2nd Place: D3025: Non-consumptive effects of an insect predator on the dynamics of its prey's disease

The larvae of Chaoborus punctipennis (F: Chaoboridae) are voracious predators of Daphnia dentifera (Crustacea: Cladocera). Upon detecting Chaoborus, D. dentifera produces exaggerated morphologies, hindering predation. D. dentifera must also defend against the fungal pathogen Metschnikowia bicuspidata. How does Chaoborus affect the life history of its prey when those prey must also defend against a pathogen? In Indiana lakes, Chaoborus populations are positively correlated with M. bicuspidata infection prevalence in D. dentifera. I hypothesized that this is due to a trade-off between D. dentifera’s defense against the pathogen and against the predator. I predicted that in D. dentifera, the size of morphological defenses produced in response to Chaoborus kairomone would be negatively correlated with the ability to fend off infection by M. bicuspidata. To test this prediction, I reared three D. dentifera clones in a fully factorial experiment with C. punctipennis kairomone (present/absent) and M. bicuspidata spores (present/absent). I repeatedly measured morphological defenses, evaluated infection status, and recorded survival and clutch size. Both predator-defense traits (size of tail spine and head) were nonnegatively or positively correlated with both pathogen-defense traits (time to infection, infection status). All defensive traits were positively correlated with clonal reproduction rate, indicating that predator-defense, pathogen-defense, and reproduction are not in a three-way trade-off. I conclude D. dentifera’s abilities to defend against this pathogen and predator are not in a trade-off. Rather, individuals better equipped to defend against one threat are likely to be well-equipped against the other while also exhibiting higher reproduction.