ABSTRACT

Traits of species that evolved to serve one function but were later modified by evolution to serve a new function are known as exaptations. While there are many examples of such traits, the process by which they evolve is still poorly understood. This project will advance our understanding of how evolution reshapes the genetic blueprint of species traits to create new, novel innovations. Traits associated with gliding and flying, like feathers, are some of the most notable examples of exaptations. Unfortunately, most gliding species are already highly specialized, making it difficult to study the process by which exaptation has occurred. Geckos, which are the focus of this research project, are an exception. Geckos have evolved gliding structures multiple times from flaps of skin used in camouflage and there are multiple species that together represent the complete transition from general to highly specialized gliding ability. These evolutionary replicates allow the researchers to test whether exaptation of particular traits follows predictable patterns and also provide a means of measuring how form and function interact to affect rates of evolution. This research will provide research training to undergraduates, graduate students, and a postdoc in genetic, morphological, bioinformatic, and image analysis methods. The public also will be engaged by developing an educational program at the Sam Noble Museum that will feature age-appropriate information and learning activities related to gliding in geckos.

This research will determine the consequences of gliding-associated exaptations of geckos within a context of evolutionary relationships. Two primary research questions will be addressed: (1) whether gliding structures represent exaptations that evolve in a predictable way, and (2) whether these traits or the associated functional shift represent key innovations leading to shifts in the rate of evolution in the affected clades. The PIs will address these questions by combining field, laboratory, and computational approaches. Fully resolved evolutionary trees will be estimated for gliding geckos and related lineages. Structural variation in gliding and non-gliding geckos will be surveyed using a combination of external observation, diceCT, and histology. Developmental similarities among gliding taxa will be assessed by analyzing embryonic morphology and developmental gene expression patterns in a set of exemplar taxa. Relative cryptic and gliding performance values will be measured by both observing live animals and by experimenting with models to document the functional shift from camouflage to gliding. Phylogenetic comparative analyses will be employed to identify patterns of phenotypic and lineage diversification and their relationships to morphological and functional change in this group. A significant volume of new DNA sequence data; morphological data, including numerous full-body CT scans; and performance data will be produced and be of broad interest and use to the scientific community.

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