An initial supply of arriving propagules, which could be larvae, seeds, juveniles, or adults of a species, is required to establish a population in a new area. We often don’t know the number of propagules or their frequency of arrival because this is very difficult to measure in real-time. As a result, we study propagule pressure* to better understand how the number or frequency of arriving organisms helps to explain invasion patterns or predict future invasion risks. Because all introductions require some individuals to be delivered, propagule pressure is an underlying factor even if the actual supply of propagules arriving is unknown or unknowable. The concept is also studied in other fields of ecology, including restoration, re-introduction, conservation, and marine science, often using the term supply-side ecology*.

Our lab is working to understand propagule pressure and how it impacts species establishment in marine systems. In a recent experiment, published in May 2017 in Biological Invasions (Simkanin et al. 2017), we manipulated ascidian* larvae to test a well-documented pattern in marine invasions – that artificial structures are more invaded than natural ones. In this experiment, we wanted to know if artificial habitats are really more likely to be invaded or is it simply that artificial habitats tend to be in areas with a larger supply of propagules, such as ports and marinas. In order to test this, we conducted a dosing experiment in which we controlled the amount of propagules (larval Botrylloides violaceus) introduced to dock and rock habitats. We found that higher dose sizes did increase invasion success, but habitat also matters - artificial habitats/docks were invaded more easily than the natural benthic rock treatments.  

This summer, we began experiments with native Eastern Oysters (Crassostrea virginica) in the Rhode River and plankton communities in the laboratory to test the effect of propagule pressure on oyster recruitment and phytoplankton invasion dynamics. These studies were led by two of SERC’s 2017 interns, Katie Clark from the College of the Atlantic and Maria Gonzalez from the University of Puerto Rico.  In order to understand settlement and survival of Eastern Oysters, we are looking at how oyster populations are affected by the number of arriving larvae, the frequency of larval arrival, and the established fouling community. Similarly, we established plankton communities in small aquaria and added different levels of a novel species to mimic an invasion and monitor the outcome. 

Contacts

Ian Davidson, DavidsonI@si.edu

Christina Simkanin, SimkaninC@si.edu