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Interspecific Variation in the Female Sexual Attractiveness Pheromone of Garter Snakes

of the Red-sided Garter Snake, Thamnophis sirtalis parietalis ... Male red-sided garter snakes preferentially courted red-sided and red-spotted females ...

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Interspecific Variation in the Female Sexual Attractiveness Pheromone of Garter Snakes

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  1. Interspecific Variation in the Female Sexual Attractiveness Pheromone of Garter Snakes Emily Uhrig Mentors: Dr. Robert Mason, Oregon State University Dr. Michael LeMaster, Western Oregon University

  2. Interspecific Variation: + Species 1 Species 2 Prezygotic Isolation Benefit? Prevents production of hybrids (inviable or reduced fitness…)

  3. Interspecific Variation: Cope’s Gray Tree Frog Hyla chrysoscelis Black-chinned Mountain Tanager (Anisognathus notabilis) Blue-winged Mountain Tanager (Anisognathus somptuosus) Eastern Gray Tree Frog Hyla versicolor Vocalizations • Frequency • Duration Coloration

  4. Interspecific Variation: Chemical Silver Y moth (Autographa gamma) Essex Y moth (Cornutiplusia circumflexa) (Z)-7-dodecen-1-ol (Z)-7-dodecenyl acetate

  5. Introduction: Pheromone: A chemical cue produced by an individual that affects the physiology and/or behavior of a member of the same species.

  6. Interspecific Variation: General Question Do vertebrate pheromone systems exhibit the interspecific variation necessary for pheromones to function as mechanisms of reproductive isolation?

  7. Model System: The Red-sided Garter Snake Thamnophis sirtalis parietalis

  8. Model System: Vomeronasal Organ:

  9. Model System: Female Sexual Attractiveness Pheromone of the Red-sided Garter Snake, Thamnophis sirtalis parietalis • Potential variation: • Quantity • Absence/presence • Relative concentrations

  10. Interspecific Variation: Question Does the female sexual attractiveness pheromone vary between garter snake species?

  11. Interspecific Variation: Red-sided Garter Snake (Thamnophis sirtalis parietalis) Red-spotted Garter Snake (Thamnophissirtalisconcinnus) Sympatric Sympatric Plains Garter Snake (Thamnophis radix) Northwestern Garter Snake (Thamnophis ordinoides) Subspecies Allopatric

  12. Behavior Trials: Courtship Preference Tests • Male red-sided garter snakes preferentially courted red-sided and red-spotted females over northwestern and plains females.

  13. Interspecific Variation: Hypothesis The chemical profile of the female sexual attractiveness pheromone will exhibit interspecific variation. Predictions • Relatively little difference between the pheromone profiles of red-sided and red-spotted. • Significant difference between the pheromone profiles of red-sided and plains. • Significant difference between the pheromone profiles of red-spotted and northwestern.

  14. Interspecific Variation - Chemical Analysis:  Collection  Hexane Wash Extraction  Fractionation  GC/MS    

  15. Interspecific Variation - Chemical Analysis: Measures of Pheromone Variation: 1) Quantitative 2) Qualitative # of Compounds Present Relative [individual compounds] (?) = (?) (?) mg = mg % MK (of total lipids)

  16. Results: Interspecific Variation in Pheromone Quantity: Relative Amount of Pheromone Expressed on Surface of Females

  17. Results: Interspecific Variation in Pheromone Quality: Number of Unique Methyl Ketones Expressed

  18. Results: Interspecific Variation in Pheromone Quality: Relative Concentrations of Individual Methyl Ketones

  19. Results: Non-metric multi-dimensional scaling plot of individual pheromone profiles Thamnophis sirtalis parietalis Thamnophis sirtalis concinnus Thamnophis radix Thamnophis ordinoides

  20. Conclusion: Predictions Red-sided vs. red-spotted: little difference Red-sided vs. plains: significant difference Red-spotted vs. northwestern: significant difference • Pheromone Quantity • Red-sided significantly different from other species • Newly emerged… • Pheromone Quality • Significant differences between all four species

  21. Conclusion: Do vertebrate pheromone systems exhibit the interspecific variation necessary for pheromones to function as mechanisms of reproductive isolation? Future Work Include behavioral tests with males of other species Are they “fine-tuned” enough to recognize the variation?

  22. Acknowledgements: Dr. Robert Mason Dr. Michael LeMaster Dr. Kevin Ahern HHMI Chelsey Miller Rocky Parker Chris Friesen Everyone in the Mason lab

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