How do large numbers of species coexist when they utilize the same, or very similar, resources? This has been one of the central motivating questions of ecology, particularly tropical ecology, for more than a century. I investigate mechanisms of coexistence, from tradeoffs between specialization and competitive dominance, to cryptic resource partitioning, to the role of different types of environmental fluctuations. This work involves formulation, empirical calibration, and analysis of ecological models at multiple scales: from individual physiology and energetics to species interactions, demography and connectivity.

What makes some species common and others rare? Why do different species’ abundances vary from place to place to such different degrees? Modern biodiversity theories often make competing predictions about the degree to which coexisting species’ abundances vary, and about the spatial and temporal dynamics of those abundances. We apply contemporary biodiversity models to gain insights into the relative importance of factors such as environmental fluctuations and differences in species’ ecological traits in driving these patterns of commonness and rarity. Two dramatically different reef bioregions on either side of the Isthmus make Panama ideal comparative natural laboratory for such work: in the Tropical East Pacific, one group of corals overwhelmingly dominates in the marginal reef conditions there, while in the Caribbean, former community dominants have collapsed to a tiny fraction of their historical abundances.

Fishing directly and profoundly impacts the abundances of the species that fishers target, but what impact does it have on the rest of the ecosystem, and how do contemporary management tools like no-take marine reserves mediate these impacts? Our group tackles a range of research problems related to these core questions, including how marine reserve networks influence the recovery of fished populations and fisheries yields, to identifying benchmarks for the sustainability of non-selective, multi-species fisheries, to understanding how levels of critical ecosystem functions depend on the extent and trophic structure of fishing.

Today’s coral reefs respond to a very different environment than those to which modern coral reefs have been exposed for hundreds of thousands, and probably millions, of years. These dramatic changes in the physical and chemical environment have impacts that range from higher mortality and reduced growth and reproduction of organisms, to changes in the biogeochemical rates that determine whether reef structures grow or dissolve. This has profound implications for how reef organisms interact with each other, and how they will evolve in the coming decades and centuries. In addition to studying the ongoing changes experienced by today’s reefs, I am interested in using the fossil record to understand how profound environmental upheavals in the past led to reorganizations in the structure and functioning of marine ecosystems.

Photosynthesis is a complex process for capturing carbon from the atmosphere. Multiple steps in this process can control the maximum rate of carbon capture. We use a combination of manipulative experiments and field observations to understand the rate-limiting steps for photosynthesis in different tropical tree species. We also study how environmental conditions and plant ontogeny might influence which step is rate-limiting.

Species may differ in their heat tolerance but they also differ in the extent to which they experience heat, based on their architecture, morphology, and physiology. New technologies enable us to monitor temperatures of leaves in the canopy at a larger scale than traditional methods that involved attaching thermocouple wires to leaves. Monitoring canopy temperatures in diverse forest plots allows us to identify the species that experience the highest temperature extremes. We study these species in more detail to evaluate their physiological capacity to withstand high temperatures, and analyze the relative importance of architecture, morphology, and physiology as predictors of “overheating” of plants.

Little is known about high-temperature thresholds for reproduction in wild plants, but studies on crops suggest that reproduction may fail at 30–39°C. If thresholds for reproduction are universal, tropical species are close to exceeding them, as temperatures there already routinely exceed 30°C. As temperatures continue to rise, seed production may drastically change in tropical forests, with consequences for species composition and community dynamics. Through experiments and field observations, we are studying tropical tree species’ vulnerability to heat-induced sterility, with the ultimate goal of understanding how rising temperatures may change forest community composition.