Using Citizen Science Data to Reveal the Role of Ecological Processes in Range Changes of Grasshoppers and Crickets in Britain
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Using citizen science data to reveal the role of ecological processes in range changes of grasshoppers and crickets in Britain Björn Beckmann PhD University of York Biology May 2017 Unter Druck entstehen Diamanten. (Hans-Jochen Steinhagen) 2 Abstract Climatic and land use changes are affecting the distributions of many species and habitats. A detailed understanding of these impacts is critical for conservation and adaptation planning, but much interspecific variability remains unexplained. One reason may be that studies have tended to consider only effects of changes in mean climate, not of annual variation. Using data of the Orthoptera Recording Scheme and additional field observations, I investigated effects of species traits and seasonal variability in weather on the pattern and process of distributional changes of grasshoppers and crickets in Britain over recent decades. I found large changes in the distributions of several species, and relatively greater increases for habitat generalists, species that oviposit in vegetation, and for those with a southerly distribution. In a study of the rapid range expansion of two wing-dimorphic species, Conocephalus discolor and Metrioptera roeselii, I found some of the first evidence for effects of seasonal weather on annual colonisation rates, and for an interaction between the effects of temperature and precipitation. The findings suggest that for some species weather may concentrate dispersal into waves in climatically favourable years. This may increase successful establishment through greater numbers of colonists, and may also be advantageous in fragmented landscapes, allowing species to invest in dispersal only sporadically and under favourable conditions. The results also highlight the importance of considering interactive effects of temperature and precipitation when examining species’ responses to climatic variability. Studies like these are made possible by large-scale, long- term distribution recording by volunteers. However, the unstructured and evolving nature of this “citizen science” makes the data prone to biases that need to be taken into account during analysis. I reviewed current recording of Orthoptera and the scope for its development, and propose a protocol for Orthoptera abundance monitoring by volunteers for future research and conservation applications. 3 List of Contents Abstract 2 List of Contents 4 List of Figures 6 List of Tables 8 Acknowledgements 10 Author's declaration 11 1. Introduction 12 1.1 Species ranges and range changes: introduction, definition and importance 12 1.2 Drivers of distribution change 15 1.3 Suitability and importance of insects as study systems 18 1.4 Effects of climate and land use change on insect distributions 20 1.5 Mechanisms and processes of insect range changes under climate and land use change 23 1.6 Citizen science for distribution data 34 1.7 Thesis: aims, main questions and layout 38 2. Critical overview of Orthoptera Recording Scheme data 40 2.1 Abstract 40 2.2 Scope and operation of the recording scheme 41 2.3 Assessment of scheme data 63 2.4 Distribution trend analysis 72 2.5 Conclusion 87 3. Two species with an unusual combination of traits dominate responses of British grasshoppers and crickets to environmental change 88 3.1 Abstract 89 3.2 Introduction 90 3.3 Materials and Methods 94 3.4 Results 102 3.5 Discussion 112 3.6 Conclusions 118 3.7 Acknowledgements 118 4 4. Environmental stochasticity is a strong determinant of colonisation rate under climate change 119 4.1 Abstract 119 4.2 Introduction 120 4.3 Materials and Methods 124 4.4 Results 133 4.5 Discussion 144 4.6 Conclusion 155 5. Informing a standardised method for Orthoptera abundance and site monitoring 157 5.1 Abstract 157 5.2 Introduction 158 5.3 Survey design 164 5.4 Sample acoustic transect count data collected 2016 177 5.5 Power analysis 178 5.6 Discussion 182 6. General Discussion 185 6.1 Summary of main findings 185 6.2 Future research, and the role of citizen science data 186 6.3 Outlook 191 Appendix to Chapter 2 192 Appendix to Chapter 3 195 Appendix to Chapter 4 206 References 219 5 List of Figures Fig. 2.1: Orthoptera species richness in Britain, Ireland and the Channel Islands. ................. 44 Fig. 2.2: Orthoptera Recording Scheme species-list recording card. ...................................... 45 Fig. 2.3: Orthoptera Recording Scheme online recording form. ............................................. 47 Fig. 2.4: Screenshots of iRecord Grasshoppers app. ............................................................... 49 Fig. 2.5: Example screenshot of iRecord verification system. ................................................. 51 Fig. 2.6: Front page of latest Orthoptera recording scheme newsletter ................................ 53 Fig. 2.7: Head of identification sheet for common grasshoppers and crickets. ..................... 55 Fig. 2.8: Screenshots of iRecord Grasshoppers app showing field guide and species identification screens. .............................................................................................. 57 Fig. 2.9: Recording coverage of four (provisional) Orthoptera atlases of Britain and Ireland.59 Fig. 2.10: Number of Orthoptera county atlases published, by decade. ................................ 60 Fig. 2.11: Counties with Orthoptera atlases, and resolutions of maps. .................................. 60 Fig. 2.12: Number of distinct records in Orthoptera Recording Scheme database by year of record, 1960-2015. ................................................................................................... 64 Fig. 2.13: Number of distinct records per hectad, 1960 to 2009. ........................................... 65 Fig. 2.14: Changes in recording effort per hectad 1960-2009 and 1980-2009. ...................... 66 Fig. 2.15: Changes in the spatial precision of distinct Orthoptera Recording Scheme records over time. ................................................................................................................. 67 Fig. 2.16: Changes in the temporal precision of distinct Orthoptera Recording Scheme records over time. .................................................................................................... 68 Fig. 2.17: Numbers of species recorded per visit (list lengths), 1960-2015. ........................... 69 Fig. 2.18: Species’ range sizes in 1980-9 and 2000-9 and calculation of relative range change index. ........................................................................................................................ 74 Fig. 2.19: Modelled annual occupancy and overall trend 1980-2009, for the Mottled Grasshopper Myrmeleotettix maculatus. ................................................................. 81 Fig. 2.20: Comparison of three distribution trend measures for Orthoptera in Britain, 1980- 2009. ......................................................................................................................... 84 Fig. 3.1. Location of four sets of “surveyed squares” with different levels of recording effort. .................................................................................................................................. 95 6 Fig. 3.2. Range changes of grasshoppers and related species in Britain between 1980-9 and 2000-9. .................................................................................................................... 103 Fig. 3.3. Grasshopper and related species range sizes in 1980-9 and 2000-9 and calculation of range change measures. ......................................................................................... 104 Fig. 3.4. Observed vs. fitted range change values. ................................................................ 111 Fig. 3.5. Range expansions of Conocephalus discolor and Metrioptera roeselii in Britain between 1980 and 2009. ........................................................................................ 113 Fig 4.1. Calculation of annual colonisation rate, using Conocephalus discolor in the year 2000 as an example. ........................................................................................................ 126 Fig 4.2. Location of 2008-2012 field survey sites in the context of the expanding distributions of the study species in southern Britain. ................................................................ 130 Fig 4.3. Histogram of colonisation distances for Conocephalus discolor and Metrioptera roeselii between 1977 and 2012. ........................................................................... 134 Fig 4.4. Interacting effects of April to July warmth and rainfall in the study year on colonisation rates of Conocephalus discolor and Metrioptera roeselii. ................. 137 Fig 4.5. Observed and modelled values of annual colonisation rate. ................................... 138 Fig 4.6. Observed and modelled values of proportions of long-winged individuals............. 142 Fig. 5.1: Phenology of Orthoptera in Britain. ........................................................................ 166 Fig. 5.2: Phenology of groundhoppers (Tetrigidae) in Britain. .............................................. 167 Fig. 5.3: Example options for timing of surveys for 2-3 annual visits. .................................. 168 Fig. 5.4: Times of day of greatest acoustic activity of Orthoptera. ....................................... 169 Fig. 5.5. Sample acoustic transect count data collected in 2016. .......................................... 177 Fig. 5.6: Estimated