Shifting effects of host physiological condition following pathogen establishment

Area of Science:

• Ecology
• Pathogen-host dynamics
• Wildlife disease

Background:

• Host persistence is crucial for wildlife conservation amid emerging pathogens.
• Pre-adaptive host traits can aid survival but their long-term evolutionary trajectory depends on heritability and environmental factors.
• Body condition is a key pre-adaptive trait, though it can be seasonally variable in wildlife.

Purpose of the Study:

• To investigate the role of host body condition in bat survival during the invasion and establishment of white-nose syndrome.
• To determine how body mass influences survival and overwinter weight loss in bats infected with the pathogen.
• To assess if directional selection on body mass occurred in the bat population post-pathogen arrival.

Main Methods:

• Longitudinal study over 7 years using bat body mass, infection status, and survival data.
• Analysis of the relationship between body mass and survival during the initial invasion and subsequent establishment of the disease.
• Examination of overwinter weight loss in relation to body mass and infection severity.
• Evaluation of population-level changes in bat mass following pathogen introduction.

Main Results:

• Higher body mass conferred a survival advantage during the initial white-nose syndrome outbreak.
• The survival benefit of higher body mass decreased after the initial epizootic.
• Heavier bats experienced greater overwinter weight loss, influenced by infection severity.
• Evidence for increased bat mass in the population after pathogen arrival was mixed, with high individual plasticity potentially limiting directional selection.

Conclusions:

• The initial survival advantage conferred by body condition can diminish over time as pathogens establish.
• Overwinter fat loss is linked to infection severity, highlighting the physiological costs of disease.
• Population-level adaptation to emerging diseases may involve shifts from pre-adaptive traits to other evolutionary responses.
• Understanding dynamic host-pathogen interactions is vital for predicting and managing wildlife disease impacts.