Urbanization processes drive divergence at the major histocompatibility complex in a common waterbird

Area of Science:

• Evolutionary biology
• Urban ecology
• Immunogenetics

Background:

• Urban sprawl is a global phenomenon, leading to wildlife adaptation.
• Genetic adaptation evidence in urban wildlife is limited, unlike phenotypic adjustments.
• Pathogen-driven selective pressures may drive host immune gene evolution in urban vs. rural areas.

Purpose of the Study:

• To investigate urbanization-related genetic differentiation in the major histocompatibility complex (MHC) of the Eurasian coot (Fulica atra).
• To assess if MHC allele composition varies with urbanization levels and time since colonization.
• To compare genetic patterns at MHC genes with neutral genetic markers.

Main Methods:

• Collected Eurasian coot samples from old urban, new urban, and rural populations in central Poland.
• Analyzed genetic differentiation at MHC class II genes using Jost's D.
• Compared MHC allele diversity and population-specific alleles between urban and rural groups.
• Utilized microsatellite markers to assess neutral genetic variation.

Main Results:

• Significant MHC class II divergence was found between the old urban population and other populations.
• Moderate, significant MHC divergence existed between the new urban and rural populations.
• Urban populations, especially the old urban one, showed reduced MHC allele diversity compared to rural populations.
• MHC genetic patterns differed from those observed in neutral microsatellite markers.

Conclusions:

• MHC allele composition in Eurasian coots is influenced by anthropogenic disturbance and duration of urban colonization.
• Local adaptation and genotype sorting likely drive observed MHC differentiation in urbanizing wildlife.
• The study highlights the role of immune gene evolution in wildlife adaptation to urban environments.