COMMUNITY ASSEMBLY RULES OF FISH ASSEMBLAGES ALONG A LARGE TROPICAL RIVER CATCHMENT: A VIEW FROM DIFFERENT PERSPECTIVES A Dissertation by EDWIN ORLANDO LÓPEZ DELGADO Submitted to the Office of Graduate and Professional Studies of Texas A&M University in partial fulfillment of the requirements for the degree of DOCTOR OF PHILOSOPHY Chair of Committee, Kirk O. Winemiller Committee Members, Lee Fitzgerald Kevin Conway Michell Lawing Head of Department, David Caldwell May 2019 Major Subject: Wildlife and Fisheries Sciences Copyright 2019 Edwin Orlando López Delgado ABSTRACT Community ecologist have studied biodiversity worldwide principally focusing on species richness. However, little is known about how species composition varies in space, time and even less about the species role in the ecosystem functioning, which is critical for natural resource management and conservation. In this study, I investigated mechanisms underlying community structure and how environmental and spatial factors influence fish taxonomic and functional (α,β) diversity along a longitudinal gradient in a nearly pristine Neotropical river. Standardized surveys were conducted during the low-water period at 34 sites within the Bita River Basin in the Colombian Llanos. Physical, chemical and landscape parameters were recorded at each site. Asymmetric eigenvector maps were used as spatial variables. To examine the relative influence of spatial and environmental variables on taxonomic and functional diversity, a distance-based redundancy analysis (db-RDA) and variation partitioning analysis were conducted. Results of these two facets of biodiversity showed that environmental filtering and stochastic dynamics might be structuring fish communities in this river system. Variation partitioning analyses for both biodiversity facets revealed that environmental features related to in-stream cover might act as filters structuring fish communities, therefore, in order to preserve fish biodiversity in this diverse river, it is crucial that habitat variability (in-stream cover) and connectivity be preserved. ii DEDICATION To my family and friends who gave courage to continue this adventure far from home. iii ACKNOWLEDGEMENTS I would like to thank specially to my Ph.D. advisor, Dr. Kirk Winemiller for all of his help, advice, wisdom, kindness and overall patience while writing this dissertation. Thanks also to my committee members, Drs. A. Michell Lawing, Lee Fitzgerald and Kevin Conway for their valuable comments and suggestions that helped me improve my research. I owe additional thanks to Dr. Francisco Villa and Gladys Reinoso for letting me used their Laboratory in Colombia, and many people who helped me during the field and laboratory work, specially to Drs. Carlos DoNacimento, Donald Charles Thaporn, Juan Gabriel Albornoz and Diana Montoya. Also, I want to thank to all the members of the Winemiller aquatic ecology lab for their support and knowledge. Thanks also go to my friends and colleagues and the department faculty and staff for making my time at Texas A&M University a great experience, and Finally, thanks to my mother, father, my son and wife for their encouragement patience and love. iv CONTRIBUTORS AND FUNDING SOURCES Contributors This work was supervised by a dissertation committee consisting of Professor Kirk Winemiller (advisor) and committee members, Drs. Lee Fitzgerald and Kevin Conway of the Department of Wildlife and Fisheries Sciences and Professor A. Michell Lawing, of the Department of Ecosystem Science and Management. The analyses depicted in Chapter 2 were conducted in part by Kirk Winemiller and Francisco Villa Navarro and were published in the Journal Freshwater Biology in 2019 (https://doi.org/10.1111/fwb.13229). All other work conducted for this dissertation was completed by the student independently. Funding Sources Graduate study was supported by a fellowship from COLCIENCIAS Colombia. Dissertation research was founded in part by World Wildlife Foundation (WWF) Colombia, Fundación Omacha, Instituto de Investigación de Recursos Biológicos Alexander von Humboldt and Grupo de Investigación en Zoología de la Universidad el Tolima. This work was also made possible by the research assistantship from the Winemiller aquatic laboratory during my last year in the Ph.D. Its contents are solely the responsibility of the authors and do not necessarily represent the official views of the funding sources. v TABLE OF CONTENTS Page ABSTRACT .................................................................................................................................... ii DEDICATION ............................................................................................................................... iii ACKNOWLEDGEMENTS ........................................................................................................... iv CONTRIBUTORS AND FUNDING SOURCES .......................................................................... v TABLE OF CONTENTS ............................................................................................................... vi LIST OF FIGURES ..................................................................................................................... viii LIST OF TABLES .......................................................................................................................... x 1. INTRODUCTION: COMMUNITY ASSEMBLY RULES OF FISH ASSEMBLAGES ALONG A LARGE TROPICAL RIVER CATCHMENT: A VIEW FROM DIFFERENT PERSPECTIVES ............................................................................................................................ 1 References ................................................................................................................................... 3 2. DO METACOMMUNITY THEORIES EXPLAIN SPATIAL VARIATION IN FISH ASSEMBLAGE STRUCTURE IN A PRISTINE TROPICAL RIVER?....................................... 7 2.1. Introduction .......................................................................................................................... 7 2.2. Methods ............................................................................................................................. 11 2.2.1. Study area .................................................................................................................... 11 2.2.2. Fish surveys ................................................................................................................ 12 2.2.3. Environmental variables ............................................................................................. 13 2.2.4. Data analysis ............................................................................................................... 14 2.3. Results ................................................................................................................................ 19 2.3.1. Elements of metacommunity structure ....................................................................... 22 2.3.2. Variation partitioning analysis .................................................................................... 25 2.4. Discussion .......................................................................................................................... 27 References ................................................................................................................................. 33 3. EXPLORING EFFECTS OF ENVIRONMENTAL AND SPATIAL FACTORS ON FISH BETA DIVERSITY IN A SPECIES-RICH NEOTROPICAL RIVER ........................................ 40 3.1. Introduction ........................................................................................................................ 40 3.2. Methods ............................................................................................................................. 44 vi 3.2.1. Study area .................................................................................................................... 44 3.2.2. Surveys ........................................................................................................................ 45 3.2.3. Environmental variables ............................................................................................. 46 3.2.4. Spatial variables .......................................................................................................... 47 3.2.5. Data analysis ............................................................................................................... 47 3.3. Results ................................................................................................................................ 51 3.4. Discussion .......................................................................................................................... 62 References ................................................................................................................................. 68 4. FISH FUNCTIONAL DIVERSITY CHANGES ALONG THE LONGITUDINAL GRADIENT OF A SPECIES-RICH TROPICAL RIVER ........................................................... 76 4.1. Introduction ........................................................................................................................ 76 4.2. Methods ............................................................................................................................. 81 4.2.1. Data collection ...........................................................................................................