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Density Dependence’ in Population Ecology

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Density Dependence’ in Population Ecology RESOLVING CONCEPTUAL CONFUSION AND QUANTIFYING CROSS-TAXA PATTERNS OF ‘DENSITY DEPENDENCE’ IN POPULATION ECOLOGY Salvador Herrando-Pérez APRIL 2012 Thesis submitted for the degree of Doctor of Philosophy Table of contents TABLE OF CONTENTS TABLE OF CONTENTS .................................................................................... 3 ABSTRACT ......................................................................................................... 5 STATEMENT OF ORIGINALITY ................................................................... 6 ACKNOWLEDGEMENTS ................................................................................ 7 FOREWORD ..................................................................................................... 10 CHAPTER 1 BACKGROUND ................................................................... 13 1.1 History in short ......................................................................... 14 1.2 Trends of use ............................................................................. 15 1.3 A survey of experts ................................................................... 19 1.4 Research plan ............................................................................ 23 1.5 Aims ........................................................................................... 25 CHAPTER 2 TERMINOLOGY ................................................................. 26 1.6 Title ............................................................................................ 26 1.7 Abstract: .................................................................................... 26 1.8 Key words .................................................................................. 26 1.9 Introduction .............................................................................. 28 1.10 The concept, not the term ........................................................ 29 1.11 Genesis of the modern vocabulary .......................................... 37 1.12 Reasons for terminological inconsistency............................... 50 1.13 Simple rules of nomenclature .................................................. 56 1.14 Density feedback and regulation are not the same ................ 59 1.15 Conclusions ............................................................................... 64 CHAPTER 3 LIFE HISTORY .................................................................... 66 1.16 Title ............................................................................................ 66 1.17 Abstract ..................................................................................... 66 1.18 Key words .................................................................................. 66 1.19 Introduction .............................................................................. 68 1.20 Methods ..................................................................................... 70 1.21 Results........................................................................................ 75 1.22 Discussion .................................................................................. 81 1.23 Conclusions ............................................................................... 82 CHAPTER 4 CLIMATE .............................................................................. 84 1.24 Title ............................................................................................ 84 1.25 Abstract ..................................................................................... 84 1.26 Key words .................................................................................. 84 1.27 Introduction .............................................................................. 86 1.28 Methods ..................................................................................... 87 1.29 Results........................................................................................ 91 1.30 Discussion .................................................................................. 94 1.31 Further directions..................................................................... 96 3 Table of contents CHAPTER 5 DEMOGRAPHIC RATES ................................................... 98 1.32 Title ............................................................................................ 98 1.33 Abstract ..................................................................................... 98 1.34 Key words.................................................................................. 98 1.35 Introduction ............................................................................ 100 1.36 Methods ................................................................................... 101 1.37 Results ..................................................................................... 104 1.38 Discussion ................................................................................ 111 1.39 Conclusions ............................................................................. 115 CHAPTER 6 CONCLUDING REMARKS .............................................. 120 1.40 Advocacy for phenomenological models .............................. 120 1.41 Regulation overshadows density dependence ...................... 124 1.42 A terminological advance for ecology................................... 128 1.43 Final statement ....................................................................... 131 BIBLIOGRAPHY............................................................................................ 134 APPENDIX A1 - HISTORICAL ACCOUNT ............................................... 167 1.44 Chronicle of density dependence .......................................... 167 1.45 Biogeographical notes on Nicholson and Andrewartha ..... 173 APPENDIX A2 - QUESTIONNAIRE ............................................................ 175 1.46 Statements ............................................................................... 175 1.47 Respondents ............................................................................ 177 1.48 Comments on population limitation ..................................... 178 1.49 Quotes on population regulation ........................................... 179 APPENDIX A3 - TERMINOLOGY: EXAMPLES AND COMMITTEE .. 180 1.50 Examples of proposed terminology ...................................... 180 1.51 ESA committee on ecological nomenclature ........................ 181 APPENDIX A4 - LIFE HISTORY: DATA .................................................... 186 1.52 Base data ................................................................................. 186 1.53 GPDD caveats ......................................................................... 187 1.54 Criteria for data selection ...................................................... 188 1.55 High-quality data subset ........................................................ 189 APPENDIX A5 - LIFE HISTORY: MORE RESULTS ............................... 191 1.56 Single-species population models .......................................... 191 1.57 Model support and effect sizes .............................................. 192 1.58 Examination of measurement error ..................................... 199 APPENDIX A6 - DEMOGRAPHIC RATES: DATA ................................... 201 APPENDIX A7 - DEMOGRAPHIC RATES: MORE RESULTS .............. 210 1.59 Frequencies of compensatory and depensatory feedbacks . 210 1.60 Model support ......................................................................... 212 4 Abstract ABSTRACT Density dependence represents a causal relationship between the size of a population and at least one of its measureable demographic rates. It encapsulates the demographic and evolutionary role of a range of social and trophic mechanisms (e.g., cannibalism, competition, cooperation, parasitism, predation), whose effects on crowding and extinction are themselves modified by the population‟s abundance (density feedback). The concept is applied in conservation and management to assess critical matters such as harvest quotas, pest/invasion control and thresholds of extinction. I review the use of density dependence in ecology. I quantify a temporal increase in the number of ecological papers examining this concept across an augmenting number of study taxa, and little consensus around the meaning of density dependence and associated concepts in a questionnaire survey among 136 ecologists (Chapter 1). Next, I revise the vocabulary of density dependence in a historical context, finding more than 60 terms, many of which are polysemous, synonymous, or grounded in opinionated statements; I name five unequivocal qualifiers of density feedback (compensatory, delayed compensatory, overcompensatory, depensatory/Allee effect) linked to known population phenomena (stability, cycles, chaos, decline), and dissect the semantic differences between density dependence and population regulation (Chapter 2). Using empirical methods, I show that the strength of density feedback increases with the pace of species‟ life histories (Chapter 3), yet is only negligibly correlated with coarse climatic gradients (Chapter 4). These results suggest that broad life-history information can assist management and conservation actions when detailed demographic data are unavailable; and that many demographic processes might operate at spatial scales specific to populations, not species. Subsequently, I provide the first empirical cross-taxa
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