How do populations evolve to cope with changing biotic and abiotic
environments? What traits are affected by adaptation to (for example) temperature?
How do trait correlations promote or constrain adaptation to novel environments?
Broadly, I am interested in the evolutionary ecology of microbes (primarily phytoplankton)
in the context of the ecological community. I use ecological and evolutionary theory to
inform empirical trait-based approaches to the study of microbial adaptation to novel
temperature, nutrient, light, and zooplankton grazer environments. My research relies heavily on
experimental evolution, ecological (e.g. competition) and physiological experiments, and
meta-analysis of (co)variation in microbial physiological traits.
Evolutionary responses of marine diatoms to temperature selection
My primary project at present focuses on evolutionary adaptation of the marine diatom Thalassiosira pseudonana to temperatures above and below its thermal optimum. I culture T. pseudonana at the lower and upper extremes of its thermal niche and track the evolution of traits such as the lower critical temperature, upper critical temperature, thermal optimum, thermal niche width, and also physiological traits associated with growth and nutrient uptake kinetics, over time. Recently, we detected significant evolutionary change in thermal the optima of several of our experimentally evolving cultures (see "Big News", left)!
I use competition experiments to assess relative fitness of evolved v. ancestral strains of T. pseudonana at a given temperature, and also of strains evolved at different temperatures. A major innovation facilitating these experiments is the competition chamber (below), which uses a semi-permeable, polycarbonate membrane to separate populations, allowing them to compete for a common resource pool without coming into direct contact with one another.
I am currently working on a meta-analysis of microbial thermal traits (thermal optimum, upper/lower critical temperatures, niche width) across the entire range of temperatures at which life is known to exist. In particular, I am interested in how these traits co-vary, and how variation and covariation differ among various functional and taxonomic groups (e.g. marine and freshwater phytoplankton, bacteria, archaea). I will eventually incorporate phylogenetic techniques to elucidate historical patterns in thermal trait evolution. I presented my preliminary findings at the 2015 Astrobiology Science Conference in Chicago. Link to AbSciCon 2015 poster
I am currently working on a number of modeling projects and experiments that are at various stages of development. In particular, I am becoming increasingly interested in the thermodynamics of intracellular biochemistry (see, e.g., Ratkowsky et al. 2005, J Theor Biol), and in the relationships between the temperature-dependence of intracellular processes and that of per-capita population growth. Other topics of interest include temperature-dependence of UV-induced DNA damage and repair and implications for the generation of novel genetic diversity in phytoplankton, local adaptation of phytoplankton, and resurrection ecology. My background is in community ecology, so I tend to approach all of my questions from an ecological perspective.
Copyright 2011 by Daniel R. O'Donnell. All rights reserved. Last modified: GMT