Brain-body coevolution in incipient versus established primate species-evaluating Simpson's "most important...

Area of Science:

• Evolutionary biology
• Comparative genomics
• Primate evolution

Background:

• Understanding the tempo and mode of phenotypic evolution is crucial for evolutionary biology.
• Distinguishing between gradual microevolutionary changes and those occurring during speciation is a key challenge.

Purpose of the Study:

• To investigate whether speciation involves fundamentally different processes than microevolution.
• To analyze the contribution of speciation to phenotypic variation in brain and body size among primate species.

Main Methods:

• Phylogenetic comparative analysis of primate brain and body sizes.
• Decomposition of phenotypic covariance into speciational and anagenetic components.

Main Results:

• Approximately 50% of speciation events show accelerated phenotypic change in brain and body size.
• Speciational changes account for about 58% of phenotypic variation among extant primate species.
• Speciational changes in brain and body size are less correlated than gradual microevolutionary changes, indicating relaxed allometric constraints.

Conclusions:

• Phenotypic evolution is accelerated during speciation events.
• Speciation involves unique evolutionary events not typically observed during microevolutionary timescales.
• The strong allometric constraint on brain and body size is relaxed during speciation.