The influence of soil disturbance on seed dispersal by ants in roadside environments - southern NSW, Australia Zsofia Palfi BSc (MSc), Babes-Bolyai University A thesis submitted in fulfilment of the requirements for the degree of Doctor of Philosophy Charles Sturt University Faculty of Science School of Environmental Sciences Albury, NSW 2640 Australia June 2017 ii Table of Contents Table of Contents .................................................................................................... iii List of Figures ......................................................................................................... vii List of Tables ............................................................................................................ ix Certificate of Authorship .......................................................................................... xi Acknowledgements ............................................................................................... xiii Abstract .................................................................................................................. xv Chapter 1 : Introduction .......................................................................................... 17 1.1 Seed dispersal ....................................................................................................... 19 1.2 Seed dispersal by ants ........................................................................................... 21 1.2.1 Benefits gained through myrmecochory ....................................................... 22 1.2.2 The fate of ant-dispersed seeds ..................................................................... 24 1.2.3 Habitat disturbance effects on myrmecochory ............................................. 26 1.3 Thesis overview ..................................................................................................... 28 1.3.1 Thesis chapter style ........................................................................................ 29 1.3.2 Research outputs from the thesis .................................................................. 30 Chapter 2 : Research methodology.......................................................................... 33 2.1 Study area: Lockhart Shire .................................................................................... 35 2.1.1 Roadside environments – study context ....................................................... 36 2.1.2 Acacia pycnantha Benth. – a common myrmecochorous plant .................... 37 2.1.3 Roadside sites selection criteria ..................................................................... 38 2.1.4 Collecting seeds for ant sampling .................................................................. 41 2.1.5 ‘Cafeteria’ style experiment ........................................................................... 41 iii Chapter 3 : Soil disturbance effects on the composition of seed-dispersing ants in roadside environments .......................................................................................... 45 3.1 Introduction .......................................................................................................... 48 3.2 Methods ................................................................................................................ 51 3.2.1 Composition of seed-dispersing ants ............................................................. 51 3.2.2 Sampling vegetation characteristics .............................................................. 52 3.2.3 Statistical analyses ......................................................................................... 52 3.3 Results ................................................................................................................... 55 3.3.1 Species richness of seed-dispersing ants ....................................................... 55 3.3.2 Individual species analyses ............................................................................ 58 3.3.3 Functional group composition ....................................................................... 60 3.3.4 Habitat characteristics ................................................................................... 64 3.4 Discussion .............................................................................................................. 66 3.4.1 Disturbance effects on seed-dispersing ant species ...................................... 67 3.4.2 Individual species abundance patterns ......................................................... 69 3.4.3 Functional group approach to understand ant composition ......................... 72 3.4.4 Conclusion ...................................................................................................... 74 Chapter 4 : The influence of soil disturbance on ant-seed interactions in roadside environments ......................................................................................................... 77 4.1 Introduction .......................................................................................................... 80 4.2 Methods ................................................................................................................ 83 4.2.1 Exclusion experiment - seed removal by ants vs. vertebrates ...................... 83 4.2.2 Ant-seed interactions ..................................................................................... 85 4.2.3 Data analyses ................................................................................................. 86 4.3 Results ................................................................................................................... 89 4.3.1 The exclusion experiment .............................................................................. 89 4.3.2 Seed removal rates ........................................................................................ 90 iv 4.3.3 Ant-seed interactions ..................................................................................... 92 4.4 Discussion .............................................................................................................. 97 4.4.1 Seed removal by ants vs. vertebrates ............................................................ 97 4.4.2 Ant-seed interactions ..................................................................................... 98 4.4.3 Conclusion .................................................................................................... 103 Chapter 5 : Seed dispersal mechanism by ants in roadside environments .............. 105 5.1 Introduction ........................................................................................................ 108 5.2 Methods .............................................................................................................. 111 5.2.1 Seed dispersal distances .............................................................................. 111 5.2.2 Secondary seed dispersal events - relocation distances from ant nest entrances ............................................................................................................... 112 5.2.3 Data analyses ............................................................................................... 113 5.3 Results ................................................................................................................. 115 5.3.1 Dispersal distances in relation to anthropogenic soil disturbance .............. 115 5.3.2 Frequency of seed dispersal events ............................................................. 120 5.3.3 Secondary dispersal distances from nests ................................................... 124 5.4 Discussion ............................................................................................................ 125 5.4.1 Benefits of soil disturbance to large bodied ants ....................................... 126 5.4.2 I. purpureus activity in roadside environments ........................................... 128 5.4.3 Conclusion .................................................................................................... 130 Chapter 6 : Synthesis of the results ....................................................................... 133 6.1 Directions for future studies ............................................................................... 140 6.2 General conclusion .............................................................................................. 143 Appendices ........................................................................................................... 145 References ........................................................................................................... 149 v vi List of Figures Figure 2.1. Lockhart Shire in southern New south Wales. .............................................. 35 Figure 2.2. Distribution of Acacia pycnantha on road sections in the Lockhart Shire, as surveyed by Spooner et al. (2004) (adapted from Spooner 2005c). .............................. 38 Figure 2.3. Typical minor rural road of varying roadside width, wide (top) and narrow (bottom) with remnant Eucalyptus trees, in the Lockhart Shire study area. ................. 39 Figure 2.4. Location of the study sites (n = 24) in the Lockhart Shire council, NSW, Australia. Minor roads are omitted for clarity. (Source of map: Spatial Data Analysis (SPAN), Charles Sturt University, https://six.nsw.gov.au/). ..........................................