No less than five EEB graduate students were awarded Doctoral Dissertation Improvement Grants from the National Science Foundation. Hearty congratulations to Jordan Bemmels, Jen-Pan Huang, Chuan Li, Jeff Shi and Andréa Thomaz.

Jordan Bemmels’ project is called “A hypothesis test for cryptic northern refugia in bitternut and shagbark hickory, with implications for migration and adaptation.” His advisor is Professor Chris Dick.

The DDIG will support Bemmel’s research into the locations of glacial refugia for temperate tree species from eastern North America. “During the peak of the ice age around 21,500 years ago, glaciers covered much of northern North America and climatic conditions forced temperate forests into refugia along the Gulf of Mexico and southern Atlantic Coast,” Bemmels explained. “Recent research has suggested that there may have been additional cryptic refugia located much farther north, such as in the southern Appalachians and Ozarks, but this idea has been controversial. Determining where tree species survived the ice age is important for understanding how trees have migrated and adapted in response to past climate changes, and will have implications for forestry and conservation biology. Using bitternut and shagbark hickory as a study system, I will combine genetic data from populations across the United States with computer simulations in order to test competing hypotheses about glacial refugia. This will be the first time that a level of statistical support for the presence of cryptic refugia will be determined.

“Understanding migration and adaptation of trees in response to historical climate change will help us manage the forests of today and in a warming world.” He will receive $18,250 over two years.

Jen-Pan Huang’s project title is “The species versus subspecies conundrum: quantitative assessment from integrating multiple data types under a single Bayesian framework in Hercules beetles.” He is advised by Professor L. Lacey Knowles.

Huang’s project description follows: “Are there differences in how species and subspecies are designated among disparate groups of organisms? If so, surveys of biodiversity could be biased, potentially either under- or over-estimating levels of species diversity. I will address this issue using genetic data and morphology of two groups of Hercules beetles (genus Dynastes), where diversity patterns differ between North and South America, perhaps because of differing applications of species versus subspecies designations. Through quantitative assessments of the observed differences between taxa, I will test if genetic and morphological differences between species are more pronounced than those found between subspecies. Knowledge gained by this research will demonstrate how taxonomy can be assessed consistently, objectively, and quantitatively across distinct groups of organisms and between geographic regions. Such a standardized approach is critical to avoiding potential biases in biodiversity surveys of species diversity and the identification of taxa in need of conservation.”

“The importance of species delimitation extends beyond immediate taxonomic goals in systematics with the resulting taxonomic treatments having profound implications for other fields, ranging from studies in evolution and ecology to conservation biology,” said Huang, who was awarded just over $20,000 for two years.

Chuan Li’s project “The fitness landscape of a yeast tRNA gene," is advised by Professor Jianzhi Zhang.

Li explained her project: “Mutation provides the raw material for all genetic variation and evolution.  The distribution of the fitness effects of all mutations, known as the fitness landscape, is of fundamental importance for understanding almost all evolutionary processes. This project will generate the first large-scale fitness landscape of a gene in any cellular organism.  The data will offer unprecedented details of the fitness effects of mutations, including properties of genetic interaction among mutations (i.e., epistasis) and provide an invaluable opportunity to test many theoretical models that depend on assumptions about the fitness landscape and epistasis. These theoretical models apply to many important phenomena such as the origins of multidrug resistance in pathogens and the domestication of animals and plants. The gene to be studied is a budding yeast tRNA gene. The rich information about the tRNA structure will allow a molecular-level mechanistic interpretation of the fitness landscape, helping understand why certain tRNA mutations cause disease. The methodology developed here can be used to study other genes or in other organisms.” Li was awarded just over $19,000 for a two-year term.

Jeff Shi’s project, “Form, function, and modularity in the modern bat skull: a model for understanding the evolution of phenotypic complexity,” is coadvised by Professors Catherine Badgley and Dan Rabosky.

Jeff described his project: “Bats are one of the most species-rich groups of modern mammals, and are particularly known for their ecological diversity. Bats fill numerous ecological niches worldwide, performing a variety of ecosystem functions and services. Evolutionary biologists often study ecological diversity in conjunction with morphology, as physical traits can be closely tied to performance and function. The bat skull has a highly complex shape that encodes information about ecological interactions. My research will synthesize museum collections with cutting-edge imaging technology and shape analyses to model the evolution of a highly complex biological structure. With a number of undergraduate assistants, I am using microCT scanning technology to visualize and render modern bat skulls in three dimensions. This project will help us understand the complex relationships among ecosystem functions, services, ecological interactions, and evolutionary processes.” Shi will receive just over $19,000 over two years.

Andréa Thomaz’s dissertation project title is “Riverscape genetics: testing the role of river properties with population-genetic models in Neotropical freshwater fishes.” Her advisor is Professor L. Lacey Knowles.

“Genetic data can provide a window into the factors that structure and drive divergence among populations,” Thomaz explained. “For example, it has the potential to reveal how current and past landscapes features determine population structure. However, such inferences are challenging without methodologies to predict the genetic signature under such conditions. The proposed work will be a step towards addressing this knowledge gap with an application to a freshwater fish biodiversity hotspot – the Atlantic Coastal Rainforest of Brazil. However, the proposed work will do more than just enhance knowledge about freshwater fishes in this particular ecosystem. The approach can be broadly applicable to riverine environments in other world regions, and will also provide insights into the properties of rivers that make them critical to conservation efforts because of their impact in population persistence and movement patterns of organisms living in the rivers.

"This research will use computer simulations to generate expected patterns of genetic variation so the impact of specific river properties (e.g., the length of river segments, the number of connecting tributaries, and the flow regime) on movement patterns of an endemic tetra can be discerned. Such a mechanistic understanding will be instrumental to interpreting past studies that have documented differences in genetic variation between different regions, but without tests like those developed here, were unable to determining why the processes structuring biodiversity might differ among regions. As such, the work will provide a general tool that can advance our understanding of the processes generating biodiversity patterns.” Thomaz was awarded just over $20,000 for a two-year period.

The NSF awards DDIGs in selected areas of the biological sciences. These grants provide partial support of doctoral dissertation research to improve the overall quality of research including costs for doctoral candidates to participate in scientific meetings, to conduct research in specialized facilities or field settings, and to expand an existing body of dissertation research.