Pathogen exposure reduces sexual dimorphism in a host's upper thermal limits

Area of Science:

• Ecology
• Evolutionary Biology
• Environmental Science

Background:

• Climate warming and global change are increasing species' exposure to thermal stress and shifting pathogen distributions.
• Species' upper thermal limits and infection susceptibility are critical for population persistence in changing environments.
• Individual variation within populations, particularly between sexes, influences responses to environmental stressors.

Purpose of the Study:

• To investigate the combined effects of bacterial infection and heat stress on male and female Daphnia.
• To determine if sex influences thermal tolerance and susceptibility to infection.
• To assess the implications of sex-specific responses for population-level resilience.

Main Methods:

• Exposing male and female Daphnia to controlled bacterial infection.
• Subjecting infected and uninfected Daphnia to static heat stress.
• Measuring survival and other relevant physiological responses.

Main Results:

• Uninfected female Daphnia exhibited higher resistance to heat stress compared to males.
• Bacterial infection significantly reduced the thermal resistance advantage of female Daphnia.
• Sex-specific differences in stress response were observed, with infection impacting females more severely in relation to heat tolerance.

Conclusions:

• The interplay between host sex, infection, and thermal limits is a critical, yet often overlooked, factor in predicting population viability.
• Ignoring sex-specific responses can lead to an underestimation of population vulnerability to multiple, interacting stressors.
• Future research and conservation strategies must incorporate sex as a key variable when assessing ecological responses to global change.