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theses

Temperature dependency of consumer–resource interactions is of fundamental importance for understanding and predicting the responses of food webs to climate change. Previous studies have shown temperature-driven shifts in herbivore consumption rates and resource preference resulting from differences in resource nutrient content, but little is known about the role of nutrition in temperature-driven shifts in predator-prey interactions. I performed a laboratory experiment to study the effects of increased temperatures and prey macronutrient content (lipid dense or protein dense) on interaction strengths and predator nutrition using wolf spiders (Pardosa sp) as study model. Additionally, I tested the effects of local thermal adaptation or acclimatization on predator nutritional demands using a field reciprocal transplant experiment between low (26°C) and high (15°C) elevations using two common spider species (Leucauge sp and Cyclosa sp) present along the elevation gradient. Spider feeding rates increased with warmer temperatures, but feeding responses differed depending on prey macronutrient content. Spiders fed lipid dense prey showed a sharp, rapidly saturating increase in feeding rates while those fed protein dense prey showed more gradual increases with increasing temperature. My transplant experiment revealed that populations from Leucauge sp and Cyclosa sp consistently showed higher prey mass consumption at the low elevation/warmer site than their counterparts from a high elevation/cooler site. The strong elevation differences on prey mass consumption are consistent with acclimatization responses to contrasting thermal environments. Overall, rising temperatures affected predator-prey interactions by increasing the strength of interactions and the demands of both, energy and protein by predators. Further, my findings suggest that spiders are able to increase their feeding rates and prey mass consumption in response to temperature changes over a short time period, which might represent important buffers against climate change.

ETD_9017

M.S.

Includes bibliographical references

by Ryan Walker

doi:10.7282/T30005DJ

ETD graduate

The author owns the copyright to this work.