Meeting Abstract
Olfactory receptors (ORs) are the largest multigene family in mammals. Among animals that have been examined, OR numbers vary widely, ranging from ~100-2000. The number of ORs in an animal’s repertoire is often an indication of olfactory acuity, and percent of pseudogenized ORs are found to be high in mammals that have shifted to reliance on visual systems. Olfaction has been poorly studied in most bird groups. Chicken (Gallus gallus), that does not demonstrate reliance on olfaction, has ~500 OR genes. Black (Coragyps atratus) and turkey (Cathartes aura) vultures occupy the same habitat, yet demonstrate differing reliance on discrete sensory systems for foraging. Limited data indicate that black vultures do not use olfaction, but rather appear to be dependent on vision to locate food, while turkey vultures rely on olfaction, capable of foraging using smell alone. Turkey and black vultures present an opportunity to study the underlying genetic basis for reliance on olfaction in two related avian species. Additionally, investigation of the OR repertoires in these species will contribute to our knowledge of what evolutionary changes are necessary in order for animals to shift reliance on sensory systems. We found that turkey vultures have approximately three times as many OR genes compared to the chicken and our outgroup, the red-tailed hawk (Buteo jamaincensis). Surprisingly, black vultures have an intermediate number of OR genes between turkey vultures and red tailed hawks. These results suggest that black vultures may use olfaction more than currently thought. Our results also indicate that a large amount of OR duplication occurred after the divergence between vultures and hawks.
