Multi-Scale Patterns of Ground-Dwelling Spider (Araneae) Diversity in Northern Canada
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Multi-scale patterns of ground-dwelling spider (Araneae) diversity in northern Canada Department of Natural Resource Sciences McGill University Montréal, Québec, Canada April 2013 A thesis submitted to the Faculty of Graduate Studies and Research in partial fulfillment of the requirements for the degree of Master in Science © Sarah Loboda 2013 TABLE OF CONTENTS LIST OF TABLES ....................................................................................... iii LIST OF FIGURES ...................................................................................... iv LIST OF APPENDICES ............................................................................... vi ACKNOWLEDGMENTS ........................................................................... vii PREFACE AND CONTRIBUTION OF AUTHORS .................................. ix ABSTRACT / RÉSUMÉ ............................................................................... x CHAPTER 1: GENERAL INTRODUCTION, LITERATURE REVIEW AND OBJECTIVES ..................................................................................... 1 General introduction ................................................................................... 1 Patterns and spatial scale ............................................................................ 2 Diversity partitioning ................................................................................. 4 Patterns in arthropod diversity ................................................................... 6 Arctic arthropods ........................................................................................ 7 Spiders as model taxon ............................................................................... 9 Objectives ................................................................................................. 11 Literature cited ......................................................................................... 12 CHAPTER 2: MULTI-SCALE PATTERNS OF GROUND-DWELLING SPIDER (ARANEAE) DIVERSITY IN NORTHERN CANADA ........ 23 Abstract .................................................................................................... 24 Introduction .............................................................................................. 25 Methods .................................................................................................... 27 Sampling design ........................................................................... 27 i Environmental variables ............................................................... 29 Vegetation ............................................................................ 29 Climate ................................................................................. 30 Statistical analyses ........................................................................ 30 Spatial variation in spider assemblage structure ................. 30 Comparison of composition ................................................ 31 Multi-scale patterns of α and β diversities ........................... 31 Vegetation and climate ........................................................ 32 Results ...................................................................................................... 33 Multi-scale patterns of spider diversity ........................................ 33 Multi-scale patterns of the dominant families .............................. 35 Climate and vegetation ................................................................. 36 Discussion ................................................................................................ 37 Diversity patterns at the continental scale .................................... 38 Diversity patterns at the regional scale ......................................... 39 Diversity patterns at the local scale .............................................. 40 Diversity patterns of the dominant families ................................. 41 Vegetation and climate ................................................................. 42 Conclusion ................................................................................................ 43 Acknowledgments .................................................................................... 44 Literature cited ......................................................................................... 45 CHAPTER 3: GENERAL CONCLUSIONS AND FUTURE WORK 81 Literature cited ......................................................................................... 83 ii LIST OF TABLES Table 1. Observed (SRobs) and estimated total species richness (Chao1 and Jack1 ± confidence interval) of ground-dwelling spiders (Araneae) per site of the three ecoclimatic regions. Completeness=SRobs/Jack1*100. Ecoclimatic regions: A=Arctic, S=Subarctic, NB=North-Boreal. Sites: HA=Hazen Lake, NU; IQ=Iqaluit, NU; CB=Cambridge Bay, NU; BA=Banks Island, NU; CH=Churchill, MB; SC=Schefferville, QC; TO=Tombstone mountains, YT; KU=Kugluktuk, NU; GB=Goose Bay, LB; MO=Moosonee, ON; YE=Yellowknife, NT and NW=Norman Wells, NT........................................................................................55 iii LIST OF FIGURES Figure 1. Individual-based rarefaction curves of the species richness of ground- dwelling spiders in three ecoclimatic regions (Arctic, Subarctic and North- Boreal), in northern Canada...................................................................................56 Figure 2. Abundance and diversity of ground dwelling spider families in twelve sites of northern Canada, sampled in 2010 and 2011. For each site, the abbreviation of the name, the number of species, a pie graph of the diversity by family and a bar graph with the relative abundance of the two most common families of spiders is given. Sites: HA=Hazen Lake, NU; IQ=Iqaluit, NU; CB=Cambridge Bay, NU; BA=Banks Island, NU; CH=Churchill, MB; SC=Schefferville, QC; TO=Tombstone mountains, YT; KU=Kugluktuk, NU; GB=Goose Bay, LB; MO=Moosonee, ON; YE=Yellowknife, NT and NW=Norman Wells, NT........................................................................................57 Figure 3. Non-metric multidimensional scaling (NMDS) ordination of spider species composition of 72 replicates, described by the relative abundance of 306 spider species. Although all sites were included in the same ordination in a and b, in the upper right plot b, inverse triangle represent western sites and dark circles represent eastern sites. Western sites (c; 176 spider species) and eastern sites (d; 200 spider species) were then plotted separately with site names to ease interpretation. Ellipses depict ecoclimatic regions in plot.....................................58 Figure 4. Percentage of continental diversity (γ=306 species) and Shannon diversity explained by α and β components. Observed species diversity was partitioned for the most diverse family of spiders, the Linyphiidae (169 species), and for the most abundant family of spiders, the Lycosidae (32 species). Gamma diversity was partitioned into mean diversity within trap (α1), between traps (β1), between replicates (β2), between sites (β3) and between ecoclimatic regions (β4). Asterisk indicates that the observed diversity at a level is significantly different than random expectations (***: significantly higher than expected (P<0.01), **: iv significantly higher than expected (P<0.05) and *: significantly lower than expected (P>0.9))...................................................................................................59 Figure 5. Percentage of spider species richness (306 species) and Shannon diversity explained by α and β components within each ecoclimatic region: Arctic (γ=37 species), Subarctic (γ=170 species) and North-Boreal (γ=231 species). Regional diversity was partitioned into mean diversity within trap (α1), between traps (β1), between replicates (β2) and between sites (β3). Asterisk indicates that the observed diversity at a level is significantly different than random expectations (***: significantly higher than expected (P<0.01), **: significantly higher than expected (P<0.05) and *: significantly lower than expected (P>0.9))..................................................................................................................60 Figure 6. RDA biplot of the Hellinger-transformed spider data constrained by environmental variables, scaling 2, for the a) entire community, b) the Arctic ecoclimatic region, c ) the Subarctic ecoclimatic region and d) the North-Boreal ecoclimatic region. Environmental variables selected by the forward selection: gramcov=cover of graminoids, moscov=cover of mosses, lichcov=cover of lichens, forbcov=cover of forbs, maxveght=maximum vegetation height, long=longitude, sd.pd= standard deviation of active layer’ depth, mean.pd= average depth of active layer, maxT= maximum temperature of the warmest month of the site, DJA0= degree days above zero at the site, DJB0= degree day below zero at the site, AP= annual precipitation...................................................61 v LIST OF APPENDICES Appendix 1. Location of the Northern Biodiversity Program study sites in northern Canada and relationship between hierarchical nested design and diversity partitioning components.........................................................................................62 Appendix 2. Table of sampling dates, spatial and environmental variables per site. Sites: HA=Hazen Lake, NU; IQ=Iqaluit, NU; CB=Cambridge Bay, NU; BA=Banks Island, NU; CH=Churchill, MB; SC=Schefferville,