Summary: 2032
Ecology, 82(7), 2001, pp. 2032­2044
2001 by the Ecological Society of America
DIRECT AND INDIRECT EFFECTS OF ALKALOIDS ON PLANT FITNESS
VIA HERBIVORY AND POLLINATION
LYNN S. ADLER,1,2,3
RICHARD KARBAN,2
AND SHARON Y. STRAUSS1
1Center for Population Biology, 2320 Storer Hall, University of California, One Shields Avenue,
Davis, California 95616 USA
2Department of Entomology, University of California, One Shields Avenue, Davis, California 95616 USA
Abstract. Herbivores and pollinators can simultaneously exert selective pressures on
plant traits via direct and indirect effects. Net selection on plant traits, such as defensive
chemistry, may be difficult to predict from studying either of these interactions in isolation.
In this study, alkaloids were manipulated experimentally in the hemiparasitic annual plant
Castilleja indivisa (Scrophulariaceae; Indian paintbrush) by growing these parasites with
bitter (high-alkaloid) or sweet (low-alkaloid) near-isogenic lines of the host Lupinus albus
(Fabaceae) in the field. To evaluate the effect of herbivores, half of the Indian paintbrush
plants were randomly assigned to a reduced-herbivory treatment using insecticide, and the
other half to a natural-herbivory treatment. Floral traits, bud and fruit herbivory, pollination,

Source: Adler, Lynn - Department of Plant, Soil and Insect Sciences, University of Massachusetts at Amherst

Collections: Environmental Sciences and Ecology