<p><a>Natural
enemy ecology strives to integrate the fields of disease ecology and community
ecology to forge a broader understanding of how pathogens and predators structure
communities. To advance this field, we need a greater emphasis on: 1)
quantifying pathogen-mediated effects on community structure and comparing
these effects to those observed with predators and 2) determining the
interactive effects of combined natural enemies on communities. I conducted a mesocosm experiment designed to
assess the individual and combined effects of predators (dragonfly larvae and
adult water bugs) and a pathogen (ranavirus) on a larval amphibian community.
Additionally, I conducted laboratory experiments to assess whether ranavirus
exposure increases the vulnerability of tadpoles to predation. In my laboratory
experiments, I found that virus exposure increased predation rates with dragonflies,
but not water bugs. For tadpoles in the
dragonfly treatments, the probability of survival for virus-exposed tadpoles
was 66-77% lower compared to unexposed tadpoles. This data suggests that
predators may selectively remove infected individuals from the population,
which can enhance the magnitude of the healthy herds effect. I found that the risk level of the predators
largely explained effects on the community.
For instance, high-risk dragonflies reduce overall survival to 30%
whereas low-risk water bugs only reduced survival to 67%. Additionally, I found
that virus reduce survival to 62%, which was comparable to effect of the
low-risk predator. Interestingly, all three natural enemies influenced
community structure (i.e. species relative abundance) in unique ways. These results demonstrate that pathogens can
have effects similar to predators on communities, and that natural enemy
identity is important when considering impacts on community structure. When
predators were combined with the virus, I found that mortality was relatively
unchanged from the predator-only treatments suggesting less than additive
effects of combined natural enemies.
This result was driven by the healthy herds effect; the presence of dragonflies
reduced overall infection prevalence in the community to 7% compared to 30% in
the virus-only treatment. This effect
was observed in the water bug treatments, to a lesser degree, suggesting that
predator risk or efficiency contributes the magnitude of the effect. Collectively, my work demonstrates the
importance of examining the individual and combined effects of natural enemies
on ecological communities.</a></p>
| Identifer | oai:union.ndltd.org:purdue.edu/oai:figshare.com:article/7403813 |
| Date | 17 January 2019 |
| Creators | Turner S. DeBlieux (5930597) |
| Source Sets | Purdue University |
| Detected Language | English |
| Type | Text, Thesis |
| Rights | CC BY 4.0 |
| Relation | https://figshare.com/articles/Individual_and_combined_effects_of_natural_enemies_on_amphibian_communities/7403813 |
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