Host defense alteration in Caenorhabditis elegans after evolution under ionizing radiation

Area of Science:

• Evolutionary biology
• Ecotoxicology
• Genetics

Background:

• Environmental stressors can impose fitness costs on other traits, influencing population evolution.
• Host defense is energetically costly but vital for survival.
• Understanding these costs is crucial for assessing the evolutionary impact of stressors like pollution.

Purpose of the Study:

• To investigate the effects of adaptation to gamma radiation on host defense in Caenorhabditis elegans.
• To determine if there is an evolutionary trade-off between fitness under radiation and defense against a bacterial pathogen.
• To evaluate the long-term consequences of radiation exposure on host defense mechanisms.

Main Methods:

• Experimental evolution of Caenorhabditis elegans populations under varying doses of gamma radiation (0, 1.4, 50.0 mGy.h⁻¹).
• Assessment of population fitness across 20 generations (transfers).
• Evaluation of host defense by exposing populations to Serratia marcescens after a period in a common garden environment.

Main Results:

• Populations exposed to 50.0 mGy.h⁻¹ showed increased fitness over time, indicating local adaptation.
• Host defense against Serratia marcescens was reduced in populations adapted to radiation, demonstrating a cost to defense.
• A trade-off was observed between fitness and host defense in control populations, but a positive correlation in irradiated populations.

Conclusions:

• Adaptation to one stressor (radiation) can incur costs on defense against a subsequent stressor (pathogen), even after the initial stressor is removed.
• Some Caenorhabditis elegans populations evolved resistance to radiation that conferred cross-resistance to pathogens.
• These findings underscore the importance of considering evolutionary dynamics in ecotoxicology and ecological risk assessment.