# Turtle genomic novelty is driven by the evolution of ecological robustness

## TL;DR

Turtle evolution is shaped by genes related to stress tolerance and immunity, suggesting ecological robustness is a key adaptation.

## Contribution

A novel comparative genomic method reveals conserved patterns of accelerated genes linked to stress and immunity in turtles.

## Key findings

- Shared turtle traits are unlinked with sudden increases in fast-evolving genes.
- Accelerated genes in turtles are conserved across close relatives and linked to stress tolerance and immunity.
- The appearance of accelerated genes in turtles occurs at a roughly constant rate over time.

## Abstract

Turtles are striking among vertebrates in their unique diversity of morphology, ecology, and life-history. A robust physiology is often seen as the primary driver of turtle evolution, and this is increasingly studied in comparative genomics frameworks. Here, we use a genomic-scale dataset from across turtles and a novel comparative method to examine the genomic forces driving evolution in the group. Our approach addresses the correlation structures across species and genes flexibly via Mahalanobis distances from gene-wise pairwise genetic matrices, relaxing the assumption of an overarching species phylogeny. Analysis of outliers in this space reveals that close relatives, notably Cryptodira and Emydidae, share the most accelerated genes, and functional enrichment further indicates that these genes are involved in stress tolerance and immunity. These results reinforce ecological robustness as a core adaptation in turtles, and point to neutral processes as contributing to the genes with accelerated evolution in animals.

•Shared turtle traits are frequently unlinked with jumps in numbers of fast evolving genes•Numbers of shared accelerated genes are conserved, suggesting low rates in this form of novelty•The appearance of accelerated genes in turtles follows a roughly constant rate through time•Turtles share accelerated rates in genes for stress tolerance, immunity and gene regulation

Shared turtle traits are frequently unlinked with jumps in numbers of fast evolving genes

Numbers of shared accelerated genes are conserved, suggesting low rates in this form of novelty

The appearance of accelerated genes in turtles follows a roughly constant rate through time

Turtles share accelerated rates in genes for stress tolerance, immunity and gene regulation

Zoology; Molecular biology; Evolutionary biology