The establishment of non-native plant species in relation to climate and land use in Britain Alison Rosemary Jukes PhD University of York Department of Biology December 2013 1 Abstract Human transport of species around Earth has led to the intentional and accidental introduction of many species into new regions. Introduced species can have significant impacts outside their native ranges, with a range of positive and negative ecological effects on native biota, community productivity and nutrient cycling. Climate and land use are major determinants of non-native species distributions, with climate setting the broad limits to plant distribution and productivity, and with human activity associated with different land uses affecting the dispersal and success of introduced species. There is potential for future changes in land use and climate to have an impact on distributions of non-native species, due to possible changes to transport, establishment and spread. This thesis uses records of plant species in Britain to determine patterns of non-native species richness with climate and land use, predict possible changes with climate change, quantify establishment of non-native species and to examine levels of establishment for groups of non-native species with different traits (Plant Functional Types). Models were used to examine the relationship between species richness of non-natives and natives with climate variables and land cover types, and projected climate data was used to predict possible future changes. An establishment index was calculated to quantify establishment of non- native species; it was found that date of introduction and range size are not necessarily good predictors of level of establishment and that well established species are less likely to be associated with urban areas than poorly established species. Distributions and establishment of Plant Functional Types were examined, showing that some groups have distinct patterns with land cover related to where they are most likely to be introduced. The least established groups show greater associations with land cover than with climate. Climate and land use changes have the potential to allow new species to establish and to allow already established species to spread due to shifts or expansions in their potential climatic ranges. Future studies of non-native species should attempt to distinguish between time since arrival and the level of establishment because the two may not be associated. 2 Contents Abstract....................................................................................................................................2 Table of contents.....................................................................................................................3 List of figures............................................................................................................................6 List of tables...........................................................................................................................11 Acknowledgements...............................................................................................................13 Declaration.............................................................................................................................14 Chapter 1: General introduction.....................................................................................15 1.1 Rationale.............................................................................................................15 1.2 Non-native plant species.....................................................................................17 1.3 Pathways of introduction....................................................................................21 1.4 Establishment of non-native plant species.........................................................23 1.5 Climate and land use...........................................................................................30 1.6 Plant Functional Types .......................................................................................34 1.7 Theoretical framework…………………………………………………………………………………….35 1.8 Thesis overview...................................................................................................37 Chapter 2: Materials and methods.................................................................................40 2.1 Data.....................................................................................................................40 2.1.1 Botanical data.....................................................................................40 2.1.2 Climate data........................................................................................46 2.1.3 Land use data......................................................................................46 2.1.4 Projected data.....................................................................................48 2.2 Analyses..............................................................................................................49 2.2.1 Species’ distribution modelling...........................................................49 2.2.2 Selection of statistical techiniques......................................................52 Chapter 3: Non-native plant species richness in relation to climate and land use............55 3.1 Abstract...............................................................................................................55 3.2 Introduction........................................................................................................56 3 3.3 Methods..............................................................................................................59 3.3.1 Data.....................................................................................................59 3.3.2 Analyses..............................................................................................60 3.4 Results.................................................................................................................64 3.4.1 Patterns of non-native species richness with climate and land use...64 3.4.2 Modelling species richness.................................................................68 3.4.3 Recorder effort...................................................................................78 3.4.4 Importance of climate and land use variables....................................86 3.4.5 Predicted changes using projected climate data................................89 3.5 Discussion...........................................................................................................98 3.5.1 Patterns of non-native species richness with climate and land use...98 3.5.2 Importance of urban land cover.........................................................99 3.5.3 Predicting distributions using models...............................................101 3.5.4 Changes in species richness with projected climate data.................102 3.5.5 Recorder effort.................................................................................103 3.5.6 Implications and conclusions............................................................104 Chapter 4: Establishment of non-native plant species ...................................................105 4.1 Abstract.............................................................................................................105 4.2 Introduction......................................................................................................106 4.3 Methods............................................................................................................109 4.3.1 Data...................................................................................................109 4.3.2 Calculation of an establishment index..............................................111 4.3.3 Analyses............................................................................................112 4.4 Results...............................................................................................................114 4.4.1 Relationship between time since introduction and establishment..114 4.4.2 Relationship between range size and establishment........................118 4.4.3 Modelling species with different levels of establishment................120 4.4.4 Establishment with climate and land use.........................................123 4.5 Discussion.........................................................................................................126 4.5.1 Time since introduction, range size and establishment....................126 4.5.2 Predicting distributions using models...............................................127 4.5.3 Establishment with climate and land use.........................................128 4.5.4 Implications and conclusions............................................................129 4 Chapter 5: Distribution and establishment of Plant Functional Types............................131 5.1 Abstract.............................................................................................................131 5.2 Introduction......................................................................................................132 5.3 Methods............................................................................................................135 5.3.1 Data...................................................................................................135