EVOLUTIONARY DIFFERENTIATION IN SEXUALm AND LIFE HISTORY IN POLYPLOID AGAMK ANTENNARIA PARLM (ASTERACEAE) bu UAMARIE O'CONNELL A thesis submitted to the Department of Biology in conformity with the requirements for the degree of Master of Science. Queen's University Kingston, Ontario, Canada September, 1997 copyright O Lisa Marie O'Connell, 1997 National Library Bibliothèque nationale ($1 of Canada du Canada Acquisitions and Acquisitions et Bibliographie Services seMces bibliographiques 395 Wellington Street 395, rue Wellington Ottawa ON K1A ON4 OttawaON K1AON4 Canada Canada You6ie Votmrd~ Ovr Rh9 Nom, nifBrence The author has granted a non- L'auteur a accordé une licence non exclusive licence dowing the exclusive permettant à la National Library of Canada to Bibliothèque nationale du Canada de reproduce, loan, distri'bute or sell reproduire, prêter, distribuer ou copies of this thesis in microfom, vendre des copies de cette thèse sous paper or electronic formats. la forme de microfiche/nlm, de reproduction sur papier ou sur format électronique. The author retains ownership of the L'auteur conserve la propriété du copyright in this thesis. Neither the droit d'auteur qui protège cette thèse. thesis nor substantid extracts from it Ni la thése ni des extraits substantiels may be printed or othenvïse de celle-ci ne doivent être imprimés reproduced without the author's ou autrement reproduits sans son permission. autorisation. ABSTRACT Antemarin parlinii is a hexaploid agamic complex found in deciduous forests and old fields throughout east-central North America. Northern and eastem populations of this dioecious plant conçist of females only ("female" populations) while southeastem populations contain both sexes ("mixed- sex"). Some individuals reproduce sexually, some through gametophytic apomixis (asexual seed production), while others may practice a mixture of sexual and apomictic seed production. 1investigated the pattern of variation in sexuality within and among populations and found that populations were highly differentiated in sexuality, and there was little or no variation in sexuality within populations. I also found no evidence that individuals commonly practiced partial apomixis. Natural seed set was measured in fifteen female and nine mixed-sex populations in Ohio, Ontario and Québec. Female populations had a high autonomous seed set (average 75%), whereas in mixed-sex populations seed set was positively correlated with population size and the propotion of males, indicating a strong reliance on sexual reproduction. In a pollinator exdusion experiment conducted in the field in Ohio, plants in two female populations set more than 70% of their seeds, while there was no evidence of autonomous seed set in two mixed-sex populations. Similar results were obtained in a pollination experiment in a common greenhouse environment. Overall these three experiments indicate that female populations are asexual and mixed-sex populations are sexual. I found that apomictic and sexual A. parlinii occupy different habitats where their ranges ovêrlap. Apornicts tend to occur in disturbed and ephemerd habitats while sexuals occur in more stable woodland habitats. I found that apomicts had a higher reproductive output than sexuals, producing more capitula per inflorescence, florets per capitulum and twice as many seeds per inflorescence. Diaspores from asexual plants had rnorphological traits, such as a larger pappus-toseed ratio and more barbs per pappus, which increased seed free-faU time, an estimate of dispersal potential. The combination of asexuality with an inaeased reproductive output and seed dispersa1 potential cm lead to a superior colonizing ability of apomictic A. parlinii and partly explain observed distributional differences between apomictic and sexual populations. ACKNOWLEDGMENTS 1 am indebted to numerous people who helped me throughout this thesis. I thank my supervisor Chris Eckert for hiç help and encouragement through regular "vibory jugs" at the grad club every step along the way. 1 also thank Bob Montgomerie and Heather Proctor for advice throughout this study, and Katherine Mavraganis, Marcel Dorken, and Matthew Routley for proofreading this manuscript. Thank you also to Joel Shore and Brian Cumming for helpful comments to help me improve thiç thesis. My time spent in Ohio would not have been as enjoyable without the help and Company of my field assistants MqlAllen and Russ Groves. 1 am particularly grateful to the Linehan family, John, Rita, Molly, Patick, Devin, and Christina for their hospitality by feeding me and providing a roof over my head on those cold, wet, spring nights in Ohio. 1 also thank the curators at the CAN, DAO, OS, and BH herbaria for access to Antennaria specimens. 1 am also grateful to the managers at the Kitty Todd Nature Conservancy Preserve, Toledo metro parks (Oak Opening Nature Preserve), Irwin Prairie Nature Preserve and Lake county metro parks (Indian Point) where 1 conducted parts of this study and collected plants. This work was partly funded by a Natural Sciences and Engineering Research Council postgraduate fellowship. TABLE OF CONTENTS 1 General introduction.............................................. -1 Medianismsofapo~s........................................ 7 Partialapo- ............................................... 4 Selectionforapo- .......................................... 6 Polyploidy and hybridization.................................. -7 Geographical parthenogrnesis................................. -8 Antennaria (Asteraceae) ....................................... 9 Herbanumswey ............................................ 12 2 The evolutionary significance of variation in sexuality in polyploid agamic Antemaria parlinii .......................................... 18 Materials and Methods ............................................. 21 Studypopulatiom............................................ 21 Natural seed set in female and mixed-sex populations .......... 23 Field pollinator-exclusion expriment ........................ -25 Greenhouse pollination experiment ........................... 26 Resdts ............................................................ 27 Nahual seed set in female and mixed-sex populations .......... -27 Pohator-exdusion experiment ............................... 32 Greenhouse pollination experiment ........................... 32 Discussion ......................................................... 36 Variation in sexuality among and within populations ...........36 PartialapomWs .............................................. 38 Dismptive selection for sexuality ............................. -42 3 Differences in distribution and colonizing ability between apomictic and sexual populations of Antennan'a parlinii ...................... 43 Materials and Methods ............................................. 46 Habitatsurvey ................................................ 46 Popdationsurvey............................................. 46 Reproduaiveoutput.................................... 46 Diaspore measurements................................. 48 Free-fautest ................................................. 50 Germination experirnent ...................................... 52 Results............................................................ 53 Habitat differences between asexual and sexual populations ......53 Differences in reproductive output between asexual and sexual populationç ................................................. 53 Relation between diaspore traits and free-fall time .............. -57 Differences between asexual and sexual populations in diaspore traits ............................................................. 57 Germination differences in asexual and sexual populations ....... 63 Discussion......................................................... 63 Habitat differences ........................................... 63 Reproductiveoutput......................................... 65 Dispersal abiliq.............................................. 66 Differences in cornpetitive ability .............................. 69 4 General discussion and conclusions ................................ 71 Mainhdings ................................................ 71 Partialapomixis .............................................. 71 Differences in reproductive output and dispersa1 potential ....... 72 Habitat differentiation ........................................ 73 Evolutionary origin of associations between sexuality. reproductive output. seed dispersal and habitat distribution .................74 APPENDICES ...................................................... 86 VITA ..............................................................92 vii LIST OF TABLES 2-1: Analysis of variation in natural seed set in female and mixed-sex populations of An tmnaria parlinii. ............................ -29 2-2: The effect of pollinator exclusion on seed set in female and rnixed-sex populations of Antennaria parlinii ............................ .34 3-1: Correlations arnong pappus traits in Antennaria parlinii. ...........5 1 3-2: Anaiysiç of variation in reproductive output in Antennaria parlinii .56 3-3: Multiple regression of the effect of pappus traits on free-fall time in Antemaria parlinii. ...........................................59 3-4: Analysis of variation in diaçpore traits in Antennaria parlinii. ......61 LIST OF FIGURES 1-1. Range map of Antennaria parlinii and its three progenitor species . .11 1-2. Distribution of herbarium collections