Introduction to special issue

Resolving ruminants

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Science  21 Jun 2019:
Vol. 364, Issue 6446, pp. 1150-1151
DOI: 10.1126/science.aay2379

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An adult female reindeer (Rangifer tarandus) in Cairngorms, Scotland, UK. Reindeer are ruminant mammals that exhibit species-specific adaptations to their harsh Arctic distribution.

PHOTO: MARK HAMBLIN/NATUREPL.COM/GETTY IMAGES

Ruminants are one of the most diverse groups of mammals. All members have a specialized digestive organ known as the rumen, as well as other organs that permit them to subsist on plants. These adaptations allow ruminants to digest foliage more efficiently than other mammalian species and may underlie the success of this clade. Additionally, most ruminant species have impressive bony outgrowths, collectively referred to as headgear, that may aid in mate selection. These varied ornaments, some of which are exclusive to males, include the horns carried throughout the lives of sheep, antelope, and cattle, as well as the annually regenerating deer antlers, one of the fastest-growing tissues of any mammal. Here, Science presents three studies that use genomic analyses to resolve the evolutionary relationships among the major ruminant lineages, identify the genes involved in the evolution of headgear, and examine how reindeer adapted to the long days and nights of the Arctic region. These studies allow us to better appreciate the familiar domestic cows, sheep, and deer and their wild relatives and to peer into the adaptations underlying the antelopes, giraffes, bison, and pronghorn that occupy the world's grasslands.

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