Research

We study population and community dynamics in primarily coastal marine ecosystems with the goal of understanding the impacts of global change and the actions that could foster abundant wildlife and healthy ecosystems for all to enjoy. We use statistical tools, field ecology, population genomics, and mathematical modeling to understand general patterns that extend across larger spatial scales, deeper in time, and across a wider range of species than would be possible with more traditional techniques. A sampling of our projects is below.

How do marine communities respond to climate change?

Climate change is not just an increase in temperature or change in environmental conditions; it’s also a velocity across the seascape as species’ preferred conditions move to new locations. While it’s clear that species distributions shift as climates change, our understanding of the mechanisms, causes, and consequences remain limited. Can all species keep up with rapid climate velocities? How does climate interact with other factors, like habitat, currents, fishing, food web dynamics, and evolution? How do individual species response scale up to entire communities? To date, we’ve focused on North American coastal species and fisheries, building large databases of observations against which we can test broad hypotheses, as well as developing case studies, mathematical models, and field systems to explore  dynamics in more detail.

Population persistence across space and time

IMG_3255_mod_cropThe effects of global change are ultimately mediated by local population dynamics, which depend on the balance between reproduction, survival, and dispersal. Ecologists typically examine these issues as metapopulation dynamics, and yet marine species present a fascinating challenge to classical metapopulation theory based on the balance of extinctions and recolonizations. Extinctions in the ocean are rare, even though—paradoxically—many marine subpopulations appear unable to persist on their own (i.e., without immigration). Mathematical models suggest how this might occur: network effects through the abundant exchange of offspring that balance the losses from mortality. This theory, however, remains poorly tested in the natural world. We use clownfish (Amphiprion species) in the Philippines as a model system and apply field observations, population genetics, modeling, and oceanographic tools.

Temporal genomics in a changing world

Evolution has received little attention in the context of contemporary global change, and yet it has the potential to be exceptionally important and widespread. Through the process of evolutionary rescue, for example, adaptive evolution can restore positive growth to declining populations and help avoid extinction during rapid environmental change. However, the extent to which evolutionary rescue is common across species and the genomic architecture that underlies rapid adaptive evolution remain unclear, particularly in vertebrates.

There are limits to what we can infer about the interactions of evolutionary and ecological processes from contemporary genomic patterns, however, and we are using natural history collections and full- or sub-genome DNA sequencing from historical specimens to, in effect, rewind time and study evolution as it happened. Current projects focus on Atlantic cod (Gadus morhua), little brown bats (Myotis lucifugus), and coastal fishes of the Philippines.

Comparative population dynamics

Why do populations fluctuate so dramatically through time? This question has fascinated ecologists since the field’s beginning, but there are no simple answers. Instead, the key questions address the relative importance of diverse processes across species and ecosystems, including intra- and interspecific interactions, environmental change, dispersal, and evolutionary responses. For example, patterns of extinction risk on land usually follow a classic pattern: organisms with large body size, slow growth, and small ranges are the most vulnerable. The oceans have long been assumed to follow similar patterns, but our work has revealed that patterns are nearly the opposite: small, fast-growing species are in fact most likely to decline to low abundance in the sea. The fundamental but surprising differences between land and sea reflect substantial differences in the history of human influence, with habitat transformation driving much of the extinction risk on land, while predation from humans remains a primary driver in the ocean. Ongoing research addresses the prevalence, causes, and consequences of synchrony in marine species. The approaches we use tend to be either comparative (integrating information on taxonomy, traits, environment, and human impacts across hundreds of species) or genomic (reconstructing population histories using DNA, ancient DNA, and Approximate Bayesian Computation).

How do we measure the value of clean water, abundant wildlife, and protection from storms?

Guerryetal2012Fig4iFor centuries, our societies have been better off thanks to a wide range of benefits provided by coastal ecosystems. These include obvious goods like food from fishing and aquaculture, but also more subtle services like coastal protection from mangroves, or newly emerging services like wave energy. While we can list these benefits qualitatively, understanding their magnitude has been much more elusive. How do human activities alter these benefits? Can we manage coastal ecosystems for a wide range of benefits, or are there important tradeoffs? How do we predict the goods and services we’ll get from a natural or a disturbed seascape?