The evolution of immunity in relation to colonization and migration

Area of Science:

• Evolutionary Biology
• Immunology
• Ornithology

Background:

• Colonization and migration significantly influence biodiversity patterns.
• Pathogens are predicted to play a key role in these processes, but empirical evidence is limited.
• Understanding the impact of disease on species' movements and evolution is crucial.

Purpose of the Study:

• To investigate the effect of pathogen diversity on bird colonization and migration patterns.
• To examine the evolutionary consequences of migration on the immune systems of songbirds.
• To explore the relationship between host-pathogen interactions and the evolution of immune gene diversity.

Main Methods:

• Phylogenetic analyses of 1,311 Afro-Palaearctic songbird species.
• Comparative analysis of colonization frequencies between regions with differing pathogen loads.
• Assessment of major histocompatibility complex class I (MHC-I) gene diversity in relation to migratory behavior and origin.

Main Results:

• Colonization from high-pathogen (sub-Saharan Africa) to low-pathogen (Palaearctic) regions was up to 20 times more frequent than the reverse.
• Long-distance migration evolved 3 times more frequently in African-resident species compared to Palaearctic-resident species.
• Species that colonized the Palaearctic or evolved long-distance migration exhibited reduced diversity in major histocompatibility complex class I genes.

Conclusions:

• Changes in pathogen communities during colonization and migration shape immune system evolution.
• Reduced major histocompatibility complex class I diversity may reflect an adaptation to lower pathogen loads or a trade-off in immune function.
• This study provides evidence for the role of disease in shaping broad-scale patterns of avian colonization, migration, and immune evolution.