Faculty Seed Grant Projects

Characterizing the Poison Ivy-Avian Mutualism

Investigators:

Global changes such as elevated CO2 are likely to have complex effects on plants, animals, and their interactions, but predicting these impacts requires a detailed understanding of plant-animal mutualisms. Poison ivy responds to elevated CO2 levels by producing more allergenic forms of urushiol, responsible for the characteristic skin rashes on humans. The ecological impacts of changing urushiol chemical composition on both poison ivy and the wildlife that eat it have not been considered. There is circumstantial evidence that Poison Ivy (PI) seeds eaten by native birds provide manifold advantages to this noxious native plant and its avian frugivores but here we propose detailed studies of those potential benefits.

Anecdotal and specific reports suggest native birds eat PI seed. Birds swallow the seed intact, digest the fleshy mesocarp, and expel the remaining seed in the guano. The benefits to the PI seed are two-fold: 1) mechanical and acid scarification promotes seedling germination, and 2) seed dissemination. We recently identified an endophytic fungus (Colletotrichum fioriniae) of PI that is paradoxically also a phytopathogen of PI seedlings. PI seeds would therefore also potentially benefit from avian digestion because the fungal pathogen-infected mesocarp is removed.

House Finch, Carpodacus mexicanus, isolatedThere are many potential advantages to native birds that eat PI seeds. PI seeds are energy dense, comprised of 47% lipid. PI seeds also contain the allergen urushiol[9], which has antibacterial properties against the human intestinal symbiont Helicobacter pylori. Likewise, anacardic acid (the penultimate intermediate in urushiol biosynthesis) has broad antimicrobial and anti-parasite activities. Thus, urushiol may act as an antibiotic against avian microbial pathogens. Alternatively, endophytic bacteria residing in PI seeds could colonize the avian gut and stimulate mucosal immunity.

Research objective 1: Characterize the effects of avian digestion on poison ivy (PI) seed germination and microbiome. 

Research objective 2: Characterize the impact of poison ivy (PI) seeds on the avian gut microbiome. 

The results from these studies will yield new insights into potential positive roles of poison ivy urushiol that have not previously been a focus of research.  Such putative roles on avian health may provide resiliency to migrating passerine bird species during a time of continued climate change.