Experimental evidence of frequency-dependent selection on group behaviour

Area of Science:

• Evolutionary Ecology
• Behavioral Ecology
• Social Behavior

Background:

• Intraspecific variation is crucial for adaptation, but the mechanisms maintaining it are not fully understood.
• In social species, collective traits can vary between groups, influencing population dynamics.
• Negative frequency-dependent selection, where rare types have an advantage, is a potential mechanism for maintaining variation.

Purpose of the Study:

• To investigate if negative frequency-dependent selection maintains between-group variation in social spider colonies.
• To determine the role of collective foraging phenotypes (bold vs. shy) in driving these dynamics.
• To assess the impact of the local 'phenotypic environment' on group success.

Main Methods:

• Engineered neighborhoods of social spider colonies with distinct bold or shy foraging phenotypes.
• Monitored colony fecundity in situ under varying frequencies of bold and shy colonies.
• Analyzed the relationship between colony phenotype frequency and reproductive success.

Main Results:

• Bold colonies exhibited a rare-type advantage, increasing their fecundity when infrequent.
• This advantage diminished as the frequency of bold colonies increased in a neighborhood.
• Shy colonies did not show frequency-dependent success; their performance was linked to resource availability.
• Bold colonies' foraging advantage was lost in high-frequency bold neighborhoods due to prey depletion.

Conclusions:

• Negative frequency-dependent selection can maintain between-group variation in social spider populations.
• The success of collective traits depends not only on the group's phenotype but also on the surrounding 'phenotypic environment'.
• Understanding selection on group traits requires considering the ecological context and competition between groups.