Collaborative Proposal: Developmental and Genetic Pathways to Phenotypic Convergence in a Radiation of Groundwater Salamanders

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Cave organisms as unrelated as insects and salamanders often have shared features – such as lack of eyes, pallid coloration, and elongated limbs. Life underground provides different challenges from life on the surface, and those challenges favor relatively rapid changes in appearance (and other, more subtle characteristics) at the population level. Those rapid changes lead to convergence in the appearance of many cave organisms, but the genetic and developmental processes that lead to repeated changes in different organisms are largely unknown. The Edwards Plateau of central Texas has an extensive, though fragmented, network of springs, caves, and aquifers that host numerous, diverse, underground salamanders. These salamanders attain reproductive maturity while retaining features (such as gills) that are characteristic of immature salamanders, and many of them show eyes reduced in size and development to varying degrees, along with other characteristics associated with living underground (e.g. an enhanced sense of smell). These characteristics have evolved independently and repeatedly in the various species, and this research will integrate information derived through a variety of approaches to shed light on the mechanisms that enable new structures and functions to evolve. This project is timely because in addition to enhancing understanding of the evolution of sensory systems, it will highlight and clarify the diversity of salamanders in central Texas at a time when human population growth and commercial development further threaten species that have been identified as being in danger of extinction. Finally, this project will serve as a platform to train numerous undergraduates in STEM research.The researchers will use an integrative, hierarchical approach combining genetic, developmental, and phylogenetic perspectives to study the mechanisms that drive convergence in phenotypes of subterranean Groundwater Salamanders. Results from micro-computed tomography imaging, histology, transcriptomics, and exon sequencing will demonstrate the degree of morphological convergence in sensory systems (visual, olfactory, and lateral line) across subterranean lineages. Comparative transcriptomics will be employed to examine the developmental genetic mechanisms of organ system reduction and signatures of molecular convergence at the protein-coding level in sensory-system genes.This 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.