Collaborative research: Understanding the role of developmental bias in the morphological diversification of bat molars

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The evolution of animal form has been uneven, radiating in fits and starts, and exploring some forms but not others. Why this pattern exists has long been a fundamental question in biology. One possible explanation can be found in the very nature of the way that animals grow from an egg into an adult, i.e., in their development. The genes that control animal development interact in networks. Some genes in these networks interact with many other genes, while others are more peripheral and isolated. This project tests the hypothesis that most evolution in animal form occurs through changes in peripheral network components, and in the aspects of form that those peripheral components make, while central genes and their associated forms are conserved among species. To test this hypothesis, this project investigates the patterns and drivers of tooth evolution in an ecologically diverse animal group, noctilionoid bats. This project is expected to be among the first to characterize the organization of the gene networks that control animal form, and the impact that this organization has on the way evolution proceeds. This project is therefore expected to illuminate mechanisms that have shaped the evolution of animals over the history of life on earth. This project will also directly increase participation of students from underrepresented groups (URMs) in research and contribute to public education. These goals will be achieved by involving URM undergraduates from Puerto Rico in project research, training postdoctoral scientists in URM mentorship, and showcasing project results at the Burke Museum.This project’s goal is to characterize and model the evolution of developmental GRN modules and resulting morphologies, using the radiation of noctilionoid bats and their molars as a model system. This project's central hypothesis is that a conserved core module of the molar GRN controls the initial formation of molar traits that are conserved across species, with evolutionary modification of network sub-modules leading to interspecific morphological variation. To test this, two aims will be completed. In Aim 1, the team will quantify morphology of developing lower first molars (m1) in representative noctilionoids, and adult m1s across all extant noctilionoid genera. Data will be used to reconstruct the development and evolution of noctilionoid m1 morphology, and identify conserved and variable traits over developmental and evolutionary time. In Aim 2, the team will map gene expression over m1 development in representative noctilionoids, functionally test the ability of observed expression differences in key molar developmental pathways to generate variable m1 morphologies, reconstruct GRN modules for bat m1s in computational space, and link GRN modules to m1 morphological diversity. Using data from both aims, the team will also use machine-learning techniques to reverse-engineer a computational model that will predict m1 phenotypes resulting from variation in developmental modules. Through this research, this project will characterize the role of developmental biases in morphological evolution within an adaptive radiation, functionally link shifts in gene expression to the evolution of morphology among closely related species, and generate a predictive model for morphological evolution across a hyper-diverse mammal groupThis award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.