Areas of my active research include:
Divergence and adaptation along elevation gradients
Why do similar species replace each other in different climates, such as from cool to warm, wet to dry, or low to high elevations? Are the boundaries between species set by the environment, by competition, or by other factors? I investigate these questions through the lens of protein-coding mitochondrial genes, the 13 metabolic genes with their own history and evolution distinct from the rest of the genome. While people have long thought that these genes were constrained from evolving much, given how essential they are to life, we now know that species often show evidence of selection on mitochondrial genes for performance under specific conditions of temperature, nutrition, and elevation. I am currently assembling a database of mitogenomes to compare related species living at high and low elevations and see whether and how selection may have impacted mitochondrial function to adapt species to differing climates.
Impacts of temperature at multiple levels of organization
Temperature is a pervasive environmental factor governing where organisms are found and how they evolve. While temperature causes chemical reactions to run faster, there has long been debate about how exactly this process scales up through the cells, tissues, and entire bodies of organisms, and why organisms experience limitations at lower temperatures than the molecules that compose them. In a recent meta-analysis, we looked at how the rates of processes at three different levels of organization–enzymes, mitochondria, and whole organisms–change with increasing temperature, and found that higher/more-complex levels actually experience greater relative rate increases than lower levels for a given rise in temperature. Because mitochondria control the flux of energy and oxygen, their response to temperature might be key for integrating enzyme kinetics with organismal limitations. In work with swordtail fishes described below, I plan to test several hypotheses about mitochondrial performance and temperature.
Mitonuclear interactions in hybrid zones
Mitochondria contain their own genome, but they don’t encode all of the genes they need to provide energy to our bodies. They also rely on a handful of nuclear genes, and these two sets of genes work tightly and intimately together. These ‘mitonuclear interaction’ are the basis for co-evolution between the mitochondrial and nuclear genomes–selection on either can exert selection for compatibility with the other. When genes that have not evolved together are forced to work together, such as in hybrid offspring from two different species, incompatibilities can be revealed with potentially disastrous consequences for hybrid individuals.
