On October 1, the seventh cohort of graduates from the Museum’s Richard Gilder Graduate School—the first Ph.D.-degree-granting program for any museum in the Western Hemisphere—will receive Doctor of Philosophy degrees in Comparative Biology at a commencement ceremony in the Milstein Hall of Ocean Life. We’re profiling these soon-to-be Ph.D.s.
For Rachel Welt, a funny thing happened on the way to medical school. She fell in love with iguanas—well, with environmental biology, which led her to develop a passion for iguanas.
“About halfway through college,” says Welt. “I realized that if ecology and biodiversity really interest me, I could apply the lab skills I had developed through medical research in a different way.”
She added an environmental biology minor to her pre-medical studies and went on to earn a master’s degree in ecology and systematics, at the same time earning an advanced certificate in conservation biology. For her master’s thesis, she studied the genetic response of populations of field mustard (Brassica rapa) to a climate change event. In 2012, hoping to shift her focus in the direction of biodiversity and conservation, she volunteered to work at the Museum with herpetologist Christopher Raxworthy in the Division of Vertebrate Zoology on his ongoing research on Madagascar and the origins of its unique biodiversity.
“DNA is DNA,” she says, explaining the transition from research on plant genetics to her work as a volunteer using gene sequencing to identify new cryptic species of Madagascar’s herpetofauna, different species that look virtually the same but have diverged in other ways.
“There is a lot to be discovered when you look beyond the morphology of these frogs, geckos, iguanas, and chameleons. With this work, we used DNA sequences to barcode these cryptic species.”
By the time she entered the Richard Gilder Graduate School in 2014 with Raxworthy as her principal advisor, she had narrowed her focus—and fascination—to one family of iguanas (Opluridae) whose isolated presence on Madagascar has long been a biogeographic mystery. In 2016, after years of working only with DNA samples in the lab, she traveled to Madagascar to meet her subjects first hand—field work she discussed on Facebook Live.
“It was amazing,” she says, “It was so important to finally have the chance to put everything into context and understand Madagascar’s landscape, and to actually see many of these unique animals for the first time.”
For her Ph.D. dissertation, she investigated the evolutionary history of Madagascar’s iguanas, the events driving their diversification, and their conservation status. Back in the lab, she completed extensive genetic studies that suggested as many as eight previously unrecognized species, double their previously known diversity. Since finishing her doctoral studies, Welt has stayed on at the Museum to confirm, fully describe, and formally name these new species.
“These iguanas are very special—they are found nowhere else on Earth,” she says. “My ultimate goal is to understand the threats to their survival and their vulnerability to environmental factors from climate change to rapid habitat loss.”