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Carol Pollock
Emeritus Professor of Teaching
Department of Zoology
University of British Columbia
Animals Can Run Away, but Plants Must Stay: Responses to Herbivory

In this PowerPoint-driven case study, students consider the many challenges faced by plants and discuss which of these might induce a morphological response. Examples of phenotypic variation within a plant species are presented and students discuss in small groups how to determine whether the observed variations have a genetic basis. The concept of a "common garden" experiment, in which plants are grown in a common environment and variation is measured, is elucidated and discussed. A specific example of phenotypic variation is introduced: Plectritis congesta from islands without herbivores (deer) are taller than the same species from islands with deer. An experiment with simulated herbivory is described and students are asked to predict results, assessing whether modification of pattern of growth is an induced response or a constitutive defense. A field experiment involving deer predation is introduced. The morphological response of Plectritis to predation is presented as an evolutionary tradeoff. The case is appropriate for introductory general biology (majors and non-majors), ecology, and plant biology courses and, with some modification, introductory evolution courses.