Eye size and investment in frogs and toads correlate with adult habitat, activity pattern and breeding ecology

Frogs and toads (Amphibia: Anura) display diverse ecologies and behaviours, which are often correlated with visual capacity in other vertebrates. Additionally, anurans exhibit a broad range of relative eye sizes, which have not previously been linked to ecological factors in this group. We measured relative investment in eye size and corneal size for 220 species of anurans representing all 55 currently recognized families and tested whether they were correlated with six natural history traits hypothesized to be associated with the evolution of eye size. Anuran eye size was significantly correlated with habitat, with notable decreases in eye investment among fossorial, subfossorial and aquatic species. Relative eye size was also associated with mating habitat and activity pattern. Compared to other vertebrates, anurans have relatively large eyes for their body size, indicating that vision is probably of high importance. Our study reveals the role that ecology and behaviour may have played in the evolution of anuran visual systems and highlights the usefulness of museum specimens, and importance of broad taxonomic sampling, for interpreting macroecological patterns.

Methods
Here we include three anuran datasets and one vertebrate dataset in support of the above work investigating eye-body allometry and relative eye size across anurans: 1) a set of morphological data gathered from preserved anuran museum specimens, 2) a set of morphological data collected from fresh anuran specimens, 3) a set of ecological traits and source references for the anuran species in our study, and 4) a set of morphological data compiled from published work on vertebrate eye size. The latter two datasets were supported by published materials, and references for each are posted in an associated pdf file. 

Details on the collection of these data can be found in the associated manuscript (DOI: 10.1098/rspb.2020.1393), and all code for analyzing these datasets and producing figures from the manuscript is available on GitHub: https://github.com/knthomas/anuran-eye-size. Explanations of each data file follow.