Female preference counteracts negative frequency dependent selection for a stable polymorphism in a livebearing fish

Area of Science:

• * Evolutionary biology
• * Behavioral ecology
• * Animal behavior

Background:

• * Polymorphism, the coexistence of multiple phenotypes, is crucial for natural selection.
• * Negative frequency dependent selection (NFDS) often maintains polymorphism, favoring rare types.
• * In Girardinus metallicus, males exhibit plain (common) and black (rare) morphs.

Purpose of the Study:

• * To investigate if female choice generates NFDS in Girardinus metallicus mating polymorphism.
• * To determine female preference between common plain and rare black male morphs.
• * To explore potential alternative advantages for rare morphs.

Main Methods:

• * Mate choice assays with females exposed to one morph prior to testing.
• * Direct competition assays between male morphs.
• * Observation of mating activity and display behaviors.

Main Results:

• * Females preferred the male morph they were previously exposed to, contradicting NFDS via female choice.
• * Rare black morphs showed higher mating activity and aggression.
• * Black morphs perform mating displays, but female preference for this display was not evident.

Conclusions:

• * Female preference in Girardinus metallicus may disrupt existing polymorphism.
• * Alternative advantages, such as aggression and mating activity, may maintain rare morphs.
• * The function of black morph mating displays may extend beyond courtship, possibly including aggressive mate guarding.