Evolution of host manipulation specificity in trophically transmitted parasites

Area of Science:

• Ecology
• Evolutionary Biology
• Parasitology

Background:

• Trophically transmitted parasites often alter host phenotypes to facilitate predation by the next host in their life cycle.
• The specificity of this host manipulation varies, with some parasites increasing vulnerability only to the correct predator, while others increase it indiscriminately.

Purpose of the Study:

• To develop a theoretical model addressing the evolution of manipulation specificity in trophically transmitted parasites.
• To simultaneously model the evolution of manipulation intensity and manipulation leakage (non-host predator vulnerability).

Main Methods:

• Developed a general analytical model analyzing parasite evolution in intermediate hosts.
• Considered three competing outcomes: predation by the suitable next host, predation by non-host predators, and natural mortality.
• Derived conditions for favored manipulation and the joint evolutionarily stable strategy for intensity and leakage.

Main Results:

• Dead-end predation by non-host predators provides a selective incentive for manipulation specificity.
• Specificity evolves only when the costs of achieving it (e.g., reduced fecundity) are sufficiently low.
• The evolution of specificity is primarily determined by the manipulation pathway, not the intensity of non-host predation.

Conclusions:

• Parasite manipulation strategies are shaped by a trade-off between increasing transmission and avoiding dead-end predation.
• The evolution of specific manipulation is contingent on the energetic or physiological costs associated with achieving that specificity.