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

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

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

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

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

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

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

Vomeronasal Organ: Model System:

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

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

Red-sided Garter Snake (Thamnophis sirtalis parietalis) Red-spotted Garter Snake (Thamnophis sirtalis concinnus) Plains Garter Snake (Thamnophis radix) Northwestern Garter Snake (Thamnophis ordinoides) Subspecies Sympatric Allopatric

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

Interspecific Variation: Hypothesis The chemical profile of the female sexual attractiveness pheromone will exhibit interspecific variation.  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. Predictions

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

Measures of Pheromone Variation: 1) Quantitative2) Qualitative # of Compounds Present Relative [individual compounds] = mg % MK (of total lipids) (?)(?) (?)(?)(?)(?) Interspecific Variation - Chemical Analysis: = mg

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

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

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

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

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

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?

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