Date of Award

Fall 2013

Degree Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Forestry and Natural Resources

First Advisor

Robert K. Swihart

Committee Chair

Robert K. Swihart

Committee Member 1

Jeffrey D. Holland

Committee Member 2

Michael R. Saunders

Committee Member 3

Michael A. Steele

Committee Member 4

Yssa D. DeWoody

Abstract

The metapopulation paradigm has emerged as an important tool to understand the dynamics of species living in fragmented landscapes. In this dissertation, I investigate the unpredictable nature of resource availability for species living in human-dominated heterogeneous and dynamic landscapes in the context of its consequences for long-term regional persistence of species. In particular, I test theoretical advancements in metapopulation ecology following a two-pronged approach - via experiments in the lab and observations in the field - using insects. In chapter 1, I introduce the concept of metapopulation ecology in the context of its relevance for dynamics of species living in fragmented landscapes and describe my objectives. In chapter 2, I investigate the main and interactive effects of resource availability (constant vs. diminishing), patch connectivity (low vs. high), and dynamics of patch configuration (static vs. dynamic) on landscape and patch level colonization, extinction and abundance of red flour beetles (Tribolium castaneum) as well as metapopulation stability. Patch connectivity and configuration interacted to influence beetle abundance and stability, with intermediate connectivity and patch dynamics leading to greater persistence. In chapter 3, I test predictions of a spatially realistic and temporally dynamic metapopulation model to assess and compare metapopulation capacity and persistence for red flour beetles in experimental landscapes differentiated by resource structure (homogeneous vs. heterogeneous), patch connectivity (high vs. low) and patch dynamics (fast vs. slow), but with the same background destruction rate. Once again, interactive effects predominated. Intermediate patch dynamics and connectivity, coupled with density-dependent emigration promoted persistence in heterogeneous landscapes. In chapter 4, I develop a characterization of northern red oak (Quercus rubra) and white oak (Q. alba) trees as resource patches for two generalist and one specialist species of acorn weevil (Curculio) and employ a Bayesian state space formulation of single-species multi-year dynamic occupancy modeling to examine the effect of niche breadth, forest structure and fragmentation on their patch occupancy and vital rates. The specialist species exhibited greater occupancy than generalists, but its less preferred host tree appeared to serve as a sink that created greater fluctuations in the specialist metapopulation than in those of the generalist species. Thus, generalists occurred on a lower proportion of usable trees but were buffered by access to more suitable patches and greater patch-specific survival. In Chapter 5, I extend the hierarchical modeling framework to develop multi-species multi-year dynamic occupancy models to estimate site-specific occupancy, survival and colonization of nine Curculio species on their primary host tree(s) species, particularly oaks and shagbark hickory (Carya ovata), and examine the effect of spatio-temporal variability in resource availability (mast) on the community level coexistence of these weevils. Local coexistence of weevil species appeared to be promoted by coupling of a spatial storage effect caused by differential host suitability and a temporal storage effect caused by prolonged diapause. Both storage effects were more pronounced for generalists. In chapter 6, I summarize the key findings of my investigation and briefly discuss their broader implications and future directions for research.

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