1 Dispersal and the distributions of mammals: moving towards improved predictions Sarah Louise Whitmee A thesis submitted for the degree of Doctor of Philosophy from the Division of Biology, Department of Life Sciences, Imperial College London 2 Abstract Climate change is predicted to become a major cause of species loss in the coming century. Shifts in d istribution as a response to changing conditions have already been observed for many terrestrial organisms. A species’ capacity to respond to climate change will depend greatly on its ability to track suitable conditions; those unable to track optimum conditions will be under increased threat of local extinction. There is, therefore, a need to include dispersal parameters in models that forecast the impact of climate change on species distributions, but this is limited by a paucity of dispersal data for many species. In this thesis I develop predictive models of dispersal ability to improve estimates of both distance and rate of dispersal in mammals. Chapter 2 presents a database of empirically derived dispersal distances for mammals and an analysis of the probability distribution of those distances, aimed at describing the ‘tail’ of the kernel, important in understanding long distance dispersal. Chapter 3 assesses the explanatory power of species’ life history and ecology, within a phylogenetic framework, to predict dispersal distances. Chapter 4 examines the roles of dispersal and colonisation ability in mediating the extent to which a species can fill its potential environmental niche and quantifies the effects of model accuracy and projection extent on this approach. Chapter 5 utilises a new technique for identifying patterns of geographic and phylogenetic constraint to examine the dual roles of evolutionary history and environment in determining a species’ ability to fill its potential environmental niche. This thesis helps to clarify controls on range limits and to incorporate such controls into species distribution models. By providing more accurate predictions of the impacts of climate change on species range size and location, this work helps us to better understand the threat to species diversity from global change. 3 Declaration All work presented in this thesis is my own, with the following acknowledgements: Most datasets used in this thesis, apart from the database of dispersal distances, were compiled by others, and I cite the data sources throughout and reference published software and code where appropriate. I also made use of some programming code kindly provided by others: Emmanuel Paradis kindly provided R code used in chapter 1 to analyse dispersal kernels. Lynsey McInnes provided R code for model simplification and model selection in chapter 2. Susanne Fritz and David Orme wrote the ArcInfo macros to extract species’ grid cell occurrences for range filling analyses in chapters 3 and 4. Rob Freckleton and Natalie Cooper provided R code for the joint analysis of spatial and phylogenetic signal in range filling in chapter 4. Chapter 3 is formatted for submission to the Journal of Animal Ecology and was co- authored with my thesis supervisor David Orme. While the submitted version will use ‘we’, I have converted these to ‘I’ for the thesis chapter. Chapter 4 is formatted for submission to Diversity and Distributions and was co- authored with my thesis supervisor David Orme. While the submitted version will use ‘we’, I have converted these to ‘I’ for the thesis chapter. Chapter 5 was co-authored with my thesis supervisor David Orme. While the submitted version will use ‘we’, I have converted these to ‘I’ for the thesis chapter. 4 Acknowledgements from the chapters Chapter 3. We are grateful to Lynsey McInnes, Alex Pigot, Yael Kisel, Albert Phillimore, Georgina Mace, Rob Ewers, Uta Berger and an unknown reviewer for helpful comments on the manuscript. Kate Jones and all PanTHERIA members for access to the PanTHERIA life history trait database. Chapter 4. We are grateful to Lynsey McInnes, Alex Pigot, Albert Phillimore, for helpful comments on the manuscript. Maria Dickinson for discussions and advice on choice of environmental variables. Kate Jones and all PanTHERIA members for access to the PanTHERIA life history trait database. Chapter 5. We are grateful to Rob Freckleton and Natalie Cooper for providing code and helpful comments on the methods. Natalie Cooper, Lynsey McInnes and Albert Phillimore, for helpful comments on the manuscript. 5 Acknowledgements Firstly, I would like to thank my supervisor David Orme for help and support over the last four years. Thanks for keeping faith in me and always having an open door. Thanks also to my friends and colleagues at Silwood Park. Lab mates Alex, Lynsey and Mel for putting up with me, providing chocolate, cakes, encouragement and advice, all very important and in that order. Thanks as well to Alex, Mel and David for putting up with Bailey and the pervasive smell of dog food in the office – you are all stars. Extra thanks to Ally, Natalie and Susanne for guidance, help and support – I was so lucky to have you all around. Also thanks to Gio and Maria for help with species distribution modelling issues, and a general good moan about the topic. Thanks to Hannah and Mel for keeping me company through the last lonely months of writing up, both the company and the tea were much appreciated! Thanks to Kate Jones for access to the PanTheria database and her patience when I kept telling her I couldn’t work how on earth average values were calculated. A big thanks to the extended Whitmee family, especially Anthony, Susan and Kipper the dog, for many hours of dog sitting, glasses of wine and good laughs. Thanks and lots of love to my Mum and Dad for always encouraging me to do what I wanted, even if you thought I may never grow out of being a student. Special thanks to my mum for helping in the last crazy week of writing up and puppy madness, Finally thanks to Bruce and Bailey. Bailey - although you will never know it you have made me laugh every day since you arrived, and kept me sane throughout the last couple of years. Bruce – what can I say? I wouldn’t be here without your love and support. You have kept me going when I felt like giving up and kept me smiling when things went bad. Thanks chuck, I hope to make you very proud of me. 6 Table of contents Abstract..................................................................................................................... 2 Declaration................................................................................................................ 3 Acknowledgements ................................................................................................... 5 Table of contents....................................................................................................... 6 List of Figures ........................................................................................................... 8 List of Tables ............................................................................................................ 9 Chapter 1: Introduction.............................................................................................10 1.1 Defining and describing dispersal ................................................................12 1.2 Mammals as a model system ........................................................................14 1.3 Modelling dispersal .......................................................................................15 1.4 The importance of including dispersal estimates in species distribution modelling .............................................................................................................19 1.5 Conclusions ...................................................................................................21 1.6 Thesis aims and summary ............................................................................22 Chapter 2. Data collection and kernel analysis..........................................................26 2.1 Introduction ..................................................................................................26 2.2 Quantifying dispersal ability ........................................................................26 2.3 Database creation ..........................................................................................29 2.4 Data entry protocols .....................................................................................30 2.5 PanTheria trait database ..............................................................................34 2.6 Description of data and data quality ............................................................35 2.8 Dispersal kernel data ....................................................................................39 Chapter 3. Predicting dispersal distance in mammals: A trait based approach ...........43 3.1 Abstract .........................................................................................................43 3.2 Introduction ..................................................................................................44 3.3 Methods .........................................................................................................46 3.4 Results ...........................................................................................................54 3.5 Discussion ......................................................................................................62 7 Chapter 4. Comparative estimates