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Biology doctoral graduate receives prestigious NSF postdoctoral fellowship

Daren Card, awarded the NSF Postdoctoral Research Fellowship in Biology.
Daren Card, awarded the NSF Postdoctoral Research Fellowship in Biology.

A recent doctoral graduate in biology from The University of Texas at Arlington has received a prestigious grant from the National Science Foundation to pursue postdoctoral research focusing on limb loss in a group of Australian lizards.

Daren Card, who is receiving his Ph.D. in Quantitative Biology in this summer, was awarded the NSF Postdoctoral Research Fellowship in Biology, a three-year grant worth $207,000. His main advisor will be Scott Edwards, a professor of zoology at Harvard University, curator of ornithology in the university’s Museum of Comparative Zoology, and a member of the National Academy of Sciences.

“I was obviously very excited when I found out about the award,” Card said. “Dr. Edwards had already told me he could support me coming to Harvard regardless of the award, but getting this fellowship gives us a lot more flexibility with the project and is a great accomplishment in itself. Given my career goal of being a tenure-track faculty member, having this type of award can be helpful for getting a job and certainly sets me up well to pursue a project that others will likely find interesting.”

Card’s research will involve studying the evolution of limblessness in an Australian group of skink lizards. Much of the first year of his fellowship will be spent doing field work in Australia, with the following two years to be spent mainly at Harvard.

“Limblessness is well known in snakes, but few realize that several other groups of squamate reptiles (lizards and snakes) have also lost limbs independently,” Card said. “Skink lizards alone have several limb loss events, and I’ll be studying a genus in Australia named Lerista where reduced limb morphology has evolved within the past 20 million years. Across this group, different species have different fore- and hind-limb states ranging from a full pentadactyl, or 5-digit, limb to total limblessness, with many combinations in between.

“The recent radiation of so many limb morphologies provides a great morphological series in which to explore how digit and limb loss occur, versus a group like snakes where species became limbless over 100 million years ago.”

Card explained that he and his colleagues will be generating high-quality genomes for a couple of species and resequencing the genome of dozens of other species to better understand how many times different limb states have evolved.

“Existing work indicates that each limb state probably evolved at least a couple times independently within this group, but our genome data will give us far greater power to figure this out,” he explained. “We’ll also be taking more refined measurements of limb state using cutting-edge CT scanning techniques to understand skeletal and muscle morphology in limbs – it is still an open question whether the same digits are lost in species with the same limb state. These data will also be helpful for truly understanding how morphology varies across this group.”

Card’s research will also involve some developmental biology work, including the sampling of embryos at different stages of limb development in a limbed and limbless species. CT scanning will be used to understand the morphological details of development, and he and his colleagues will also collect gene expression and epigenetic (i.e., gene expression regulation) data across developmental stages.

“In total, our approach can be used to understand the genetics behind normal limb development and how certain genetic changes impact development and lead to different limb and digit morphologies,” he said. “This will obviously be important for this project, but some of our work may have human health ramifications as well.”

Card said the training and experience he received during his doctoral studies at UTA have prepared him well for the work he will be doing as part of the NSF fellowship and beyond. He praised his faculty advisor, Todd Castoe, assistant professor of biology, for his guidance and encouragement.

“I’ve worked on a lot of projects during my Ph.D. studies. Todd’s lab has been a great environment for learning to become a professional scientist,” Card said. “I can’t say enough about how great Todd’s mentoring style and effort have been. I’ve contributed in small ways to many projects, ranging from genome assemblies of species to venom evolution to repeat element evolution.”

In spring 2015 Card received an NSF Doctoral Dissertation Improvement Grant (DDIG) for his main dissertation project, which focuses on island dwarfism in Central American populations of the Boa imperator snake (a species of the boa constrictor). Card and his colleagues have been able to establish that dwarfism has occurred independently at least twice and are also testing the hypothesis that convergent dwarfism is driven by convergent genetic or molecular mechanisms. The project is ongoing.

“This work has strong parallels with my postdoc project in limblessness, so many of the same overall questions are motivating both projects,” he said.

Other projects to which Card contributed in Castoe’s lab include the investigation of whether patterns of natural selection could be detected over only one or two generations in the invasive Burmese python population in Florida; and research aimed at understanding what mechanism snakes use to accomplish parthenogenesis, a form of reproduction in which an egg can develop into an embryo without being fertilized. Both of those projects are ongoing as well.

Castoe says Card is particularly unique and talented because of the wide breadth of science research that he conducted during his doctoral studies, which included population genetics, functional genomics, software design, work on invertebrates, human diseases, and snake organ regeneration.

“It is a remarkable achievement that Daren has secured an NSF grant to support his three-year postdoctoral fellowship, and even more impressive that this fellowship will be conducted in the laboratory of one of the most prominent researchers in his field, Dr. Scott Edwards,” Castoe said. “Daren is among the best Ph.D. students I have met, both within and outside of my lab and institution, and has significantly contributed to the success of research in my laboratory, and to the success of other graduate and undergraduate students he has mentored at UTA.

“In the six years since he started his Ph.D., he has grown to become an extremely competent and productive scientist, and mastered a broad range of computational and laboratory skills. As a faculty mentor for Daren throughout his Ph.D. work, I have been consistently impressed with his work ethic, intelligence, and commitment to his community.”

The NSF Directorate for Biological Sciences (BIO) awards Postdoctoral Research Fellowships in Biology to recent doctoral degree recipients to support research and training in selected areas supported by the BIO Directorate . The fellowships encourage independence at an early stage of the research career to permit Fellows to pursue their research and training goals in the most appropriate research locations.