Paleobiology, Macroevolution & Macroecology

I am  interested in patterns and processes observable and inferable from the fossil record. My research organisms range from marine plankton to mammals and the time spanning the data I use usually covers much of the Cenozoic (the last 65 million years). I collaborate with geologists, paleontologists, evolutionary biologists, ecologists,systematists, statisticians, mathematicians and physicists. 

Extinction

The only thing we know for certain about species is that in the finite future, any given extant species will become extinct. In fact, most of all species that ever lived on Earth are extinct.  I study biological traits and environmental factors that promote population declines and/or enhance extinction risk. I believe that what we learn about extinction from the fossil record can be useful for helping us make conservation decisions today.

Collaborators: Paul Harnik, Seth Finnegan and many others

Diversification

Diversification is the summed process of extinction and speciation. Although we can to some extent infer past evolutionary dynamics using inferred phylogenetic relationships among living organisms, extinction erases a lot of information. Like many of my colleagues, I aim to integrate information from both the fossil record and from extant organisms in order to reconstruct diversification and evolutionary history.

Collaborators: John Finarelli and many others

Geographic Range Dynamics

The geographic range, occupancy, the number and abundance of populations are dynamic over the lifetime of any given species. Although ecologists have long observed that species ranges and population abundance can vary greatly on ecological time scales (100s of years), paleontologists have long assumed, implicitly or explicitly that these properties are stochastically constant over the geological time scale.

Recent work confirmed that species take a very long time to achieve a maximal frequency of occurrence and that they do not maintain this maximum for long. Analogously, species also take a long time to decline to non-existence. We call this "the hat" model or trajectory. An important consequence of this observation is that extinction and origination events are difficult to robustly estimate using sampled fossil occurrence data.  We try to i) get around this by incorporating “the hat” in our diversification modeling framework and we also try to ii) understand what drives “the hat.”

Collaborators: Daniele Silvestro, Hans Jullius Skaug, Tore Schweder, Torbjørn Ergon

Biotic Interactions

No man is an island. Likewise, no biological entity exists without both direct and indirect interactions with other such entities. Little is known about how biotic interactions affect evolutionary change in a natural setting. We use fossilized interactions among encrusting bryozoa to study the evolution of competitive overgrowth. The question that remains is whether biotic interactions alone suffice for driving lasting evolutionary change. Van Valen’s Red Queen remains elusive but this research hopes to catch a glimpse of the Red Queen in action.

Collaborators: Paul D. Taylor, Kjetil Voje, Barbara Fischer, Nils Christian Stenseth

Process and observation based modeling

The observed fossil record is the result of both biological as well as sampling (including geological, chemical, discovery, description) processes. In order to infer biological processes from the fossil record, we also have to model the “nuisance” sampling processes. I adopt capture-recapture and occupancy modeling approaches first developed in population ecology to account for incomplete sampling while simultaneously estimating parameters of interest such as extinction, speciation and occurrence. 

Collaborators: Jim Nichols, Torbjørn Ergon

Stasis

The term "living fossils" was coined by Charles Darwin. Darwin lumped multiple, non-mutually exclusive phenomena under the umbrella of "living fossils." In my Ph.D. dissertation, I tried to show how misleading focusing on "long-lived" taxa is when these taxa are not considered in a relative context: "long-lived" relative to whom? How persistent must a taxon be before it is considered a statistical outlier in a distribution of taxon lifespans? Is a statistical outlier the same as a biological outlier? 

The crucial question is whether persistence and "constrained" morphological evolution are expected to be the norm, given what we know about the rate of microevolution in the lab and in the wild and given what we know about the environmental changes that have occurred throughout the Phanerozoic. It appears that stasis and punctuated evolution are the norm in the fossil record but why this is so is currently an open-ended question. 

Collaborators: Scott Lidgard