Patterns and mechanisms of phenotypic plasticity in poison frog tadpoles

A well-known scientific debate is whether traits develop through nature (produced by genes) or nurture (environmentally induced), but the answer is almost always somewhere in between: environmental cues impact the ways genes are expressed. The broad theme of my dissertation is to uncover patterns of how traits, such as behavior and morphology, change in response to different environmental cues, and how the duration and ontogenetic timing of exposure may impact phenotypic responses. To ask these questions I studied tadpoles of the Dyeing poison frog (Dendrobates tinctorius), a poison frog native to South America. Tadpoles in general are excellent systems to study plasticity, as they respond to myriad biotic and abiotic environmental cues through behavior, morphology, and physiology. Examining the environmental effects in D. tinctorius tadpoles is especially ecologically relevant, as the pools they inhabit in the wild vary considerably in water quality, resource availability, and the number of hetero- and conspecifics. Additionally, D. tinctorius tadpoles are aggressive and cannibalistic, making conspecific cue a potentially conflicting signal of predation, competition, and nutritional resources. In my dissertation, I explore patterns and mechanisms of phenotypic plasticity across timescales of minutes (chapter one), weeks (chapter two), and months (chapter three) of tadpole development. Overall, I found that tadpoles are phenotypically plastic in response to environmental cues at different time scales. First, I found that tadpoles responded differently to acute cues of food, predation, and conspecifics. More specifically, in response to chemical cues signaling an injured conspecific, tadpoles increased exploration while minimizing overall activity, suggesting a cue-dependent behavioral strategy that maximizes exploration while reducing the risk of detection by conspecific cannibals. Second, I found that tadpoles reared in the absence of conspecifics cues grew faster and were more aggressive than those raised in the presence of conspecifics, suggesting that the optimal phenotypes of these characteristics varies depending on social context. However, we also found that activity level, exploratory rate, space use, gut length, excreted corticosterone, and general correlation across traits did not differ significantly between groups, suggesting a potential advantage of trait stability. Finally, I found that D. tinctorius tadpoles develop and maintain a glucocorticoid “stress” response early in development. Given the importance of glucocorticoids in movement of energy across the body, this early production and stability in glucocorticoid production likely helps them respond to challenges across development. Taken together, my findings illustrate that conspecific cues are interpreted as distinct from either food or predation cues in a cannibalistic species where they can represent both. Further, the change in certain phenotypes in response to conspecific cues, along with the potential of the glucocorticoids as a mechanism to facilitate reactions to environmental conditions across development, highlights developmental flexibility that promotes survival in complex environments. Overall, this work highlights how organisms navigate complex environments by integrating diverse cues, demonstrating the critical role of phenotypic plasticity at acute, long-term, and developmental timescales.

Name thesis:degree_name

Ph.D.

Level thesis:degree_level

Dissertation

Discipline thesis:degree_discipline

Biology

Grantor

University of Illinois Urbana-Champaign

Year dc:date

2025

Author dc:creator

• Surber-Cunningham, Lisa Louise

Contributors dc:contributor

• Fischer, Eva
• Bell, Alison
• Heath, Katy
• Fully, Becky
• Rojas, Bibiana

• Anurans
• Plasticity
• Aggression
• Dendrobatidae
• Larva

Statement dc:rights

• Copyright 2025 Lisa Surber-Cunningham

Language dc:language

en, eng

Handle dc:identifier

https://hdl.handle.net/2142/130074

OAI record oai:identifier

https://www.ideals.illinois.edu/oai-pmh?verb=GetRecord&metadataPrefix=etdms&identifier=oai%3Awww.ideals.illinois.edu%3A2142%2F130074