Research
Cytonuclear co-evolution and incompatibility
All eukaryotes have not just a nuclear genome but one or more organelle genomes as well. Nuclear and organelle genomes must cooperate together closely to carry out functions essential to the cell, and yet there is also room for conflict. How do these co-evolutionary dynamics influence the evolution of genetic divergence and incompatibility between populations? During my dissertation in Laura Galloway's lab at the University of Virginia I addressed these questions using the herb Campanula americana. See here for more information.
Reproductive polymorphism and the maintenance of genetic diversity
Facultative parthenogens can switch between asexual and sexual reproduction. The ability to switch is often environmentally dependent and the capacity and cues required to switch are subject to local adaptation. However, the extent to which genetic polymorphism in this plastic reproductive strategy is stably maintained within populations, and the influences of ecological factors on the dynamics of reproductive polymorphism remain unclear. I am currently addressing this topic at a postdoctoral fellow in Alan Bergland's lab at the University of Virginia using the model faculative parthenogen, Daphnia pulex. See here for more information.
Variation in photoperiod in wild sunflowers
Many species in seasonal environments use daily and annual fluctuations in environmental characteristics like day length and temperature to regulate development and successfully achieve the optimal annual timing of reproduction. While the gene regulatory networks underlying the perception and response to seasonal cues are well described, how these networks can be modified to adjust environmental sensitivity to these cues is not well understood. Wild populations of the common sunflower show exceptional intraspecific variation in their photoperiod requirements with some populations flowering earlier in short days, others flowering earlier in long days, and still others having evolved photoperiod insensitivity. As a postdoctoral research associate in Benjamin Blackman’s lab at the University of Virginia I used QTL mapping to characterize the genetic architecture of shifts in photoperiod and identify potential candidate genes.
Genetic structure of an alpine caddisfly
Both historical and contemporary events can influence the genetic structure of a species. As a master's student at the ETH Zürich I carried out research characterizing the genetic structure of an alpine caddisfly, Allogamus uncatus in the lab of Chris Robinson at EAWAG. Using COI sequencing I identified multiple clades structured by river drainages, a possible signature of recolonization after the last glaciation. A finer-scale genetic structuring was found at the valley level, with most haplotypes endemic to single valleys, indicating little contemporary gene flow. I also collaborated with a PhD student in the lab to examine the impact of an extreme climatic event , the European heat wave in summer 2003, on the spatio-temporal genetic structure of 8 caddisfly populations. We found that patterns of genetic differentiation changed markedly in response to the climatic event, leading to rapid genetic divergence between valleys within 1-2 years.
Reproductive isolation in copepods
Characterizing patterns of genetic divergence and reproductive isolation within a species can give insight into the processes contributing to the early stages of speciation. As an undergraduate in the lab of Suzanne Edmands at the University of Southern California, I had the opportunity to work on a project characterizing patterns of genetic divergence and reproductive isolation in the intertidal copepod, Tigriopus californicus. We found that genetically divergent, reproductively isolated clades of T. californicus are separated by a narrow boundary (less than 12 km) in Baja California, Mexico, with no obvious barriers to dispersal. Reproductive isolation in T. californicus is often asymmetrical and due in part to cytonuclear incompatibility, leading to my career long interest in cytonuclear co-evolution and incompatibility.
See here for more information.