I am interested in the evolution of the ecological niche, and how ecological processes shape the evolutionary trajectories of populations and species. The distribution of a species is largely a reflection of its ecological niche, and a major part of my research aims to understand the ecological and evolutionary processes that shape the distribution patterns that we observe in natural populations. My research integrates community ecology, population biology, and phylogenetics; I use field experiments, molecular methods, anatomical techniques, and comparative methods to address a variety of questions about the evolution of the ecological niche in plant populations and species.
I have worked in a variety of plant community types, ranging from salt marshes to serpentine grasslands. I am particularly attracted to studying plant species that inhabit ecologically stressful or marginal habitats. In these habitats, ecology often leaves a particularly strong imprint on the evolution of populations and species. Endemics to ecologically stressful habitats often provide striking examples of niche evolution, and offer a rich context for experimentally examining how selection, gene flow and the genetic architecture of populations interact to direct - or restrict - the process of adaptation. Environmental variation across the distribution of a population or species can produce a mosaic of selective pressures, while concurrently structuring patterns of gene flow by influencing the direction and magnitude of seed dispersal and pollen transport. In these systems, I address questions such as "What ecological and genetic factors restrict this species to this habitat type?" "What are the patterns of adaptation across the distribution of this population (or species)?" and "How do various ecological factors influence patterns of gene flow across the species' distribution, and what are the evolutionary consequences of that gene flow?"
The need for a general understanding of the processes that drive species' distribution patterns is particularly urgent in the face of global change. Our ability to predict which species can track a rapidly changing climatic conditions through dispersal and those that must adapt in situ (or go extinct) largely hinges on our understanding of the processes setting current population and species boundaries. Restoration efforts, which strive to create (or recreate) niche space for target taxa, often involve changing current distribution patterns and the introduction of non-local genotypes to increase population sizes or enhance genetic variation in a population. To truly predict the consequences of these actions, and to help make informed decisions about future restoration efforts, more research is needed that simultaneously investigates the ecological and evolutionary processes that limit species' ranges.
I have several projects under way, most of which currently focus on patterns of niche evolution in plant species endemic to California vernal pool wetlands. My specific research questions include: (1) What are the ecological and evolutionary causes of the within-pool distribution pattern of Lasthenia fremontii, a vernal pool endemic restricted to specific elevations within pools? (2) How do depth, flowering phenology and pollinator preferences influence patterns of gene flow in Lasthenia fremontii? (3) How do competition and ecological factors associated with pool depth influence the expression of additive genetic variation and selection for depth preference in Lasthenia fremontii? (4) What are the patterns of ecological niche differentiation in the Lasthenia clade, and how do divergence patterns vary with spatial scale? (5) Has invasion of the vernal pool habitat been associated with the evolution of reduced dispersal ability in Lasthenia lineages? (6) Has invasion of the vernal pool habitat been associated with the evolution of various leaf ecophysiological traits Lasthenia lineages?