Susan Williams, Ph.D.

The Williams Lab

Amanda Newsom, Ph.D. Candidate

ajnewsom@ucdavis.edu

Interactions among introduced species are less frequently studied than are interactions between introduced and native species. In the worst cases, these interactions may exacerbate the negative effects of introduced species on native communities. 

I use multiple methods to understand the impacts of multiple introduced and invasive species. For my dissertation, I am looking at interactions among introduced species across systems and at the details of introduced species interactions on the mudflats of Bodega Harbor, Tomales Bay, and San Francisco Bay. 

The model system I work with includes the introduced predators Philine orientalis (Tortellini slug), Carcinus maenas (European green crab), and their introduced and native infaunal prey, as well as native predators such as Cancer spp.  Last summer, I found that in the laboratory, Philine slowed the predation rate of Carcinus by about 16% on the introduced Asian gem clam (Gemma gemma). This result is most likely due to the copious mucous secreted by Philine, which drops precipitously to a pH of ~1 when a slug is mechanically disturbed. Philine may also interfere with native crab feeding.

Pictures of Philine orientalis and the mucous it secretes-

Philine orientalis, also known as the introduced Tortellini slug.

The slug is in my hand with mucous dripping off of it. The pH of this mucous can be approximately neutral, or extremely acidic if the animal is mechanically disturbed.

The Williams Lab