Patterns in Nature: The Analysis of Species Co-Occurrences

Description

What species occur where, and why, and why some places harbor more species than others are basic questions for ecologists. Some species simply live in different places: fish live underwater; birds do not. Adaptations follow: most fish have gills; birds have lungs. But as Patterns in Nature reveals, not all patterns are so trivial. Travel from island to island and the species change. Travel along any gradient—up a mountain, from forest into desert, from low tide to high tide on a shoreline —and again the species change, sometimes abruptly. What explains the patterns of these distributions? Some patterns might be as random as a coin toss. But as with a coin toss, can ecologists differentiate associations caused by a multiplicity of complex, idiosyncratic factors from those structured by some unidentified but simple mechanisms? Can simple mechanisms that structure communities be inferred from observations of which species associations naturally occur? For decades, community ecologists have debated about whether the patterns are random or show the geographically pervasive effect of competition between species. Bringing this vigorous debate up to date, this book undertakes the identification and interpretation of nature’s large-scale patterns of species co-occurrence to offer insight into how nature truly works. Patterns in Nature explains the computing and conceptual advances that allow us to explore these issues. It forces us to reexamine assumptions about species distribution patterns and will be of vital importance to ecologists and conservationists alike. Contents Preface Part I. The Distribution of Species on Islands Chapter 1. Patterns or Fantasies? Species Co-occurrences The Night Sky Effect Patterns in Nature Finding the Null What This Book Is About How This Book Is Organized Chapter 2. Diamond’s Assembly Rules Robert MacArthur, 1930– 1972 Special Islands and Their Birds What Is a Checkerboard Distribution? Incidence The Theoretical Context The Cuckoo Doves Patchy Distributions Summary Chapter 3. The Response of Connor and Simberloff The Backlash How Likely Are Checkerboards? Prior Expectations The Analysis of Vanuatu Summary Part II. A Technical Interlude Chapter 4. How to Incorporate Constraints into Incidence Matrices Definitions and Notation The Numbers of Null Matrices and the Effect of Constraints The Hypergeometric Distribution The Three Ecological Constraints Proposed by Connor and Simberloff in Their Studies of Birds and Bats on Islands Incidence Why Constraints? And What Does “Representative” Mean? Summary Chapter 5. How to Fill the Sample Null Space Null Space Creation Algorithms Creating a Uniform Random Sample Null Space The Trial-Swap Algorithm Summary Chapter 6. How to Characterize Incidence Matrices Then You Need a Metric . . . The Metric of Connor and Simberloff (1979) Wright and Biehl (1982) Harvey et al.’s (1983) Review of Null Models in Ecology Stone and Roberts (1990, 1992) and Roberts and Stone (1990) Why Ensemble Metrics Fail—An Example Summary Part III. Reanalysis and Extensions Chapter 7. Vanuatu and the Galápagos The Birds of Vanuatu The Birds of the Galápagos Summary Chapter 8. The Birds of the Bismarck and Solomon Islands The Issue of Superspecies The Patterns Taxonomic Sieving and Incidence Effects Which Genera Develop Checkerboards? Caveats When the Incidences Do Not Overlap Summary Coda Chapter 9. Species along a Gradient The Herptofauna of Mount Kupe, Cameroon Why Do the Results Differ from Previous Results? The Second Question: Do Species Form Distinct Communities? Summary Chapter 10. Applications to Food Webs: Nestedness and Reciprocal Specialization Nestedness Groupings of Species Interactions Summary Chapter 11. Coda MacArthur’s Original Vision The Patterns Themselves The Need for Null Hypotheses References Index