Changes to plant distributions in Britain Alexandra Katherine Bell PhD University of York Biology June 2015 Abstract Species distributions always have and will change, and there are a number of controlling factors involved in their overall distribution. Climate is considered one of the strongest drivers of changes to species distributions, and due to historical climate change, has played an important part in current species distributions. A large number of species have changed their distributions in the past century, which can largely be attributed to current anthropogenic climate change. This study uses the Botanical Society of Britain and Ireland (BSBI) vascular plant database to explore changes which are occurring to native plant species distributions in Britain. Studies are carried out to assess how and where plant species distributions are changing. Initially the northern range margin of southerly distributed native plant species were used to determine if there was a poleward shift as would be expected with a warming climate. Results show that, unlike animal species which have advanced north, plant species are not advancing towards the pole and a large number are in fact retracting at their northern edge. This is a clear indication that although the climate is changing, other factors are having a stronger influence on many plant species distributions in Britain. As it is known historically that plant species will follow climate change it is likely that human disturbance such as agricultural intensification and urbanisation are stronger drivers of distribution changes in Britain. Natural dispersal mechanisms are no longer facilitating spread in a large number of species due to these barriers. However, human mediated dispersal may become the main disperser in the future by carrying seeds beyond their natural range. There is however evidence that Bee orchids (Ophrys apifera Huds.), a species which is wind dispersed, with seeds carried on currents due to the dust like seeds, are successful in spreading and have in recent years been occurring in a broader range of habitats to where they are considered to traditionally occur. This is likely to be an example of a species that is benefiting from the warmer climate and has facilitated its spread into previously un-colonised areas. Therefore I conclude that at present the majority of species distributions used in this study have not responded to climate as expected due to other anthropogenic factors, however humans may become the most important disperser, facilitating species spread into new locations and some species may start to infill in their range and spread by natural means if propagules are easily dispersed long distances. 2 Table of contents Abstract 2 Table of contents 3 List of Figures 6 List of Tables 10 Acknowledgements 12 Declaration 13 1. General Introduction 14 1.1. Environmental change 14 1.1.1. Climate change 15 1.1.1.1. Historic climate change 15 1.1.1.2. Current/anthropogenic and future climate change 16 1.1.1.3. British climate and climate change 20 1.1.2. Anthropogenic Environmental impacts on plants 21 1.1.2.1. Phenology 22 1.1.2.2. Distribution change 23 1.1.2.2.1. Historical distribution change 25 1.1.2.2.2. Latitudinal range shift (north shift) 27 1.1.2.2.3. Altitudinal shift 28 1.1.2.2.4. Alpine flora 29 1.1.2.2.5. Treelines 30 1.1.2.2.6. Distribution infilling 31 1.1.2.3. Increased CO2 and global warming 32 1.1.2.4. Nitrogen deposition affects on plants and interactions with sulphur 34 1.1.2.5. Habitat loss and fragmentation 36 1.1.2.6. Habitat invasion and invasive species 37 1.2. Extinction of species 39 1.3. Conservation and biodiversity loss 40 1.4. Plant life history 42 1.4.1. Habitats and geology 43 1.4.1.1. Ellenberg indicator values 44 1.4.1.2. Functional groups 44 1.4.2. Plant dispersal 45 1.5. Plant collectors and plant distribution data 48 1.5.1. Botanical Society of Britain and Ireland and plant distribution data 48 1.6. Knowledge gaps and objectives 49 1.6.1. Chapter 2: Northern range margin shift and how humans have impacted on dispersal 49 1.6.1.1. Aims and hypothesis 50 1.6.2. Chapter 3: Chapter 3: Distribution infilling and habitat change: a case study using the Bee Orchid Ophrys apifera 51 1.6.2.1. Aims and hypothesis 51 2. Northern range margin change 52 3 2.1. Abstract 52 2.2. Introduction 52 2.3. Aims 55 2.4. Method 56 2.4.1. Northern range margin shift 56 2.4.2. Data filtering and date classes 57 2.4.3. Calculating the northern range margin 62 2.4.4. Phylogenetic influences 62 2.4.5. Accounting for recorder effort 63 2.4.6. Ellenberg values 64 2.4.7. Dispersal 65 2.4.8. Persistence 66 2.5. Results 67 2.5.1. Northern range margin shift 67 2.5.2. Phylogenetic influences 70 2.5.3. Comparison of native only records and incorporation of introduced records 71 2.5.4. Comparing northern range margin shift with change in range size 74 2.5.5. Taxa trait data, Ellenberg values 76 2.5.6. Taxa trait data, dispersal 78 2.5.7. Persistence 81 2.6. Discussion 85 2.6.1. Northern range margin shift 85 2.6.2. Ellenberg values 87 2.6.3. Dispersal 89 2.6.4. Persistence 89 2.7. Conclusion 90 3. Habitat change, distribution infilling and Bee orchids 114 3.1. Abstract 114 3.2. Introduction 114 3.2.1. Niche shift 114 3.2.2. Ophrys apifera Huds. life history and background information 117 3.3. Aim 122 3.4. Method 123 3.4.1. 2011 Field Work: in site variation, comparisons between quadrats with and without Bee orchids 123 3.4.1.1. Field work 123 3.4.1.2. Statistical analysis 126 3.4.1.2.1. Detrended Correspondence Analysis 126 3.4.1.2.2. Logistic Regression 126 3.4.2. Underlying bedrock change in old and new sites using BSBI data 127 3.4.2.1. Classification of sites by age and underlying bedrock 127 3.4.2.2. Statistical analysis 129 3.4.3. 2012 Field work: Comparisons between new and old Bee orchids sites site habitat 129 3.4.3.1. Statistical analysis 132 3.4.3.1.1. Detrended Correspondence Analysis 132 3.4.3.1.2. Logistic Regression 132 4 3.5. Results 133 3.5.1. 2011 field work: Results 133 3.5.1.1. All quadrat analysis (without soil analysis data) 133 3.5.1.2. Analysis for subset of samples with soil sample data 137 3.5.2. Underlying bedrock data analysis 140 3.5.3. Results for 2012 field work: comparing old and new Bee orchid habitat 145 3.6. Discussion 155 3.6.1. 2011 Field season 155 3.6.1.1. Without soil analysis 155 3.6.1.1.1. Field work 155 3.6.1.1.2. Analysis 156 3.6.2. Underlying bedrock analysis 156 3.6.3. 2012 Field season 158 3.7. Conclusion 160 4. General discussion 161 4.1. Overview of findings 161 4.2. Distribution changes 163 4.3. Dispersal 166 4.4. Human mediated dispersal 169 4.5. Habitat and environmental conditions 170 4.6. Climate and plants 170 4.7. Conservation implications 171 4.8. Synopsis and concluding remarks 174 Appendices Appendix I 175 Appendix II 180 Appendix III 192 Appendix IV 203 Appendix V 218 Appendix VI 227 Appendix VII 235 Abbreviations 237 References 238 5 List of Figures Figure 2.1: Distribution maps of Epilobium tetragonum. a) DC1 showing distribution after step 1 of data cleaning, b) DC1 showing distribution after step 2 of data cleaning, c) DC1 showing distribution after step 3 of data cleaning, d) DC1 showing distribution after step 4 of data cleaning, e) DC2 showing distribution after step 1 of data cleaning, f) DC2 showing distribution after step 2 of data cleaning, g) DC2 showing distribution after step 3 of data cleaning, h) DC2 showing distribution after step 4 of data cleaning, i) map of Epilobium tetragonum taken from New Atlas of the British and Irish flora (Preston et al. 2002) 60 Figure 2.2: Distribution maps of Lysimachia nummularia. a) DC1 showing distribution after step 1 of data cleaning, b) DC1 showing distribution after step 2 of data cleaning, c) DC1 showing distribution after step 3 of data cleaning, d) DC1 showing distribution after step 4 of data cleaning, e) DC2 showing distribution after step 1 of data cleaning, f) DC2 showing distribution after step 2 of data cleaning, g) DC2 showing distribution after step 3 of data cleaning, h) DC2 showing distribution after step 4 of data cleaning, i) map of Epilobium tetragonum taken from New Atlas of the British and Irish flora (Preston et al. 2002) 61 Figure 2.3: Maps showing 10x10 km squares with limited recorder effort: a) squares with <1 British species recorded in one or both of the date classes in blue (not Recorded squares), and b) squares with <10% of British species recorded in one or both of the date classes in green (not Well Recorded squares) 64 Figure 2.4: Scatter plots showing northern range margin (km north on UK Ordnance Survey grid) of taxa on the x and y axis, plotting results from recorded against well recorded squares for a) native only records for DC1, b) native only records for DC2, c) incorporating introduced records for DC1, d) incorporating introduced records for DC2.