys not sympatric with Centruroides were only weakly resistant. Such systematic covariation between venom toxicity in the scorpions and venom resistance in the mice is consistent with a coevolutionary, arms race hypothesis. en_US
dc.rights I hereby certify that, if appropriate, I have obtained and attached hereto a written permission statement from the owner(s) of each third party copyrighted matter to be included in my thesis, dissertation, or project report, allowing distribution as specified below. I certify that the version I submitted is the same as that approved by my advisory committee. I hereby grant to NC State University or its agents the non-exclusive license to archive and make accessible, under the conditions specified below, my thesis, dissertation, or project report in whole or in part in all forms of media, now or hereafter known. I retain all other ownership rights to the copyright of the thesis, dissertation or project report. I also retain the right to use in future works (such as articles or books) all or part of this thesis, dissertation, or project report. en_US
dc.subject predatory behavior en_US
dc.subject physiological adaptation en_US
dc.subject neurotoxin resistance en_US
dc.subject asymmetrical selection en_US
dc.subject predator and dangerous prey en_US
dc.subject coevolutionary arms race en_US
dc.title Coevolution Between Grasshopper mice (Onychomys spp.) and Bark and Striped Scorpions (Centruroides spp.) en_US PhD en_US dissertation en_US Zoology en_US

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