COMPARATIVE SEED ECOLOGY OF NATIVE AND ALIEN PLANTS OF OPEN UPLANDS ...

164 Pages·2000·9.06 MB·English

COMPARATIVE SEED ECOLOGY OF NATIVE AND ALIEN PLANTS
OF OPEN UPLANDS
Christopher Sean Blaney
A thesis submitted in conformity with the requirements
for the degree of Master of Science
Graduate Department of Botany
University of Toronto
O Copyright by Christopher Sean Blaney 1999
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COMPARATNE SEED ECOLOGY OF NATIVE AND
ALIEN PLANTS OF OPEN UPLANDS
Master of Science 1999
Chnstopher Sean Blaney
Department of Botany
University of Toronto
Plant invaders may gain an advantage over natives because only enemy-free species are likely
to invade (the predator filter hypothesis), or because invaders lose enemies while moving to a
new area (the predator escape hypothesis). Working at the Joker's Hill Field Station, near
Newmarket. Ontario, 1 bave combined site descriptions, surveys. and experiments to
investigate the role of predaton and pathogens in seed ecology, and to understand their role in
the establishment and spread of exotic species.
Results indicate that seeds of both natives and exotics suffered significant losses to above-
ground predators and below-ground pathogens. Losses vaned among species and habitats;
wrtlands had particularly high levels of fungal mortality. Aliens and natives did not
consistently differ in their susceptibility to predators and pathogens, even when analyzed using
methods that controlled for phylogenetic biases. These results suggest natural enemies of seeds
do not as a general rule determine invasive ability.
ACKNOWLEDGEMENTS
Many people contributed to making my time as a Master's student enjoyable and rewarding, and
1 will do my best to recognize them al1 here. To those 1 have left out, my apologies, 1 am wnting
this just hours before I have to submit, but to everyone my deepest thanks.
First and foremost 1 should recognize the efforts of my supervisor Professor Peter Kotanen, who
was unceasingly attentive to my needs and generous with his tirne, advice and funding. 1 could
not have completed this project without his help. He has gone well above the effort required of a
supervisor and has taught me a great deal. 1 feel privileged to have worked with him as a student
and as a friend. 1 have also benefitted greatly from the guidance and suggestions of al1 of the
mernbers of n~ysu pervisory cornmittees, which have included Profesors David Wedin, Spencer
Barrett. Robert Jefferies and Gary Sprules. Aside from my committee, Professor Linda Kohn
provided advice on a nurnber of issues related to soi1 fungi, and Professor Peter Bal1 was always
ready to assist in the identification of tricky plant specimens. Interactions with many student
colleagues have helped shape and sharpen rny academic skills as well providing happy
diversions. Che Elkin. Marc Johnson, Luc Bussiere, Brendon Larson, Patrick Lorch, Andrea
Case and rny fellow seed bank afficionado Esther Chang deserve special mention in this regard.
Jutta Stein, Greenhouse Technician at the University of Toronto at Mississauga deserves
pürticular individual recognition. She went to great efforts to ensure my plants survived in the
greenhouse. She always made space for my odd assortment of rather weedy specirs, even when
they were spreading into ber pots. Her efforts not only allowed me to complete my thesis, but
also enabled me to confidently have a life on weekends, knowing the crucial plants were well
taken care of.
My work was aided substantially by the numerous field and laboratory assistants, paid and
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unpaid, who spent time in the Kotanen lab Michelle Tseng, Sonya Carl, Arthur Poon, Joel
Sotomayor, Sandra Benvenuto, Sheenagh Bell, Bill Kilburn, Carl Rothfels, Vijanti Ramlogan,
Reagan Szabo, Marc Johnson and Uyen Dias. Not only did they offer able assistance on many
difficult and repetitive tasks, they left me with many of my best, lasting memories of my time at
Erindale.
At the Joker's Hill field site, property manager William Fox was always available when needed
and was generous with the sites resources. The donors of the property, Murray and Marvelle
Koffler should also be recognized. They have given the University of Toronto a unique gift, the
value of which it is only just beginning to fully recognize. The Joker's Hill property is a rare
jewel in the southem Ontario landscape and was a joy to work at.
I would also like to recognize my parents, who first inspired my love for the natural world and
who have always been entirely supportive of my interests. Finally. to Becky Whittam, who has
been my most important source of encouragement, sympathy. sustenance (literal and spiritual)
and serene working conditions in the difficult tirnes leading to thesis completion. I thank you for
your love and patience.
TABLE OF CONTENTS
Contents Page
ABSTRACT
ACKNOWLEDGEMENTS
TABLE OF CONTENTS
LIST OF TABLES
LIST OF FIGURES
-
CHAPTER 1 General Introduction
Overall Introduction
Biological Invasions
Seeds and Their Enemies
Predator Escape and Predator Filter Hypotheses
The importance of phylogeny
Old Fields
Objectives
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CHAPTER 2 Vegetation of Joker's Hill
Introduction
Site overview
Landfons and early human history of Joker's Hill
Native plant communities: The historie setting
Old fields: The study system
Survey Methods
The local species pool: Overall vascular plant species
Species presence and abundance for main tkld sites
Seed bank estimation for main field sites
Results and Discussion
Overall vascular plant species pool
Rare native plant species
Species presence and abundance at main field sites
Seed bank estimation for main field sites
Conclusions
Contents - Pape
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CHAPTER 3 Experimental Survey of Native and Alien Seed Mortality 36
Introduction 37
Methods 40
Study site 40
Experimental Sp ecies 4 1
Treatments 44
Soi1 srtrfnce seed predatinn experiment 44
Seed bank mortalin, experiment 45
Analysis 46
Resu lt s 47
Soi1 surface seed predation experiment 47
Seed bank mortality experirnent 53
Discussion 72
Soi1 surface seed predation 72
Predator iden tity 72
Overd seed rernovcrl 72
Patterns in trentmerrt efects 74
Seed bank mortality experiment 75
Fwzg i d e a ddition 75
Inv zrrebrate e.rclusion 76
Tenzporal pattern in seed recovery 77
Treatment efsecrs vs. seed size 78
Twonomic pattenz 78
Aliens vs. Natives 79
Contents Pape
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CHAPTER 4 Comparative Experiments on Fungal and Habitat
Effects on Seed Bank Mortality
Introduction
Methods
Study site
Experimental Species
Treatments
Analysis
Results
Overüll seed recovery
Overall effects of fungicide addition
Variation in seed recovery between species
Variation in recovery by origin
Discussion
Does fungal mortality influence seed persistence in the soi1 seed bank?
Do seed recovery and fungal mortality vas, between wetland and
upland meadows?
Does fungal mortality Vary betwren closely related natives and alirns?
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CHAPTER 5 General Conclusions
Achievernent of thesis objectives
a) to provide background information on the site and biological
setting of the experiments
b) to determine whether seeds suffer significant losses to predators
before incorporation into the seed bank
to deterrnine whether seeds suffer significant losses to seed predators
C)
and uathooens in the seed bank
Contents Page
CHAPTER 5 (cont'd)
d) to discover whether seed losses to naturd enemies differ
among species 104
e) to determine whether seed losses to natural enemies differ
between habitats 1O 4
f) to determine whether seeds of native and alien species differ
in their susceptibility to natural enemies 105
g) to determine whether differences in seed losses between
natives and aliens occur independent of their phylogenetic
relationship 105
Limitations of the work 1 O5
General Conclusions 1 O6
LITERATURE CITED 1 O7
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APPENDIX 1 Vascular Plants of Joker's Hill 1
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APPENDIX II Rare Native Vascular Plants of Joker's Hill XX
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APPENDIX III Birds of Joker's Hill XXI 1
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APPENDIX IV Mammals of Joker's Hill XXVI
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APPENDIX V Reptiles and Amphibians of Joker's Hill XXVII
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LIST OF TABLES
Table 2.1. Species present at Dead Man's Curve and Wet Meadow field sites, within
the area of the Kotanen plots.
Table 2.2. Abundance of species found in intensively sampled plots at Dead Man's
Curve field site.
Table 2.3. Abundance of species found in intensively sampled plots at Wet Meadow
field site.
Table 2.4. Geninable seed banks (mean seedslm22 SEM) from top and bottoni
halves of cores from Dead Man's Curve and Wet Meadow field sites,
fall 1997 and spring 1998 trials.
Table 2.5. Garminable seed bank (mean seeds/m2 to IO cm depth t SEM) at the
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Dead Man's Curve field site, fdl 1997 and spnng 1998.
Table 2.6. Germinable seed bank (mean serdslrn2 to IO cm depth SEM) at the
Wet Meadow field site, fdl 1997 and spring 1998.
Table 3.1. Experimental species for seed bank mortrility and soi1 surface seed
predation experiments, indicating presence on Joker's Hill research
station property, and at the Dead Man's Curve research site.
Table 3.2. Resuks of seed predation experiment: Mean proportional seed recovery
+. SEM.
Table 3.3. Results of 3-factor randomized block factorial ANOVAs on overall,
nativeand alien data from seed predation experiment.
Table 3.3. Seed predation experiment; vertebrate exclosure and invertebrrite
e~closuree ffects on seed recovery by species, with seed weights.
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