UBC Theses and Dissertations
Across intermediate spatial scales, a specialist insect herbivore responds to climate and host plant size, not host density West, Emily
Herbivory can have important consequences for plant-population dynamics, causing changes in population growth rate, abundance, local expansion, spread and even the evolution of life history and defense traits. Studies at large spatial scales such as latitudinal gradients spanning the equatorial region to the poles, have yielded broad generalizations in patterns of herbivory. At local population scales, the effects of herbivory are often context specific, limiting extrapolation. Less described in the literature is whether patterns of herbivory manifest in between these two disparate spatial scales. At intermediate, regional scales, my research indicates that patterns of herbivory that manifest in local populations are obscured. Within a regional study area, in the southern interior of British Columbia, I found Mecinus janthiniformis, a stem mining weevil, did not respond to host plant (Linaria dalmatica) density across sites, but rather to host size. At 36 of the 39 sites sampled, herbivores were found to distribute themselves according to host plant density within populations. The direction of this effect however varied by site, resulting in no pattern at the regional scale. In conjunction with earlier research, my results suggest plant populations experiencing herbivory in different spatial patterns (i.e. more herbivory in high or low density patches) may result in different outcomes for plant population spread and persistence over time.
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