Evolution of Sensory Systems in Frogs and Lizards

As an interface between the environment and the organism, sensory systems play pivotal roles in shaping ecological characteristics and complex behaviors, such as mate choice and species recognition. Thus, understanding how sensory systems function and evolve can provide vital insight into the diversity of ecological transitions that have occurred across the animal tree of life and also the evolution of novel structures. A new research trajectory for the lab is the understand the role that sensory systems play in the diversification of frogs and lizards. The lab has two NSF grants to pursue this exciting research: the first is an international collaboration that is co-sponsored by the UK Natural Environment Research Council and aims to understand the evolution of frog vision, and the second is to understand the evolution of epidermal glands in lizards, including novel structures that may share deep homology with existing sensory systems.

Frog vision is dramatically understudied and we know details of the visual systems for very few of the >6,600 extant species that have evolved over 265 million years. Having just secured NSF funding for this endeavor, investigating vision systems in frogs is a new and exciting trajectory for the lab. With my collaborators Dr. Rayna Bell (Curator of Amphibians and Reptiles at the Smithsonian Institute) and Dr. Jeffrey Streicher and Dr. David Gower (Herpetology curators at the Natural History Museum of London), we will examine the functional, genomic, and  molecular evolutionary histories of frog vision from recent to tree-of-life timescales using microspectrophotometry, transcriptome and exome sequencing, and morphological analysis of the eye. Our two specific aims are to (1) identify major patterns in vision evolution across the anuran tree of life, and then to (2) test hypotheses of adaptive vision evolution in a comparative framework (Figure 5). For example, we hypothesize that fossorial frogs will have smaller eyes and a reduced spectral diversity compared to more typical frogs, and perhaps show inactivated or silenced phototransduction genes.

Figure 1 Full Proposal

The second of our sensory systems project that is funded by NSF aims to understand the evolution of epidermal glands in lizards and whether they represent structures that have originated independently or if they are conserved despite not being present in multiple families. Lizards use these glands for communication by depositing secretions onto environmental surfaces that provide signals for species recognition, territoriality, and sexual selection. One of our main goals is to understand the evolution of epidermal glands over time with respect to their potential deep homology: do glands from distantly related species use the same molecular and cellular machinery or have they evolved divergent developmental pathways despite have similar morphologies and functions? While COVID interrupted this project over the past year, we are excited to start making progress as we are finally able to do field work again!

Here are some cool papers that have come from these projects, with more to come soon!
Thomas, K. N., D. J. Gower, R. C. Bell, M. K. Fujita, R. K. Schott, and J. W. Streicher. 2020. Eye size and investment in frogs and toads correlate with adult habitat, activity pattern and breeding ecology. Proceedings of the Royal Society B 287:20201393

Shrimpton, S. J., J. W. Streicher, D. J. Gower, R. C. Bell, M. K. Fujita, R. K. Schott, and K. N. Thomas. 2021. Eye-body allometry across biphasic ontogeny in anuran amphibians. Evolutionary Ecology 35: 337–359