Genetic variation in infestation with a directly transmitted ectoparasite

Area of Science:

• Ecology
• Evolutionary Biology
• Genetics

Background:

• Coevolutionary studies assume host genetic variation in parasitism.
• Field estimates of this variation are scarce.
• Directly transmitted parasites offer a robust test for genetic variation in abundance.

Purpose of the Study:

• To investigate genetic variation in the abundance of the chewing louse Hirundoecus malleus on its barn swallow host Hirundo rustica.
• To determine if parasite intensity has a genetic basis in a natural host-parasite system.

Main Methods:

• Studied Hirundoecus malleus abundance on Hirundo rustica.
• Analyzed parasite intensity resemblance between parents and offspring.
• Utilized extra-pair paternity analysis to partition genetic and environmental effects.
• Compared parasite intensity in within-pair and extra-pair offspring.

Main Results:

• No significant difference in louse prevalence or abundance between male and female hosts.
• A highly significant positive resemblance in parasite intensity between offspring and parents.
• Resemblance in parasite intensity was maintained for within-pair offspring but not for extra-pair offspring.
• No significant common environment effects detected.

Conclusions:

• The abundance of directly transmitted parasites, Hirundoecus malleus, has an additive genetic component in barn swallows.
• Host genetics play a role in susceptibility or resistance to parasitism.
• Environmental factors do not significantly explain parasite intensity resemblance between parents and offspring.