# Ecological Trait Differences Are Associated with Gene Expression in the Primary Visual Cortex of Primates

## TL;DR

This study finds that differences in primate visual traits and ecology are linked to gene expression patterns in the primary visual cortex.

## Contribution

The study identifies trait-dependent gene expression differences in primate visual cortex related to ecological and visual traits.

## Key findings

- 4–25% of genes are differentially expressed in primates with varying color vision, habitat use, group size, and diet.
- Humans and chimpanzees show the most distinct gene expression differences despite a relatively recent evolutionary split.
- Results indicate a mix of species-specific and trait-dependent gene expression evolution in primate visual cortex.

## Abstract

Primate species differ drastically from most other mammals in how they visually perceive their environments, which is particularly important for foraging, predator avoidance, and detection of social cues. Background/Objectives: Although it is well established that primates display diversity in color vision and various ecological specializations, it is not understood how visual system characteristics and ecological adaptations may be associated with gene expression levels within the primary visual cortex (V1). Methods: We performed RNA-Seq on V1 tissue samples from 28 individuals, representing 13 species of primates, including hominoids, cercopithecoids, and platyrrhines. We explored trait-dependent differential expression (DE) by contrasting species with differing visual system phenotypes and ecological traits. Results: Between 4–25% of genes were determined to be differentially expressed in primates that varied in type of color vision (trichromatic or polymorphic di/trichromatic), habitat use (arboreal or terrestrial), group size (large or small), and primary diet (frugivorous, folivorous, or omnivorous). Conclusions: Interestingly, our DE analyses revealed that humans and chimpanzees showed the most marked differences between any two species, even though they are only separated by 6–8 million years of independent evolution. These results show a combination of species-specific and trait-dependent differences in the evolution of gene expression in the primate visual cortex.