Nicholas A. Levis

Nick Levis
I am interested in how the environment shapes the characteristics of organisms within and between generations. To explore this interest, I investigate the ecological, evolutionary, and developmental causes and consequences of phenotypic plasticity--the ability of an individual organism to alter its phenotype in direct response to environmental conditions. 

Specifically, I focus on studying resource polyphenisms—the occurrence of environmentally induced discrete intraspecific morphs showing differential niche use—because doing so acts as a nexus for integrating intra- and interspecific species interactions with molecular developmental mechanisms of plasticity. More generally, the study of resource polyphenism serves as a gateway that feeds into diverse fields ranging from molecular biology to community ecology and has led me to explore the ecological, evolutionary, and molecular origins of novelty, diversity, and adaptation.

By leveraging the strengths of diverse taxa, such as diplogastrid nematodes and amphibian larvae, I have been able to address important questions about phenotypic plasticity at various levels of biological organization. Please see below for synopses of some of my ongoing and past projects.




Evaluating the molecular bases of genetic assimilation
As a postdoc at Indiana University (with Erik J. Ragsdale), I used comparative genomics and functional genetics (via CRISPR/Cas9) to investigate the evolutionary mechanisms and targets of the loss of plasticity in various nematode lineages. In this study, I found that a regulator of nongenetic inheritance is associated with multiple macroevolutionary losses of plasticity, decreases environmental sensitivity, and promotes accumulation of selectable nongenetic variation, supporting the notion that nongenetic inheritance might be a "bridge" to genetically canalized phenotypes. In addition, I have used experimental evolution to explore the molecular changes associated with repeated divergence in plasticity following environmental change. Together, this work sheds important light on how the molecular mechanisms regulating plasticity evolve and how their changes contribute to evolutionary innovation and diversification.
 
For more information on my current laboratory:
https://ragslab.bio.indiana.edu/




Plasticity-led evolution in nature
My dissertation work at the University of North Carolina (with David W. Pfennig) explores how phenotypic plasticity mediates adaptive evolution and diversification. Using spadefoot toad tadpoles, I have focused on experimentally testing predictions of the 'plasticity-led' hypothesis of adaptive evolution. This work is needed to help inform recent debates on what role, if any , plasticity plays in the evolution of adaptive traits in the wild. Through a series of studies, we have shown that a novel tadpole ecomorph likely arose as an environmentally-induced developmental variant that was refined by selection into an adaptive polyphenism. We also have evidence that some populations are becoming fixed for the formerly induced morph (they are undergoing genetic assimilation). Finally, I have also used the spadefoot system to investigate the molecular and ecological drivers of  morphological diversification within species.

For an episode of the Big Biology podcast where David Pfennig and I discuss plasticity-led evolution in spadefoots:
Season 4 — Big Biology Podcast#episode78

For more information on my PhD laboratory: 
https://www.davidpfenniglab.com/

For a video about spadefoot research done in the Pfennig Lab:
Pfennig spadefoot research video




Amphibian responses to anthropogenic stress
My Master's research at Western Kentucky University (with Jarrett R. Johnson) was a logical extension from my undergraduate research experience in that it investigated the physiological responses of organisms to environmental stressors. However, it had a more apparent applied value with respect to conservation initiatives and global change. I evaluated the interactive effects of UV-B radiation and glyphosate-based herbicide on larvae of the spotted salamander (Ambystoma maculatum). It appears that moderate UV-B radiation can be beneficial in certain contexts and that its interaction with a common herbicide may be surprising. In addition, the morphology, but not swim performance changed depending on herbicide formulation (e.g., aquatic versus terrestrial). This research may become more important as humans continue to modify the landscape and alter woodland habitats.

For more information on my Master's laboratory: http://people.wku.edu/jarrett.johnson/index.html




Ecophysiological cryobiology 
I received my B.S. in Zoology from Miami University in 2012. While there, I investigated (with Richard E. Lee) cross-tolerance between desiccation and freezing stress. My colleagues and I found that rapid, mild desiccation (~6h and ~10% body water) significantly improved freeze tolerance at the tissue and whole organism levels in the goldenrod gall fly (Eurosta solidaginis). This experience helped me appreciate the intensity and rapidity with which the environment can influence organismal phenotypes and fitness.  

For more information on my undergraduate laboratory: http://www.units.miamioh.edu/cryolab/