Quantifying intraspecific variation in host resistance and tolerance to a lethal pathogen
Bennett M Hardy1,2,3, Erin Muths4, W Chris Funk1,3
1Graduate Degree Program in Ecology, Colorado State University, Fort Collins, Colorado, USA.
The Journal of Animal Ecology
|May 22, 2024
Summary
Wyoming boreal toads show higher tolerance and resistance to the deadly amphibian fungus Batrachochytrium dendrobatidis (Bd) compared to Colorado populations. Intraspecific variation is crucial for understanding population declines and informing conservation efforts.
Area of Science:
- Ecology
- Conservation Biology
- Pathogen-Host Dynamics
Background:
- Amphibian declines due to the fungal pathogen Batrachochytrium dendrobatidis (Bd) are a significant conservation concern.
- Boreal toads (Anaxyrus boreas boreas) in Colorado have experienced severe declines from Bd, while populations in Wyoming appear less affected.
- Intraspecific variation in host tolerance and resistance can influence population-level disease outcomes.
Purpose of the Study:
- To investigate intraspecific variation in tolerance and resistance to Batrachochytrium dendrobatidis (Bd) in wild boreal toad populations.
- To determine if differences in tolerance and resistance explain regional variations in Bd-induced population declines.
- To assess the utility of a multi-state modeling approach for understanding dynamic infection processes.
Main Methods:
- A common garden infection experiment was conducted using post-metamorphic boreal toads from four populations (two in Colorado, two in Wyoming).
- Toads were exposed to Batrachochytrium dendrobatidis (Bd) and monitored for changes in mass, pathogen burden, and survival over eight weeks.
- A multi-state modeling approach was used to estimate weekly survival and transition probabilities between infected and cleared states.
Main Results:
- Wyoming boreal toads exhibited significantly higher tolerance to Bd infection, demonstrated by increased survival probabilities compared to Colorado toads under identical pathogen loads.
- Wyoming toads also displayed greater resistance, with a higher probability of clearing the infection and a longer time to reach peak pathogen burdens.
- Strong intraspecific differences in both tolerance and resistance were observed between the studied populations.
Conclusions:
- Intraspecific variation in tolerance and resistance to Batrachochytrium dendrobatidis plays a critical role in explaining differential population declines in boreal toads.
- Conservation strategies, including captive breeding and translocation, should consider this intraspecific variation.
- The multi-state modeling framework provides valuable insights into hidden disease dynamics when assessing host tolerance and resistance.
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