Skull variation in Afro-Eurasian monkeys results from both adaptive and non-adaptive evolutionary processes

Area of Science:

• Primatology
• Evolutionary Biology
• Quantitative Genetics

Background:

• Afro-Eurasian monkeys represent the most species-rich primate family, originating in the Miocene.
• While molecular and fossil data illuminate evolutionary divergence, the underlying evolutionary processes remain less understood.

Purpose of the Study:

• To investigate the relative importance of natural selection and genetic drift in shaping primate diversity.
• To analyze evolutionary processes across different taxonomic levels within Afro-Eurasian monkeys.

Main Methods:

• Application of quantitative genetics theory tests.
• Analysis of a large cranio-mandibular morphometric dataset (n > 3000).
• Comparative approach with studies on New World monkeys, apes, hominins, and other vertebrates.

Main Results:

• Natural selection significantly contributes to the diversification of Afro-Eurasian monkeys, particularly in size-related traits.
• Genetic drift is a better explanation for skull divergence within the Colobinae subfamily, especially in African colobines.
• Habitat fragmentation is a likely driver for increased genetic drift in African colobines.

Conclusions:

• Understanding evolutionary pressures is crucial for assessing the vulnerability of primate taxa, many of which face population decline.
• Genetic drift poses a significant threat to the genetic diversity and resilience of African colobines due to small and declining populations.
• Identifying adaptive pressures aids in prioritizing conservation efforts for threatened primate species.