Data from: True UV color vision in a female butterfly with two UV opsins

In true color vision animals discriminate between light wavelengths,
regardless of intensity, using at least two photoreceptors with different
spectral sensitivity peaks. Heliconius butterflies have duplicate UV opsin
genes, which encode ultraviolet and violet photoreceptors, respectively.
In H. erato, only females express the ultraviolet photoreceptor,
suggesting females (but not males) can discriminate between UV
wavelengths. We tested the ability of H. erato, and two species lacking
the violet receptor, H. melpomene and Eueides isabella, to discriminate
between 380 and 390 nm, and between 400 and 436 nm, after being trained to
associate each stimulus with a sugar reward. We found that only H. erato
females have color vision in the UV range. Across species, both sexes show
color vision in the blue-range. Models of H. erato color vision suggest
that females have an advantage over males in discriminating the inner
UV-yellow corollas of Psiguria flowers from their outer orange petals.
Moreover, previous models (McCulloch et al., 2017) suggested that H. erato
males have an advantage over females in discriminating Heliconius
3-hyroxykynurenine (3-OHK) yellow wing coloration from non-3-OHK yellow
wing coloration found in other heliconiines. These results provide some of
the first behavioral evidence for female H. erato UV color discrimination
in the context of foraging, lending support to the hypothesis (Briscoe et
al., 2010) that the duplicated UV opsin genes function together in UV
color vision. Taken together, the sexually dimorphic visual system of H.
erato appears to have been shaped by both sexual selection and
sex-specific natural selection.