Some three million years ago, a spectacular natural experiment began when the Isthmus of Panama finally closed, a process that began several million years earlier.

For terrestrial organisms, the formation of the Isthmus created a land bridge that connected North & South America, allowing for massive migrations of plants & animals.

For marine organisms, the story unfolded quite differently. Where once a single tropical ocean flowed, the land bridge became a marine barrier, altering ocean currents & causing different physicochemical environments to emerge.

These radically different conditions are reflected in the resident benthic communities. Many species went locally extinct after the Isthmus closed (e.g., coral, fish, bivalves) and gene flow ceased.

Yet pairs of closely related sister species (geminates) thrive on either side today. Some of these species pairs are so similar that morphology alone is not enough to tell them apart.

How did the close of the Isthmus affect the evolution of microorganisms, the structure of microbial communities, and the function of host-associated microbiomes?

In this project, we make use of contrasting (a) geographic regions, (b) benthic habitats, (c) environmental gradients, and (d) host biology, to understand the evolutionary divergence of marine microbiomes in changing environments & their functional significance in different systems.

We also look more generally at microbial communities from a variety of habitats and envrionments around Panama and beyond.

There are many great reviews about the effects the rise of the Isthmus of Panama had on the evolution of terrestrial and marine organisms, including Lessios (2008), Leigh et. al. (2013), and O’Dea et al. (2016).