I am an ecologist interested in the relationships between plants and their herbivores, and how these interactions shape communities and ecosystems. Specifically, I study the importance of chemical signals to these dynamic interactions using a combination of field and laboratory experiments. My unique approach utilizes skills in behavioral assays of consumers (planktonic, benthic, and terrestrial), bioassay-guided fractionation of secondary metabolites of algae and invertebrates and mesocosm and field experiments.
Current and Past Projects
1. Induced responses of algae to herbivores
Numerous species of plants and prey induce morphological, chemical, or behavioral defenses in response to cues associated with consumers. Despite the importance of induced responses to community structure, we know relatively little about the ecology of these interactions in phytoplankton and seaweeds. Recent work in my lab demonstrated that 1) seaweeds may indirectly influence competitive interactions between herbivore species via inducible responses and 2) some phytoplankton responses are surprisingly herbivore-specific. We are also testing the importance of inducible responses to the timing and size of phytoplankton blooms.
2. Geographic variation in plant-herbivore interactions
Although we have a good sense of the diverse taxa exhibiting inducible defenses, our knowledge of how inducible defenses within a species vary spatially is surprisingly poor. We are currently examining geographic variation in inducible defenses in three different systems and scales; salt marsh plants along the east coast, seaweeds across 1000s of km, and seaweeds across 10-100s of km.
3. Human-induced alteration of intertidal communities
Rocky intertidal communities are highly valued because of their visibility and accessibility to people and their ecological importance. However, people can negatively impact these communities both knowingly and unknowingly. Using field caging experiments, we are addressing the following two questions: 1) Does trampling influence barnacle communities and if so, how do these influences vary with ontogeny and site? and 2) Does predator removal indirectly alter plant production and diversity in southern California salt marshes? Additionally, we have started studying the impact of people on harvested snails in San Diego.
4. Long-term ecological monitoring
Rocky intertidal communities provide critical habitat to marine and terrestrial species and these habitats are threatened by a variety of stressors including climate change, invasive species, pollution, and human trampling. Unfortunately, we currently lack baseline data on the health and natural variability of these communities in some regions and, thus, are unable to predict the occurrence and consequences of such environmental changes. We are developing a long-term, low-cost protocol that will detail procedures for monitoring this habitat in New England. We are especially interested in broad-scale comparisons (e.g. Atlantic vs. Pacific shores).
5. Learned aversions in marine consumers
Learning provides an ecological response to changing prey availability and defenses by allowing consumers to add novel foods to their diets while reducing the risk of consuming noxious foods. Unfortunately, how consumers learn to accept or avoid new foods is better understood for terrestrial than for marine consumers where studies of diet learning have been infrequent. We are conducting comparative studies of learning among consumers to improve our understanding of learned aversions and the prey that exploit these behaviors in their consumers.
Miller, L.P. and J.D. Long (in press). A tide prediction and tide height control system for laboratory mesocosms. PeerJ. Preprint.
Warneke, A.M. and J.D. Long (2015). Copper contamination impairs herbivore initiation of seaweed inducible defenses and decreases their effectiveness. PLOS ONE 10: e0135395.
Kwan, C.K., E. Sanford, and J.D. Long (2015). Copper pollution increases the relative importance of predation risk in an aquatic food web. PLOS ONE 10: e0133329.
Long, J. D. and L.D. Porturas (2014). Herbivore impacts on marsh production depend upon a compensatory continuum mediated by salinity stress. PLOS ONE 9: e110419.
Bracken, M. E. S., R. Dolecal, and J.D. Long (2014). Community context mediates the top-down versus bottom-up effects of grazers on rocky shores. Ecology 95: 1458-1463.
Dolecal, R.E. and J.D. Long (2014). Chemically mediated foraging by subtidal marine predators: a field test of tritrophic cues. Marine Ecology Progress Series 498:161-171.
Long J.D., G. Toth, and H. Pavia (2013). Proximate and ultimate causes for transatlantic variation in seaweed defenses. Marine Ecology Progress Series 493:83-89.
Dolecal, R.E. and J.D. Long (2013). Ephemeral macroalgae display spatial variation in relative palatability. Journal of Experimental Marine Biology and Ecology 440:233−237.
Long, J.D., L. Porturas, E. Jones, C. Kwan, and G.C. Trussell (2013). Seaweed traits linked to wave exposure determine predator avoidance. Marine Ecology Progress Series 483:143-151.
Long, J.D. (2013). Merging chemical ecology studies across the salinity divide. Ecology 94:2112-2113.