Linking manipulative experiments to field data to test the dilution effect.

Area of Science:

• Ecology
• Disease Ecology
• Conservation Biology

Background:

• The dilution effect hypothesis posits that increased biodiversity can reduce disease transmission risk.
• Few studies have mechanistically linked laboratory findings to field patterns for the dilution effect.
• Amphibian populations worldwide face threats from diseases like chytridiomycosis, caused by Batrachochytrium dendrobatidis (Bd).

Purpose of the Study:

• To test the dilution effect hypothesis in an amphibian-Bd system.
• To link mechanistic laboratory experiments with field data on disease prevalence.
• To determine if host traits predict disease dilution and amplification.

Main Methods:

• Conducted laboratory experiments on tadpole feeding behaviors and Bd infection.
• Analyzed field data on amphibian species richness, host identity, and Bd prevalence.
• Controlled for environmental and anthropogenic factors in field data analysis.

Main Results:

• Tadpoles filter-feed Bd zoospores; suspension feeders showed greater dilution potential.
• The suspension feeder *Gastrophryne carolinensis* diluted chytridiomycosis risk, while the benthos feeder *Bufo terrestris* amplified it.
• Field data confirmed *Bufo* spp. as positive and *Gastrophryne* spp. as negative predictors of Bd prevalence, aligning with lab findings.

Conclusions:

• The study supports the dilution effect hypothesis in the amphibian-Bd system.
• Disease dilution and amplification are predictable based on host feeding traits.
• Linking mechanistic experiments with field data establishes ecological relevance and causality for the dilution effect.