View metadata, citation and similar papers at core.ac.uk brought to you by CORE provided by Lincoln University Research Archive Ecology of the naturalisation and geographic distribution of the non-indigenous seed plant species of New Zealand. A thesis submitted in partial fulfilment of the requirements for the Degree of Doctor of Philosophy at Lincoln University by Hazel A. W. Gatehouse Lincoln University 2008 ii iv Abstract of a thesis submitted in partial fulfilment of the requirements for the Degree of Ph.D. Ecology of the naturalisation and geographic distribution of the non- indigenous seed plant species of New Zealand. by Hazel A. W. Gatehouse The naturalisation and subsequent spread of non-indigenous plant species (NIPS) is a major problem for most regions of the world. Managing plant invasions requires greater understanding of factors that determine initial naturalisation and distribution of wild NIPS. By the year 2000, 2252 NIPS were recorded as wild (1773 fully naturalised and 479 casual) in New Zealand. From published literature and electronic herbaria records, I recorded year of discovery of wild populations, and regional distribution of these wild NIPS. I also recorded species related attributes hypothesised to affect naturalisation and/or distribution, including global trade, human activities, native range and biological data; and regional attributes hypothesised to affect distribution, including human population densities, land use/cover, and environmental data. I used interval-censored time-to-event analyses to estimate year of naturalisation from discovery records, then analysed the importance of historical, human activity, biogeographical and biological attributes in determining patterns of naturalisation. Typically, NIPS that naturalised earlier were herbaceous, utilitarian species that were also accidentally introduced and/or distributed, with a wide native range that included Eurasia, naturalised elsewhere, with a native congener in New Zealand. In the year 2000, 28% of wild NIPS occupied only one region, 18% occupied two regions, decreasing incrementally to 2.5 % for nine regions, but with 13.5% occupying all ten regions. I used generalised linear models (GLMs) with binomial distribution to determine predictors of whether a wild NIPS occupied ten regions or not, and GLMs with Poisson distribution for wild NIPS occupying 0 – 9 regions. As expected, the dominant effect was that species discovered earlier occupied more v regions. Utilitarian wild NIPS that were also accidentally introduced and/or distributed, and wild NIPS with a native congener tended to be more widely distributed, but results for other attributes varied between datasets. Although numbers of wild NIPS recorded in regions of New Zealand were sometimes similar, composition of wild NIPS was often very different. I used nonmetric multidimensional scaling (NMDS) to determine dissimilarity in composition between regions. Then, after reducing correlation between predictor variables using principal components analyses (PCAs), I tested the importance of regional variables in determining the regional composition of wild NIPS using metaMDS. The density of human populations best explained the dissimilarity in composition, but temperature gradients and water availability gradients were also important. In the year 2000 more than 1100 (60%) of the 1773 fully naturalised NIPS in mainland New Zealand had each been recorded in Northland/Auckland and Canterbury, and at the other end of the scale, Southland and Westland each had fewer than 500 (30%). I used GLMs to analyse the importance of people and environment in determining the numbers of wild NIPS in each region. Because I conducted multiple tests on the same dataset I used sequential Bonferroni procedures to adjust the critical P-value. Only human population density was important in explaining the numbers of NIPS in the regions. Overall, humans were the dominant drivers in determining the patterns of naturalisation and spread, although environment helps determine the composition of NIPS in regions. Incorporating human associated factors into studies of wild NIPS helps improve the understanding of the stages in the naturalisation and spread process. Keywords: invasion ecology, climate, plant naturalization, weed risk assessment, biosecurity, exotic, alien, invasive, weeds, spread, human input, introduction effort, minimum residence time vi Chapter 1: Introduction Chapter 1: Introduction 1 1. Background 1 2. Thesis objectives 4 3. Thesis structure 5 Chapter 2: Natural history of the wild non-indigenous seed plant species of New Zealand. 6 1. Abstract 6 2. Introduction 6 2.1. Plant introductions to New Zealand 8 2.2. Botanical records 9 3. NIPS list 11 3.1. Issues with the data 12 3.2. Numbers of NIPS 14 4. Year of discovery 19 5. Native range – number and specific region/s 23 6. Growth form and plasticity 25 7. Introduction and distribution 27 8. Additional biological attributes 29 8.1.1. Mode of dispersal 31 8.1.2. Dispersule mass 31 8.1.3. Vegetative reproduction 31 8.1.4. Start of flowering 31 8.1.5. Flowering duration 31 8.1.6. Life strategy 32 8.1.7. Plant height 32 9. Conclusion 32 Chapter 3: Estimating the year of naturalisation of the wild non-indigenous seed plant species of New Zealand using interval-censored time- to-event analysis. 35 1. Introduction 35 2. Methods 38 2.1. Database of the wild NIPS 38 2.2. Statistical analyses 38 2.2.1. Interval-censored estimation of year of naturalisation 38 2.2.2. Fitting the model 40 2.3. NIPS attributes 42 2.3.1. Native range – number and specific regions 42 2.3.2. Growth form and plasticity 44 2.3.3. Introduction and distribution 44 2.3.4. Taxonomy 45 2.3.5. Additional biological attributes 46 2.3.6. Imports 48 3. Results 50 3.1. Records of discoveries 50 3.2. Estimation of year of naturalisation 51 3.3. Significant predictors 52 3.3.1. Predictors tested individually 52 3.3.2. Summary of multivariate analyses 53 vii Chapter 1: Introduction 3.3.3. All wild NIPS 53 3.3.4. Subset of wild NIPS 56 3.4. Imports 58 4. Discussion 59 4.1. Human activities and biogeography 59 4.2. Taxonomy 62 4.3. Biology 63 5. Conclusion 64 Appendix 3.1 65 Chapter 4: Why are some non-indigenous plant species more widely distributed in New Zealand? 68 1. Introduction 68 2. Methods 70 2.1. New Zealand and its regions 70 2.2. NIPS list, status and regional presence 71 2.3. Statistical analysis 72 2.4. NIPS attributes 75 2.4.1. Year of discovery 75 2.4.2. Native range – number and specific regions 75 2.4.3. Growth form and plasticity 76 2.4.4. Introduction and distribution 77 2.4.5. Taxonomy 78 2.4.6. Additional biological attributes 79 3. Results 82 3.1. Summary of all models 83 3.2. Wild NIPS recorded or not recorded in all 10 regions 84 3.2.1. All fully naturalised NIPS 84 3.2.2. Environmental weeds 88 3.2.3. Subset with additional biological predictors 89 3.3. NIPS recorded in 1-9 regions 91 3.3.1. All fully naturalised NIPS 91 3.3.2. Environmental weeds 92 3.3.3. Subset with additional biological predictors 94 4. Discussion 95 4.1. History 96 4.2. Introduction and distribution 97 4.3. Biogeography 98 4.4. Taxonomy 100 4.5. Biology 101 4.6. Issues with the data 103 5. Conclusion 103 Appendix 4.1 105 Appendix 4.2 107 Chapter 5: Why do some regions have more wild non- indigenous plant species? 109 1. Introduction 109 2. Methods 112 2.1. New Zealand, its regions and its NIPS 112 viii Chapter 1: Introduction 2.2. Regional attributes 113 2.2.1. People 113 2.2.2. Land use/cover and environmental groups 114 2.2.3. Environmental variables 115 2.3. Analyses 117 2.3.1. Principal components analysis 117 2.3.2. Correlation between predictor variables 117 2.3.3. Dissimilarity in composition between regions 117 2.3.4. Wild NIPS Richness 118 3. Results 119 3.1. Variables 119 3.1.1. Principal Components Analysis 119 3.1.2. Correlation between predictor variables 119 3.2. Wild NIPS distributions within regions 121 3.2.1. Nonmetric Multidimensional Scaling 121 3.3. NIPS richness 124 4. Discussion 127 4.1. Human population and Land cover/use 127 4.2. Climate effects 129 4.3. Time 131 4.4. Data 131 5. Conclusion 131 Synthesis 133 5.1. Forecast: weeds 133 5.2. Predicting the invasion 134 5.3. Future directions 137 5.4. Final thoughts 137 Table 1 The number of fully naturalised and casual wild NIPS per family discovered by the year 2000, shown in decreasing order. Also shown is the % of the total wild NIPS from each family and whether or not a family is native to New Zealand. 16 Table 2: The number of wild NIPS, native species, % of total regional flora consisting of wild NIPS, the area, number of wild NIPS per log10 of the area (as used by Vitousek et al., 1996; Weber, 1997), population density and source of the information for a range of islands and countries or regions in the world, in order of decreasing numbers of wild NIPS. 18 Table 3: The 19 regions of the world according to the Kew scheme (Hollis & Brummitt, 1992) and my larger regions used in the analyses. 23 Table 4: Native region(s) of the wild NIPS of New Zealand. If a NIPS is native to more than one region it is considered a representative of each of the regions. 24 ix Chapter 1: Introduction Table 5 Number of Kew and grouped regions that the wild NIPS of New Zealand are native to. 24 Table 6 Wild NIPS classified according to growth form.