Testing alternative methods for purging genetic load using the housefly (Musca domestica L.)

Area of Science:

• Evolutionary Biology
• Population Genetics
• Animal Behavior

Background:

• Inbreeding can expose genetic load, which natural selection can then purge.
• Artificial selection may enhance purging but risks fixing deleterious alleles.
• Houseflies (Musca domestica L.) were used to test adaptation to small population sizes.

Purpose of the Study:

• To evaluate the effectiveness of artificial selection in purging genetic load.
• To assess adaptation to small population size and inbreeding in houseflies.
• To compare artificial selection with natural purging via serial inbreeding.

Main Methods:

• Replicate housefly populations were maintained at small census sizes (54 or 30) for 9-14 generations.
• Artificial selection targeted increased mating propensity and courtship performance.
• Parallel non-selection lines assessed natural purging; founder-flush lines were also tested.

Main Results:

• Newly derived wild housefly lines showed short-term mating propensity increases with artificial selection, followed by rebounds.
• Serial inbreeding reduced mating propensity in newly derived lines.
• Long-term laboratory lines showed increased mating propensity with both artificial selection and serial inbreeding, restoring initial levels.

Conclusions:

• Artificial selection's effectiveness in purging genetic load is contingent on the existing genetic load.
• Prolonged laboratory adaptation, with relaxed selection, can increase a population's responsiveness to purging protocols.
• The study highlights the complex interplay between inbreeding, selection, and adaptation in finite populations.