The Questions I Ask

When I look out into the natural world, I want to know how it works. No matter where you go, whether it be a desert or a forest, ecosystems are filled with organisms that need to make it on their own. How do organisms operate and make it on their own? The answers to this big question is even more pressing to understand because the Earth is undergoing a large climate shift at an unprecedented rate. How will life respond?

The Problem: Climate Change

Many organisms face extinction and/or range shifts to future climate change unless they are able to stay in place by acclimating or adapting. Ants are a great taxonomic group to study how species will respond to climate change because they are common and play critical roles in the ecosystem. If they become less common as a consequence of climate warming, then this could potentially lead to a negative cascading effect in the ecosystems they occupy! Additionally, ants occupy very diverse environments, which means they harbor an array of strategies that allow them to cope with stressful environments. What mechanisms, characteristics, and abilities allow some species to persist better than others?

Integrative Approach

One way to understand whether species are vulnerable or resilient to pending temperature shifts is to investigate how different species have historically adapted to changing climates. For this work, I combine field work, lab studies, and computational approaches (statistics, bioinformatics, phylogenetics) to determine the extent to which species' physiologies match their respective thermal environment.

Projects: Climate adaptation in Forest Ants.

  • How do ants respond to variable climates?

    When comparing forest ant (Aaphaenogaster picea) from South to North, their ability to withstand warm and cool temperature (thermal niche breadth) increases (in prep). This result matches how climate changes from South to North: as you move towards the poles, temperature becomes colder and more variable. In fact, we found that the limitations of the northern range of A. picea is linked to constraints in the ability to withstand extreme cold and too much temperature variability (in prep).

  • What is the molecular toolkit for responding to heat stress?

    Even though ants have colonized almost every continent on Earth except antarctica, little is known about how they cope with these thermally stressful environments at the molecular level. Thankfully, there has been a lot of work in model systems such as fruit flies, worms, yeast, etc, that have characterized proteins critical for coping with heat stress, known has heat shock proteins (Hsps). Hsps turn on in almost the same way, whether you're a fruit fly, worm, or yeast too! Specifically, Hsps sense and repair protein damage, and in turn, rescue biological activity.

    Therefore, I expected these proteins to be important for ants and thankfully, many ant genomes as well as other Hymenoptera are now publicly available, allowing me to reconstruct the evolutionary history of Hsps. I found that within the insects, there have been many gains and losses of the genes themselves, similar to how species diversify or become extinct. And this process produced a unique set of Hsps in ants and other Hymenoptera that turn on in response to temperature stress. For full details, please feel free to read the primary article published here: Nguyen et al. 2016; BMC Evolutionary Biology.

  • Photo from Alex Wild

    What type of adaptive shifts in the stress response are likely required for species to survive in a warmer world?

    We found very little evolved difference in Hsp induction between two species that experience different thermal regimes (One is found in the north and other in the south). However, when reared at a cool and warm temperature, we found that both species are able to meet the challenges associated with warm temperatures by inducing more Hsp (Helms Cahan, Nguyen, et al. 2017). Therefore, ants may utilize Hsps to acclimation as the world warms.

    Across a more diverse group of forest ants, we found that the ability to withstand heat stress is related to the local thermal environment. Species that can better take the heat, delay the onset of their stress response (turn on Hsps) and turn them on to a greater magnitude. These results suggest that more heat tolerant species have more stable proteins and can better protect them from unfolding (in prep). I have tested whether more thermally tolerant species have more stable proteins (proteome). But the data are waiting to be analyzed...

CV and Publications

  1. Nguyen AD, DeNovellis K, Resendez S, Pustilnik JD, Gotelli NJ, Parker JD, Cahan SH. 2017. Effects of desiccation and starvation on thermal tolerance and the heat-shock response in forest ants. J Comp Physiol B:1–10. Paper link

  2. Helms Cahan S, Nguyen AD, Stanton-Geddes J, Penick CA, Hernáiz-Hernández Y, DeMarco BB, Gotelli NJ. 2017. Modulation of the heat shock response is associated with acclimation to novel temperatures but not adaptation to climatic variation in the ants Aphaenogaster picea and A. rudis. Comparative Biochemistry and Physiology Part A: Molecular & Integrative Physiology 204:113–120.Paper link Data

  3. Stanton-Geddes J, Nguyen A, Chick L, Vincent J, Vangala M, Dunn RR, Ellison AM, Sanders NJ, Gotelli NJ, Cahan SH. 2016. Thermal reactionomes reveal divergent responses to thermal extremes in warm and cool-climate ant species. BMC Genomics 17:171. PDF Github repo

  4. Nguyen AD, Gotelli NJ, Helms Cahan S. 2016. The evolution of heat shock protein sequences, cis-regulatory elements, and expression profiles in the eusocial Hymenoptera. BMC Evolutionary Biology 16:15.PDF