University of Tennessee, Knoxville TRACE: Tennessee Research and Creative Exchange Doctoral Dissertations Graduate School 5-2002 Interactions among Introduced Ungulates, Plants, and Pollinators: A Field Study in the Temperate Forest of the Southern Andes Diego P. Vazquez University of Tennessee - Knoxville Follow this and additional works at: https://trace.tennessee.edu/utk_graddiss Part of the Ecology and Evolutionary Biology Commons Recommended Citation Vazquez, Diego P., "Interactions among Introduced Ungulates, Plants, and Pollinators: A Field Study in the Temperate Forest of the Southern Andes. " PhD diss., University of Tennessee, 2002. https://trace.tennessee.edu/utk_graddiss/2169 This Dissertation is brought to you for free and open access by the Graduate School at TRACE: Tennessee Research and Creative Exchange. It has been accepted for inclusion in Doctoral Dissertations by an authorized administrator of TRACE: Tennessee Research and Creative Exchange. For more information, please contact [email protected]. To the Graduate Council: I am submitting herewith a dissertation written by Diego P. Vazquez entitled "Interactions among Introduced Ungulates, Plants, and Pollinators: A Field Study in the Temperate Forest of the Southern Andes." I have examined the final electronic copy of this dissertation for form and content and recommend that it be accepted in partial fulfillment of the equirr ements for the degree of Doctor of Philosophy, with a major in Ecology and Evolutionary Biology. Daniel Simberloff, Major Professor We have read this dissertation and recommend its acceptance: David Buehler, Louis Gross, Jake Welzin Accepted for the Council: Carolyn R. Hodges Vice Provost and Dean of the Graduate School (Original signatures are on file with official studentecor r ds.) To the Graduate Council: I am submitting herewith a dissertation written by Diego P. Vázquez entitled “Interactions among Introduced Ungulates, Plants, and Pollinators: A Field Study in the Temperate Forest of the Southern Andes.” I have examined the final electronic copy of this dissertation for form and content and recommend that it is accepted in partial fulfillment of the requirement for the degree of Doctor of Philosophy, with a major in Ecology and Evolutionary Biology. Daniel Simberloff Major Professor We have read this dissertation and recommend its acceptance: David Buehler Louis Gross Jake Weltzin Acceptance of the council: Anne Mayhew Vice Provost and Dean of Graduate Studies INTERACTIONS AMONG INTRODUCED UNGULATES, PLANTS, AND POLLINATORS A FIELD STUDY IN THE TEMPERATE FOREST OF THE SOUTHERN ANDES A Dissertation Presented for the Doctor of Philosophy Degree The University of Tennessee, Knoxville Diego P. Vázquez May 2002 ii Copyright © 2002 by Diego P. Vázquez. All rights reserved. Copies of this document may be printed from this website for personal use without permission. iii A mis padres, mis primeros maestros iv ACKNOWLEDGMENTS Many people and institutions have helped me during the different stages of this work. Without their help the realization of this project would have been impossible. First of all, I want to thank my family for al- ways encouraging me to pursue my interests, and for being close to me in spite of this voluntary exile of mine. My mother and my brother Álvaro deserve a special mention here. My mother made me study Eng- lish against my will as a child; without that learning, this dissertation could have never been written. Ál- varo came twice to help me in the field. I also thank Florencia for all her love and patience; gracias Flor por aguantarme todo este tiempo. My advisor, Dan Simberloff, provided great guidance since the inception of this project. He was particularly helpful at getting the funds to support the field research, and read each of the chapters of this dissertation an uncountable number of times. Interacting with him all these years has been a very stimulat- ing and rewarding experience, both academically and personally. I also thank Marcelo Aizen, who advised on many aspects of this project and first pointed out to me the potential impact of introduced ungulates on plant-animal mutualisms; his pioneering research on plant-pollinator interactions in the southern Andes paved the way of my work. Although I was not able to appoint him to be part of my dissertation commit- tee, I have always considered him an honorary committee member. The rest of my committee members, David Buehler, Lou Gross and Jake Weltzin have all been extremely supportive and helpful, and were al- ways ready to chat whenever I needed it. Discussions with Jake on statistical issues were particularly help- ful. I also thank Mitch Cruzan and Stuart Pimm, who were both part of my original committee but had to drop out a few months ago because they could not make it to my defense. Mitch was especially helpful during the initial part of this project. Discussion with many people helped clarify my ideas. Michael Collins, Florencia Fernández Campón, Tad Fukami and Ben Sikes have always been ready to talk about my ideas. Florencia was par- ticularly helpful with the development of the abundance index used in Chapter 4. Besides my committee members, the following people read and commented on different sections of the dissertation: Marcelo Ai- zen, James Carlton, Michael Collins, Mitch Cruzan, Florencia Fernández Campón, Tad Fukami, Sean McMahon, Peter Morin, Massimo Pigliucci, María Andrea Relva, Suzanne Renner, Ben Sikes, Betsy Von Holle, Nick Waser, and five anonymous reviewers of Chapters 3 and 4. I also had invaluable help in the field and in the lab from Carolina Quintero, Juan Paritsis, Fabiola Salvador, Ben Sikes, Mariana Tadey, Deborah von Hapsburg and my brother Álvaro Vázquez. Ann Reed provided advice with the mixed model ANOVAs. The following experts helped me identify insect and plant material: Guillermo Claps (syrphid, nemestrinid and bombilid flies), Cecilia Ezcurra (plants), Steve D. Gaimardi (lauxaniid flies), Arturo Roig Alsina (bees), Christian Thompson (syrphid flies), Richard Westcott (buprestid beetles), and Norman E. Woodley (nemestrinid flies). I thank the National Parks Administration of Argentina for allowing me to work in the Nahuel Huapi and Los Arrayanes National Parks, the city of Bariloche for permission to work in the Llao Llao Municipal Reserve, and the De Bin family for kindly letting me work in Safariland. The Laboratorio Ecotono at the Universidad del Comahue in Bariloche and Mitch Cruzan at the University of Tennessee generously let me use their laboratory facilities. I also thank Paola D’Adamo, the Pérez-Serantes family (Lidia, Marcelo, and Joaquín) and the Aizen family (Marcelo, Ale, Nahuel y Marco) for their hospitality during fieldwork. This project was funded with grants from the Turner Foundation and the Foundation for Deep Ecology to Dan Simberloff, a National Science Foundation Dissertation Enhancement Grant (# 9900676) to Dan and I, and a summer graduate research grant from the Department of Ecology and Evolu- tionary Biology at the University of Tennessee. I was supported during the initial part of this work by a Fulbright Graduate Fellowship through the Institute of International Education, U.S.A. v ABSTRACT Introduced mammalian herbivores can significantly affect ecosystems. I studied the effects of introduced ungu- lates on plant-pollinator interactions in the temperate forest of the southern Andes. Introduced mammalian her- bivores, including ungulates, are a major conservation problem in this biome. I conducted field studies in eight forested sites where Nothofagus dombeyii was the dominant canopy tree. I described the interactions between fifteen common, insect-pollinated understory plants. I used these data to address two main questions. The first one is whether the susceptibility of plants and pollinators to disturbance by introduced ungulates is related to their degree of interaction specialization and interaction asymmetry. I found no relationship between degree of specialization and a species’ response to disturbance. I also found that plant–pollinator interactions tend to be asymmetric in this system; however, asymmetry of interactions did not explain the variability in species’ re- sponses to disturbance. The second question I addressed is whether introduced ungulates can affect pollination and plant reproduction indirectly by modifying plant population density. This hypothesis is different from previ- ous hypotheses of indirect effects of herbivores on plants, all of which concerned individual-level effects on vegetative and reproductive traits, whereas my hypothesis focuses on population-level effects. I found strong evidence of such an effect for only one of the species I studied, the herb Alstroemeria aurea. The general lack of evidence for indirect effects on most species may result from resistance to cattle grazing, spatial refugia, or low statistical power of my analysis. For A. aurea, additional evidence indicates that herbivores decrease the abso- lute and relative population density of this species through trampling., which in turn results in lower conspecific pollen deposition in stigmas and lower reproductive performance. Thus, my study suggests that introduced ungulates can in some circumstances affect plant-pollinator interactions significantly. However, in most cases plant-pollinator mutualisms appear resilient to the effects of introduced ungulates, and the direct effects of intro- duced ungulates on plants and pollinators are in general stronger than the indirect effect