Immune system evolution among anthropoid primates: parasites, injuries and predators

Area of Science:

• Evolutionary biology
• Immunology
• Primate ecology

Background:

• Leucocyte concentrations are a key component of the immune system.
• Variation in leucocyte concentrations may reflect evolutionary adaptation to ecological factors.
• Understanding these adaptations is crucial for comprehending primate immune system evolution.

Purpose of the Study:

• To investigate if present-day variation in baseline leucocyte concentrations in primates is an evolutionary adaptation to ecological factors.
• To test hypotheses linking leucocyte concentrations to disease transmission risk, environmental infection risk, and injury risk.
• To identify specific ecological factors that have driven immune system evolution in anthropoid primates.

Main Methods:

• Comparative analysis of leucocyte concentrations across different primate populations.
• Statistical correlation between leucocyte concentrations (lymphocyte, phagocyte, platelet) and ecological variables (host abundance, rainfall, body mass, predation rate).
• Testing three distinct hypotheses regarding the evolutionary drivers of immune variation.

Main Results:

• No association found between leucocyte concentrations and host abundance (disease transmission risk).
• Lymphocyte and phagocyte concentrations positively correlated with annual rainfall, supporting the environmental infection risk hypothesis.
• Platelet concentrations negatively correlated with body mass and positively correlated with predation rate in males, supporting the injury risk hypothesis.

Conclusions:

• Environmental disease risk and injury risk are significant drivers of immune system evolution in anthropoid primates.
• Annual rainfall, reflecting parasite prevalence, and injury risk (related to body mass and predation) have shaped immune adaptations.
• Leucocyte concentration variation provides insights into the adaptive responses of primate immune systems to ecological pressures.