My research can be categorized into the following non-mutually exclusive themes:
Intraspecific stoichiometric variation
Ecological stoichiometry has often assumed low levels of intraspecific variation in the elemental phenotype of consumers. Recent work has revealed high levels of intraspecific variation in several species, particularly in body phosphorus contents and phosphorus excretion rates, but the causes remain elusive. I believe intraspecific variation in the elemental phenotype can link microevolutionary processes to ecosystem function, and this is a focal area of my research. I am currently investigating how predators and temperature affect the elemental phenotype of aquatic consumers through changes in diet and physiology. Much of this work is on Gambusia marshi, a poeciliid fish native to northeastern Mexico, and Daphnia, a grazing crustacean zooplankter in north temperate lakes, but I have also worked on Thraulodes mayflies as well as Rhinella and Dendropsophus tadpoles in Panama.
Phosphorus cycling in aquatic ecosystems
In addition to studying variation in the storage and supply of phosphorus by animals, I am interested in what controls phosphorus availability at the ecosystem scale. This is a focal question of my post-doctoral research, for which I am studying the impacts of excess phosphorus loading on zooplankton communities and harmful algal blooms in Iowa lakes. I also collaborated with Jessica Corman studying arid calcium carbonate depositing systems such as travertine streams and mineral-rich springs in Cuatro Cienegas. Since phosphorus binds to calcium carbonate in solution, these systems often have exceptionally low biologically available phosphorus. We have studied how this process may drive phosphorus limitation in primary producers, and I am interested in how low phosphorus availability may affect higher trophic levels. I also study broad-scale geological effects on stream biogeochemistry in Panama in collaboration with Amanda Rugenski and Ben Turner.
Evolutionary ecology of fishes
Changes in the elemental composition of consumers are often related to changes in the traditional phenotype. To understand what drives variation in the elemental composition among lineages, I am involved in several projects investigating the evolutionary ecology of fishes. For this work I study Gambusia living in Chihuahuan desert springs in collaboration with Lourdes Lozano-Vilano and loricariid armored catfishes throughout Central and South America.
Metabolic ecology and bioenergetics
A large debate currently persists as to how energy-based and matter-based approaches can be united to better understand ecological phenomena. I come from an energy-focused background, and hope to use this knowledge to integrate energy into stoichiometric approaches. I have previously worked on using bioenergetics models to understand how climate change will affect feeding ecology and growth of sea lamprey in Lake Superior, and how metabolic scaling with body size affects stable isotope turnover time.
Ecology and natural history of aridland aquatic ecosystems
Most of my field-based work takes place in arid regions of Arizona and Mexico, where aquatic ecosystems are rare yet under-appreciated in the scientific literature. It is precisely this rarity that makes them extremely important in the landscape, and unfortunately, the reason many organisms that rely on them are now threatened or endangered. Through the course of my work I have worked on various projects examining the ecology and natural history of these systems and the organisms that rely on them.