Date of Award:

8-2021

Document Type:

Thesis

Degree Name:

Master of Science (MS)

Department:

Mathematics and Statistics

Committee Chair(s)

James Powell

Committee

James Powell

Committee

Barbara Bentz

Committee

John Stevens

Abstract

The mountain pine beetle (MPB, Dendroctonus ponderosae Hopkins) attacks living Pinus trees across a widespread area of western North America, causing significant ecological and economic damage. The ability to make accurate predictions of how MPB populations across this range will respond to temperatures, which affect MPB progress through life stages, is essential. Northern and southern populations of MPB are genetically different in response to temperature, requiring geographic-specific model parameters. There is not currently a predictive model for the southern MPB life cycle, despite concerns that those populations may be more susceptible to increased numbers of generations per year, which would have devastating impacts on pine forests. In this thesis I develop a novel oviposition model for populations of southern MPB, which I incorporate into a cohort model that allows estimation of previously unknown development rates for the southern MPB teneral adult stage, resulting in a complete southern MPB life cycle model.

In Chapter 2 I develop a predictive oviposition model for a southern population of mountain pine beetle using the oviposition (egg-laying) rate curve developed by McManis et al. (2019), incorporating variation in both oviposition rate and fecundity. I also introduce a method for determining the time delay before oviposition, t0. The model can return the probability of oviposition for a season of MPB attacks using phloem (inner-bark) temperature and adult MPB attack data collected from the field. I also develop an asymptotic approximation of MPB oviposition that is less complex as well as less computationally taxing. The detailed oviposition model and its asymptotic approximation are compared with other previously used modeling methods. The predictive capacity of each model is evaluated against laboratory data collected on southern MPB oviposition.

McManis et al. (2018) parameterized development from eggs through pupation for a southern MPB population, but were unable to procure developmental data for the difficult-to-observe teneral adult stage. In Chapter 3 I determine developmental rates for the teneral adult stage using a phenology model and the field data for a southern population of MPB.I first present the incorporated models as well as teneral adult rate curves tested while developing the model. Then I explain the method by which the teneral adult rate curves were parameterized and how the Brière curve was determined to be most suitable. The resulting model is validated using an additional tree from the field data. The complete model is then used to examine the potential for bivoltinism in a southern population of MPB by increasing the mean temperature and testing for the successful emergence of a second generation. My model estimates that that southern MPB are unlikely to become bivoltine in warmer temperatures due to upper developmental thresholds of teneral adults.

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