Research


Mission: Evaluate how resource landscapes affect community formation and subsequent interactions, with a particular focus on shifting resource availability and use due to environmental change and organismal development, respectively.

Keywords: complexity, biodiversity, resources, interactions, community assembly, recruitment, ecological perturbation, species addition/loss, extinction, invasion, life history, ontogeny, complex development, niche, structural refuge, size refuge


  Interests…

I see the whole world as a slew of resources mediating a complex array of interacting communities. I am fascinated by the way organisms use the resources around them, and how perturbations alter resource availability, allocation, and partitioning. Resources - food, shelter, mates, etc - drive most ecological patterns, and global change is constantly rearranging patterns of resource use and thus community dynamics. I am as interested in resources as the source of variable interactions as I am in the interactions themselves, and I am especially interested in the ecology of empty niches, or how extinctions and invasions open novel resources that act as an “evolutionary carrot on a stick”.
I use environmental change, species invasions, and resource shifts accompanying organismal development as model systems for studying shifting resource landscapes across global to organismal spatial scales. I most often focus on marine, amphibian, and insect study systems because I'm intrigued by niche shifts that accompany growth and development. When studying ecological perturbations, I hope to determine some of the carry-over effects of species with multiple distinct life phases (complex ontogeny) as they shift between habitats and resources. My research utilizes a resource-driven perspective to investigate how ecological systems are responding to human-mediated global change.

 

Projects…

Moving mangroves shift resource landscapes
INFLUENCES OF HABITAT ASSOCIATIONS & LANDSCAPE CONTEXT FOR RECRUITING COMMUNITIES: When examining the clustering of species in space, the formation of characteristic communities around habitat-forming foundation species emerges as one of the few ubiquitous patterns. However, as many species shift geographic ranges, more rapidly now in response to climate change, it becomes pertinent to investigate what form assembling communities will take when species encounter habitats out of context. Specifically, if a habitat-forming species establishes in a new area (beyond its historical range, and thus out of context), who will recruit into this habitat? My current research evaluates how assembling communities respond to shifting resource landscapes. Working in climate-impacted wetlands, I investigate how different habitat types, and shifts therein, influence assembly and use by marine crabs. Understanding how inhabitants respond to shifts from marshes to mangroves requires an assessment of habitat associations and underlying mechanisms as well as their strength relative to other formative processes (see Adler et al., 2007). Coupling these with a clearer understanding of the resource landscape from the inhabitants’ perspective should help us understand whether and how marine crustacean communities are responding to shifting coastal ecosystems. A species’ likelihood of keeping up with their shifting host depends on their dispersal potential and ability to detect and respond to relevant environmental cues (see Yang and Rudolf 2010), so a closer evaluation of both dispersal and response to habitat cues should clarify the mechanisms underlying habitat associations and community responses to shifting landscapes. By clarifying the role of physical habitat in determining species assemblages, this project is designed to illuminate realistic implications of global habitat modification on community-structuring ecological processes.

Coqui exclosure on a native ohia tree.
PREDATOR INVASIONS & FOOD WEB CONNECTANCE: Many of the world’s worst invasive animals are generalist predators. Foraging patterns in novel ranges can determine which prey are impacted and whether the predator thrives. Native prey are expected to be na├»ve and thus vulnerable; however, predators often become most invasive where they encounter abundant invasive prey. The only amphibian in the Hawaiian islands, Eleutherodactylus coqui, is a tropical tree frog that invaded in the 1980s. As a generalist predator reaching unprecedented densities, it has the potential to thrive on abundant invasive invertebrates while devastating native and endemic invertebrate species. Mapping temporal and spatial foraging patterns with lab feeding trials and stable isotope tracer field experiments (Hilo, HI, summer 2011), respectively, we determined that coqui forage both day and night, in the understory and beneath leaf litter. Thus, coqui appear to profoundly alter the connectance of food webs previously separated by space, time, and pristineness. (Initial results were presented at ESA 2012; the manuscript is in preparation.)

Differences in use of historic and novel habitats (from Johnston & Lipcius 2012)
NOVEL ECOSYSTEMS AS NATIVE NURSERIES: As species shift ranges – a phenomenon that is expanding and accelerating with climate change – it becomes increasingly important to evaluate the consequences for dependent species. When species form ecosystems, such as corals that form reefs, differences in their structure and function can affect the equivalence of historical and novel ecosystems. To evaluate the impacts of shifts from seagrass to macroalgae in the Chesapeake Bay, I compared juvenile blue crab demographics and survival trajectories in each habitat type (REU, Virginia Institute of Marine Science, summer 2007). Macroalgae provided superior survival for all juvenile crab sizes, indicating effective nursery refuge while potentially removing the ontogenetic habitat shift classically documented in blue crab nurseries. Thus, as seagrass meadows degrade throughout the Chesapeake Bay, refuge in expanding exotic macroalgae may underlie crab population recovery. (See Johnston & Lipcius 2012 under “Literature” for the full study.) Ongoing collaborations aim to test how differences in seagrass and macroalgae structural attributes drive survival and occupancy patterns.