Tasting the difference: do multiple defence chemicals interact in Müllerian mimicry?

Area of Science:

• Evolutionary Biology
• Chemical Ecology
• Animal Behavior

Background:

• Müllerian mimicry, a mutualistic relationship between unpalatable species sharing warning patterns, is traditionally thought to involve shared chemical defenses.
• Recent models challenge the mutualistic nature of Müllerian mimicry, particularly when assumptions about predator learning are altered.
• A key assumption in these models is that mimics share identical chemical defenses, which is not always observed in nature.

Purpose of the Study:

• To investigate the role of different chemical defenses in Müllerian mimicry.
• To determine if varied toxins enhance predator learning and memory compared to shared toxins.
• To provide insights into the evolution and maintenance of chemical diversity in mimicry rings.

Main Methods:

• Experimental study using domestic chicks as predators.
• Prey consisted of colored crumbs flavored with either the same or different unpalatable chemicals.
• Assessed predator learning and memory of the warning patterns associated with the chemical defenses.

Main Results:

• Two different unpalatable chemicals interacted to enhance predator learning and memory.
• Müllerian mimics with distinct chemical defenses were better protected than those with a single shared chemical.
• Birds' perception and memory of warningly colored prey are influenced by the diversity of chemical defenses.

Conclusions:

• The presence of multiple, distinct chemical defenses can strengthen Müllerian mimicry by improving predator avoidance learning.
• Chemical diversity within mimicry rings plays a crucial role in their evolution and maintenance.
• This finding helps explain the observed variation in chemical defenses among and within Müllerian mimic species.