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Project: When continents join: Insights from the great american schism on the general basis of marine adaptation and resilience

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Project title

When continents join: Insights from the great american schism on the general basis of marine adaptation and resilience

Mentor name

W. Owen McMillan,


Gamboa or NAOS, depending on the project needs and the interest of the intern.

Project summary and objectives

The Central American Isthmus (CAI) was completed roughly three million years ago, providing the backdrop for one of the most remarkable natural experiments of resilience and adaptation in tropical marine organisms. The rise of the CAI simultaneously separated marine populations and profoundly shaped the physical environments of the two newly isolated oceans. Since the completion of the CAI, the Tropical Eastern Pacific (TEP) and the Tropical Western Atlantic (TWA) have differed across most major environmental axes, including temperature, pH, dissolved oxygen and productivity, which are some of the same parameters that are now rapidly changing on a global scale. Moreover, within the TEP, seasonal upwelling in the Bay of Panama relative to a lack of upwelling in the adjacent Gulf of Chiriquí generates striking differences across many of the same environmental variables that distinguish the two oceans.

We will exploit this powerful natural phenomenon to study the intersection between past and contemporary evolutionary processes and the role they play in the resilience and adaptability of marine organisms. This project builds on decades of research that have identified so-called ‘geminate species’ (sister taxa that were separated by the rise of the CAI), which constitute replicated cases of divergence and adaptation. Specifically, we will “genome-enable” coral reef fish lineages and use this foundation to determine the relative contributions of historical demography and selection in shaping the contemporary genomes of geminate taxa. The new genomes provide the context for research aimed at characterizing genomic, epigenomic, and transcriptional variation, and determining how this variation is partitioned across different environmental seascapes. For this project, our integrated dataset will allow us to i. identify regions of the genome associated with adaptive change to the different environments that characterize the TEP and TWA, and, ii. determine whether the same regions also show evidence of adaptive divergence across similar environmental gradients within the TEP. We will couple these insights with experiments that characterize the interplay between local adaptation and phenotypic plasticity and how it varies among geminate taxa living in highly variable versus highly stable environments.

Mentorship goals

Mentor Goals and Intern benefits:

The intern will benefit from being part of the rich and diverse research community at STRI, surrounded by researchers working on all aspects of tropical biology. They will work directly with graduate students, with weekly meetings with academic staff to discuss progress and the intern’s own development and goals.

This project is highly interdisciplinary, coupling genomics with targeted experiments, to understand the role that phenotypic plasticity and genetic adaptation play in population persistence under widely different environmental conditions. The project will involve collecting specimens for genetic analysis, training in molecular techniques, genomic data analysis, establishing a tank system for controlled experiments, and collecting detailed physiological data.

The mentor will provide training in these techniques as well as guidance on general research skills. The intern should leave the position with a more holistic idea of what it takes to bring scientific investigations from inception to conclusion.

This is a full-time position that will run 3-6 months, with possibility of extension to 1 year. We are looking for someone to help with all aspects of this project from sample collecting to genomic analysis. The intern will be expected to craft a STRI Short-Term Fellowship Proposal based on questions that they find exciting. There will also be possibilities to communicate this research via conferences. In the past, interns have contributed to and been co-authors in manuscripts resulting from this research.

List of suggested readings

Lessios, H. A. (2008). The great American schism: divergence of marine organisms after the rise of the Central American Isthmus. Annu. Rev. Ecol. Evol. Syst. 39, 63–91.

O'Dea, A., Lessios, H. A., Coates, A. G., Eytan, R. I., Restrepo-Moreno, S. A., Cione, A. L., Collins, L. S., de Queiroz, A., Farris, D. W., Norris, R. D., et al. (2016). Formation of the Isthmus of Panama. Sci Adv 2, e1600883.

Leray, M., Wilkins, L. G. E., Apprill, A., Bik, H. M., Clever, F., Connolly, S. R., De León, M. E., Duffy, J. E., Ezzat, L., Gignoux-Wolfsohn, S., et al. (2021). Natural experiments and long-term monitoring are critical to understand and predict marine host-microbe ecology and evolution. PLoS Biol 19, e3001322.

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