Variation in effect of insect herbivory on Platte thistle (Cirsium canescens) between biogeographic range center and edge

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Issue Date
2020-05-01
Embargo End Date
Authors
Taylor, Mason
Advisor
Russell, F. Leland
Citation

Taylor, M. 2020. Variation in effect of insect herbivory on Platte thistle (Cirsium canescens) between biogeographic range center and edge -- In Proceedings: 16th Annual Symposium on Graduate Research and Scholarly Projects. Wichita, KS: Wichita State University, p.50

Abstract

INTRODUCTION: Insect herbivory can reduce plant fitness and population sizes, but the strength of these effects varies greatly in space. The position of a plant population within the plant species' biogeographic range is an unexplored hypothesis to explain spatial variation in herbivore effects on plants. The Abundant Center Hypothesis (ACH) states that conditions for a species will be poorer at the species' range edge than in the center and, hence, a species will be more abundant toward the range center, and scarcer toward the edge. These hypothesized changes in plant performance and abundance may have implications for the intensity of herbivore attack on plants and plants' abilities to recover from herbivory. Platte thistle (Cirsium canescens) is a monocarpic species whose range is centered in the Nebraska Sand Hills and reaches its western limit in south central Colorado. PURPOSE: This study addresses 1) How do Platte thistle rosette (juvenile thistle) survival, growth, transition to adulthood, and adult seed production differ between range edge and center? and 2) How do the effects of insect herbivory on adult seed production and seedling recruitment differ between range edge and center? METHODS: I address these questions using insect exclusion experiments on reproducing adult Platte thistles and demographic data collection on juvenile thistles at the southwestern range edge of Platte thistle in Colorado. I achieve the range edge -- range center comparison by evaluating overlap of 95% confidence intervals around range-edge and range-center parameter estimates. Range center parameter estimates are available in published literature. RESULTS: Preliminary analyses suggest a positive relationship between the size of juvenile Platte thistle and the likelihood of transition to a reproductive stage. At the southwestern range edge in Colorado, no significant effect of elevation on growth, survival, or transition to a reproductive stage occurred. CONCLUSION: Further data analyses are being performed to reveal any significant differences in effect of insect herbivory on Platte thistle seed production and seedling recruitment between range-edge and range-center.

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Description
Presented to the 16th Annual Symposium on Graduate Research and Scholarly Projects (GRASP) held online, Wichita State University, May 1, 2020.
Research completed in the Department of Biological Sciences, Fairmount College of Liberal Arts and Sciences
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