Why many Batesian mimics are inaccurate: evidence from hoverfly colour patterns

Area of Science:

• Evolutionary Biology
• Ecology
• Behavioral Ecology

Background:

• Mimicry, a classic example of natural selection, often shows imperfect similarity between harmless mimics and unpalatable models.
• Variation in mimetic accuracy is puzzling, as selection should favor highly accurate mimics.

Purpose of the Study:

• To test hypotheses explaining the persistence of inaccurate mimics in wild populations.
• To quantify pattern similarity in mimicry using a novel image analysis method.

Main Methods:

• Utilized a distance transform method on binary images to quantify pattern similarity.
• Applied the method to a group of hoverflies (mimics) and hymenopterans (models).
• Tested hypotheses regarding relaxed selection, multiple model accuracy, and trade-offs.

Main Results:

• Phenotypic variation levels were similar across most hoverfly species, contrary to relaxed selection predictions.
• No evidence suggested mimics compromise accuracy when mimicking multiple model species.
• Darker-colored hoverflies exhibited less accurate mimicry, suggesting a potential mimicry-thermoregulation trade-off.

Conclusions:

• Inaccurate mimicry may persist due to factors beyond simple selection pressures.
• A trade-off between mimicry and thermoregulation could explain reduced accuracy in darker hoverflies.
• The study highlights limitations of natural selection in shaping complex adaptations like mimicry.