In cooperation with the University of Arizona The Ecology of Parasite-Host Interactions at Montezuma Well National Monument, Arizona—Appreciating the Importance of Parasites Open-File Report 2009–1261 U.S. Department of the Interior U.S. Geological Survey This page was intentionally left blank. The Ecology of Parasite-Host Interactions at Montezuma Well National Monument, Arizona—Appreciating the Importance of Parasites By Chris O’Brien and Charles van Riper III Prepared in Cooperation with the University of Arizona Open-File Report 2009–1261 U.S. Department of the Interior U.S. Geological Survey U.S. Department of the Interior KEN SALAZAR, Secretary U.S. Geological Survey Marcia McNutt, Director U.S. Geological Survey, Reston, Virginia 2009 For product and ordering information: World Wide Web: http://www.usgs.gov/pubprod Telephone: 1-888-ASK-USGS Any use of trade, product, or firm names is for descriptive purposes only and does not imply endorsement by the U.S. Government. For more information on the USGS—the Federal source for science about the Earth, its natural and living resources, natural hazards, and the environment: World Wide Web: http://www.usgs.gov Telephone: 1-888-ASK-USGS Suggested citation: O’Brien, Chris., van Riper III, Charles, 2009, The ecology of parasite-host interactions at Montezuma Well National Monument, Arizona—appreciating the importance of parasites: U.S. Geological Survey Open-File Report 2009– 1261, 56 p. Although this report is in the public domain, permission must be secured from the individual copyright owners to reproduce any copyrighted material contained within this report. ii Contents Introduction .................................................................................................................................................................. 1 References Cited ........................................................................................................................................................ 2 Chapter 1: Parasites in a Novel Host: Implications for Parasite-Induced Trophic Transmission Introduction ................................................................................................................................................................ 4 Methods ..................................................................................................................................................................... 5 Results ....................................................................................................................................................................... 9 Discussion ................................................................................................................................................................ 16 References Cited ..................................................................................................................................................... 18 Chapter 2: The Influence of Human Visitor Activity on Spatial Patterns of Parasite Infection Introduction .............................................................................................................................................................. 20 Methods ................................................................................................................................................................... 23 Results ..................................................................................................................................................................... 26 Discussion ................................................................................................................................................................ 31 References Cited ..................................................................................................................................................... 33 Chapter 3: Making Better-informed Decisions in the Analysis of Wildlife Diseases: Hypothesis Testing, Power Analysis, and Estimating Observed Effects Introduction .............................................................................................................................................................. 36 Materials and Methods ............................................................................................................................................. 39 Results ..................................................................................................................................................................... 41 Discussion ................................................................................................................................................................ 46 Conclusions ............................................................................................................................................................. 48 References Cited ..................................................................................................................................................... 48 Acknowledgments ..................................................................................................................................................... 51 Appendixes ................................................................................................................................................................ 52 Figures 1-1. Location of Montezuma Castle NM in Arizona and aerial photograph of the Well Unit. .......................................... 2 1-2. Images of orange trematode-infected and uninfected H. montezuma. ................................................................... 6 1-3. Sex ratios of infected and uninfected amphipods from a sample of 490 H. montezuma . ..................................... 10 1-4. Proportion of females carrying brood, from the sample in figure 1. ...................................................................... 11 1-5. Swimming activity (number of line crosses) of amphipods by sex and infection condition. ................................... 12 1-6. Mean height above bottom in a 50-cm experimental chamber. ............................................................................ 13 1-7. Mean proportion of times amphipods were observed in dark side of chamber in experimental trials. .................. 14 1-8. Capture rates of non-host invertebrate predators on uninfected and infected amphipods. ................................... 15 1-9. Proportion of uninfected, trematode-infected, acanthocephalan-infected amphipods captured by waterfowl ....... 16 2-1. Life cycle of the trematode parasite (Microphallus spp.) investigated in this study. .............................................. 22 2-2. Line drawing of Montezuma Well, delimiting different habitat types within the aquatic ecosystem, as well as visitor-use trails and sampling units ............................................................................................................................. 23 iii 2-3. Estimated visitor numbers at Montezuma Well during study periods in 2003-2004 and 2004-2005 ..................... 26 2-4. Patterns of waterfowl space-use over time over the two study periods in 2003-2004 and 2004-2005. ................. 27 2-5. Results from experimental disturbance of foraging waterfowl. .............................................................................. 28 2-6. Plot of visitor number and corresponding waterfowl use of space data at Montezuma Well over a 3-day period in November 2007. ...................................................................................................................................................... 29 2-7. Plot of waterfowl abundance and trematode prevalence in amphipods over the two study periods ..................... 30 2-8. Trematode prevalence in far and near sides of Montezuma Well . ....................................................................... 31 3-1. Examples of three distributions: the negative binomial (A), poisson (B), and normal (C). .................................... 38 3-2. Histograre of sample sizes from 70 studies in Journal of Wildlife Diseases. ........................................................ 42 3-3. Probability of type II errors (y-axis) plotted for increasing sample sizes (vertically) and increasing effect sizes (x-axis) for two different base proportions for five different statistical methods. ........................................................... 43 3-4. Probability of type II errors (y-axis) by effect size (x-axis), plotted for four different statistical techniques for a range of pooled sample sizes and aggregation parameters ........................................................................................ 44 3-5. Probability of type II errors (y-axis) for increasing sample sizes (x-axis) for the analysis of abundance data using a GLM and of prevalence data and using log-linear regression ......................................................................... 45 Tables 1-1. Parameter estimates from linear models of factors that affect swimming activity in male and female amphipods. ............................................................................................................................................................... 52 1-2. Parameter estimates generated by linear models of factors that affect δC and δN values in amphipods. ............ 53 1-3. Analysis of deviance tables from logistic regression models that tested the effect