# Evolutionary adaptations generally reverse phenotypic plasticity to restore ancestral phenotypes during new environment adaptation in cattle

## TL;DR

This study shows that when cattle adapt to new environments, they often reverse genetic changes to restore ancestral traits, suggesting a general pattern in evolutionary adaptation.

## Contribution

The study reveals that evolutionary adaptations in cattle often reverse ancestral plasticity to restore ancestral phenotypes during new environment adaptation.

## Key findings

- Genetic transcriptomic changes during highland adaptation are reversed by plastic changes when cattle return to lowlands.
- Ancestral plasticity in genes is generally reversed through evolutionary adaptations, restoring ancestral expression levels.
- Biochemical and hemorheology traits in cattle tend to revert to ancestral patterns during adaptation to new environments.

## Abstract

Phenotype plasticity and evolution adaptations are the two main ways in which allow populations to deal with environmental changes, but the potential relationship between them remains controversial. Using a reciprocal transplant approach with cattle adapted to the Tibetan Plateau and adjacent lowlands, we aim to investigate the relative contributions of evolutionary processes and phenotypic plasticity in driving both phenotypic and transcriptomic changes under natural conditions. We observed that while numerous genetic transcriptomic changes were evident during the forward adaptation to highland environments, plastic changes predominantly facilitate the transformation of transcriptomes into a preferred state when Tibetan cattle are reintroduced to lowland habitats. Genes with ancestral plasticity are generally reversed by evolutionary adaptations and show a closer expression level to the ancestral stage in evolved Tibetan cattle. A similar trend was also observed at the phenotypes level, with a majority of biochemical and hemorheology phenotypes showing a tendency to revert to their ancestral patterns, suggesting the restoration of ancestral expression levels is a widespread evolutionary trend during adaptation. The findings of our study contribute to the debate regarding the relative contributions of plasticity and genetic changes in mammal environment adaptation. Furthermore, we highlight that the restoration of ancestral phenotypes represents a general pattern in cattle new environment adaptation.

Our findings reveal that while numerous genetic transcriptomic changes were observed during the forward adaptation to highland environments, plastic changes predominantly facilitate the transformation of transcriptomes into a preferred state when Tibetan cattle are reintroduced to lowland habitats. Genes exhibiting ancestral plasticity generally undergo reversal through evolutionary adaptations, resulting in closer expression levels resembling their ancestral stage in evolved Tibetan cattle. A similar trend was also observed at the phenotype level, where a majority of biochemical and hemorheology traits displayed a tendency to revert to their ancestral patterns, suggesting that restoration of ancestral expression levels is a widespread evolutionary trend during adaptation.