The 88th Annual Meeting of the American Association of Physical Anthropologists (2019)


Digestive and sensory adaptations for the grass-eating niche: Insights from the gelada (Theropithecus gelada) genome

MAREIKE C. JANIAK1, KENNETH L. CHIOU2, AMY LU3, THORE J. BERGMAN4,5, JACINTA C. BEEHNER4,6, NOAH SNYDER-MACKLER2 and AMANDA D. MELIN1.

1Anthropology & Archeology, University of Calgary, 2Psychology, University of Washington, 3Anthropology, Stony Brook University, 4Psychology, University of Michigan, 5Ecology & Evolutionary Biology, University of Michigan, 6Anthropology, University of Michigan

March 30, 2019 9:30, CC Room 25 Add to calendar

Geladas (Theropithecus gelada) are the only primates that feed almost exclusively on grass. This unique dietary niche poses distinct foraging and digestive challenges, which have likely exerted strong selective pressures on this species. Here, we investigated genetic adaptations for graminivory in digestive enzymes, taste receptors, and olfactory receptors in geladas, compared to their close phylogenetic relatives: baboons, macaques, and humans. We tested for gene families that have undergone expansion or contraction and/or have been subject to selection in the Theropithecus lineage. Preliminary results suggest that geladas have genetic adaptations for their unique graminivorous diet. We find significant expansions in gene families related to ubiquitin-conjugating enzymes (p < 0.001) and a significant contraction in the trypsin gene family (p < 0.001), which is related to protein digestion and may reflect the relatively low amount of protein, especially animal protein, in the gelada diet. Further, ALDH16A1 (aldehyde metabolism) has been under significant positive selection in geladas (χ2 = 310.89, p < 0.001), which may be linked to food detoxification. Unlike other cercopithecines, geladas do not retain any functional chitinase genes (CHIA), an enzyme that digests insect exoskeletons. Pseudogenization of these genes may be due to relaxed selection following the shift from an omnivorous to a specialized diet. Preliminary analyses of taste receptor genes suggest that geladas have 30 intact TAS2R genes and 6 pseudogenes, a lower pseudogenization rate (16.67%) than other primates (28-29%). Together, these results highlight several potential mechanisms that have allowed geladas to exploit a grass-eating ecological niche.