Evolution of toxicity in Pitohuis: I. effects of homobatrachotoxin on chewing lice (order Phthiraptera)

Auk, The, Oct 1999 by Dumbacher, John P

This study clearly demonstrates the mechanisms by which homobatrachotoxin can defend wild pitohuis against ectoparasites. However, because homoBTX affects predators and perhaps other parasites as well as lice, it is difficult to assess the relative role of louse defense in the evolution and maintenance of pitohui toxins. Naturally occurring levels of homoBTX affect New Guinea predators such as green tree pythons (Chondropython viridis) and brown tree snakes (Boiga irregularis) and are known to deter human hunters (Majnep and Bulmer 1977, Kocher-Schmid 1991). The bright orange-andblack plumage pattern of the two most toxic pitohuis, P dichrous and P kirhocephalus, probably serves as an aposematic signal for visual predators such as hawks and thus would not affect lice. Consequently, homobatrachotoxin represents a single evolutionary innovation that may simultaneously influence a broad spectrum of pitohui enemies.

ACKNOWLEDEMENTS

I thank the Papua New Guinea Department of Environment and Conservation and the PNG Research and Conservation Foundation for providing visa assistance and permission to conduct this study, and the personnel at Varirata National Park for logistical support, especially P. Ainie and Bisikau Iowa. I also thank Bulisa A. lova for helping capture birds and lice, and S. O'Steen and R. M. Gaylord for assisting with experimental design and field work. S. Arnold, J. Bergelson, D. Clayton, R. Elbel, M. Kreitman, R. Page, S. Pruett-Jones, R. Price, and M. Wade provided insightful comments on the manuscript. Chemical analyses were directed by J. W Daly and supported and carried out in the National Institutes of Health Laboratory of Bio-organic Chemistry. R. Price provided invaluable assistance in identifying lice to genus or species; however, I accept responsibility for any misidentifications. Funding for field work was provided by the University of Chicago Hinds Fund and National Geographic Society Grant 5082-93. The author was supported by a William Rainey Harper Fellowship and GAANN Ecology Fellowship from the University of Chicago.

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