May 8 2014

5:00 pm BSRB 154

EcoEvoPub Series

Graduate Student Presentations


JP Drury
Department of Ecology and Evolutionary Biology

"Character Displacement in the Wing Color Patterns of Rubyspot Damselflies (Hetaerina spp.): An Experimental Test of Alternative Hypotheses"

Previous research on rubyspot damselflies (Hetaerina spp.) demonstrated that sympatric shifts in male wing color patterns and competitor recognition reduce territorial aggression between species, supporting the hypothesis that these trait shifts were caused by agonistic character displacement (ACD), but reproductive character displacement (RCD) could explain the same pattern. A recent theoretical model parameterized for damselflies showed that RCD would completely dominate ACD if female mate recognition and male competitor recognition were both based on the same male trait. To determine if female mate recognition in rubyspots is based on species differences in male wing coloration, we carried out a phenotype manipulation experiment. Compared to control males, male H. americana that we manipulated to have wing coloration resembling a sympatric congener (H. titia) suffered no reduction in mating success with conspecific females, whether measured as pre-copulatory, copulatory, or post-copulatory discrimination. Thus, female mate recognition is not based on the species difference in male wing coloration. As expected under the ACD hypothesis, experimental males that attempted to defend territories in the same areas as heterospecific males experienced higher interspecific fighting rates and reduced survival, compared to controls. These results strengthen the hypothesis that ACD produced the sympatric shifts in male wing coloration and competitor recognition in Hetaerina.

Zac Schakner
Department of Ecology and Evolutionary Biology

"Bad Boys of Bonneville: California Sea lion predation of endangered Salmonids at the Bonneville Dam"

Managing predation of endangered animals is an issue at the interface of conservation biology and wildlife management. These issues become complex when protected species predate other at risk-populations or endangered populations, such as marine mammals targeting salmonids the west coast of the United States. Recently, California sea lions (CSL) have learned to swim hundreds of miles up the Columbia River, Oregon to the Bonneville Dam to prey on Endangered Species Act (ESA)-listed Chinook Salmon and Steelhead trout that are concentrated at the dam’s fish ladders. In addition to an overall increase of individuals visiting the dam, CSL have shifted their foraging strategies, arriving earlier in the year and staying longer, prompting lethal and nonlethal management activities to curb predation. We used 10-years of individual CSL observations at the dam to test the environmental, social and individual factors influencing recruitment, foraging success, and likelihood of return to the dam in subsequent seasons. New recruits were no more likely to arrive with conspecifics than return foragers, suggesting other cues drive recruitment to the dam. We found that days present at the dam and overall salmon run were positively associated with foraging success. We also found that some individuals were better foragers than others after controlling for different environmental effects. In addition, the number of salmon an individual takes the previous season, as well as the number of Stellar sea lions (a larger competitor) influence the likelihood an individual will return the subsequent season. By using these factors that influence recruitment, foraging, and returns to the Bonneville dam managers can take actions to reduce predation and increase the recovery of salmonids in the Pacific Northwest.















































































































































































































































































































































































































































































































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