The Pennsylvania State University The Graduate School Intercollege Graduate Degree Program in Ecology THE ROLE OF HABITAT HETEROGENEITY IN POPULATION DYNAMICS: FROM INDIVIDUAL BEHAVIOR TO METAPOPULATION STRUCTURE A Thesis in Ecology By Carrie A. Schwarz © 2006 Carrie A Schwarz Submitted in Partial Fulfillment of the Requirements for the Degree of Doctor of Philosophy May 2006 The thesis of Carrie A. Schwarz was reviewed and approved* by the following: Ottar N. Bjørnstad Associate Professor of Entomology Thesis Co-Advisor Co- Chair of the Committee Michael C. Saunders Professor of Entomology Thesis Co-Advisor Co-Chair of the Committee Donald D. Davis Professor of Plant Pathology Andrew Liebhold Adjunct Professor of Entomology Research Entomologist, Northeastern Research Station USDA Forest Service Katriona Shea Assistant Professor of Biology David Mortensen Professor of Weed Biology/Ecology Head of the Ecology IDGP *Signatures are on file in the Graduate School Abstract As human activities continue to fragment natural habitats, the need grows to be able to quantify the impacts of isolation and subdivision on population dynamics and life history strategies. Yet, most empirical and theoretical studies addressing life in a fragmented landscape leave out two sources of variation that can greatly impact predictions, results, and ultimately conservation and management decisions made. These two sources of variation are (a) variation in spatial heterogeneity experienced by different populations of the same species and (b) the inherent variation that exists between individuals making up a population. Using the forked fungus beetle, Bolitotherus cornutus, as my study organism, I looked at both empirically and theoretically the influence of habitat heterogeneity on forked fungus beetle populations from the level of life history evolution up to metapopulation dynamics. Life history traits and the role of spatial heterogeneity in the evolution of life history traits has been generally ignored, especially the influence of life history evolution on population and metapopulation dynamics. The role of habitat patch heterogeneity on diet breadth and dispersal decisions was addressed both theoretically through the development of a dynamic state variable model, as well as empirically through the large capture mark recapture study conducted in a single host species landscape and a two host species landscape. This large data set was also used to address questions related to the maintenance of multiple male mating strategies as a function of metapopulation structure and demographic stochasticity, as well as how synchrony differs between these two landscapes. I found that for all of the questions addressed in the chapters of my thesis, habitat patch heterogeneity in the form iii of host species greatly influences the outcomes of life history traits such as dispersal, oviposition decisions, as well as mating strategies and dispersal. iv Table of Contents List of Figures……………………………………………………………………………vii List of Tables……………………………………………………………………………viii Acknowledgements……………………………………………………………………….ix Chapter 1: Introduction: Metapopulation and Spatial Ecology in General: Moving Beyond Just Numerical Response in Population Dynamics……………………..1 I. Literature Cited………………………………………………………………………...13 Chapter 2: The Landscape Ecology of Host Choice in Phytophagous Insects I. Abstract………………………………………………………………………………..18 II. Introduction…………………………………………………………………………...19 III. The Model…………………………………………………………………………...23 IV. Results……………………………………………………………………………….27 V. Discussion……………………………………………………………………….……29 VI. Literature Cited……………………………………………………………………....34 VII. Tables and Figures………………………………………………………………….37 Chapter 3: Maintenance of Alternative Male Mating Strategies in a Single Host Species and Two- Host Species Metapopulation I. Abstract………………………………………………………………………………..41 II. Introduction…………………………………………………………………………...42 III. Methods……………………………………………………………………………...46 IV. Results……………………………………………………………………………….49 V. Discussion…………………………………………………………………………….54 VI. Literature Cited……………………………………………………………………....58 VII. Tables and Figures……………………………………………………….…………61 Chapter 4: The Role of Habitat Structure in Population Synchrony: A Comparison between a Single Host- Species and a Two Host-Species Metapopulation I. Abstract………………………………………………………………………………..66 II. Introduction………………………………………………………………………….. 68 III. Methods…………………………………………………………………………….. 72 IV. Results…………………………………………………………………….. ………..75 V. Discussion………………………………………………………………….…………80 VI. Literature Cited………………………………………………………………………84 VII. Tables and Figures……………………………………………………….…………86 Chapter 5: Dispersal and Patch Connectivity as a Function of Habitat Heterogeneity and Habitat Patch Size in Metapopulations I. Abstract………………………………………………………………………………..91 II. Introduction…………………………………………………………………………...93 III. Methods……………………………………………………………………………...95 IV. Results…………………………………………………………………….…………98 v V. Discussion…………………………………………………………………………..105 VI. Literature Cited………………………………………………………………….....110 VII. Tables and Figures………………………………………………………………...113 Appendix A: Code for Chapter 2 Model……………………………………………....114 vi List of Figures Figure 2-1. Plots of annual host quality decay curves used in the SDP model………….37 Figure 2-2. Host quality and proportion of hosts in the landscape impact breadth of host use………………………………………………………………………………..38 Figure 2-3. Host quality and proportion of hosts in the landscape impact dispersal decisions………………………………………………………………………………….39 Figure 3-1. Boxplot of the proportion of large horned and small horned males as a function of the number of females present in a local population………………………...61 Figure 3-2. Histogram of the range of local population sizes observed during the two year study period…………………………………………………………………………62 Figure 3-3. Boxplots of the proportion of large horned and small horned males as a function of julian date……………………………………………………………………63 Figure 3-4. Plots of large horned male, small horned male, and female recruitment rates as a function of time………………………………………………………………………………………64 Figure 4-1. Spline correlograms for sites R and S and for the two host species in site S………………………….…………………………………………………………..86 Figure 4-2. Plots of mean regional synchrony and 95% confidence intervals for site R, site S, and between sites R & S…………………………………………………..87 Figure 4-3. Plots of mean synchrony and 95% confidence intervals as a function of population size………………………………………………………………………...88 Figure 4-4: Recruitment rates of three sex categories over two year field season……...89 Figure 5-1. Plots of dispersal patterns between two host species in site S…………….113 Figure 5-2. Plots of dispersal patterns between two host species in site S broken down into the categories of females, all males, large horned males only, and small horned males only………………………………………………………………………………114 Figure 5-3. Histograms of dispersal distances…………………………………………115 Figure 5-4. Scatter plots of the effect of patch size on immigration and emigration…..116 Figure 5-5. Correlations between the number of patches and individual patch vii contributes dispersers to and the number of patches that individual patch receives dispersers from………………………………………………………………………….117 viii List of Tables Table 2-1. List of SDP model parameters………………………………………………40 Table 3-1. Recruitment model rankings for site R and site S…………………………...65 Table 4-1. Regional synchrony estimates and confidence intervals…………………….90 Table 5-1. Summary information on the number of beetles marked, sex, and dispersal………………………………………………………………………………...118 Table 5-2. Chi square values for dispersal between two host types……………………119 Table 5-3. Summary information on dispersal distance of forked fungus beetles at site R and site S…………………………………………………………………………120 Table 5-4. Summary table of linear regressions of the effect of patch size on immigration and emigration…………………………………………………………….121 Table 5-5. Summary table of the number of local populations that donate individuals to a single local population and the number of local populations that dispersers from a single population join…………………………………………………………………122 Table 5-6. Summary table of linear regressions of the correlation between the number of populations contributing dispersers to a single population and the number of populations a single population contributes dispersers to………………………………123 ix Acknowledgments I would like to thank my committee members, Ottar Bjørnstad, Michael Saunders, Donald Davis, Andrew Liebhold, and Katriona Shea for their support and assistance throughout my tenure as a Ph.D. student in Ecology. I am very thankful for the support given to me by my co-advisors, Ottar Bjørnstad and Michael Saunders. Both provided me with wonderful scientific advice and were wonderful mentors throughout my studies. I wish to thank Katriona Shea for her help and input on my research, especially on the model presented in the second chapter of my thesis. Her knowledge of stochastic dynamic programming and its applications to questions of interest in my own research was invaluable. I would like to thank all of the wonderful undergraduate students who worked with me during the summers in my field sites. Without their help and dedication the large amounts of data on which most of my research and analyses are based would not logistically have been able to be collected. Thank you so much: Mike Allen, Kris Orndorff, Erin Fleischer, Alexandria Reichart, Sara Vanlandingham, and Michelle McGregor. I would also like to extend a big thank