SCALE, PATTERN, AND PROCESS IN BIOLOGICAL INVASIONS By CRAIG R. ALLEN A DISSERTATION PRESENTED TO THE GRADUATE SCHOOL OF THE UNIVERSITY OF FLORIDA IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF DOCTOR OF PHILOSOPHY UNIVERSITY OF FLORIDA 1997 Copyright 1997 by Craig R. Allen ACKNOWLEDGEMENTS The work presented in this dissertation would not have been possible without the cooperation and encouragement of many. Foremost is the understanding of my immediate family, that is my wife Patty and now three-year-old son, Reece. Reece, while generally confused about what I was doing, nonetheless supported my effort to "write a book" in order to become a "doctor." Conflicts arose only when he needed my computer for dinosaur games. My co-advisors, W. M. Kitchens and C. S. Holling, encouraged my investigations and provided me with intellectual support and opportunity. For the same reasons, I extend my appreciation to my committee members, S. Humphrey, M. Moulton and D. Wojcik. Numerous friends and colleagues provided me with intellectual support and acted as a sounding board for ideas. Foremost are E. A. Forys, G. Peterson M. P. Moulton and J. Sendzemir as well as the entire "gang" of the Arthur Marshal Ecology Laboratory. I wish to thank all for their support and friendship. II! TABLE OF CONTENTS page ACKNOWLEDGEMENTS iii ABSTRACT viii INTRODUCTION 1 CHAPTERS 1. TRADITIONAL HYPOTHESES: INVASIONS AND EXTINCTIONS IN THE EVERGLADES ECOREGION 5 Introduction 5 Body-mass difference hypothesis 6 Diet difference hypothesis 7 Species replacement hypothesis 7 Phylogenetic hypothesis 8 Methods 8 Results 11 Discussion 14 2. LUMPY PATTERNS OF BODY MASS PREDICT INVASIONS AND EXTINCTIONS IN TRANSFORMING LANDSCAPES 18 Introduction 18 Methods and analysis 21 Species lists 21 Analysis 22 Results 26 Discussion 31 3. UNSUCCESSFUL NON-INDIGENOUS AVIFAUNA IN SOUTH FLORIDA 37 Introduction 37 Community- level variables 41 iv Landscape- level variables 43 Methods 45 Data 45 Analysis 46 Results 47 Discussion 49 4. THE SOUTH FLORIDA VERTEBRATE COMMUNITY THROUGH TIME 54 Introduction 54 Methods 56 Changes over time 56 Annual changes 57 Results 58 Changes over time 58 Annual changes 61 Discussion 62 5. PATTERNS IN STRUCTURE AND INVASION IN MEDITERRANEAN-CLIMATE ECOSYSTEMS 64 Introduction 64 Methods 66 Data sources 66 Body mass estimates 68 Analysis of mediterranean-climate vertebrate community structure .... 69 Invasions in mediterranean-climate ecosystems 70 Results 71 Analysis of mediterranean-climate vertebrate community structure .... 71 Invasions in mediterranean-climate ecosystems 76 Discussion 77 6. RARITY, ABUNDANCE AND NOMADISM IN RELATION TO SCALE BREAKS IN MEDITERRANEAN-CLIMATE ECOSYSTEMS 81 Introduction 81 Methods 83 Data 83 Rare and declining species analysis 84 Analysis of abundance 84 Analysis of nomadic birds 84 Results 85 Rare and declining species 85 Analysis of abundance 86 Analysis of nomadic birds 86 Discussion 87 7. VERTEBRATE COMMUNITY STRUCTURE WITHIN RANGES OF SCALE 89 Introduction -. 89 Methods 93 Sources of biological data 93 Description of study sites 93 Statistical analyses 96 Simulations with a null model 97 Meta-analysis 98 Community-level simulations 99 Results 99 Simulated and observed trends in segment length variance 100 Binomial test for over-dispersion of segment lengths 101 Tests for potential bias or artifact 102 Community-level simulations 102 Discussion 105 8. CONCLUSIONS AND SYNTHESIS: A HIERARCHICAL MODEL OF COMMUNITY ASSEMBLY 108 Introduction 108 Rules imposed by the landscape template 1 09 Rules partitioning species within feeding guilds 110 Rules for morphological overdispersion Ill A hierarchical model 112 Invasions and extinctions 115 APPENDICES A. DIET, FORAGING STRATA, AND BODY MASS OF VERTEBRATE SPECIES IN SOUTH FLORIDA 117 B. BODY MASSAND LUMP STRUCTURE OF VERTEBRATES IN SOUTH FLORIDA 128 C. SUCCESSFUL AND UNSUCCSESSFUL AVIAN INTRODUCTIONS IN SOUTH FLORIDA 139 D. AVIFAUNA INTRODUCED INTO SOUTH FLORIDA WITH AN INADEQUATE PROPAGULE 144 VI E. BIRDS OF MEDITERRANEAN-CLIMATE ECOSYSTEMS 145 F. MAMMALS OF MEDITERRANEAN-CLIMATE ECOSYSTEMS 172 G. ABUNDANCE, DECLINE AND NOMADISM IN THE FAUNA OF MEDITERRANEAN-CLIMATE ECOSYSTEMS 184 LITERATURE CITED 193 BIOGRAPHICAL SKETCH 206 Vll Abstract of Dissertation Presented to the Graduate School of the University of Florida in Partial Fulfillment of the Requirements for the Degree of Doctor of Philosophy SCALE, PATTERN, AND PROCESS IN BIOLOGICAL INVASIONS By Craig R. Allen December 1997 Chairman: W. M. Kitchens CoChair: C. S. Holling Major Department: Wildlife Ecology and Conservation The phenomenon of biological invasion and extinction are central foci of the field of conservation biology. Extinctions decrease diversity, and the loss of ecological function following extinctions jeopardizes other species and the continued function of ecosystems, as well as the services that they provide. Invasions may increase local diversity, but this is at the loss of global diversity. Much effort has been made to determine the processes underlying invasions and extinctions. This has primarily resulted in long lists of characteristics of invasive and declining species. These lists are usually generated by single species studies or studies of isolated communities, and have little predictive value. Similarly, the association between invasions and "disturbance" is so vague as to be of little value. Disturbance is a scale-bound measure, and association made between invasions and disturbance is of little value as long as it remains scale invariant. viii Landscape pattern is scale dependent and different sized animals living upon the same landscape perceive their environment at different scales. Increasing evidence suggests that ecosystems are structured by relatively few key processes operating at specific temporal and spatial scales. The distinct temporal frequencies and spatial scale characterizing these key processes creates hierarchical landscape structures with scale specific pattern. The scale-specific effect of key processes leads to a discontinuous distribution of ecological structure and pattern which in turn entrains attributes of animals residing on the landscape. This entrainment reflects adaptations to a discontinuous pattern of resource distribution acting on animal community assembly and evolution both by sorting species and by providing a specific set of evolutionary opportunities and constraints and leads to a discontinuous distribution of animal body masses. I tested several traditional hypotheses concerning invasions and extinctions. These hypotheses were based on body size, niche and phylogeny, and all were rejected. However, invasions and extinctions were predictable in the context of scale- specific community structure, and tended to occur at scale breaks. Additional biological variability at scale breaks was documented, including an association with abundance and nomadism. An understanding of the scale-specific nature of animals, ecological processes, and structure led to a hierarchical model of vertebrate community assembly. INTRODUCTION Several years ago I was requested to find ten 200 to 400-hectare study areas that consisted of a single habitat-type and supported relatively homogenous populations of red imported fire ants (Solenopsis invicta), Northern Bobwhite (Colinus virginianus) and white-tailed deer (Odocoileus virginianus). It took but few trips to the landscape in question, covering tens of thousands of square kilometers, to reach the conclusion that such a task was not possible. Although the desired study area size was small and the broad landform extensive, ten sites supporting homogenous populations of those species could not be found. The eventual solution was to pair study sites to remove the inherent variability among sites. Although now seemingly obvious, the reason for my difficulties were not 2 apparent at the time. A fire ant colony may exploit an area of no more than 2,500 m while a deer may operate in an area in the order of 1,000,000 m\ Fire ants, bobwhite, and deer all exploit their environment at grossly different scales. What may be relatively homogenous habitat for bobwhite, and thus support comparable populations on 200-ha study areas, is too small to capture the repeated patterns in deer density, and too large for fire ants. Because these species differ greatly in body size, their environmental perception also is grossly different. The habitat structure that each 1 2 species perceives differs, and thus their pattern of spatial distribution also differs, although the landscape is the same at a very broad scale. I have continued to study fire ants as a case study of the ecological impacts of non-indigenous species. The red imported fire ant is an ecologically disruptive non- indigenous species that has invaded most of the southeastern United States. As with many invasive species, the fire ant has been associated with "disturbed" habitats (Tschinkel 1988). One of the earliest recognized associations of invasive species was a predilection for disturbed habitats (Elton 1958). However, like many of the other suggested traits of invasive species and invaded habitats (see Chapter 1), the association with disturbed habitats has been implicitly scale- invariant. A disturbance large enough to be exploited by fire ants, for example the 1-rrr spoil pile from mosquito-ditching operations, is far too small-scale for a larger invasive species such as an armadillo {Dasypus novemcinctus). My goal for this document is to first briefly review traits of