The aim of our research is to understand the evolutionary processes, developmental mechanisms, and ecological contexts that generate morphological variation in vertebrates. As integrative biologists, we incorporate comparative anatomy, evolutionary developmental biology, phylogenetic comparative methods, and natural history to investigate functional traits across several scales of biological organization. Our research has an emphasis on the biology of frogs because of this clade’s remarkable diversity that can be leveraged to study the form, function, and evolution of anatomical traits. Anura comprises nearly 8,000 species with a world-wide distribution and extensive ecological diversity. Frogs also exhibit the highest life history diversity among all terrestrial vertebrates, and their life cycles range from direct development to fully biphasic with larval forms specialized to a wide range of ecologies that differ substantially from adults. Lastly, the embryos of frogs can be experimentally manipulated in several ways. Some of our current and recent projects are highlighted below. We collect data in the lab, in the field, and in natural history collections. Interested in learning more? Contact me at [email protected]!

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Current and previous work

Diversity and evolution of frog teeth: Teeth are complex, mineralized structures that first evolved over 400 million years ago and facilitated the diversification of jawed vertebrates. Most living fishes and tetrapods retain teeth on both jaws, but teeth have been lost completely multiple times, including in turtles, birds, and three lineages of mammals, resulting in edentulism. The evolution and diversity of amphibian teeth have been poorly studied in contrast to other vertebrates. During my PhD, I assembled the first comprehensive dataset of amphibian dental diversity using micro-computed tomography, coding the presence or absence of teeth in over 500 genera. This work revealed that teeth are invariably present in salamanders and caecilians but have been lost completely more than 20 times in living frogs (Paluh et al. 2021, eLife), more frequent than in any other vertebrate group. Repeated tooth loss in anurans is associated with a specialized diet of small invertebrates and shortened lower jaws. When present, frog teeth are typically found on the upper jaw and palate but are nearly always absent on the lower jaw. Remarkably, Gastrotheca guentheri is the only known frog with mandibular teeth. These teeth were lost in the ancestor of frogs more than 200 million years ago and re-emerged in G. guentheri during the Miocene. Using histology and 3D imaging, I confirmed that these lower jaw structures are true teeth, nearly identical in morphology, development, and replacement to upper jaw teeth of closely related species (Paluh et al. 2021, Evolution). My lab is currently analyzing quantitative data from microCT to evaluate amphibian dental diversification at a macroevolutionary scale. Amphibians possess greater tooth number variation than all mammals, ranging across species from zero to over 200 functional teeth. Comparative analyses are being implemented to test how developmental, phylogenetic, and ecological factors have impacted the tempo and mode of dental evolution. These findings highlight frogs as a unique system for investigating morphological evolution, convergent trait loss, and the re-evolution of lost traits.

Development of frog teeth: My postdoctoral work investigated the developmental-genetic mechanisms underlying normal dental development in toothed frogs, the suppression of teeth in the anuran mandible, and repeated instances of complete tooth loss. I examined cellular anatomy and gene expression via in situ hybridization across a developmental series of a toothed frog (Osteopilus septentrionalis) to characterize first-generation upper jaw teeth. Unlike other vertebrates, toothed frogs fail to develop teeth during embryogenesis and form adult dentition during the postembryonic metamorphosis. I found that the core gene regulatory network for dental competence is conserved in these late-forming teeth (Paluh et al. 2025, Royal Society Open Science), similar to odontogenic expression in other vertebrates. However, I found no molecular or histological evidence of tooth induction in the mandible, suggesting that the lower jaw of frogs has lost the competence to initiate dental development. To evaluate the repeated instances of tooth loss across frogs, my lab has raised developmental series of five distantly related edentulous species across the frog phylogeny. We are evaluating the anatomical and molecular evidence of vestigial dental development in these species. In other edentulous vertebrates (e.g., birds, turtles, mammals), early molecular signaling maintains dental competence and vestigial tooth bud rudiments often form. 

Origin of a morphological innovation: Morphological traits typically evolve via modification and differentiation of pre-existing structures. However, new traits can also seemingly arise de novo. The mechanism by which novel phenotypes originate is among the least understood phenomena in evolutionary biology, yet morphological novelties are frequently considered ecologically and evolutionarily significant. Co-option is a proposed mechanism for generating major morphological transitions, in which an ancestral gene regulatory network is re-deployed in a new developmental context. The evolutionary origin and developmental genetics of the unique tadpole feeding apparatus is entirely unknown, which is composed of unique keratinized mouthparts. We have recently demonstrated that gene expression patterns of tadpole keratinized mouthparts and frog teeth overlap (Paluh et al. 2025, Royal Society Open Science), suggesting that these structures are more closely related than previously hypothesized. My lab is now investigating whether the novel mouthparts of tadpoles originated by partially co-opting the developmental program that typically mediates mineralized tooth formation. Using an experimental approach, we are testing if the same developmental genes are functionally required during keratinized mouthpart and tooth development using expression manipulation methods and comparative transcriptomics. We are also developing CRISPR protocols in non-model frogs.