Document: MAR-3-84-8

From people to pathogens: Are parasites responding to anthropogenic disturbance?

POTEET, M.F.*

University of California, Berkeley, CA 94720 USA ¹

Abstract:
Recent work suggests that patterns of parasitism in wildlife are changing due to anthropogenic alteration of habitats. In this study, I assess whether anthropogenic disturbance, in this case logging, alters patterns of parasitism and I further assess which processes might drive these changes. Through systematic censuses and experimental tests, I ask: 1) Are parasite prevalence and intensity in stream communities affected by clear-cut logging; 2) can changes in host density associated with logging explain altered parasite levels; 3) what aspects of parasite transmission are disrupted by logging-induced disturbances? I focus this study on a trematode that obligately and sequentially infects Dicamptodon tenebrosus, Juga silicula, and Calineuria californica from small streams in the Cascade Mountains, OR. To determine the effects of logging on patterns of parasitism, I censused each host species for parasites from 11 creeks in heavily logged watersheds and 7 creeks in unlogged watersheds. I chose sampling sites based on watershed size, stream gradient, elevation, latitude, longitude, and severity of logging. Logging was associated with a significant decrease in mean parasite prevalence and intensity, and a decrease in the density of each host species. I then tested whether changes in host density associated with logging affected parasite transmission success. Using a randomized block design, infected hosts were caged with uninfected hosts at three densities each to evaluate the effect of host density on the recruitment and reproduction of the parasite. Parasite recruitment was sensitive to changes in stonefly density, and parasite reproduction was sensitive to changes in salamander density. Neither recruitment nor reproduction of parasites was sensitive to changes in snail density. This study links anthropogenic disturbances directly with changes in parasitism and suggests that altered mechanisms of parasite transmission drive these changes.

Keywords: parasite, amphibian, logging, disturbance

This abstract is being presented at: 12:00 PM in session:
Oral Session #2: Conservation Ecology.