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Unravelling causality from correlations: revealing the impacts of endemic ectoparasites on a protected species (tuatara)

Published online by Cambridge University Press:  16 October 2009

STEPHANIE S. GODFREY ,
JENNIFER A. MOORE ,
NICOLA J. NELSON  and
C. MICHAEL BULL
STEPHANIE S. GODFREY*
Affiliation:
School of Biological Sciences, Flinders University, Adelaide 5001, Australia
JENNIFER A. MOORE
Affiliation:
Allan Wilson Centre for Molecular Ecology and Evolution, School of Biological Sciences, Victoria University of Wellington, New Zealand
NICOLA J. NELSON
Affiliation:
Allan Wilson Centre for Molecular Ecology and Evolution, School of Biological Sciences, Victoria University of Wellington, New Zealand
C. MICHAEL BULL
Affiliation:
School of Biological Sciences, Flinders University, Adelaide 5001, Australia
*
*Corresponding author: School of Biological Sciences, Flinders University, PO Box 2100, Adelaide 5001, SA, Australia. Tel: +61 8 8201 2805. Fax: +61 8 8201 3015. E-mail: Stephanie.Godfrey@flinders.edu.au
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Summary

Understanding the impacts of endemic parasites on protected hosts is an essential element of conservation management. However, where manipulative experiments are unethical, causality cannot be inferred from observational correlative studies. Instead, we used an experimental structure to explore temporal associations between body condition of a protected reptile, the tuatara (Sphenodon punctatus) and infestation with ectoparasites (ticks and mites). We surveyed tuatara in a mark-recapture study on Stephens Island (New Zealand), which encompassed the pre-peak, peak and post-peak infestation periods for each ectoparasite. Tick loads during the peak infestation period were negatively related to body condition of tuatara. Body condition before the peak was not related to subsequent infestation rates; however, tick loads in the peak were negatively related to subsequent changes in body condition. Mite loads during the peak infestation period were not correlated with body condition of tuatara. Body condition before the peak had no effect on subsequent mite infestation rates, but mite loads of small males during the peak were negatively related to subsequent changes in body condition. Our results suggest that both ectoparasites reduce the body condition of tuatara, which has implications for the long-term conservation management of this host and its parasites.

Keywords

body conditionhost-parasite dynamicstickstrombiculid mitesconservation
Type
Research Article
Information
Parasitology , Volume 137 , Issue 2 , February 2010 , pp. 275 - 286
Copyright
Copyright © Cambridge University Press 2009

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