Footprints of Butterfly Rhodopsin Functional Evolution

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Many insects are equipped with eyes and brains that have the potential for color vision, the ability to distinguish wavelengths of light from one another regardless of intensity or brightness. This results from the expression of different kinds of light sensitive visual pigment rhodopsin molecules in photoreceptor cells. Butterfly visual systems have tremendous physiological variation in the sensitivity of their green- and red-sensitive rhodopsins to light. Like other visual pigments, red-sensitive rhodopsins may confer some adaptive advantage to those organisms that have them, such as in the detection of flowers, host plants and mates. Unlike the UV-, blue-, or green-sensitive visual pigments found in most arthropods, not all butterflies or insects have evolved red-sensitive pigments perhaps because of some basic constraint or metabolic cost of producing them. The proposed project will involve the characterization of opsin genes from a large number of nymphalid butterflies whose visual pigment absorption spectrum maximum has been measured, and whose taxonomic relationships are already known from independent molecular and morphological data. The data will be used to identify functionally important amino acid substitutions that are responsible for physiological shifts in sensitivity to light. The project will involve international collaborations and provide multi-level integrative training for a postdoctoral and graduate student in vision research, and includes an undergraduate outreach component, whereby undergraduates will be trained in basic molecular biology techniques in the PI's lab. The work will be of interest to workers in behavioral ecology, sensory biology, machine vision and comparative functional genomics.