Impact Of Environmental Variation On Host Performance Differs With Pathogen Identity: Implications For Host-Pathogen...

Area of Science:

• Ecology
• Insect Pathology
• Environmental Physiology

Background:

• Pathogen infection can significantly impact host physiology and performance.
• Environmental factors like temperature and nutrition interact with pathogen effects.
• Understanding these interactions is crucial for predicting insect population dynamics.

Purpose of the Study:

• To investigate how specialist (TnSNPV) and generalist (AcMNPV) baculovirus infections alter host performance under varying temperature and nutrition.
• To determine the specific environmental conditions (temperature and P:C ratio) that maximize host performance after pathogen challenge.

Main Methods:

• Larvae of Trichoplusia ni were exposed to either TnSNPV or AcMNPV.
• Post-exposure, larvae were reared under a factorial design of varying temperatures and protein-to-carbohydrate (P:C) ratios.
• Host performance was assessed by measuring survival, pupal weight, and development time.

Main Results:

• Virus-challenged larvae performed better on protein-biased diets, mainly due to increased survival.
• Unchallenged larvae performed best on a balanced diet.
• TnSNPV infection imposed fitness costs (reduced pupal weight, prolonged development), while AcMNPV did not.
• Optimal P:C ratio varied with virus identity and temperature; TnSNPV-challenged larvae required higher P:C, while AcMNPV-challenged larvae showed temperature-dependent P:C optima.
• Temperature reduced pupal size at balanced P:C ratios, suggesting nutrition moderates the temperature-size rule.

Conclusions:

• Pathogen identity critically influences host performance and optimal environmental conditions.
• Interactions between specialist pathogens, nutrition, and temperature can significantly alter host fitness.
• These findings have implications for the role of entomopathogens in regulating insect populations under climate change.