Remote Sensing of Forest Canopy Structure and Invasion
Canopy structure is a critical driver of forest ecosystem function. Canopy structural complexity is the multidimensional arrangement of vegetation within the canopy, which can be measured with terrestrial LIDAR. However, remote sensing technologies to measure canopy structural complexity that are more cost effective and available on a wide spatial scale are lacking. I am working with Brady Hardiman and Songlin Fei at Purdue University to improve methods of measuring canopy structural complexity with remote sensing technologies, including aerial LIDAR and satellite imagery.
We are also exploring relationships between physical canopy structure and invasive species distributions in North American forests in collaboration with researchers from Purdue University and the US Forest Service.
Dispersal Variation, Geographic Range Dynamics, and Climate Change
Dispersal is a key process influencing species persistence and geographic range limits. Most species’ distribution models assume that organisms of the same species have identical dispersal rates, but some models suggest that variation in dispersal across a species’ range may have significant consequences for the evolution of range limits. Patterns of variation in dispersal throughout a species’ range, the environmental drivers of that variation, and the influence dispersal variation has on the size and extent of species’ geographic distributions has been largely unexplored. Understanding the processes driving species’ distribution patterns is critical for conservation, as scientists strive to anticipate how organisms will respond to climate change, habitat loss, and land use change.
My PhD research investigates dispersal trait variation in a Great Lakes beach plant, American sea rocket (Cakile edentula var. lacustris, Brassicaceae), and the potential onsequences of that variation for range shifting of the species under projected climate change scenarios. Cakile edentula is an early colonist of the beach habitat along the Great Lakes, a highly dynamic habitat because of frequent disturbance by strong wind, waves, and shifting substrate. In order to persist on the dynamic beach habitat, C. edentula has a dimorphic fruit with two seed types adapted for dispersal via wind and water vectors. I am testing the hypothesis that environmental gradients in habitat quality and quantity across the Great Lakes range of C. edentula have caused different patterns of selection on dispersal traits at different positions within the species’ range, which in turn will play a role in the tracking of future climate.
Hybridization and the Evolution of Invasiveness Across Space
Hybridization can facilitate the evolution of invasiveness. Eurasian watermilfoil (Myriophyllum spicatum) and its hybrid with the native species, northern watermilfoil (M. sibiricum) are problematic invasive aquatic plants in North America. My MSc work showed that different genetic lineages of hybrid watermilfoil were more invasive than their invasive parent. Hybrids grew faster and were less sensitive to the commonly used herbicide, 2, 4-D in a common garden experiment. Furthermore, hybrids occurred more often in lakes previously treated with 2, 4-D than their invasive parent. Genetic analyses showed that many invasive lineages of hybrid milfoil were F1, however successful hybrid crosses in laboratory populations and a small number of advanced generation hybrids identified in natural populations support that hybrids are capable of sexual reproduction.