When to Reproduce? A New Answer to an Old Question

Area of Science:

• Evolutionary biology
• Parasitology
• Mathematical modeling

Background:

• Understanding parasite life-history strategies is crucial for controlling infections.
• Juvenile survival and fecundity are key factors influencing parasite population dynamics.

Purpose of the Study:

• To develop a life-history model predicting optimal parasite fitness.
• To test the model's prediction of invariant survival at maturity using empirical data.

Main Methods:

• A mathematical model was constructed assuming negative exponential juvenile survival and linear fecundity gain.
• Published data from mammalian nematode infection experiments were analyzed.

Main Results:

• The model predicted optimal fitness at a survival probability of 0.368 (e(-1)) at maturity.
• Empirical data from nematodes showed mean survival at maturity closely matched the predicted invariant.
• Control experiments with non-adapted parasite-host systems deviated from the prediction.

Conclusions:

• Fixed survival probability at maturation is an adaptive trait evolved in predictable host environments.
• Interventions increasing juvenile mortality may select for accelerated parasite development.