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Abstract Boundary Dynamics Across Habitat Edges ABSTRACT BOUNDARY DYNAMICS ACROSS HABITAT EDGES: EFFECTS ON BENEFICIAL INSECT SPECIES ABUNDANCE AND RICHNESS by Alyssa Whu Conservation practices, such as retaining forest habitat or planting field margins with flowering perennials, may enhance the abundance and diversity of beneficial insects by providing essential supplementary and complementary resources. The availability of resources influences the movements and distributions of beneficial insects across boundaries between crops and natural areas. In this study, I studied how crop and field-margin resources change the diversity and abundance of beneficial insects. Using experimental arrays of forage crops and field-margin strips planted along forest edges, I manipulated the resource quality of both forage crops and field margins. Combinations of field and margin plantings supported predictions from one or more hypotheses, but insect richness and abundance were generally higher in forage crops with higher habitat quality. My findings suggest that a greater understanding of the mechanisms driving consumer-resource interactions across natural habitat–crop boundaries is needed to guide conservation practices and enhance ecosystem services. BOUNDARY DYNAMICS ACROSS HABITAT EDGES: EFFECTS ON BENEFICIAL INSECT SPECIES ABUNDANCE AND RICHNESS A Thesis Submitted to the Faculty of Miami University in partial fulfillment of the requirements for the degree of Master of Science Department of Zoology by Alyssa-Kristine Whu Miami University Oxford, Ohio 2012 Advisor_______________________ Thomas O. Crist Reader_______________________ Ann Rypstra TABLE OF CONTENTS LIST OF TABLES ............................................................................................................................................. iii LIST OF FIGURES ........................................................................................................................................... iv ACKNOWLEDGEMENTS ............................................................................................................................... vii CHAPTER 1 – BACKGROUND AND CONCEPTUAL FRAMEWORK ................................................................... 1 INTRODUCTION ......................................................................................................................................... 1 A CONCEPTUAL FRAMEWORK .................................................................................................................. 3 CONCLUSION ............................................................................................................................................. 5 FIGURES ......................................................................................................................................................... 6 CHAPTER 2 – “Boundary Dynamics across Forest and Field Habitats: Effects on Species Richness, Abundance, and Composition of Insect Parasitoids, Pollinators and Predators.” ........................................ 8 INTRODUCTION ......................................................................................................................................... 8 METHODS ................................................................................................................................................ 10 RESULTS .................................................................................................................................................. 15 DISCUSSION ............................................................................................................................................. 18 TABLES ......................................................................................................................................................... 23 FIGURES ....................................................................................................................................................... 29 LITERATURE CITED ...................................................................................................................................... 47 Appendix 1: List of Coleoptera: Predators by family and species. ............................................................. 50 Appendix 2. List of Hymenoptera: Parasitoids by family and species. ....................................................... 51 Appendix 3: List Hymenoptera: Pollinators by family and species. ........................................................... 53 Appendix 4: List of Hymenoptera: Predators by family and species. ........................................................ 54 Appendix 5: List of Vegetation Sampled. ................................................................................................... 55 ii LIST OF TABLES Table 1. The best-fitting (lowest AIC) generalized linear mixed model of abundance for: (a) Coleoptera (Predators): distance, distance squared, margin type; (b) Hymenoptera (Parasitoids): distance, distance squared; (c) Hymenoptera (Pollinators): distance, distance squared; and (d) Hymenoptera (Predators): distance………………………………………………………………22 Table 2. The best-fitting (lowest AIC) generalized linear mixed model of richness for: (a) Coleoptera (Predators): distance, distance squared, margin type; (b) Hymenoptera (Parasitoids): distance, distance squared; (c) Hymenoptera (Pollinators): distance, distance squared; and (d) Hymenoptera (Predators): distance. ……………………………………………………………. 23 Table 3. The best-fitting (lowest AIC) generalized linear mixed model of abundance for: (a) Coleoptera (Chauliognathus pennsylvanicus): distance, and margin type; (b) Coleoptera (Photinus pyralis): distance, and margin type; (c) Hymenoptera (Figitidae sp1): margin type……………………………………………………………………………………………….24 Table 4. Ordination Statistics: Permutational Manova for ordinations using site and margin type for Vegetation Species. ………………………………………………………………………….25 Table 5. Ordination Statistics: Permutational Manova for ordinations using site, margin type and habitat (forest,edge,field) for Insect Species. ……………………………………………………26 Table 6. Summary of Findings ………….... ……………………………………………………27 iii LIST OF FIGURES Figure 1. A continuous response of species distributions across forest-field edges (left) predicts a null pattern of similar total abundance and richness (right) in forest, edge, and field habitats. ……………………………………………………………………………………………………..6 Figure 2. Patterns of species distributions (left) and total abundance and richness (right) predicted by the habitat specialization hypothesis. .........................................................................6 Figure 3. The pattern of insect species distributions in forest and high quality field habitats (left) predicts a correspondingly greater abundance in field habitat (right)……………………………7 Figure 4. Species that use complementary resources in forest and field are expected to occur along forest-field edges (left). Complementary resources use is predicted to have higher species abundance and richness along habitat edges (right), especially in enhanced margin plantings. ……………………………………………………………………………………………………..7 Figure 5. Study sites (1) Fitton property; (2) Ag Plot; (3) Fryman South; (4) Fryman North. ……………………………………………………………………………………………………28 Figure 6. Resource Quality of study sites: (1) High Quality- Fitton property; (2) High Quality - Ag Plot; (3) Low Quality - Fryman South; (4) Low Quality - Fryman North. .............................29 Figure 7. Resource Quality of study sites: (1) High Quality- Fitton property and Ag Plot ; (2) Low Quality - Fryman North and Fryman South. ……………………………………………….30 Figure 8. Flight intercept/ pan traps using Lexan™ panes inserted into the bucket, arranged perpendicularly to avoid directional wind influence. Flight intercept/pan traps were placed on a wooden stand slightly above the crop. …………………………………………………………..31 Figure 9. Insect sampling using flight-intercept/pan traps and flower visitation counts. ……………………………………………………………………………………………………32 iv Figure 10. Figure 9. Plot layout for sampling of forest vegetation for trees (20 x 20 m), shrubs (5 x 5 m) and herbs (1 x 1 m). species. ……………………………………………………………………………………………………33 Figure 11. Variation in percent cover of red clover with distance from forest edge at the four sites and plots with enhanced and unenhanced field margins. ……………………………………………………………………………………………………34 Figure 12. Variation in flower density in 1-m2 plots in plots within enhanced and unenhanced field margins at the Fitton and Ag field sites. …..………..………..………..…………………...35 Figure 13. Abundance of predatory Coleoptera by site and plots with enhanced and unenhanced field margins. Lines are predicted relationships from best-fitting general linear mixed models. ……………………………………………………………………………………………………36 Figure 14. Species richness of predatory Coleoptera by site. The effect of margin type was excluded from the best-fitting model. …………………………………….……………………..37 Figure 15. Abundance of hymenopteran parasitoids with respect to distance to forest edge at the four study sites and the two types of field margins. ……………………………………………………………………………………………………38 Figure 16. Species richness of hymenopteran parasitoids with respect to distance, plot, and margin type. The null model was the best-fitting model. distance by site. …..………………...39 Figure 17. Abundance of bees in relation to distance from forest edge and site. Abundances did not differ by field margin type. …………………………………………………..……………...40 Figure 18. Species richness of bees with respect to distance to forest-field
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