Abstract # 149:

Scheduled for Sunday, September 20, 2009 06:30 PM-09:00 PM: Session 14 (Mission Bay Ballroom CDE) Poster Presentation


E. B. Davion1,2 and R. D. Martin2
1University of Chicago, Committee on Evolutionary Biology, Culver Hall 402, 1025 E. 57th Street, Chicago, IL 60637, USA, 2The Field Museum

It has long been accepted that mammals were generally small and nocturnal for the first two thirds of their evolutionary history (210 and 65 mya). It has also been widely accepted that ancestral primates remained nocturnal, with diurnal behaviour a secondary development in some descendant lineages. Early terrestrial vertebrates were probably tetrachromatic, with 4 colour opsin genes corresponding to 4 cone types for photopic vision and a rhodopsin gene corresponding to rods for scotopic vision. Extant mammals, including most primates, are typically dichromatic, having lost 2 ancestral colour opsin genes and the corresponding cone types. Humans, apes and some diurnal monkeys are unique among mammals in being trichromatic. Cones (previously thought to be useful only for photopic vision) are consistently present in nocturnal mammals. Even more surprisingly, two different cone types (Medium/Long-wave Sensitive and Short-wave Sensitive) are commonly present in the retina of nocturnal mammals, although Short-wave Sensitive cones have been suppressed in some, including 3 groups of primates (loris group, dwarf lemurs and owl monkeys). This and other evidence has led certain authors to propose that primates had a diurnal ancestry. Recent mtDNA evidence has unexpectedly identified colugos (Cynocephalus spp.) as the sister group of primates. Using DNA sequencing to investigate the visual-pigment genes in colugos, the closest living relatives of primates, will help to shed light on the ancestral condition of primates.