Luận án tiến sĩ: Sinh thái quần thể hướng dương - ĐH Kansas

THE POPULATION ECOLOGY OF SUNFLOWERS (HELIANTHUS ANNUUS) THROUGH SPACE AND TIME by Jennifer Moody-Weis B. Missouri State University, 2000 Submitted to the Department of Ecology and Evolutionary Biology and the Faculty of the Graduate School of the University of Kansas In partial fulfillment of the requirements for the degree of Doctor of Philosophy ____________________________ Chairperson Committee Members ____________________________ ____________________________ ____________________________ ____________________________ Date Defended ________________ UMI Number: 3243462 UMI Microform 3243462 Copyright 2007 by ProQuest Information and Learning Company. All rights reserved. This microform edition is protected against unauthorized copying under Title 17, United States Code.

ProQuest Information and Learning Company 300 North Zeeb Road P. Box 1346 Ann Arbor, MI 48106-1346 The Dissertation Committee for Jennifer Moody-Weis certifies that this is the approved version of the following dissertation: THE POPULATION ECOLOGY OF SUNFLOWERS (HELIANTHUS ANNUUS) THROUGH SPACE AND TIME ____________________________ Chairperson Committee Members ____________________________ ____________________________ ____________________________ ____________________________ Date Approved________________ 2 ACKNOWLEDGEMENTS. 9 CHAPTER 1 THE MECHANISMS AND CONSEQUENCES OF SEED BANK FORMATION IN WILD SUNFLOWERS (HELIANTHUS ANNUUS). 22 METHODS AND MATERIALS.

43 CHAPTER 2 SCALING-DOWN METAPOPULATION DYNAMICS OF TWO ROADSIDE PLANT SPECIES: TRANSLATING INFORMATION FROM COARSE- TO FINE-SPATIAL SCALES. 67 MATERIALS AND METHODS. 88 CHAPTER 3 THE REGIONAL ECOLOGY AND GEOGRAPHY OF WILD SUNFLOWERS (HELIANTHUS ANNUUS): LINKING MODELS OF PRESENCE WITH MODELS OF ABSENCE. 112 METHODS AND MATERIALS.

153 3 Acknowledgements I am lucky to have had so many wonderful mentors and friends here at KU. I would not have accomplished as much without their support, advice, and friendship. All of my committee members (Dr. Helen Alexander, Dr.

Bryan Foster, Dr. John Kelly, Dr. Town Peterson, and Dr. Steve Egbert) have been extremely helpful and I thank them all for their time and help throughout the dissertation process.

I especially want to thank Helen. I could not have asked for a better advisor. She is an excellent scientist, teacher, and mentor. I have learned much from her, and I cannot enumerate the ways that she has helped me.

I have benefited from her grasp of statistics, her ability to see the big picture, and her kindness and understanding. I respect her ability to balance her personal and professional lives. She is a role-model for anyone in science. I thank Helen for all of the above and for her friendship and support throughout this process.

I hope that we will continue to work together in the future. I am also grateful for Town Peterson’s enthusiasm about my sunflower GARP project. Without his expertise and help, that chapter would not have come to fruition. Special thanks to Dr.

Dan Crawford for serving on my orals committee at the last minute. Never in my life have I been surrounded by such a terrific group of friends as I have had here at KU. In particular I would like to thank Lisa Castle, Tim Dickson, Beth Davis, Jenny Hopwood, Anna Clarke, Bridgett Chapin, Debbie Baker, Cathy Collins, Erin Questad, Irene Khavin, and Abby Reft. Without them life in Lawrence would have been dull.

They have kept me motivated when I needed the extra push. I feel especially grateful for my friends of the knitting group, the weekly ritual of 4 gossip, pizza, root beer, brownies, and knitting is among my best memories of my time in Lawrence. Of course, the research needed to complete a dissertation requires funding, and I am thankful for the funding that supported me while at KU. Grant money from the USDA (9904008 and 9601405) awarded to Helen Alexander, funded me as a Research Assistant for several semesters.

This investigation was supported by the University of Kansas General Research Fund allocation #2301446. The department of Ecology and Evolutionary Biology supported me with a teaching assistantship for several semesters. I also received a Sigma Xi grant, which allowed me to conduct the large-scale sunflower surveys. I have had wonderful help with field work.

Thanks to Danielle Brunin, Shad Woodworth, Lisa Castle, and Jason Emry. The staff at the Kansas Field Station and Ecological Reserves (KSR) has been incredibly helpful to me. Dean Kettle, KSR’s Associate Director, helped me locate the field for my seed bank experiment. Galen Pittman has always been available to answer my questions.

I especially thank Bruce Johanning, who tilled all of the plots for my seed bank study. Without his skill and expertise, I would not have been able to complete that experiment. Finally, the support of my family has been important to my success as a graduate student. My husband, Stephen, has been very patient throughout the whole process.

He let me move him away from family and friends for me to fulfill my goals, and I am extremely thankful for that. He has been the main buttress in my support system: reading my papers, listening to my complaints, helping to grade papers, and 5 driving me across country to count sunflowers (among many, many other things). I love him with all my heart. The rest of my family (Mom, Chuck, Dad, Linda, Grandma, Becky, Zach, Amy, Roger, Randi, and Scott) have also be supportive and understanding of my goals and dreams.

Special thanks also to Lily Cat for keeping me company while writing. 6 Abstract Explicitly incorporating space and time into population ecology has offered insight into environmental influences on population processes. In this dissertation, I explored the population ecology of wild, annual sunflowers (Helianthus annuus L., Asteraceae) at three spatial scales, using multi-year studies. In Chapter 1, I experimentally examined, at the 1.3 m scale, the roles of soil disturbance and seed density on seed bank formation and resulting populations.

I found that seedling establishment required large soil disturbances, and soil disturbances following seed dispersal were essential for forming seed banks. Larger seed banks increased seedling emergence the following year, but, due to density- dependent survival and reproduction, larger seed banks did not produce more inflorescences. Scaling-down methods provide a way to estimate fine-scale ecological patterns from data collected at coarser scales. In Chapter 2, I applied fractal-based scaling-down methods to occupancy and to the dynamics processes of colonization and extinction.

Using multi-year surveys of roadside sunflower populations in both Kansas (24 km) and Nebraska (19 km), I predicted colonization and extinction rates at the 80 m scale from data at coarser scales. I applied these methods to data from roadside surveys of Silene latifolia Poir. In general, scaling of occupancy and colonizations was more successful than for extinctions, and all three variables scaled better in Helianthus than in Silene. Several possible explanations 7 exist.

For example, the greater reliance of sunflower establishment on disturbance and on the seed bank for colonizations may contribute to the differential scaling success between Helianthus and Silene. Modeling the ecological niche of generalist species, like sunflowers, is difficult because they have broad climatic tolerances. For Chapter 3, I collected extensive records of observed sunflower presence and absence (every 1.6 km for 5333 km in the Great Plains) and used these data and high resolution satellite imagery (500m) to develop highly accurate ecological niche models using GARP (Genetic Algorithm for Rule-Set Production). Models particularly predicted the absence of sunflowers in the eastern portion and the presence of the plant in the western portion of the study area well.

8 Introduction Ecologists seek to understand how interactions with the environment influence the diversity and distribution of organisms. Within this broad discipline, population ecologists focus on how births, deaths, and migration determine the size and distribution of populations (Harper 1977; Hanski 1999; Caswell 2001). Population ecology has its roots in agriculture, and many early studies were concerned with the effects of competitors, pests, and diseases on economic crop yield (Harper 1977). The foundations laid by these early studies have provided strong support for subsequent research, as the realm of population biology has branched out to include demography, life-history evolution, population viability analysis, and metapopulation dynamics, to name a few.

Most early studies were conducted without explicit consideration of spatial structure or spatial scale, and traditionally population ecology has not focused on the consequences of space on populations (Weins 1999). In the past several decades, all of ecology, including population ecology, has been undergoing a paradigm shift; the integral role of spatial structure and scale in ecological processes has been established (May 1989; Levin 1992; Weins 1999; Kratz et al. This paradigm shift has been driven by several emerging fields of study. First, the development of metapopulation theory brought with it formal recognition that populations are not isolated and that the processes of population colonization and extinction act together to maintain regional persistence of a species (Levins 1969; Prince et al.

1985; Hanski 1999; Menéndez & Thomas 2000; Silvertown & 9 Antonovics 2001; Hanski & Gaggiotti 2004). Second, the 1980’s saw the development of landscape ecology, which focuses explicitly on the interactions between spatial patterns and ecological processes (Turner 2005). Third, the threat to biodiversity posed by invasive species has led scientists to search for properties of landscapes (i. connectivity, fragmentation) that may promote or hinder biological invasions (Moody & Mack 1988; With 2002).

Fourth, the recognition of global climate change has focused attention on how species’ distributions will respond to global climate change. Understanding these changes often requires study across coarse spatial scales, taking into account the heterogeneity of the landscape (Thuiller et al. Of course, recognition of the importance of space to ecological processes has included other fields of study (i. island biogeography, conservation), and has affected all aspects of ecology.

As a result of the paradigm shift, to quote Weins (1999), “we can no longer ignore spatial variation and pattern, nor can we continue to cling to the belief that the scale on which we view systems does not affect what we see”. Many population ecologists have embraced the paradigm shift, and, in doing so, have gained new insights into the dynamics and distributions of populations: by integrating landscape and population ecology methods, in explicitly examining the effect of scale, and through a biogegraphical approach. Studies integrating landscape and population ecology have examined how landscape structure (i. fragmentation, connectivity of habitat patches) and factors generating that structure (i.

disturbance, succession) influence migration (Jonsen et al. 2001; Engen et al. 2002), spread of 10 invasive species (Moody & Mack 1988; With 2002), extinction risks (Kramer-Schadt et al. 2005), and metapopulation persistence (Kallimanis et al.

Explicit examination of the same processes at multiple spatial scales has demonstrated, for example, variation in migration (Englund & Hambäck 2004), parasitism (Norowi et al. 2000), and metapopulation structure (Menéndez & Thomas 2000). By studying variation in population processes across a species’ geographic range, thus taking a biogeographic approach, ecologists have compared invasiveness of species in their native and non-native range (Grigulis et al. 2001; Hierro et al.

2005), and investigated the determinants of species’ ranges (Brewer & Gaston 2002; Brewer & Gaston 2003; Castro et al. Related to the importance of spatial scale in ecological studies is the idea that temporal changes and scales also influence ecological processes (Schneider 2002). For example, landscape structure can change through time due to both disturbance and succession, which, in turn, can influence the extinction rates of plant populations (Wimberly 2006). Population growth rates, often assumed in population models to be constant through time, may vary through time with significant consequences for conservation efforts (Menges et al.

Finally, many plant species use dormant propagules, such as seeds, as a means of dispersal through time, impacting population dynamics (Kalisz & McPeek 1993; Menges & Quintana-Ascencio 2004), species evolution (Templeton & Levin 1979; McCue & Holtsford 1998), and community composition (Leck et al. 1989; von Blanckenagen & Poschold 2005). 11 Thus, study of a species across multiple spatial scales, and for several years, can provide insights on how the landscape influences the population dynamics and regional distribution of a species. As such, my dissertation explores the population ecology of wild sunflowers (Helianthus annuus) at three spatial scales, using both experimental and modeling approaches.

I have focused on sunflowers in my dissertation for several reasons.