Heterospecific aggression bias towards a rarer colour morph

Area of Science:

• Evolutionary Biology
• Behavioral Ecology
• Ichthyology

Background:

• Phenotypic diversity in color polymorphisms is common, but the selective pressures maintaining different morphs are not fully understood.
• Interspecific aggression's role in maintaining color morph diversity is rarely studied, despite aggression's importance in social dominance.

Purpose of the Study:

• Investigate heterospecific aggression patterns directed by Hypsophrys nicaraguensis towards color polymorphic cichlids in the genus Amphilophus.
• Determine if interspecific aggression influences the frequencies of different color morphs within a population.

Main Methods:

• Field-based study in a Nicaraguan crater lake.
• Observed territorial interactions between H. nicaraguensis and polymorphic Amphilophus species.
• Used model intrusions to quantify aggression levels towards different color morphs.

Main Results:

• H. nicaraguensis frequently shared territories with the color polymorphic A. sagittae.
• H. nicaraguensis exhibited significantly higher aggression towards the gold morph compared to the dark morph of Amphilophus species.
• This aggression pattern was consistent across sympatric Amphilophus species.

Conclusions:

• Interspecific aggression by H. nicaraguensis imposes a cost on the gold color morph.
• This aggression may contribute to the lower-than-expected frequency of the gold morph.
• Heterospecific aggression is an important factor to consider in understanding morph frequencies and coexistence in natural populations.