AN ABSTRACT OF THE THESIS OF Eric Layani Berlow for the degree of Doctor of Philosophy in Zoology presented on 9 June, 1995. Title: Patterns and Dynamics of Context-Dependency in the Marine Rocky Intertidal Abstract approved: Redacted for Privacy Bruce A. Menge Abstract approved: Redacted for Privacy Jane Lubchenco As ecologists are being called upon to predict the consequences of human perturbations to natural communities, an important goal is to understand what factors drive variability or consistency in nature. In the rocky intertidal of San Juan Island, Washington, a comparative experimental approach was used to investigate spatial and temporal variation in community organization. The effect of predation on B. glandula varied dramatically over small spatial scales between microhabitats but was remarkably consistent over time withing a given microhabitat. The effects of predation on S. cariosus varied over time within the same microhabitat. By repeating previous landmark experiments at our study site, and replicating these experiments across microhabitats, the domain of applicability of previous experimental information was greatly expanded. In an early successional assemblage on the Oregon coast, I tested the hypothesis that, when the direct effect of one species on another increases in relative strength, its total effect (direct + indirect) is less variable or conditional than if the link between those species is weak. The effect of strong predation by whelks was less sensitive to the presence of additional species and more consistently dampened natural variation between experimental starting dates and between individual replicates within a given experiment. In contrast, the outcome of weak predation was more spatially and temporally variable in sign, and whether it magnified or dampened differences between individual replicates varied between experiments. Consequently the mean total effect of weak predation generally did not differ significantly from zero. However, in some cases, the range of variation (both within and between experiments) in the effect of weak predation exceeded the magnitude of the strongest total effect observed. Longer term results of the experiments on the Oregon coast examined the role of historic factors in influencing the degree to which successional paths are canalized and repeatable or contingent and variable. Succession in mid-intertidal patches in the mussel bed displayed complex patterns of historic effects that varied between species and between different stages of succession. Despite its potential complexity, this system exhibited some consistent and repeatable patterns of succession. Some important canalizing, or noise-dampening forces in this system included: 1) physiological and life- history constraints, 2) compensatory responses of functionally redundant species, and 3) strong interactions between species. Patterns and Dynamics of Context-Dependency in the Marine Rocky Intertidal by Eric Layani Berlow A THESIS submitted to Oregon State University in partial fulfillment of the requirements for the degree of Doctor of Philosophy Completed 9 June, 1995 Commencement June 1996 Doctor of Philosophy thesis of Eric L. Berlow presented on June 9, 1995 APPROVED: Redacted for Privacy Co-Major Redacted for Privacy Co-Maj Redacted for Privacy Head of Department of Zoology Redacted for Privacy Dean of I understand that my thesis will become part of the permanent collection of Oregon State University libraries. My signature below authorizes release of my thesis to any reader upon request. Redacted for Privacy Eric L. Berlow ACKNOWLEDGMENTS Science is inherently a social phenomenon. Many people have been instrumental in shaping my world view, my thought processes, the questions that have fascinated me, and the approaches I have taken to answer them. Most of those people, of course, are people I have never met. But of those that I have been fortunate enough to know, some who have had particularly strong effects on me (both direct and indirect), deserve particular recognition. While this thesis focuses on the importance of context-dependency, I am indebted to Nadine, Sheldon and Alexa Berlow, Mary Berlow, Celine, Arys, and Patrick Layani, and Jeanne Panek for their truly context-independent love and encouragement. It is only with these solid pillars of support that I have been able to so freely and confidently explore what life has to offer. Nadine and Sheldon also provided the foundation of a bicultural setting that stretched my synapses and shaped much of my current thinking. Jeanne Panek has been a truly dialectical inspiration. In the past 4 years she has taught me that it is possible to simultaneously take oneself more seriously and less seriously; to be both more self-confident, but less over-bearing; to be both more independent, yet less selfish; to give freely, yet receive graciously, and to pursue ideas and dreams will boundless energy, while being flexible enough to change course quickly when new opportunities arise. She allowed me to better appreciate what graduate school had to offer by making it less central to my life, and she has given me reason to simultaneously savor the present and eagerly anticipate the future. Hugh Lefcort single-handedly saved me during my first year in Oregon. At times when I felt like a foreigner in a strange land, he, Jeanne Panek, and Bill Langford spoke my native tongue and gave me family. Mental wanderings on different, yet overlapping, paths with all three have shaped my thinking and my approach to science in countless, intangible ways. Edwin McGowan and Jim Norwalk are responsible for introducing me to the wonders of nature despite our growing up in a pot-hole-riddled city in the Rust Belt. They have been a constant reminder that nature comes before theory. On the other hand, Roy Kreitner, Dave Shenk, Jeremy Benjamin, and Rebecca Holcombe introduced me to the value of abstraction, of thinking about thinking, and of exploring commonalities between disparate fields of inquiry. Needless to say, my advisors Bruce Menge and Jane Lubchenco have made enormous contributions to my thesis and many other aspects of my education and development. With different thinking styles and sometimes contrasting approaches to science, they have been complementary mentors. Bruce's incessant curiosity and enthusiasm in the field, his untiring patience and unabashed honesty, and his ability to manage complex, multivariate information as if he were playing with a Leggo set is a constant reminder of what true science is supposed to be like. Jane's direct and incisive thinking style, her people skills, and her energetic devotion to bridging the gap between basic and applied research have provided an inspirational model for what dedicated scientists can offer society. I am also grateful to my other committee members. Mark Hixon's incredible capacity for synthesis has taught me that, yes, it is possible to summarize all of community ecology in a one-page flow chart. Bruce McCune has expanded my thinking by encouraging me to turn my brain inside-out and think upside-down and backwards. Gary De Lander has convinced me that Nutra-Sweet must be an essential micro-nutrient. All have been patient with my sometimes non-linear style of communication. I would also like to thank all my siblings in the Lubmengo family and the other members of the fifth-floor gang for all their help, encouragement, and camaraderie. In particular Gary Allison, Carol Blanchette, Dave Booth, Mark Carr, Jeff Harding, Dwayne Meadows, Karina Nielsen, Annette Olson, Deirdre Roberts, Eric Sanford, Cynthia Trowbridge, and Peter van Tame len have all helped out in various ways. Carol Blanchette served as my steady model for stress management and helped to ground my convoluted thinking in reality. Sergio Navarrete served as my mentor and surrogate advisor. Many late-night (but never early morning) and sometimes heated discussions with Sergio influenced much of my thinking about ecology. Collaborations in joint research projects, engaging discussions in the field about experimental design, and his generous advice about statistics shaped, not only the ideas presented in this thesis, but also my general thinking about the process of science. I also learned more about the subtleties of the English language from Sergio's eloquent communication style than from any native speaker I've ever met. I am extremely grateful to all the individuals who got up before sunrise to work spring and summer low tides or huddled around the Coleman lantern after sunset during stormy winter low tides. They volunteered their time to hours of data collection and physical labor in often cold, rainy weather, and, miraculously, came back for more the next day. Maybe it was the lack of mosquitoes. While the list of individuals is long and all the help was invaluable, I would like to particularly acknowledge Alexa Berlow, Kamichia Buzzard, Bryon Daley, Steve Howard, Sarah Lucas, Cathy Needham, Jeanne Panek, Brian Profit, Tara Panek, Stephanie Suskie, and Evie Wieters. I am also very grateful to Betsy and Alice King for providing privileged, first-class access to Fogarty Creek, a field site with aesthetic appeal in any weather. I thank the financial support I received from Sigma Xi Grants-in-Aid of Research, a Phycological Society of America Croasdale Fellowship, Holt Marine Education Fund Grants, OSU Zoology Department Teaching Assistantships, ZoRF (the Zoology Department Research Fund), generous support from Sheldon M. Berlow, National Science Foundation projects OCE 88-11369 amd OCE 92-17459 to Bruce Menge, and an Andrew Mellon Foundation grant to Bruce Menge and Jane Lubchenco. TABLE OF CONTENTS Page CHAPTER I GENERAL INTRODUCTION- 1 CHAPTER II GENERALIZING FROM FIELD EXPERIMENTS: SPATIAL AND TEMPORAL VARIATION IN COMMUNITY ORGANIZATION 5 Abstract 5 Introduction 6 The System 9 Methods 13 I. Patterns of community structure 13 II. Effect of Semibalanus on the distribution of whelks and limpets 14 III. Measurement of physical conditions inside/outside Semibalanus beds 16 IV. Predator manipulations: Effects of Semibalanus on whelk and limpet foraging. 18 Data Analysis 24 Results 26 I.