Mahurin Honors College Capstone Experience/Thesis Projects



Document Type



  1. Phenotypic plasticity, although ubiquitous, may not always be advantageous. In cases where individuals expressing an induced phenotype outperform non-induced individuals, the phenotypic plasticity is considered adaptive. Conversely, if the individuals with an induced phenotype underperform relative to non-induced individuals, then the plasticity is maladaptive. A final possibility is that both induced and non-induced individuals perform equally well (or poorly). This would be a case of non-adaptive (i.e. neutral) phenotypic plasticity.
  2. We investigated the mode of phenotypic plasticity induced by four glyphosate-based herbicides in larvae of the spotted salamander, Ambystoma maculatum (Shaw, 1802), by determining whether the herbicides induced different morphologies, if morphology was correlated with escape swim performance, and how induced individuals performed relative to non-induced controls.
  3. Different herbicide formulations led to production of significantly different head and tail morphologies, and tail morphology correlated with fastest escape speed. However, escape speed did not vary among treatments. In addition, three out of four herbicide treatments experienced accelerated growth rates, in terms of lateral size of tails, but the tail shapes were either similar to preliminary controls or intermediate between preliminary and final controls.
  4. These observations suggest that herbicide-induced morphology is case of non-adaptive phenotypic plasticity, and that there is potentially a trade-off between growth and development for larvae exposed to different formulations.
  5. Understanding the functional significance of induced phenotypes is important for determining their importance in shaping an organism’s ecological interactions and evolutionary trajectories. Under more natural conditions, our observed changes in morphology may dramatically affect salamander fitness and play a role in either mitigating or accelerating population declines.

Advisor(s) or Committee Chair

Dr. Michael Collyer


Biology | Ecology and Evolutionary Biology | Terrestrial and Aquatic Ecology