The research of the Lowry lab is centered on identifying the genetic and genomic mechanisms of ecological adaptations and how those adaptations contribute to the formation of new species. A key goal of our research is to link adaptive genetic variation with features of the natural landscape. To understand the physiological, developmental, and genetic mechanisms of adaptive divergence between plant populations, the Lowry lab is focused on research in two major emerging model systems for evolutionary genomics: Monkeyflowers (Mimulus) and Panicum grasses, including the bioenergy crop switchgrass. Two large communities of collaborative scientists have established extensive genomic and molecular biology resources for these systems.
The role of chromosomal rearrangements in adaptation and speciation
One of the major ongoing projects in the Lowry Lab is a quest to understand how chromosomal inversions contribute to adaptation and reproductive isolation. Inversions have been thought to be involved in ecological adaptations ever since pioneering cytogenetic analyses in Drosophila revealed that inversion polymorphisms track environmental gradients. Chromosomal inversions are also very important for human health, as they underlie many genetic diseases and affect the geographic distribution of insect vectors of pathogens. While inversions have been associated with adaptation and human disease, the mechanisms by which inversions affect phenotypic divergence between populations are unknown.
During graduate school, Lowry discovered a major chromosomal inversion polymorphism that is involved in adaptive divergence and reproductive isolation between coastal perennial and inland annual ecotypes of Mimulus guttatus in western North America. The inversion contributes to massive changes in the overall phenotype of the plants and local adaptation in nature. Now we would like to determine the evolutionary, molecular genetic, and physiological mechanisms by which the inversion has contributed to this important evolutionary transition. To accomplish that goal, we plan on taking multiple approaches, including whole genome resequencing, global gene expression analysis through RNA-sequencing, examination of how the inversion influences hormone levels, and molecular tricks.
Understanding the mechanisms of adaptation along environmental gradients
The Lowry Lab is very interested in determining the genetic mechanisms of the morphological, physiological, and life-history transitions that accompany adaptation to habitats that differ in soil water availability. The chromosomal inversion, mentioned above, is involved in one such transition. More recently, we have become interested in parallel adaptive transitions of this sort in Panicum grasses. This includes the bioenergy crop switchgrass (Panicum virgatum), which may be used in the future for production of cellulosic ethanol and other biofuels. Switchgrass has both upland and lowland ecotypes that are adapted to dry and wet habitats, respectively. Since 2010, Lowry has been working to develop a genetic mapping population derived from a cross between two northern upland and two southern lowland individuals. We plan to use this mapping population to better understand the genetic mechanisms of adaptation to both Upland and Lowland habitats as well as to the latitudinal gradient of natural selection across the Great Plains of North America.
Development of a new model system for climatic adaptation and bioenergy research
The Lowry lab is working on similar questions of adaptation to differences in soil water availability in a new model genomic system, Panicum hallii. P. hallii is closely related to switchgrass, but is much easier to work with due to a short generation time, smaller size, and simpler (diploid) genetics than P. virgatum. We are in the process of sequencing the complete genomes of nearly 100 population accessions of P. hallii from across the southwestern United States. We are particularly interested in the adaptive divergence of P. hallii populations across the Chihuahuan and Sonoran Deserts. Hot, dry desert valleys that divide “sky island” mountain ranges characterize both of those desert regions. We aim to understand the mechanisms of adaptive divergence between the sky islands and desert valley populations. This research will serve as both a model for the evolution of adaptation to future climate change and as a model for improvement of switchgrass as a bioenergy feedstock.