Rainfall drives adaptation in Ethiopian sheep

Rainfall may have a significant influence on the evolution of sheep in Ethiopia, researchers have found.

Genetic variations in sheep DNA are more linked to precipitation levels than to temperature or altitude, analysis of their genetic make-up and climatic data suggests.

Scientists also identified specific genes that may be involved in the adaptation to environmental factors.

A better understanding of environmental adaptation in native livestock breeds may help inform breeding and management strategies in tropical countries such as Ethiopia, where one-third of smallholders own sheep.

Genome and climate

The study, led by the Roslin Institute and Centre for Tropical Livestock Genetics and Health (CTLGH), analysed the DNA of indigenous sheep living in different parts of Ethiopia.

The group sought to investigate if the environment had influenced changes in the sheep’s DNA to help them to thrive in different climates.

In one of the largest studies based on a single region, the researchers analysed the genomes of 94 sheep from 12 different areas of Ethiopia and examined them alongside detailed climatic information for each of the geographic regions.

Researchers compared the genomes of the sheep and found more than 3 million small differences in specific segments of their DNA. They then looked at the altitude, temperature and rainfall in each of the 12 geographical regions in the study and measured how many times these genetic variations occurred in sheep living under each of the environmental conditions.

There was a stronger association between the frequency of these genetic variations and precipitation levels compared with temperature or altitude, suggesting that rainfall is a more important environmental driver for genetic adaptation in Ethiopian sheep.

Researchers from the Roslin Institute, Scotland’s Rural College (SRUC) and the International Livestock Research Institute (ILRI), which are strategic partners of CTLGH, and the International Centre for Agricultural Research in the Dry Areas (ICARDA) worked with collaborators from the University of Nottingham, Libya, Ethiopia and Australia on the study.

Ethiopia is an ideal setting to investigate environmental adaptation in livestock, owing to its large range of climatic conditions and the rich genetic diversity of its livestock. By examining related sheep populations from a limited geographical region, our study was able to focus more specifically on the impact of environmental variables, giving us a greater degree of confidence in our results.

Dr Pam Wiener

This study provides a foundation to investigate further the effects of climate on small ruminant populations. The dataset we have generated is also a valuable resource to design new genomic technologies to support Ethiopian sheep farmers and help to mitigate the effects of the changing climates we now see in tropical ecosystems.

Dr Emily Clark

The study, published in Genome Biology and Evolution, was funded by a Global Challenges Research Fund Data and Resources Grant awarded to the Roslin Institute through the Biotechnology and Biological Sciences Research Council (BBSRC), and by the CGIAR Research Program on Livestock through ILRI and ICARDA. The research was also supported by the Bill & Melinda Gates Foundation and the UK Foreign Commonwealth and Development Office (FCDO) through CTLGH.

** The Roslin Institute is part of the University of Edinburgh’s Royal (Dick) School of Veterinary Studies. **

Related links

Scientific publication

Study could help breed healthier Ethiopian poultry

Gene map to aid studies of key traits in sheep

CTLGH website

_{Image credit: Adebaby Kebede}