Erika Hersch-Green, evolutionary biologist and assistant professor of biological sciences at Michigan Technological University, has received a National Science Foundation CAREER award to investigate how increased nitrogen and phosphorus availability across different
temperature and water regimes alters the primary productivity of some plants, while
reducing the growth of others. Hersch-Green will examine how the amounts of nutrients
available to plants determine which plants thrive or wither due to their specific
genome attributes.

“For evolutionary biologists, one of the main goals is to match the genotype of organisms
to what they look like — their phenotype,” Hersch-Green said. “Historically, evolutionary
biologists have focused on how natural selection for protein function or genetic drift
has shaped evolutionary landscapes, as well as the mapping of genotype to phenotype.
My research is taking a slightly different perspective, looking at how molecular attributes
of organisms interact to reduce the material cost of building genomes. I am examining
whether natural selection operates to reduce the cost to a plant species of building
genomes, rather than how natural selection acts on proteins, which is a novel approach.”

Hersch-Green is conducting her research across several grassland sites distributed
across North America, focusing on two common North American grassland plants: fireweed
and goldenrod.

Prairie Plants and Polyploidy

Hersch-Green’s research examines how nutrients affect plants that vary in their genome
size. Genomes are made up of nucleic acids and cells, which cost plants a significant
amount of nitrogen and phosphorus to build. And, some of these plants are polyploids
with varying numbers of chromosomes — which, in turn, affects genome size. 

“The cost of building genomes and a nutrient environment influence physiological tradeoffs
of primary processes like photosynthesis and growth versus secondary tradeoffs like
defense compounds,” Hersch-Green said. “My research takes a multifaceted approach.
I’m combining molecular cytological [chromosomal] and physiological phylogenetic [appearance]

Hersch-Green will examine mechanistic tradeoffs in 10 Nutrient Network consortium sites distributed across the American West Coast and Midwest, including a new site
at Michigan Tech’s Ford Center and Research Forest featuring gardens planted in particular arrangements to test particular mechanisms.
The sites vary in climate zones, temperature and available moisture.

Using fireweed and goldenrod, Hersch-Green will look specifically at tradeoffs in
size between the plants’ genome — their total genetic code — and their transcriptome
— the parts of the genome transcribed into RNA molecules. RNA codes, decodes, regulates
and expresses genes. Hersch-Green will use different nutrient environments with different
cytotypes of each plant to measure certain functional traits. By combining data from
multiple plants, the creatures that pollinate plants or eat the plants (known as “consumer
community assemblages”), and time series phylogenetic modeling and experiments — Hersch-Green
hopes to gain insights into the roles of material costs and genome size in biodiversity

Her work provides a system-level understanding of how eutrophication — the increasingly
dense growth of particular plants at the expense of other species brought on by increasing
nutrient inputs — are affecting individual organisms and multi-species communities
by looking at their interactions. Ultimately, this research will generate genomic
tools for other species as well.

Stem-based STEM Education

Every CAREER award features an education component. Hersch-Green’s approach features
multiple methods to enhance scientific literacy for middle schoolers, high schoolers
and undergraduates. At Hersch-Green’s Ford Center site, she is working with a STEM
educator to formulate different science communication and botany modules based on
photosynthesis research conducted by Hersch-Green and graduate students in her lab.
She is also collaborating with Erin Smith, director of the Humanities Digital Media
Zone and faculty advisor to Cin/Optic Communication and Media Enterprise students,
to create a series of educational modules.

The goal of any CAREER award is to effect change beyond the field of study through
novel research and education. Hersch-Green’s research, through two prairie plants,
examines how community diversity, from plant to pollinator to herbivore, is changing
— and in broad terms, how that affects biodiversity.

Michigan Technological University is a public research university, home to more than
7,000 students from 54 countries. Founded in 1885, the University offers more than
120 undergraduate and graduate degree programs in science and technology, engineering,
forestry, business and economics, health professions, humanities, mathematics, and
social sciences. Our campus in Michigan’s Upper Peninsula overlooks the Keweenaw Waterway
and is just a few miles from Lake Superior.

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