Tag: Erika Hersch-Green

In Print: Erika Hersch-Green and Angela Walczyk

Congratulations to Dr. Angela Walczyk (recent Ph.D. from Biological Sciences) and her advisor Dr. Erika Hersch-Green for their two new publications! You can access the papers here:

Erika Hersch-Green
Erika Hersch-Green

1. Exciting findings that genome size can affect resource requirements and genomic/transcriptomic functional trait trade-offs. 


Premise: Increased genome-material costs of N and P atoms inherent to organisms with larger genomes have been proposed to limit growth under nutrient scarcities and to promote growth under nutrient enrichments. Such responsiveness may reflect a nutrient-dependent diploid versus polyploid advantage that could have vast ecological and evolutionary implications, but direct evidence that material costs increase with ploidy level and/or influence cytotype-dependent growth, metabolic, and/or resource-use trade-offs is limited.

Methods: We grew diploid, autotetraploid, and autohexaploid Solidago gigantea plants with one of four ambient or enriched N:P ratios and measured traits related to material costs, primary and secondary metabolism, and resource-use.

Results: Relative to diploids, polyploids invested more N and P into cells, and tetraploids grew more with N enrichments, suggesting that material costs increase with ploidy level. Polyploids also generally exhibited strategies that could minimize material-cost constraints over both long (reduced monoploid genome size) and short (more extreme transcriptome downsizing, reduced photosynthesis rates and terpene concentrations, enhanced N-use efficiencies) evolutionary time periods. Furthermore, polyploids had lower transpiration rates but higher water-use efficiencies than diploids, both of which were more pronounced under nutrient-limiting conditions.

Conclusions: N and P material costs increase with ploidy level, but material-cost constraints might be lessened by resource allocation/investment mechanisms that can also alter ecological dynamics and selection. Our results enhance mechanistic understanding of how global increases in nutrients might provide a release from material-cost constraints in polyploids that could impact ploidy (or genome-size)-specific performances, cytogeographic patterning, and multispecies community structuring.

Angela Walczyk
Angela Walczyk

2. Finding that tetraploid Giant Goldenrods may be pre-adapted to be good invaders but that polyploidy per se does not increase phenotypic plasticity. 


Polyploidy commonly occurs in invasive species, and phenotypic plasticity (PP, the ability to alter one’s phenotype in different environments) is predicted to be enhanced in polyploids and to contribute to their invasive success. However, empirical support that increased PP is frequent in polyploids and/or confers invasive success is limited. Here, we investigated if polyploids are more pre-adapted to become invasive than diploids via the scaling of trait values and PP with ploidy level, and if post-introduction selection has led to a divergence in trait values and PP responses between native- and non-native cytotypes. We grew diploid, tetraploid (from both native North American and non-native European ranges), and hexaploid Solidago gigantea in pots outside with low, medium, and high soil nitrogen and phosphorus (NP) amendments, and measured traits related to growth, asexual reproduction, physiology, and insects/pathogen resistance. Overall, we found little evidence to suggest that polyploidy and post-introduction selection shaped mean trait and PP responses. When we compared diploids to tetraploids (as their introduction into Europe was more likely than hexaploids) we found that tetraploids had greater pathogen resistance, photosynthetic capacities, and water-use efficiencies and generally performed better under NP enrichments. Furthermore, tetraploids invested more into roots than shoots in low NP and more into shoots than roots in high NP, and this resource strategy is beneficial under variable NP conditions. Lastly, native tetraploids exhibited greater plasticity in biomass accumulation, clonal-ramet production, and water-use efficiency. Cumulatively, tetraploid S. gigantea possesses traits that might have predisposed and enabled them to become successful invaders. Our findings highlight that trait expression and invasive species dynamics are nuanced, while also providing insight into the invasion success and cyto-geographic patterning of S. gigantea that can be broadly applied to other invasive species with polyploid complexes.

Erika Hersch-Green Receives NSF CAREER Award

Erika Hersch-Green, plant evolutionary ecologist and associate professor of Biological Sciences, received a National Science Foundation CAREER Award. She will investigate how specific attributes of plants, such as their genome size, influence community biodiversity responses to increased nitrogen and phosphorus availability. Hersch-Green’s approach combines molecular, cytological, physiological, and phylogenetic techniques.  

Erika Hersch-Green
Erika Hersh-Green

Hersch-Green is conducting her research on three fronts. First, she is currently gathering fresh data and merging it with information from experimental grassland sites around the world. These sites have plots with different nutrient treatments, allowing her to examine how response patterns vary depending on climate conditions. Second, she is conducting controlled greenhouse studies to better understand mechanisms that focus on two common grassland plants: fireweed and goldenrod, both of which she has studied before. Lastly, she developed a new research site at Churning Rapids, north of Hancock and south of McClain State Park. There she is extending her research to look at how disturbance patterns affect levels of biodiversity. 

She is also exploring ways to improve students’ scientific literacy and engagement in research.  To accomplish this, she is incorporating students in grades 6 through 12 and undergraduates in research, enhancing research involvement in the classroom, facilitating effective scientific communication skills of graduate students, and promoting collaboration among undergraduate students and faculty in the Departments of Biological Sciences and Humanities. These students will produce video content that will be used to enhance education and public understanding of biological science and ecology.

To summarize, Hersch-Green aims to provide a system-level understanding of how nutrient eutrophication—the increasingly dense growth of particular plants at the expense of other species—and landscape disturbances affect individual organisms and multi-species communities by looking at their interactions.

Although she is passionate about her research, Hersch-Green is also deeply committed to the educational component of her CAREER award. Her educational goals are to increase both scientific literacy and engagement of high school and university students on critical topics related to nutrient eutrophication, biodiversity, evolutionary adaptation, and awareness of related STEM (science, technology, engineering, and math) career pathways. 

This blog post initially appeared in the Fall 2022 Biological Sciences Newsletter. Read this article and others like it today.