Cooperation facilitates the colonization of harsh environments

Area of Science:

• Evolutionary Biology
• Animal Behavior
• Ecology

Background:

• Cooperative breeding in animals has been linked to harsh environmental conditions (high temperatures, unpredictable rainfall).
• Previous research assumed harsh environments were a primary driver for the evolution of cooperation.
• The causal order of environmental conditions and cooperative breeding had not been empirically tested.

Purpose of the Study:

• To investigate the evolutionary causality between environmental harshness and the development of cooperative breeding.
• To determine whether harsh environments lead to cooperation or if cooperation facilitates adaptation to harsh environments.

Main Methods:

• Phylogenetic analyses were conducted on a large dataset of 4,707 bird species.
• The study examined evolutionary relationships and trait evolution across species.

Main Results:

• Causality was found to be reversed: cooperative breeding facilitates the colonization of harsh environments, not the other way around.
• Cooperative breeding likely evolved in ancestors from cooler, more predictable environments with high relatedness (low polyandry).
• Polyandry increased significantly after cooperative breeders invaded harsh environments, suggesting cooperation stabilizes under limited independent breeding options.

Conclusions:

• Cooperative breeding is an adaptation that enables species to invade and thrive in challenging ecological niches.
• This challenges the long-held view that environmental harshness is the main driver for cooperative breeding evolution.
• Cooperation plays a crucial role in niche invasion across various biological levels.