Research

My research primarily concerns the co-evolution of the Proterozoic biosphere (2.5-0.539 billion years ago) and eukaryotic life — a topic I approach by studying modern marine organisms and environments

The ecology of microbial eukaryotes

The Proterozoic biosphere witnessed the origin of eukaryotic life — perhaps the most significant evolutionary event since the origin of life itself. How the global environment of the Proterozoic, including atmospheric oxygen levels perhaps a hundredth of what they are now, shaped the ecology and evolution of the earliest eukaryotes represents a major thread of historical geobiological research. By studying the effects of deoxygenation on the community structure of microbial eukaryotes in Saanich Inlet — a persistently anoxic fjord on the coast of Vancouver Island, British Columbia, Canada (see map below) — the control of oxygen concentration on microbial eukaryotic ecology can be tracked and quantified. These fundamental relationships can then be used to 1) reconstruct the earliest eukaryotic ecosystems on Earth, and 2) predict the microbial eukaryotic responses to ongoing marine deoxygenation.

Saanich Inlet, the primary field site for this research, is a persistently anoxic fjord on the southeast side of Vancouver Island, British Columbia, Canada, and serves as a model ecosystem for exploring the relationships between marine oxygen availability and microbial community dynamics. This research is part of a 10-year time-series experiment based at the University of British Columbia. You can read about our results here.

Eukaryogenesis

The distinction between eukaryotic cells from the cells of bacteria and archaea has been famously called “the greatest single evolutionary discontinuity to be found in the present-day living world” (Stanier et al., 1963). Over the past decades, it has become increasingly clear that the origin of the eukaryotic cell (“eukaryogenesis”) likely occurred via the fusion of at least one bacterial lineage and one archaeal lineage in a process known as “symbiogenesis.” At the same time, considerable debate persists concerning the nature of this ancestral partnership. Specifically, what were the metabolic capacities of both the archaeal host and the bacterial symbiont during eukaryogenesis, and what was the initial basis of their coupling? How did the free-living bacterial ancestors of the mitochondrion become internalized by an archaeal host? What environmental conditions (both global and local) were required for this major evolutionary transition? When did this bacterial-archaeal partnership even occur? Answering these questions — given their innate complexity — requires combining disparate approaches spanning both the Earth and life sciences, from micropaleontology and geochemistry to microbial ecology and physiology. As eukaryogenesis itself required the partnership of at least two unlike, yet complementary, microorganisms, continued progress in eukaryogenesis research depends on the ongoing cooperation of scientists from different disciplines.

The origins of eukaryotic multicellularity

Multiple eukaryotic lineages have transitioned from microscopic, single-celled morphologies to macroscopic, multicellular ones. The Phanerozoic Eon — literally ‘the age of visible life’ — is defined by its unprecedented abundance of multicellular forms. While animals and red algae (specifically florideophytes) appear to be the oldest groups to display ‘complex’ multicellularity, brown algae (specifically the kelps, or laminarialeans) appear to be the youngest, located much closer in time to the modern day than to the origin of these other groups (see figure below). How (and why) these different eukaryotic lineages obtained multicellularity, and how the global environment may have influenced these transitions, remains largely unknown. By studying the effects of dissolved oxygen concentration and other environmental variables on the physiology and colony-forming behavior of microbial eukaryotes, the potential role of ancient environmental conditions in controlling the multiple origins of eukaryotic multicellularity can be better constrained.

Early animal ecophysiology

The co-evolution of biospheric oxygen availability and early animals is a perennial theme of historical geobiology, going back to the origin of the field itself. Indeed, the abrupt (and relatively late) appearance of animal fossils in the rock record has long puzzled Earth historians. Beginning in the mid-20th century, a number of Earth and life scientists developed the idea that low atmospheric oxygen levels prevented the origin and expansion of animal life until right before the time of the earliest animal fossils, when atmospheric oxygen rose to levels supportive of animals for the first time. While many aspects of this narrative have been refined (and refuted), ideas on how various aspects of early animal evolution were controlled or dictated by changing oxygen levels remain widespread. To test these scenarios, and to constrain how environmental oxygen concentration fundamentally controls animal physiology and metabolism, experiments on modern animals — particularly non-bilaterian taxa like sponges and ctenophores (see below) — are essential.