Comparative studies of the population ecology and life history patterns of an alkaline salt lake insect

223 Pages·2013·1.39 MB·English

by  Herbst, David B.

AN ABSTRACT OF THE THESIS OF
David B. Herbst for the degree of Doctor of Philosophy
in Zoology and Entomology presented on March 6, 1986
.
Title: COMPARATIVE STUDIES OF THE POPULATION ECOLOGY AND
LIFE HISTORY PATTERNS OF AN ALKALINE SALT LAKE INSECT:
EPHYDRA (HYDROPYRUS) HIANS (DIPTERA:EPHYDRIDAE)
Redacted for Privacy
Abstract approved:
-v-- U
rank,,P. Conte (Zoology)
1;
Redacted for Privacy
or J. Brookes (Entomology)
Seasonal abundance and life history traits were
compared between populations of the brine fly ERhydra
(Hydrokyrus) hians Say (Diptera:Ephydridae), from two
western Great Basin alkaline salt Lakes. Abert Lake,
Oregon, has a relatively low salinity (20-30 g/1 total
dissolved solids) and more co-inhabitant benthic species
than the higher salinity Mono Lake, California (75-90 g/l).
During a period of declining salinities at both lakes, the
abundance of this osmoregulating insect decreased at Abert
Lake, and increased at Mono Lake. This suggests that
abundance may be maximized at intermediate salinities due
to biotic limitations imposed by competing and predatory
species at dilute salinities, and physiological limitations
imposed by osmotic stress at high salinities.
Experimental rearing of larvae at high salinities, or
reduced algal food supply levels, produced low survival,
prolonged development, and smaller size at maturity. When
food is not limiting, Mono Lake larvae exhibit greater
independence of the inhibitory effects of increased salt
concentration compared to larvae from less saline Abert
Lake. Selection for enhanced salt tolerance may thus have
occurred at Mono Lake, but appears to be limited above 150
g/1 because survival of first instars, and maturation of
final instars are impaired at 200 g/l. Besides direct
physiological effects, increased salinity also reduces
algal growth and may thereby limit food availability to E.
hians.
Heritable differences in body size exist between
populations in addition to environmentally induced changes
in growth and size. Abert flies are inherently larger than
Mono flies, and develop more rapidly at comparable
salinity. Reduction in pupal size severely curtails
emergence, and any small-bodied adults that do emerge
possess only slight lipid stores, and have a low resistance
to starvation. Improvements in algal food supplied to
adults increases the proportion of flies reproducing,
fecundity, and egg production rates. Reproductive effort
has a negative impact on survival only when food is
limiting.
These results suggest that direct and indirect effects
of changing salinity may play an important role in shaping
life history patterns and regulating population dynamics of
the alkali fly.
COMPARATIVE STUDIES OF THE POPULATION ECOLOGY
AND LIFE HISTORY PATTERNS
OF AN ALKALINE SALT LAKE INSECT:
EPHYDRA (HYDROPYRUS) HIANS SAY
(DIPTERA:EPHYDRIDAE)
by
David B. Herbst
A THESIS
submitted to
Oregon State University
in partial fulfillment of
the requirement for the
degree of
Doctor of Philosophy
Completed March 6, 1986
Commencement June 8, 1986
APPROVED:
Redacted for Privacy
Prof ess(ory.ogy in Aire(' of major
Redac'---t- ed for Privacy
ProfesttiAf Ep-Comology in charge of major
Redacted for Privacy
Chairman of Department c/Zoology
Redacted for Privacy
Chairman of Department of Entom ogy
Redacted for Privacy
Dean of Gra ate Schoo<
Date thesis is presented March 6, 1986
Typed by David B. Herbst for David B. Herbst
ACKNOWLEDGEMENTS
Through these many years of study I am grateful to
have had the freedom to explore the paths where my
interests have led. I owe sincere thanks for guidance and
contributions along these paths to my thesis advisors Drs.
Frank P. Conte and Victor J. Brookes, and the other members
of my committee: Drs. P.B. McEvoy, C.J. Bayne, R.W.
Castenholz, C.D. McIntire, N.H. Anderson, and J. Beatty.
In addition, other OSU faculty members including Drs. C.E.
King, H.K. Phinney, and S.V. Gregory have freely provided
their expertise and advice.
There are many friends and colleagues without whom my
work would have been far less enjoyable and productive,
they include: Dan Bean, Dean Blinn, Katie Boula, Tim
Bradley, Nick Collins, Gayle Dana, Joe Furnish, John
Harris, Eldon Horst, Bob Jellison, Wayne Mathis, Jim
McIver, John Melack, Jim Mende, Andy Pollack, Joseph
Scheiring, Dave Shuford, Karl Simpson, Stuart Sloan, Scott
Stine, Tim Such, Evan Sugden, Peter Vorster, Dave Winkler,
and Jeff Witcosky. For their hospitality on my visits to
Mono Lake, and their genuine interest and concern I would
like to thank David and Sally Gaines, and Meredith and
Larry Ford.
For their constant loving support, patience, and
encouragement I wish to thank all my family Len, Kay,
Rebecca, Suzanne, and Dorothy Herbst. I am thankful also
to Faye Cummins for sharing all the joys, frustrations, and
growth over these years, and for her excellent artwork
(Figure II.1).
I also wish to acknowledge the funding support
provided by the United States Fish and Wildlife Service,
Sigma Xi, The American Museum of Natural History, the
Oregon State University Department of Zoology, the Mono
Lake Foundation, and the Los Angeles Department of Water
and Power.
Finally, I would like to give tribute to the ancient
desert seas of the Great Basin and the allegories of the
alkali fly, from which I have gained inspiration and
humility on my sojourns.
TABLE OF CONTENTS
Page
I. COMPARATIVE STUDIES OF THE POPULATION ECOLOGY
AND LIFE HISTORY PATTERNS OF AN ALKALINE SALT
LAKE INSECT: EPHYDRA (HYDROPYRUS) HIANS SAY
(DIPTERA:EPHYDRIDAE)
INTRODUCTION
1
II. AUTECOLOGY AND NATURAL HISTORY OF AN ALKALINE
SALT LAKE INSECT: EPHYDRA (HYDROPYRUS)
HIANS SAY (DIPTERA :EPHYDRIDAE) 6
Introduction 6
Methods 9
Benthic Sampling 9
Temperature and Salinity Effects
on Development 10
Results and Discussion 13
Life Cycle and Natural History of
the Alkali Fly 13
Microhabitat Associations at Mono Lake 19
Temperature and Salinity Effects 20
III. BENTHIC SPECIES DIVERSITY AND PHENOLOGY IN
RELATION TO THE PHYSICAL AND CHEMICAL
ENVIRONMENTS OF GREAT BASIN ALKALINE SALT LAKES 31
Introduction 31
History and Physicochemical Environments
of Abert and Mono Lakes 32
Methods 37
Sample Sites 37
Temperature and Salinity 38
Benthic Fauna 39
Benthic Flora 40
Results 42
Salinity 42
Temperature 43
Benthic Fauna 43
Benthic Flora 46
Discussion 49
IV. COMPARATIVE POPULATION ECOLOGY OF
EPHYDRA HIANS SAY (DIPTERA:EPHYDRIDAE) IN
ALKALINE SALT LAKES OF THE WESTERN GREAT BASIN 65
Introduction 65
Methods 68
Relative Abundance Censusing 68
Body Size 70
Reproductive Condition 70
Results 72
Population Dynamics of Ephydra hians ... 72
Body Size 74
Reproductive Condition 74
Discussion 76
V. DEVELOPMENTAL EFFECTS OF SALINITY AND ALGAL
FOOD AVAILABILITY ON THE ALKALI FLY
EPHYDRA HIANS (DIPTERA:EPHYDRIDAE) 98
Introduction 98
Methods 101
Population Sources 101
Adult Rearing and Egg Collection 101
Osmotic Stress on Larval Development 102
Food Supply Restrictions on Larval
Development 105
Results 107
Effect of Osmotic Stress on Larval
Development 107
Effect of Food Restriction on Larval
Development and Survivorship 109
Influence of Pupal Size on Adult
Emergence 109
Discussion 111
VI. THE INFLUENCE OF FOOD AND BODY SIZE ON
REPRODUCTION AND LONGEVITY OF AN ALKALINE
LAKE SHORE FLY, EPHYDRA HIANS SAY
(DIPTERA:EPHYDRIDAE) 125
Introduction 125
Methods 129
Field Collection 129
Laboratory Rearing 130
Experimental Design 131
Eggs and Lipid Content in Flies from
Field Populations 134
Statistical Analysis 135
Results 136
Starvation Effects 136
Male Longevity 136
Female Longevity 137
Fecundity and Stored Lipids of
Field-Collected Flies 139
Reproduction in Experimental
Feeding Studies 140
Timing of Reproduction 142
Correlation Among Adult Life
History Traits 144
Discussion 146
VII. GROWTH OF THE FILAMENTOUS GREEN ALGA
CTENOCLADUS CIRCINNATUS BORZI
(CHLOROPHYCEAE) IN RELATION TO ENVIRONMENTAL
SALINITY 171
Introduction 171
Methods 174
Algae Collection and Cloning 174
Culture Media 174
Experimental Inoculations 175
Culture Harvesting 176
Chlorophyll and Water Content 177
Results 178
Effect of Salinity on Growth 178
Chlorophyll Content 179
Cell Form and Water Content 180
Discussion 183
BIBLIOGRAPHY 196
APPENDICES
Appendix 1. Sample site habitat descriptions.. 202
Appendix 2. Mono Lake: Seasonality and
composition indices of benthic
algae 204
Appendix 3. Abert Lake: Seasonality and
composition indices of benthic
algae 205
Appendix 4. Biochemical composition of
Ephydra hians 206