Researchers report gene losses in mammalian herbivores and carnivores that suggest convergent evolutionary pathways of dietary specialization. Mammals are generally classified as herbivores, carnivores, or omnivores, with each dietary specialization correlating to structural and functional specialization of the entire digestive system. Because many of these specializations developed independently of one another, it is unclear if herbivory or carnivory evolved through similar genetic changes in independent evolutionary lineages. Michael Hiller and colleagues studied gene loss in the sequenced genomes of 16 mammalian herbivorous species and 15 mammalian carnivorous species. Herbivores had repeated losses of genes connected with triglyceride digestion inhibition and pancreatic enzyme secretion, leading to increased triglyceride digestion efficiency and continuous secretion of digestive enzyme precursors. The latter adaptation may be in response to herbivores frequently grazing throughout the day, requiring near-continuous enzyme secretion. Carnivores lost genes connected with appetite regulation, glucose production, and detoxification of plant xenobiotics. They also lost the antimicrobial immune gene NOX1, which is associated with defense against microbes in the gut. Carnivores typically have half as much gut microbial diversity as herbivores and therefore, a diminished need for such defenses. According to the authors, the convergent losses highlight the genetic foundations of physiological differences between mammals that adapted to specialized diets.
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Article #18-18504: "Convergent gene losses illuminate metabolic and physiological changes in herbivores and carnivores," by Nikolai Hecker, Virag Sharma, and Michael Hiller.
MEDIA CONTACT: Michael Hiller, Max Planck Institute of Molecular Cell Biology and Genetics, Dresden, GERMANY; tel: +49-3512102781; e-mail: hiller@mpi-cbg.de
Journal
Proceedings of the National Academy of Sciences