Invasive plants in the Turks and Caicos Islands By Chloe Hardman A thesis submitted in partial fulfilment of the requirements for the degree of Master of Science and the Diploma of Imperial College of London. September 2009 Table of Contents ITRODUCTIO........................................................................................................7 1.1 Invasive species: a threat to biodiversity .............................................................7 1.1.1 Biotic homogenisation ..................................................................................7 1.1.2 Extinctions ....................................................................................................7 1.2 Why are invasive species interesting to science? ................................................7 1.3 How can invasion science inform conservation?.................................................8 1.4 Policy responses.................................................................................................10 1.4.1 International ................................................................................................10 1.4.2 National.......................................................................................................11 1. 5 Why is research needed in TCI? .......................................................................11 1.6 Aims and objectives...........................................................................................12 1.7 Terminology.......................................................................................................13 1.8 Scope of the study..............................................................................................13 2. BACKGROUD IFORMATIO .....................................................................14 2.1 Impacts of invasive species................................................................................14 2.1.1 The focal species and their impacts ............................................................14 2.2 Quantifying the impact of invasive species .......................................................16 2.3 Predicting suitable habitat for invasive species using MaxEnt..........................18 2.4 Surveying resident awareness of invasive plants...............................................19 2.5 Study Area .........................................................................................................20 2.5.1 Overview.....................................................................................................20 2.5.2 Origins of the flora......................................................................................22 2.6 History of TCI....................................................................................................22 2.6.1 Overview.....................................................................................................22 2.6.2 Disturbance on each island .........................................................................23 2.7 Current political situation ..................................................................................23 2.8 Biodiversity threats and conservation work in TCI ...........................................23 2.8.1 Development...............................................................................................23 2.8.2 Climate Change...........................................................................................24 2.8.3 Current conservation in TCI .......................................................................24 3. METHODS .............................................................................................................24 3.1 Habitat preference data ......................................................................................24 3.1.1 Data Analysis..............................................................................................25 3.2 Impact of Casuarina equisetifolia on native plant communities.......................27 3.2.1 Data analysis:..............................................................................................28 3.3 Resident awareness survey ................................................................................28 3.3.1 Data analysis:..............................................................................................29 4. RESULTS ..............................................................................................................29 4.1 MaxEnt predictions of suitable habitat ..............................................................29 4.1.1 Cumulative maps ........................................................................................32 4.2 Influence of disturbance on presence of invasive plants ...................................36 4.3 Impact of Casuarina equisetifolia on native species richness...........................38 4.3.1 T-test on species richness............................................................................38 4.3.2 General Linear Model for factors affecting native species richness...........39 4.4 Binary maps showing suitable habitat of invasive and endemic plants.............42 4.5 Public awareness survey ....................................................................................43 4.6 Further non-native species observed..................................................................45 2 4.7 Additional outputs..............................................................................................46 5. DISCUSSIO.........................................................................................................47 5.1 Status of invasive plants in TCI.........................................................................47 5.2 Implications for conservation ............................................................................50 5.2.1 Control programs ........................................................................................50 5.2.2 Biosecurity..................................................................................................52 5.2.3 Habitat manipulation...................................................................................53 5.2.4 Improving public awareness .......................................................................53 5.3 Strengths and limitations of the study................................................................54 5.3.1 Strengths .....................................................................................................54 5.3.2 Limitations ..................................................................................................55 5.4 Future research...................................................................................................57 5.5 Conclusion .........................................................................................................58 6. REFERECES.......................................................................................................59 7. APPEDICES……………………………………………………………………68 Appendix 1: Background information and methods………………………………... 79 Appendix 2: Results …………………………………………………………………80 Appendix 3: Maps……………………………………………………………………90 Table of figures Figure 1: The invasion process and management strategies possible at each stage ......8 Figure 2: Map of the Northern Caribbean Region.........................................................1 Figure 3: Map of the Turks and Caicos Islands .............................................................1 Figure 4: Contributions of environmental predictors...................................................31 Figure 5: Contributions of environmental predictors without roads..............................1 Figure 6: Predicted suitable habitat for C. equisetifolia ..............................................33 Figure 7: Predicted suitable habitat for L. leucocephala .............................................34 Figure 8: Predicted suitable habitat for all five focal invasive plants .........................35 Figure 9: Number of presence and absence points in different disturbance levels......36 Figure 10: Box plot of native species richness in invaded and uninvaded plots .........38 Figure 11: Proportion of people who noticed an increase in each plant........................1 Figure 12: Concept diagram showing the “Extinction of experience” phenomenon...50 Table of tables Table 1: Human populations on the nine islands surveyed..........................................23 Table 2: Environmental variables used in MaxEnt......................................................26 Table 3: Number of presence points used for each species .........................................30 Table 4: Effect of disturbance on proportion of presence points.................................37 Table 5: Minimal adequate model for native species richness ....................................40 Table 6: Species found only in uninvaded plots .........................................................40 Table 7: Species only found in uninvaded plots ..........................................................41 Table 8: Species found in both uninvaded and invaded plots......................................41 Table 9: Non-native species with invasive potential observed in TCI ........................46 Table 10: Expected costs and benefits of invasive plant control.................................52 3 List of acronyms and abbreviations AUC: Area Under Receiver Operating Curve CBD: Convention on Biological Diversity DECR: