Colour polymorphism is associated with lower extinction risk in birds

Area of Science:

• Evolutionary Biology
• Conservation Biology
• Zoology

Background:

• Color polymorphisms influence phenotypes through selection and demography.
• Polymorphisms may enhance adaptability to environmental changes by enabling alternative strategies and niche exploitation.
• The influence of color polymorphism on species' global change response is debated.

Purpose of the Study:

• To investigate the relationship between avian color polymorphism and extinction risk.
• To differentiate the conservation implications of true polymorphism versus geographic color variation.
• To assess if color polymorphism confers resilience against specific extinction drivers.

Main Methods:

• Compiled a comprehensive database of color polymorphism for 10,394 extant bird species.
• Distinguished between true polymorphism (sympatric morphs) and geographic color variation (parapatric/allopatric).
• Utilized the IUCN Red List to assess extinction risk, controlling for factors like range size, habitat breadth, life history, and phylogeny.

Main Results:

• Polymorphic bird species exhibit a lower risk of extinction compared to nonpolymorphic species.
• This protective effect holds after accounting for significant ecological and evolutionary factors.
• However, polymorphic species were not less vulnerable to specific threats like habitat alteration, climate change, or invasive species.

Conclusions:

• Color polymorphism appears to act as a buffer against general environmental changes, potentially due to higher genetic diversity or alternative strategies.
• The study highlights the importance of distinguishing between true polymorphism and geographic variation in conservation.
• Further research is needed to elucidate the mechanisms underlying this adaptive advantage and develop threat-specific sensitivity indices.