Evolution of compound eye morphology underlies differences in vision between closely relatedDrosophilaspecies

Abstract

AbstractInsects have evolved complex visual systems and display an astonishing range of adaptations for diverse ecological niches. Differences in eye size within and betweenDrosophilaspecies provide the opportunity to study the impact of eye structure on vision. Here we further explored differences inD. mauritianaand its sibling speciesD. simulansand confirmed thatD. mauritianahave rapidly evolved larger eyes as a result of more and wider ommatidia thanD. simulanssince their recent common ancestor. The functional impact of eye size, and specifically ommatidia size, is often only estimated based on the rigid surface morphology of the compound eye. Therefore, we used 3D synchrotron radiation tomography to measure optical parameters in 3D, predict optical capacity, and compare the modelled vision toin vivooptomotor responses. Our optical models predicted higher contrast sensitivity forD. mauritiana, which we verified by presenting sinusoidal gratings to tethered flies in a flight arena. Similarly, we confirmed the higher spatial acuity predicted forDrosophila simulanswith smaller ommatidia and found evidence for higher temporal resolution.