Meeting Abstract
P1.183 Saturday, Jan. 4 15:30 The visual and molecular ecology of Tarsius MORITZ, G.L.*; ONG, P.S.; PERRY, G.H.; DOMINY, N.J.; Dartmouth College; University of the Philippines, Diliman; Penn State University; Dartmouth College gillian.l.moritz@dartmouth.edu
The color vision of most mammals is based on the presence of two cone-opsin photopigments – the long wavelength sensitive (L-) opsin and the short wavelength sensitive (S-) opsin. While color is barely perceivable at night for humans, there is remarkable diversity in the color vision of nocturnal primates. Some species are colorblind resulting from the functional loss of the S-opsin gene, whereas others maintain two intact opsin genes and thus the capacity for dichromatic color vision. For nocturnal primates, the advantages of making chromatic distinctions at night are unclear. Such variation could be due to a state of evolutionary disequilibrium (i.e., a relatively recent shift to nocturnality from a diurnal ancestor) or it may be adaptive and maintained by natural selection (as evidenced in the dichromatic aye-aye, Daubentonia madagascariensis). Tarsiers (genus Tarsius) are instructive because their visual system extends to the Eocene. They have relatively enormous eyes, a vestigial fovea, and are devoid of a tapetum lucidum. While the tarsiers of Borneo (T. bancanus) express an M-opsin gene, those from the Philippines (T. syrichta) and Sulawesi (T. tarsier) express an L-opsin gene. To explore the evolutionary significance of opsin functionality in nocturnal primates, we have taken an integrative approach utilizing molecular ecology and visual modeling. We first used a population genetics approach to estimate dN/dS ratios for intergenic and S-opsin gene sequences from Philippine tarsiers. Next, we modeled the responses of T. bancanus and T. syrichta color vision phenotypes to common prey items under nocturnal light levels. Our results suggest that opsins are functional and potentially adaptive in lineages with long-standing nocturnal behavior.
