Ph.D. Graduates: 2023

The Richard Gilder Graduate School has produced 44 Ph.D. graduates since the first cohort matriculated in 2008. 

Alumni of the comparative biology program hold positions in science, academia, education, and museums around the world. Here are the four doctoral graduates of 2023.

Alexandra Grace Walling

Alexandra Grace Walling stands in the Museum's Hall of Biodiversity, viewing a wall of specimens.

Walling investigated the unique modes of metabolism in bacteria with a specific focus on the evolution of phototrophy—the ability to capture and use sunlight for energy. By sequencing, assembling, and annotating the entire genomes of two bacteria in the group Erythrobacteraceae, Alexandra generated the first comprehensive species phylogeny using genomic data for a total of 91 members of the Erythrobacteraceae family. Her research revealed multiple cases of the exchange of phototrophy genes and other genetic material across distantly related forms via horizontal gene transfer. Walling is currently pursuing her postdoctoral research at the University of Rhode Island.

Nayeli Gutiérrez Trejo

Nayeli Gutiérrez Trejo stands next to a column of shelves containing collections, and holds a wooden frame containing small boxes of insect specimens.

In her studies of the evolutionary history of milkweed longhorn beetles (genus Tetraopes), Gutiérrez Trejo focused on their molecular ecology and relationship to the usually-toxic host plants they feed on. By integrating the natural history, molecular ecology, and interactions of Tetraopes and their affiliated hosts, she generated the most robust evolutionary history ever for this group, helping scientists better understand the origins of these beetles and their co-evolutionary interactions with their host plants. Her longstanding interest in the diversity of beetles across different ecosystems has taken her on scientific expeditions around the world for extensive fieldwork, and she has described a variety of new insect species from her expeditionary and museum collection research.

Hollister Wade Herhold

Hollister Wade Herhold sits at a lab table with a microscope and a box containing insect specimens.

Herhold applied new genomic and imaging methods in the study of the respiratory systems of insects and related arthropods. Using the Museum’s advanced imaging facilities, including high-resolution x-ray micro-CT scanning, to generate holistic pictures of the entire respiratory systems of 13 insect orders, he produced a landmark three-dimensional visual atlas of insect respiratory systems. His comparative genetic analyses and detailed visualizations enhance the understanding of the relationships between insect respiration and movement, including the origins and evolution of flight, establishing an invaluable platform for future research. Herhold, who has a degree and industry experience in computer science, was a volunteer in the Division of Invertebrate Zoology at the Museum before beginning his Ph.D. at the Richard Gilder Graduate School.

Tobit Liyandja

Tobit Liyandja stands near a body of water holding a fish specimen in both hands.

Liyandja researched the evolutionary ecology and diversity of central African fishes in the carp genus Labeo, a major regional economic food resource. He explored Labeo distributions across different regions of the Congo River, the third largest river in the world, to better understand the mechanisms contributing to diversity, population, and genetic interchange across the genus, with significant applications for sustainable fishery management, finding that the Congo and Nile-Sudan river systems and Ice Age climate changes played central roles in the evolutionary radiation of carp species throughout Africa. Liyandja will continue his research through a postdoctoral appointment and Presidential Fellowship at the University of Toronto, in collaboration with the Royal Ontario Museum.


Fall 2024 Enrollment

Next application deadline: December 15, 2023

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