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RELATIONSHIPS AMONG AQUATIC INSECTS,
HYDROPERIODS, AND WETLAND FUNCTIONAL
PLANT GROUPS IN CENTRAL OHIO
DISSERTATION
Presented in Partial Fulfillment of the Requirements for
The Degree Doctor of Philosophy in the Graduate
School of the Ohio State University
By
Michael J. Bailey, MS.
*****
The Ohio State University
2001
Dissertation Committee: Approved by
D. L. Denlinger
D. J. Horn, Advisor
D. C. Smith Advisor
A. A. Snow Department of Entomology UMI Number 3031168
UMI
UMf Microfbrnraaattas Copyright 2002 by Bell & Howell Information and Learning Company. All rights reserved. This microform edition is protected against unauthorized copying under Title 17, United States Code.
Bell & Howell Information and Learning Company 300 North Zeeb Road P.O. Box 1346 Ann Arbor, Ml 48106-1346 Copyright by
Michael J. Bailey
2001 ABSTRACT
This study investigated relationships among functional wetland plant groups,
insects, and hydroperiods in Central Ohio wetlands on Morrow Meadows Pond, Hoover
Nature Preserve, and the Hebron Fish Hatchery. The orthopteran Conocephalus fasciatus
was collected in a wide range of wetland types especially those with ruderal-type plants
and unpredictable hydroperiods. In contrast, Conocephalus brevipennis preferred tussock
and interstitial plants in more predictable hydroperiods. The pygmy backswimmer.
Neoplea striola, was found in ponds with longer hydroperiods, tall tussocks and clonal dominants. Its life history fits the autumnal pool template: long life, predictable seasonal growth rates, and overwintering in water or moist litter. The coleopterans,Haliplus immaculicollis, Hydrovatus pustulatus and Enochrus oechnts also preferred clonal dominant stands with stable hydroperiods compared to Copelanis glyphicus which was collected only in temporary pools with ruderals, reed interstitials, and short tussocks.
Conceptually, the temporary pool template selects for emergent*plants that either grow fast and reproduce in dry periods, or, for plants that tolerate flooding stress and grow slowly. It also selects for aquatic insects that have short life spans, long-diapause eggs, and quick growth rates. The semi-permanent pond template selects for competitive plants that tolerate long periods of flooding and for invertebrates that may be large predators, lack desiccation resistant stages, and develop over longer time intervals.
ii To my parents and
Barbara Squires
m ACKNOWLEDGMENTS
I am most grateful to my advisors Dr. David J. Horn and to Dr. C. David Smith for their
continuous encouragement, guidance, and friendship during my graduate study. I also
express sincere appreciation to other members of my advisory committee, Drs. Allison
Snow and David L. Denlinger, for their suggestions and comments. The technical
assistance of Jana Chordas is gratefully acknowledged.
This study was made possible with support of The Ohio State University, the
Ohio Division of Wildlife, and City of Columbus Recreation and Parks Department. I thank Joan McMahon, Faye Militante, William and Marsha Driscoll for their unshakable faith in me.
IV CURRICULUM VITAE
March 14,1955 ...... Bom — El Paso, Texas
1978 ...... B.S., University of
Missouri, Columbia, Missouri
1994...... M.S. Zoology, The Ohio State
University, Columbus, Ohio
1995-present...... Graduate Teaching Assistant
and Lecturer at The Ohio State
University, Columbus, Ohio
PUBLICATIONS
Bailey, M. J., 1994. Lacustrine environments of the prothonotary warbler. M.S. Thesis.
The Ohio State University, Columbus, OH
FIELD OF STUDY
Major Field: Entomology TABLE OF CONTENTS
Abstract ...... ii
Dedication...... iii
Acknowledgments ...... iv
CurriculumVitae ...... v
List of Tables...... viii
List of Figures...... x
Chapter 1 : Introduction...... 1
Chapter 2: Methods...... 10
Site descriptions and locations...... 10
Hydroperiods and wetland classifications ...... 12
Vegetation analysis...... 13
Aquatic insect analysis...... 15
Chapter 3 : Wetland plants, hydroperiods, and grasshoppers ...... 17
Introduction...... 18
Methods - study sites, hyroperiods, wetland plants ...... 20
Methods - Orthoptera...... 21
VI Results - study sites, hydroperiods, wetland plant types ...... 22
Results - plant comparisons...... 32
Results - Orthoptera...... 39
Discussion...... 49
Chapter 4: Wetland plants, hydroperiods, and Neoplea striola...... 53
Introduction...... 54
Methods - study sites, hydroperiods, wetland plants ...... 57
Methods - organic matter and invertebrates ...... 57
Results...... 58
Discussion...... 73
Chapter 5: Wetland plants, hydroperiods, and Coleoptera...... 80
Introduction...... 82
Methods - study sites, hydroperiods, wetland plants ...... 83
Methods - invertebrates ...... 84
Results- hydroperiods, wetland plants, invertebrates ...... 86
Discussion...... 103
References...... 113
vu LIST OF TABLES
Table Page
2.1 Central Ohio wetland descriptions and sampled insects ...... 16
3.1 Classification of wetland plants from Central Ohio into functional plant groups...... 23
3.2 Classification of wetlands by the Stewart and Kantrand (1971) prairie pothole method...... 27
3.3 Comparison of plant traits on Hoover Nature Preserve wetlands ... 33
3.4 Summary results of the discriminant functional analysis on wetland plants ...... 35
3.5 Comparison of plant traits on Hebron Fish Fish Hatchery...... 38
3.6 List of grasshopper species found in Central Ohio wetlands 40
3.7 Comparison of grasshopper transect coimts on Hoover Nature Preserve...... 41
3.8 Comparison of grasshopper counts on Morrow Meadows by sweep n et...... 45
3.9 Comparison of grasshopper county on Hebron Fish: Hatchery 46
3.10 Comparison of grasshopper counts on Morrow Meadows Pond by stalk and catch ...... 47
4.1 Organic matter comparisons in Central Ohio...... 60
4.2 Functional plant groups and hydroperiods in Central Ohio 63
4.3 Mean plant trait values from Hoover Nature Preserve...... 66
viii 4.4 Mean plant trait values from Hebron Fish Hatchery...... 68
4.5 Stepwise statistics from a plant discriminant frmctionaal analysis.. 69
4.6 Discriminant analysis summary statistics on Hoover Nature Preserve and Hebron Fish Hatchery plants ...... 70
4.7 Comparison ofNeoplea striola counts in different plant groups 74
4.8 Habitat template and life history strategies ...... 76
4.9 Conceptual framework relating influences of dense emergent macrophytes to adaptations ofNeoplea striola...... 79
5.1 Habitat description of aquatic Coleoptera...... 85
5.2 Hebron Fish Hatchery plant groups and hydroperiods...... 87
5.3 Functional plant group trait measurements, Hebron Fish Hatchery.. 91
5.4 Stepwise statistics from Hebron Fish Hatchery plant groups 92
5.5 Summary statistics from plant discriminations, Hebron sites 95
5.6 Coleoptera coimts from the Highway Marsh...... 99
5.7 Coleoptera counts from the Hole Marsh...... 100
5.8 B. fraternus and E. ochreus counts in clonal dominants and flooded ruderals ...... 101
5.9 Summary counts of three Coleopteran species taken from dry basins. 102
5. Ifr Conceptualized life history strategies of C.glypkiats taaé its associated functional plant groups...... 104
5.11 Conceptualized Ufe history strategies ofH. pustulatus and its associated functional plant groups...... 105
5.12 Conceptualized life history strategies ofP. subcupreus and its associated functional plant groups...... 106
5.13 Conceptualized life history strategies o f aquatic plants and aquatic insects in temporary pools and semi-permanent ponds 107
ix LIST OF FIGURES
Figure Page
1.1 Functional Plant Groups...... 04
3.1 Hoover Nature Preserve hydroperiods...... 25
3.2 Hebron Fish Hatchery hydroperiods...... 31
3.3 Discriminant function scores from plant groups in Central Ohio ... 37
3.4 Average grasshopper counts from sweep net samples through functional plant groups...... 42
4.1 Comparison of FPOM and CPOM in plant groups...... 62
4.2 Hydroperiods of functional plant groups in Central Ohio...... 65
4.3 Plant group discriminant function scores from Hoover Nature Preserve and Hebron Fish Hatchery ...... 71
5.1 Hebron Fish Hatchery hydroperiods...... 89
5.2 Plant group discriminant function scores from the Hole Marsh 93
5.3 Discriminant function scores of short tussocks and clonal dominants on the Hebron Fish Hatchery...... 97 CHAPTER 1
INTRODUCTION
Hydroperiods have played an important role in determining the distribution of
both plants (Menges and Waller 1983, Mitsch and Gosselink 1993) and invertebrates
(Schneider 1999, Wiggins et al. 1980) in wetlands. Life history strategies may have been shaped by the pattern of water disappearance especially whether this pattern occurred in a predictable or unpredictable manner (Williams 1996). For example, in the Tinaja wetlands from southeastern Utah, shallower pools were found to have shorter, less predictable hydroperiods, lower rates o f predation, and lower rates of competition compared with deeper pools with longer hydroperiods (Anderson et al. 1999). In a
Wisconsin study, short duration ponds supported invertebrate taxa with high growth rates and extraordinary desiccation resistance, while long duration ponds supported taxa with longer life cycles and less desiccation resistance (Schneider 1999).
Hydroperiods alsa act as filters or templates for community organization
(Schneider and Frost 1996). In frequently disturbed wetland systems, physical stresses exerted a dominant influence over community composition. Conversely, as hydroperiods lengthened and the time between disturbances decreased, biotic interactions among species increased in importance. Wiggins et al, (1980) suggested that colonizing stotegies of terrestrial plants
growing in the basins o f temporary pools were the obverse of aquatic invertebrate
strategies. These plants generally exploited drying phases or declining pool stages while
aquatic insects exploited flooding phases.
Grimes (1977) classified plants into three groups based on life-history strategies: competitors, stress tolerators, and ruderals. Different strategies resulted from different selection pressures such as disturbance, stress, and competition. Stresses, such as shortages of minerals and water, restricted plant production while disturbances such as mowing, wind forces, desiccation, and frost caused destruction of biomass. Competitors, one type of functional group, excluded other plants from fertile, relatively undisturbed environments by maximizing vegetative spread and capture of resources. Competitors were characterized by perennial life spans, high dense canopies of leaves, extensive lateral spread above and below ground, and flowering after periods of maximal productivity. Stress tolerators, another functional group, endured conditions of limited productivity and were found in low disturbance and high stress environments. They were perennial, grew slowly, and produced a wide range of growth forms. Ruderals, the last group, were adapted to high disturbance and low stress environments. These atmual colonizers grew rapidly, flowered at the end of temporary favorable periods, and maximized seed production.
In another plant classification scheme, Boutin and Keddy (1993) placed wetland plants into three functional groups: ruderals, matrix, and interstitials (Fig 1.1). Species were classified according to traits that emphasized function, such as nutrient ability,
2 Figure 1.1
Diagram and characteristics of the functional plant groups (Boutin and Keddy 1993) used in this research. Ruderals colonized sites in disturbed areas with high light gradients, interstitials were found in gaps with varying light and disturbance gradients, while matrix were present in sites with low light gradients and high productivity. annuals perennials perennials perennials
short stems short stems short or tall stems tall stems
high% low% low% low % flowering flowering flowering flowering
shallow shallow shallow deep roots roots roots roots
many stems many shoots tussock form clonal spread
RUDERAL REED TUSSOCK CLONAL INTERSTITIAL INTERSTITIAL DOMINANT MATRIX
Figure 1.1 competitive ability, stress tolerance, and cUsper^ ab il^ . Ruderals colonized gaps and
disturbed areas especially sites with high light gradients and many regenerative
opportunities. This group emphasized reproduction and growth of photosynthetic tissue
as evidenced by their annual life span, high rate of flowering the first year, little lateral
spread, and low below ground to above ground biomass ratio. Interstitials, a group with
clumped growth forms, were found in small gaps growing on sites with varying light and
disturbance gradients. These plants were perennial, emphasized vegetative spread, grew
to shallow rooting depths, and produced low flowering rates in their first year. The last
group, competitors, also emphasized vegetative spread but was found in habitats with low
light gradients and high productivity; such sites experienced decreased disturbance
frequencies and decreased regeneration opportunities. Competitors flowered at low rates
in their the first year, expanded vegetatively, were peretmial, and produced deep, massive
below ground structures. Both Grimes (1979) and Boutin and Keddy (1993) distinguished between ruderals and long-lived perennials while Grubb (1986) used interstitial and matrix categories in classifying prairie plants.
Menges and Waller (1983) evaluated the distribution of floodplain herbs with respect to elevation, flooding firequency, and light gradients. These authors also used
Grimes’ (1977) classification scheme but designated some species as a mix of two groups, such as competitive-ruderals or stress-tolerant competitors. The highest floodplain elevations with the least amount of flooding were dominated by tall competitive forbs, small perennial herbs (stress-tolerant competitors), and tallannuals
(competitive-ruderals). The lowest elevations with the greatest flooding firequencies
5 supported flood tolerant sedges (stress-toierators) and small, fast maturing aimual forbs
(ruderals) such as Polygonum pensylvanicum and Bidens spp. A flooding event here
could be classified as either a “disturbance” to true ruderals or as a “stress” to stress
tolerators such asCarex spp. and Leersia oryzoides.
Temporary water fauna evolved strategies in environments that were firee firom
both competition and vertebrate predation but were constrained by the disappearance of
water (Williams 1996). Invertebrate adaptations included highly flexible life cycles,
temperature linked development, possession of diapausing eggs, and high powers of
dispersal. Traits of non-seasonal aquatic insects in unpredictable hydroperiods included
short life spans, highly vagile adults, long-diapause eggs, extraordinary resistance to dehydration, high fecundity, and differential development. In more predictable hydroperiods, insects were less fecund, lived longer as adults, and grew in seasonal cycles. They also produced shorter-term diapausing eggs which hatched with the historically optimum time that water reappeared. Williams (1985) reported two essential features of aquatic invertebrates in temporary pools: (1) an ability to withstand unfavorable environments with water loss, low oxygen concentrations, high salinity, and high light intensity and (2) an ability to synchronize life-cycles with the occurrence of water. MacArthur and Wilson (1967) noted the loss of water in temporary ponds was a major selective pressure on insects which adapted by evolving higher powers of dispersal, more rapid growth rates, shorter life spans, and smaller sizes. Wiggins et al. (1980) categorized Canadian temporary water invertebrates into . . . _ ... — — ■ -- T ,i„ - - ..... -
four groups based on their adaptations and strategies: Group I, Overwintering
Residents spent their entire life in ponds, dispersed passively, and remained dormant
during the dry season; Group n. Overwintering Spring Recruits were capable of active
dispersal, remained dormant during the unfavorable season, but deposited eggs in ponds
before they dried in spring; Group m, Overwintering Summer Recruits actively
dispersed, were dormant during the unfavorable season, but deposited eggs in dried pond
basins, and finally; Group IV, Non-wintering Spring Migrants actively dispersed to
temporary waters in spring, reproduced, then returned to permanent waters during the
unfavorable season. Although one prime requisite for all animals in temporary waters
was rapid rate of growth during the wet phase, the synchrony between pool and animal
cycles was closer in Groups II and in than in Groups I and IV. Invertebrates in Groups II
and ni were more likely to be univoltine compared with multivoltine Groups I and IV.
Diapause in many temporary pool species probably served as a timing adjustment to avoid the vicissitudes of transient waters.
Wiggins et al.(1980) also emphasized differences in adaptations between species using temporary vernal pools or temporary autumnal pools. Vernal pools formed in the spring, experienced frequent water level fluctuations, and remained dry for 8-9 months, while autumnal pools held water for 8-9 months and recharged in autumn. Longer development times and facultative responses to early flooding such as post-embryonic growth were expected in species using autumnal pools. Neckles et al. (1990) suggested semi-permanent flooding of marshes eliminated
environmental cues for oviposition, embryonic development, and hatch among some
temporary water taxa. Conversely, residents of permanent waters such as the dragonfly
Leucorrhinia Intacta produced drought intolerant eggs and larvae that required eleven
months to two years of development (Wissinger and Gallagher1999).
Cyclic colonizers also played an important role in shaping the community
structure of wetlands because these invertebrates completed one or more generations in
temporary waters then wintered in permanent habitats (Wissinger 1977). Some cyclic
colonizers displayed both K-selected and r-selected traits depending upon the generation
and the environment. “Establishment generations” in temporary pools were small or
wingless, grew rapidly, reproduced at an early age, and were highly fecund. In contrast,
“overwintering generations” in permanent waters grew long wings, were reproductively
immature, and allocated resources for winter survival.
This research examined two major questions. First, were species of semi-aquatic
and aquatic insects associated with particular functional plant groups in central Ohio?
And second, could the life history strategies of aquatic insects be associated with the life
history strategies of the aquatic plants, as driven by a hydroperiod template? For
example, shallow pool environments may support both ruderal and interstitial plants which evolved strategies either to grow quickly in short benign periods or to grow slowly and tolerate flooding stress. Semi-aquatic insects frequenting these plant groups may exhibit higher powers of dispersal and may be better able to cope with the unpredictability of annual plant communities. Truly aquatic insects in a shallow pool
8 template may display traits such as long term diapausing eggs, extraordinary desiccation
resistance, avoidance behaviors in response to temporary draw downs, quick larval
growth, and high dispersal abilities. Alternately, deeper more stable pools may be
colonized by competitive plants that emphasize vegetative spread and capture of
resources. Aquatic insects coexisting with competitive plants may have long-lived adult
stages, long development times, short term diapausing eggs, and hatch times that coincide
with optimal prey abundance. Competition may strongly influence community structure
in both plant and animal groups found in wetlands with longer hydroperiods.
The first analysis in this research examined associations among two semi-aquatic
orthopterans (Tettiigonidae), hydroperiods, and different functional plant groups. The
slender meadow grasshopper, Conocephalusfasciatus, a long-winged species, frequented both dry upland fields and damp locations in Canada, while another slender meadow grasshopper, Conocephalus brevipennis, a short-winged species, inhabited more moist locations and shady spots (Vickery and Kevan 1985). The second analysis described associations among the pygmy backswimmer,Neoplea striola (Hemiptera), hydroperiods, and different plant groups. This true bug preferred clear, permanent, static waters with sedges according to a Connecticut study (Gittelman 1974). In the last analysis, relationships among aquatic beetles (Coleoptera), hydroperiods, and different plant groups were examined. A conceptual framework is also presented which associated plant and invertebrate life history strategies in temporary pools and semi-permanent wetlands. CHAPTER 2
METHODS
SITE LOCATIONS AND DESCRIPTIONS
Research was conducted at three study areas in central Ohio. The first
area, consisting of four smaller wetlands on Hoover Nature Preserve near Hoover
Reservoir, Delaware County, was sampled for plants, hydroperiods, and invertebrates
from March to September 1999. Each wetland exhibited a distinct hydroperiod with
different plant groups: Mud-hen Marsh, 1.98 ha, with a monoculture ofPhalaris
arundinacea (reed canary grass) growing in water through midsummer; Hoover
Meadows Wet Upland site, 0.51 ha, with species such as Juncus effusus (soft rush) and
Verbena hastata (blue vervain) adapted to withstand flooding in spring (Galatowitsch and
van der Walk 1994); Hoover Meadows Shallow Swamp, 0.20 ha, dominated by Carex lupuliformis (hop sedge) and flooded into early summer; and finally Hoover Meadows
Deep Swamp, also ha, with bothSeirpus eyperinus (wool grass} which tolerated shallow flooding into midsummer and Polygonum hydropiperoides (mild water-pepper), a mudfiat annual that colonized this site’s exposed basin after draw downs. Hoover
Meadows was located on the northeast side of Hoover Reservoir approximately 1.3 km south of the Village of Galena while Mud-hen Marsh was located on the northwest
10 boundary of Hoover Reservoir separated from the Hoover Meadows by 4.1 km. All
wetlands were buffered by old field communities with Solidago (goldenrod) forbs and
Crataegus (hawthorn) trees. The drought of 1999 seemed to have little effect on Hoover
Preserve wetlands in spring and early summer as hydroperiods on these sites were within
normal ranges for wet prairies (held water in spring) and shallow emergent wetlands
(held water into mid-summer) (Galatowitsch and van der Walk 1994).
The second study area, also sampled for plants, hydroperiods, and
invertebrates from March to September 2000, consisted of three different wetlands in the
Ohio Division of Wildlife’s Hebron Fish Hatchery, Licking County, Ohio. Two of these
wetlands, described here as Hole Marsh and Highway Marsh, were approximately 1.6 ha
with well-defined vegetative zones surrounding open water. The clonal dominant matrix,
Typha angustifiolia (narrow leaf cattail) occurred in deeper waters with Seirpus validus
(soft bulrush) while the tall tussock, S. eyperinus, grew in both shallower marsh waters
and on raised moimds in a deep water inlet. The third wetland, a 0.3 ha matrix of
temporary pools, was located approximately 30 meters north of the Hole Marsh. These pools supported plants such asJ. effusus, Carex vulpinoidea (fox sedge) and V. hastata.
Mowed fields and woodlots surrounded Hebron Fish Hatchery wetlands.
The third study area, a 2.5 ha semi-permanent wetland named Morrow Meadows
Pond near Chesterville, Ohio in Morrow County, was sampled for plant data and invertebrate abundances from July to September 2000. Four major vegetative zones encompassed this pond; an upland disturbed moist soil zone 'mih. Ambrosia artemisiifolia
(common ragweed) and Bidens eemua (sticktight); a middle elevation sedge meadow
11 zone dominated by Leersia oryzoides ^rice cutg a ss)i a lower elevation shallow emprggnt
zone o fP. arundinacea; and finally; a mudflat zone in the deeper part of the basin which
became exposed in late summer and was colonized mainly by the annuals Polygonum pennsylvanicum (Pennsylvania smartweed) and Echinochloa crus-galli (barnyard grass).
Morrow Meadows Pond was buffered by agricultural fields.
HYDROPERIODS AND WETLAND CLASSIFICATIONS A staff gauge (Mitsch and Gosselink 1993), placed in the predominant vegetative zone of each wetland, was used to record water depths approximately once every 10 days from March to July on wetlands in Hoover Nature Preserve and the Hebron Fish
Hatchery. In three of these sites, Mud-hen Marsh, Hoover Meadows Wet Upland, and
Hoover Meadows Shallow Swamp, gauges were located in the deepest part of their basins. After reviewing hydroperiod graphs and common plants, wetlands were then designated as either wet prairies, sedge meadows, shallow emergent wetlands, or semi permanent wetlands using the Stewart and Kantrand (1971) fi-eshwater prairie system.
This system classifies entire basins by common species and hydroperiods. For example, wet prairies were dominated by grasses with short hydroperiods while semi-permanent wetlands supported tall emergent plants such as hard-stemmed bulrush {Scirpus actus) and hybrid cattail (Typha glauca) which tolerated longer hydroperiods.
12 VEGETATION CLASSIFICATION AND AN ^Y SIS
In September when plants were fully mature, twenty-five samples of the more
common species were (1) randomly chosen from each vegetative zone on Hoover Nature
Preserve and Hebron Fish Hatchery wetlands and (2) measured for five adult traits
associated with function: total height, total number of tillers or shoots, stem diameter at
ground level, diameter of either the rhizome or main root below ground, and depth of the
rhizome or main root (Boutin and Keddy 1993). Data were recorded on a total of 225
mature plants in three different functional groups.
Most plant species in central Ohio had already been classified into functional
groups by either Boutin and Keddy (1993) or Meneges and Waller (1983). For this
study, the Boutin and Keddy (1993) classification scheme was chosen because many of
their species were present on central Ohio research sites and because these authors
analyzed species associated with lentic environments, not floodplain environments.
Ruderals, one type o f functional group, were annual, flowered at high rates their first year, and produced little lateral growth. Perennials were separated into two other functional groups; interstitials which spread as discrete clumps and matrix which expanded clonally and covered entire gaps. Compared to ruderals, matrix and interstitials grew slower, flowered at low rates in their first year, and emphasized greater vegetative spread especially underground biomass. P. persicaria was a ruderal, J. effusits a reed interstitial, S. cyperinus a tall tussock interstitial, and P. arundinacea a clonal dominant matrix. Because of its similarity to S. cyperinus with a compact tussock growth form,
13 few shoots, shallow rooting depth, and perennial life span (Britton and Brown 1970), the
sedge C. lupuliformis was designated as a short tussock interstitial. The forb. Ambrosia
artemisiifola (common ragweed), was designated as a ruderal because it occurred in
disturbed soils on higher floodplain elevations, and because both Grimes (1979) and
Lindsey et al. (1961) classified British species of Ambrosia as competitive ruderals. L
oryzoides, a grass, was placed in the short tussock interstitial group because (1) it shared
similar tussock characteristics such as slow growth, short height, narrow xeromorphic
leaves, a non-terminal shoot apex, and stress tolerance to continuous flooding, and (2) it grew in the same hydroperiods as sedges which are tussocks (Menges and Waller 1983).
E. crus-galli, P. pennsylvanicum, and B. cernua were classified as ruderals because of their annual life spans and ability to colonize mudflats (Galatowitsch and van der Walk
1994). Plants were identified using keys from Britton and Brown (1970) and confirmed by John Furlow, herbarium specialist at the Museum of Biological Diversity, The Ohio
State University, Columbus, OH.
Canonical discrimination analysis (Morrison 1976) was used to evaluate differences among the functional plant groups and demonstrate that a priori classifications were appropriate. This analysis determined which variables contributed most to a linear discrimination among groups by a stepwise approach and computed probabilities that each plant belonged to its designated group (SPSS version 10.0 1998).
These probabilities were summarized as correct classification rates. The stepwise approach first chose the single best discriminating variable then paired it with the remaining variables one at a time until a second best discriminating variable was chosen.
14 Resulting plots of discrimination scores on each function were helpful in visualizing group separations along gradients derived from trait data. Plant measurements were compared with Kruskal-Wallis and Mann-Whitney U non-parametric tests using
SYSTAT 5.2 (1992). Voucher specimens were retained at The Ohio State University
Museum of Biological Diversity.
INSECT ANALYSIS
Because insects were collected with a variety of different methods and sampling devices depending upon the species and wetland type (Merritt and Cummings 1986), 1 discuss their capture techniques in the upcoming chapters. Insects counts in the different functional plant groups at independent sites were compared with Kruskal-Wallis and
Mann-Whitney U non-parametic tests, while counts at dependent sites were compared with Friedman non-parametric tests using SYSTAT 5.2 (1992). Table 2.1 summarizes wetland site locations and particular insects sampled at each location.
15 Site and Year Wetland Description Sampled Insects
Hoover Nature wet prairie Conocephalus fasciatus Preserve sedge meadow Conocephalus brevipennis Delaware County shallow emergent Neoplea striola 1999 deep emergent
Morrow Meadows wet prairie Cononcephalus fasciatits Pond sedge meadow Conocephalus brevipennis Morrow County shallow emergent 2000 mudfiat
Hebron Fish wet prairie Conocephalus fasciatus Hatchery* sedge meadow Conocephalus brevipennis Licking County deep emergent Neoplea striola 2000 Paracymus subcupreus Hydrovatus pustulatus Copelatus glyphicus
® Hole Marsh on the Hebron Fish Hatchery contained fish.
Table 2.1 Summary of Central Ohio wetland site locations, habitat descriptions, and insects sampled in each location.
16 CHAPTERS
RELATIONSHIPS AMONG WETLAND FUNCTIONAL
PLANTS, HYDROPERIODS, AND TWO GRASSHOPPER (TETTIGONHDAE)
SPECIES OF CENTRAL OHIO
Abstract: This study investigated the relationships among two species of grasshoppers
(Tettigoniidae), functional plant groups, and hydroperiods. The long-winged
Conocephalaus fasciatus was collected in a variety of wetlands with different hydroperiods and in a variety of plant groups such reed interstitial, short tussock interstitial, and ruderal. The short-winged Conocephalus brevipennis frequented tall tussock interstitials, a plant group that colonizes wetlands with longer, more stable hydroperiods. In general, grasshopper abundances were associated with different hydroperiod stresses or disturbances which shaped plant life-history strategies. For example, the wide ranging C. fasciatus preferred more disturbed environments with either annual plant groups which emphasized quick growth and high seed production, or, with short tussock interstitials which tolerated flooding stress and reproduced with low, constant efforts. Conversely,C. brevipennis favored sites with lesser amounts of
17 disturbance and large perennials- ■ which -. - — — i maximized ^------:-----■ • vegetative ; growth : - and storage : ^ .^of 9 - —
nutrients. This research also suggests C. fasciatus is a cyclic colonizer that migrates from
reed and short tussock interstitials in wet prairies to mudflat ruderals in small ponds or
shallow emergent marshes each year. A life-history classification schemeemphasizing
habitat predictability and adversity may be useful in predicting both plant and
grasshopper distributions and density responses in wetlands.
INTRODUCTION
Watcher et al. (1988) suggested grasshopper community composition, species
diversity, and abundance were associated with an elevational gradient and temperatures
and not necessarily with plant species richness, diversity, or cover in the Rocky
Mountains and Oregon. Conversely, Anderson (1964) indicated that Montana grasshoppers selected habitats that contained preferred host plants and different physical structures although changes in vegetation were not directly responsible for initial fluctuations in population density. In another study with Montana rangeland grasshoppers
(Kemp et al. 1994), both plant and grasshopper species composition changed over environmental gradients of precipitation/elevation and plant community complexity. Fire frequency and topography impacted local grasshopper assemblages and plant communities in the Konza Prairie, Kansas (Evans 1998) as forb and mixed feeding grasshoppers became more abundant with decreased fire frequency. Joem (1993) suggested grasshopper species preferred specific microhabitats and were non-randomly distributed, and Anderson et al. (1979) reported that thermal and hydric stress influenced
18 habitat selection in two species of short-homed grasshoppers. One spwies, with an
elaborate repertoire o f thermoregulatory behaviors, frequented bare patches of ground,
while the other species, with fewer thermoregulatory behaviors and less desiccation
stress, was found in patches of dense vegetation. In Point Pelee Ontario, Urquhart (1941)
discussed a variety of factors limiting the habitat distribution of Saltatoria such as rates
of evaporation, air temperature, vegetation type, soil pH, selective oviposition, and
grasshopper morphology. He suggested rates of evaporation limited grasshopper
distributions most. Grasshopper abundances were also directly related to rainfall and its
effect on the quantity and quality of vegetation (Kemp and Cigliano 1994) as evidenced by the drought of 1988 in Montana, which reduced plant production 51% and reduced grasshopper species richness in 1989. Scoggan and Brusven (1973) reported that habitat alterations and disturbances had profound effects on grasshopper assemblages in Idaho.
Bandwing species favored unstable soils and early serai vegetation while slantfaced species preferred stable grassy areas. Mulkem (1972) classified north central Great Plains grasshoppers as monophagous, oligophagous, pleophagous, and polyphagous; survival, growth, development, and fecundity were affected by host plants.
Wiens (1976) investigated features of population responses to patchy envirorunents and he suggested vegetational patchiness was govemed by factors such as climate, soil, the vegetation itself (allelopathy, shading), consumers, and biotic disturbances. Under field conditions, individuals should choose ideal habitat types based on fitness prospects which were a function of habitat quality and population density.
19 Fielding and Brusven (1995)^ reported . -that plant - "u--— life-history ,r-. ^ stratemes were ------
helpful in understanding species and community-level traits of different grasshopper
assemblages in southern Idaho. Grasshoppers favoring stress tolerant or competitive plant
groups occurred in lower densities, with narrower habitat breadths and narrower diet
breadths, than species found in more disturbed habitats with annual plant communities.
Of the three axes used by Grimes (1977,1979) to model plant communities, disturbance
accounted for more variation in grasshopper distributions than competition or stress.
This study investigated associations of C. fasciatus, the long-winged slender
meadow grasshopper, and C. brevipennis, the short-winged slender meadow grasshopper,
among wetland functional plant groups, hydroperiods, and wetland types. In southem
Canada, C fasciatus was abundant in both dry upland fields and near bodies of water
(Vickery and McE. Kevan 1985). With its fully developed tegmina, this long-winged
species may habitually disperse to nearby wetlands and maximize use of both predictable
(competitive) and unpredictable (ruderal) plant groups. Conversely, C. brevipennis was
abundant in more moist locations such as swamps and the margins of rivers of southem
Canada. With its short tegmina, this short-winged grasshopper may be more sedentary
and favor wetlands with longer hydroperiods and competitive plants. I hypothesized that
these Tettigoniidae frequented different wetland plant species with different plant life-
history strategies as driven by hydroperiods.
SAMPLING METHODS - HYDROPERIODS, PLANTS, WETLAND TYPES Chapter 2 describes sampling methods used to record hydroperiods, measure wetland plants, and classify wetland types.
20 SAMPLING METHODS - ORTHOPTERA On Hoover Nature Preserve wetlands in 1999, grasshoppers were sampled by
sweep netting the diSerent functional plant groups both in June, during nymphal stages,
and in July, during nymphal and adult st%es. By mid-July, ruderals had germinated on
the Hoover Meadows Deep Swamp mud-flats and produced another possible food source
for Conocephalinae which forage on the flowers and leaves of certain forbs and the fruits
of grasses and sedges (Gangwere 1961). Because of Hoover Nature Preserve’s smaller
wetlands, a total of six sweep net transects was taken in each functional plant group, one
transect per week. 1 walked slowly and swept 25 times back and forth using 180° arc
with a standard 40-cm-diameter net between 1000 and 1300 hours (EDT) on sunny to
partly sunny days. On Morrow Meadows Pond and the Hebron Fish Hatchery in 2000,
adults were also sampled by sweep netting in August and September, a time period that coincided with germination and growth of the ruderals E. crusgalli and P. persicaria on exposed mudflats. Following the same procedures as above, 1 sampled eight transects in each vegetative zone at the rate of one per week.
On Hoover Nature Preserve sites in July, and on Hebron Fish Hatchery sites in
September, 1 also used a flush-stalk-capture technique (Przybysweski and Capinera 1990) to sample Orthoptera in the different plant groups. This technique consisted of walking transects, one to two per week depending upon the size of the site, and collecting the first
25 flushed grasshoppers. This method may reduce bias associated with sweeping in dense vegetation which underestimates geophilous species or early instars. A total of
21 225 individuals was collected from Hoover Nature Preserve wetlands, and a total of 400
individuals was collected from Hebron Fish Hatchery wetlands.
Nymphal C fasciatus and C brevipennis were separated by three traits: a
pronotal-to-head length ratio of approximately 0.18 mm forfasciatus C. and 0.27 mm for
C. brevipennis, a smaller and more slender body of C. fasciatus compared with a more
robust C. brevipennis, and a darker brown stripe on the pronotum and occiput of C.
brevipennis compared with C. fasciatus (Blatchley 1920). Species were identified with
keys from Vickery and McE. Kevan (1985) and Blatchley (1920), and voucher specimens
were retained at The Ohio State University Entomology Department Collection.
Grasshopper counts in the different functional plant groups were compared with Kruskal-
Wallis and Mann-Whitney U non-parametic tests using SYSTAT 5.2 (1992).
RESULTS HYDROPERIODS, PLANTS, AND WETLAND CLASSIFICATIONS Plants from Central Ohio were placed in the following functional groups:J. effusus, reed interstitial; C lupuliformis, C. vulpinoidea and L oryzoides, short tussock interstitials; S. cyperinus, tall tussock interstitial; T. angustifolia and P. arundinacea, matrix; sbA Polygonum spp=, B. eerrma, E. crus-galli, and A artemisiifolia, as ruderals
(Table 3.1).
The Hoover Meadows Wet Upland site held water periodically from February through early May in 1999 (Fig 3.1 and Table 3.2); such hydroperiods occurred commonly in wetlands classified as wet prairies and sedge meadows (Galatowitsch and van der Walk 1994) with 7. effusus, V. hastata, Solidago gramniflora (lance-leaved
22 Species Literature Designation Designation Used In This Research
Juncus effimis reed interstitial reed interstitial Boutin and Keddy (1993)
Carex Itqniliformis none tussock interstitial (short)
Carex vulpinoidea none tussock interstitial (short)
Leersia oryzoides stress tolerator tussock interstitial Menges and Waller (1983) (short)
Scirpus cyperinus tussock interstitial tussock interstitial Boutin and Keddy (1993) (tall)
Phalaris arundinacea clonal dominant matrix matrix Boutin and Keddy (1993)
Typha angustifolia none thoughTypha glauca matnx was listed as a clonal dominant matrix by Boutin and Keddy (1993)
Table 3.1 Classification of wetland plants from Central Ohio into functional groups based on the Boutin and Keddy (1993) classification scheme. (CONTINUED) 23 Table 3.1: CONTINUED
Polygonum sp, mudflat annual ruderal Galatowitsch and van der Walk (1994)
Echinochloa crus-galli mudflat annual ruderal Galatowitsch and van der Walk (1994)
Bidens cernua mudflat annual ruderal Galatowitsch and van der Walk (1994)
Ambrosia artemisiifolia mudflat annual ruderal Galatowitsch and van der Walk (1994)
24 Figure 3.1
Hydroperiods of wetland basins and functional plant groups on Hoover Nature
Preserve in 1999. Top recordings are from the Hoover Meadows Uplands site with reed interstitials and the Hoover Meadows Deep Swamp with tall tussock interstitials. Bottom recordings are from the Hoover Meadows Shallow Swamp with short tussock interstitials and from Mud-hen Marsh with matrix.
25 40 /% tali tussock interstitial reed interstitial
30 B I 20 I 10
Feb Mar Apr May June
40 matrix short tussock interstitial
30 I OI 20 I 10
Feb Mar Apr May June
Figure 3.1
26 Site Classiflcation Hydroperiod Typical Plant Name Zone
Hoover Meadows wet prairie and tolerates a few Verbena hastata Upland sedge meadow weeks to a few Solidago gramniflora months of spring Carex tribuloides flooding Juncus effusus
Hoover Meadows sedge meadow tolerates a few Leersia oryzoides Shallow Swamp (short plants) months of spring Carex lupuliformis flooding
Hoover Meadows shallow emergent tolerates flooding Scirpus cyperinus Deep Swamp (tall plants) into midsummer
Hoover Meadows mudflat exposed in summer Polygonum sp. Deep Swamp Mudflat
Mud-hen Marsh sedge meadow tolerates a few Phalaris arundinacea and shallow months of spring emergent flooding
Hole Marsh deep emergent tolerates flooding Typha angustifolia Deep Water semi-permanent for several years Scirpus validus
Hole Marsh sedge meadow tolerates a few Scirpus cyperinus Inlet shallow water months of spring Polygonum sp flooding or flooding into mid-summer
Hole Marsh sedge meadow tolerates a few Phalaris arundinacea Edge shallow water weeks to a few Juncus effiisus months of spring flooding
Table 3.2 ClassüBcatioii of wetlands in Central Ohio by the Stewart and Kantrand
(1971) prairie pothole method. (CONTINUED)
27 Table 3.2 (CONTINUED) — , - — ------— ------■
Highway Marsh deep emergent tolerates flooding Typha angustifolia Deep Water semi-permanent for several years Scirpus validus
Highway Marsh sedge meadow tolerates a few Scirpus cyperninus Shallow Water months of spring Homalocenchrus flooding oryzoides
Highway Marsh wet prairie and tolerates a few Carex vulpinoidea Wet Prairie sedge meadow weeks toa few Junus effUsus months of spring Solidago spp. flooding Carex tribuloides
Temporary Pools wet prairie and tolerates a few Carex vulpinoidea Sedge meadow weeks to a few Juncus effiisus months of spring Solidago spp. flooding Carex tribuloides Verbena hastata Morrow Meadows sedge meadow tolerates a few Leersia oryzoides Pond - Shallow months of spring Water flooding
Morrow Meadows mudflat exposed in late Polygonum sp. Pond - Mudflat summer
Morrow Meadows semi-permanent tolerates shallow Typha angustifolia Pond - Deep Water marsh flooding for several years
28 goldenrod) and Carex tribuloides (blunt broom sedge). The Hoover Meadows Shallow
Swamp and Mud-hen Marsh were flooded from spring to late May; such hydroperiods
were normally recorded in sedge meadows. Hoover Meadows Shallow Swamp plants
included the short tussock interstitial C. lupuliformis, L oryzoides, and Eupatorium perfoliatum (boneset) while a matrix, P. arundinacea, covered the entire Mud-hen Marsh
basin. The Hoover Meadows Deep Swamp held surface water until mid-July, a longer
hydroperiod characteristic of shallow emergent wetlands. The tall tussock interstitialS.
cyperinus, surrounded this basin’s fringes while the ruderals, P. persicaria and P. hydropiperoides, germinated on its mudflats in summer. In comparison with the other
Hoover Meadows wetlands, water levels were most variable on the Hoover Meadows
Wet Upland site.
On the Hebron Fish Hatchery, temporary pools supportedV. hastata,
S. gramniflora, and the reed interstitial J. effmus', these wet prairie plants were commonly associated with shorter hydroperiods. The sedge C. lupuliformis also colonized temporary pools though it occurred in the deeper ones (Fig 3.2 and Table 3.2). The tall tussock interstitial, S. cyperinus, was present in shallower marsh waters while the matrix,
T. angustifolia, tolerated deeper marsh waters.
Large stands of the short tussock interstitialL. oryzoides were found in middle elevations around Morrow Meadows Pond (Table 3.2). This species normally grows in sites designated as sedge meadows which flood for I to 2 months in spring. The
29 Figure 3.2
Hydroperiod recordings from wetland plant zones on the Hebron Fish Hatchery in 2000.
Matrix species were present in more stable hydroperiods compared to tall and short tussock interstitials
30 27 matrix tall tussock Interstitial short tussock interstitial
-S* 18
I
I 1%i f It I I % I I I I I I f I t I I t I r t
I I
Apr May Jun Jul Aug
Figure 3.2
31 matrix,...... P. arundinacea, a shallow —— - -. — — emergent -, ~. species,- “ — . grew ——.. — on - lower elevations in deeper
waters while the ruderals, P. pennsylvanicum and E. crus-galli, sprouted on the pond’s
exposed mudflats after a late summer draw down. Other ruderals such as A.
artemisiifolia and B. cernua, grew on higher elevations near crops.
PLANT COMPARISONS
In each wetland, plant strategies were associated with different stresses or disturbances; ruderals colonized mudflats on basins with long hydroperiods, reed interstitials were associated with shorter hydroperiods, tussock interstitials grew in sites with both long and short hydroperiods, and matrix were associated with the longest, least variable hydroperiods.
Height (x^ = 79.0, df = 3, P < 0.01), number of shoots = 56.2, df= 3, P <
0.01), stem diameter (%^ = 76.7, df = 3, P < 0.01), root diameter (x^ = 59.6, df = 3, P <
0.01) and root depth (x^ = 35.1, df = 3, P < 0.01) varied significantly among species
(Table 3.3) on Hoover Preserve.S. cyperinus, the tallest plant (187.30 + 3.80 cm) produced the largest root diameters (1.23 + 0.09 cm) while J. effusus, the smallest plant
(53.16 + 3.22 cm) produced the smallest root diameters (1.35 + 0.09 cm) and the highest number of shoots (21.08 + 2.08). Compared to reed interstitials and short tussock interstitials, tall tussock interstitials and matrix groups were taller and had larger stem diameters, traits indicative of competitive plants.
In a separation of four plant groups on Hoover Nature Preserve by traits, height contributed most to the discrimination among them, followed by shoot number, stem
32 Species Juncus Carex Scirpus Phalaris P effusus lupuliformiscyperinus arundinacea
Functional reed tussock tussock matrix Group interstitial interstitial interstitial “short” “tall” Height 53.16 + 3.22 74.56 + 4.02 187.30 + 3.80 163.81 +6.75 79.0 <0.01 (cm) No.of Shoots21.08+2.08 3.08 + 0.20 3.84 + 0.26 4.40 + 0.60 56.2 <0.01 (counts) Stem Diam. 0.36 + 0.02 0.60 + 0.02 0.91+0.04 0.46 + 0.02 76.7 <0.01 (cm.) Root Diam. 0.40 + 0.2 0.33 + 0.01 1.23 + 0.09 0.44 + 0.04 59.6 <0.01 (cm.) Root Depth 1.35 + 0.09 2.8+0.02 2.26 + 0.21 1.84 + 0.20 35.1 <0.01 (cm.)
Trait comparisons between short tussock and tall tussock interstitial groups were also significant when tested by Mann Whitney U; Height (Z = -6.04; P < 0.01), Shoot No. (Z = -2.09; P = 0.04), Stem Diam. (Z = -3.27; P < 0.01), Root Diam. (Z = -6.21; P < 0.01), Root Depth (Z = -2.04; P = 0.04).
Table 33 Comparison of plant traits (mean + SE) (N = 2S) growing on Hoover
Nature Preserve wetlands.
33 diameter, and root diameter (Table 3.4) (Fig 3.3). The first canonical function accounted
for 72.6% of the variance among species with high positive loadings on height (0.759)
and root diameter (0.331), while the second canonical function accounted for 14.6% of
the variance with high negative loadings on stem diameter (-0.815). Canonical
discrimination correctly classified 95% of the plant samples into their designated groups.
J. effimis, a reed interstitial, and C. lupuliformis, a short interstitial tussock, were
associated with negative scores on the first discriminant function corresponding to a
gradient with shorter heights, smaller root and stem diameters, and greater numbers of
shoots.S. cyperinus, a tall tussock interstitial, and P. arundinacea, a matrix, received
positive scores on the first function. These values were associated with increased height,
fewer numbers of shoots, and larger root diameters.
Height (%^ = 64.81 ; d f=2: P < 0.01), number of shoots (%^ = 53.84; df = 2; P
<0.01), stem diameter (%^ = 65.92; df = 2; P < 0.01), root diameter (%^ = 65.91; df = 2; P
< 0.01), and root depth = 42.24; df = P < 0.01) varied significantly among species on the Hebron Fish Hatchery (Table 3.5). Matrix species were taller (173.02 + 2.65 cm), produced fewer shoots 1.00 + 0.01), greater stem diameters (2.92 + 0.19 cm), greater root diameters (3.86 + 0.21 cm), and rooted deeper (5.35 + 0.34 cm) then tall tussock and short tussock interstitials. Of the five traits sampled on Hebron Fish Hatchery plants, height also contributed most to the discrimination among them followed by root diameter
(Table 3.4). The first function accounted for 95.7% of the variance between groups with high positive loadings on plant height (0.85) and root diameter (0.55) while the second
34 Step Number Variable Statistic Funct. I Funct. 2 Correct Entered Wilks’lambda Coefif. Coefif. Class. %
Hoover Nature Preserve
1 height 0.138 0.759 0.646 95% 2 shoot num. 0.054 -0.323 0.414 3 stem diam. 0.025 0.288 -0.815
4 root diam. 0.331 0.331 -0.085
Hebron Fish Hatchery
1 height 0.141 0.846 -0.534 100% 2 root diam. 0.068 0.550 -0.836
Table 3.4 Summary results of the stepwise discriminant analysis on wetland plants in Hoover Nature Preserve and Hebron Fish Hatchery. Coefficients are standardized under each function.
35 Figure 3.3 Discriminant function scores of different plant groups in Central
Ohio. The top graph presents scores from Hoover Nature Preserve plants. Its first discriminant function is composed of high loadings on height (0.759) and root diameter (0.331). The bottom graph presents scores from Hebron Fish Hatchery plants. Its first discriminant function is also composed of high loadings on height
(0.846) and root diameter (0.550).
36 4 matrix 3 reed interstitial « 2 1 0 □ J □ -1 □ °o a B I -2 Û CO □ -3 short talltussQck interstitial interstitial -4 J L I______-2 0 2 Discriminant 1 Scores
5 4 3 I matrix 2 short tussock interstitial 1 tall tussock S interstmal E 0 a -1 □□ □ o □□ □ ' -2 -3 L i^qg-L -7 •2 3 Discriminant 1 Scores
Figure 3.3
37 Functional Tussock Tussock Clonal P Group Interstitial Interstitial Dominant "Short"' “Tall”'
Height (cm) 59.46 + 2.03 130.32 + 2.99 173.02 + 2.65 64.81 <0.01
No. of Shoots 8.2 + 1.01 2.84 + 0.48 1.0 + 0.00 53.84 <0.01
Stem Diam. (cm) 0.38 + 0.01 0.70 + 0.01 2.92 + 0.19 65.92 <0.0
Root Diam. (cm) 0.35 + 0.01 1.10 + 0.05 3.86 + 0.21 65.91 <0.01
Root Depth (cm) 2.17 + 0.21 2.45 + 0.12 5.35 +.0.34 42.24 <0.01
" Trait comparisons between short tussock interstitials and tail tussock interstitials were tested by Mann Whitney U: Height (Z = -6.06; P < 0.01), Shoot No. (Z = -4.71; P < 0.01), Stem Diam. (Z = -6.08; P < 0.01), Root Diam. (Z = -6.80; P < 0.01), Root Depth (Z =-1.350; P = 0.18).
Table 3.5 Comparison of traits (mean + SE) on plants (N = 25) growing on the Hebron Hatchery Marsh.
38 function accounted for 4.3% of —the variation .. _with high negative loadings on — root —-diameter •= — (0.836). This discrimination correctly classified 100% of the plants. Compared to the other two groups, scores firom the matrixT. angustifolia on the first function were positive and associated with more competitive traits found in stable environments: increased height, larger stem and root diameters, and deeper root depths (Fig 3.3 and
Table 3.4). Scores of the short tussock interstitial C.lupiluformis were negative and associated with characteristics common to plants growing in more variable hydroperiods such as shorter heights, smaller root and stem diameters, and shallower rooting depths.
Tall tussock interstitials were characterized by intermediate traits; as such, their scores fell between the short tussock interstitial and matrix scores.
In summary, matrix species were separated fiom reed interstitials by taller heights and larger root diameters, traits associated with competitors emphasizing vegetative spread but not quick reproduction. Both short and tall tussock interstitials exhibited intermediate characteristics, traits common to plants that tolerated stress and reproduced with low, constant efforts.
ORTHOPTERAN LIST AND COMPARISON
Table 3.6 lists the grasshopper species collected firom the different wetlands either by sweep netting or stalk and catch samples. C. fasciatus, C. brevipennis, and
Orchelimum silvaticum firequented moister sites while Melanoplus femurrubrum and
Melanoplus differentialis firequented drier sites.
On Hoover Preserve, C.fasciatus was abundant in all wetlands; sweep net counts
39 Species Species Species
Conocephalus fasciatus Melanoplus femurrubrum Orchelimum volatum Conocephalus palustrisMelanoplus differentialisOrchelimum silvaticum Conocephalus brevipennis Oecanthus nivens Eunemobius carolinus Scudderia furcata Oecanthus fultoni Orchelimum vulgare Nemobius fasciatus Oecanthus quadripunctatusTetrigidea lateralis Dichromorpha viridis
Table 3.6 List of grasshopper and cricket species in Central Ohio collected hy either sweep netting or stalk and catch in 1999 and 2000.
were not significantly different among plant groups = 6.33; df = 3; P = 0.097) (Table
3.7 and Fig 3.4). This meadow grasshopper was collected in both reed interstitials with short hydroperiods (0.83 + 0.48) and in matrix (3.00 ±1.10) with longer hydroperiods.
When sampled by stalk and catch methods, C. fasciatus was collected in higher numbers from tall tussock interstitials (11.67 ±0.88) compared to lower numbers in reed interstitials (4.67 ± 2.02). Higher counts from tall tussock interstitials in the Hoover
Meadows Deep Swamp may be the result of two processes: (1) large stands of the ruderal
P. persicaria germinated on exposed mudflats among clumps of S. cyperinus (2) and adult C. fasciatus migrated from the surroimding wet prairies or pastures to this emerging food source (Capinera et al. 1997). When disturbed by stalking movements, most
40 Species Reed Short Tall Matrix P Interstitial Tussock Tussock
C. fasciatus 0.83+0.48 2.00 + 0.52 1.33+0.56 3.00+1.10 6.33 0.097
C. brevipennis 0.00 +0.00 1.00 +0.45 0.50 + 0.22 1.33 + 0.56 7.43 0.059“
a C. brevipennis counts were almost significantly different among these plant groups.
Table 3.7 Comparison of grasshopper transect counts (mean + SE) (N = 6) by sweep
netting in different functional groups on Hoover Nature Preserve wetlands in
Delaware County, Ohio 1999.
41 Figure 3.4 Average grasshopper counts on three different wetland complexes in Central Ohio, 1999 and 2000. In general, C.fasciatus was present in wide range of functional plant groups while C.brevipennis selected tall tussock interstitials and matrix groups common to wetlands with longer hydroperiods.
42 C wsdatus C brevipennis
5 I I matrix reed tafl tussock short tussock interstitial htmtitial inteislitiai
Morrow Meadows Pond 8 C fasciatus 7 C brevipennis 6 5 Ô 4 I 3 1 2 V9 1 0 short tussock matrix mudflat mudflat interstitial ruderal rudofal
Hebron Fish Hatchery C fasciatus C brevipennis 3 tS 2 §•
short tussock tall tussock interstitial interstitial Figure 3.4 43 grasshoppers flushed from ruderals growing on the Hoover Meadows Deep Swamp.
Morrow Meadows Pond sweep net counts of C.fasciatus were significantly
different = 20.80; df = 3; P < 0.01) (Table 3.8) among its plant groups. Higher
abundances were present in both ruderals (5.12 + 0.85) and the short tussock interstitial
L. oryzoides (7.38 + 1.53) while lower abundances were present in the matrix group (0.12
+ 0.12) (Table 3.7 and Fig 3.4). C. fasciatus frequented plants associated with longer hydroperiods (Z. oryzoides) and with mudflats (Polgyonum).
On the Hebron Fish Hatchery, C fasciatus sweep net counts were not significantly different (%^ = -l .32; P = 0.188) (Table 3.9) between short tussock interstitials (0.75 + 0.36) and tall tussock interstitials (0.12 + 0.12). Significantly higher stalk and catch counts occurred in short tussock interstitials (2.87 + 0.93) compared to lower counts in tall tussock interstitials (0.12 + 0.12) (%^ = -2.66; P < 0.05) (Table 3.10).
In a comparison of counts among three different annuals on Morrow Meadows
Pond, C. fasciatus was collected in significantly higher numbers (%^ = 13.80; df = 3; P <
0.01) (Table 3.9) on the mudflat grass E. crus-galli (5.2 + 0.25) compared to smaller numbers on the mudflat forb P. pennsylvanicwn (1.0 + 0.38) and upland forb B. cemua
(1.12 + 0.48). C. brevipennis sweep net counts were not sigoificantly different among
Hoover Nature Preserve plant groups (%^ = 7.43; df = 3; P = 0.059) (Table 3.7) though higher counts were evident on both short tussock interstitials and matrix, groups generally associated with longer hydroperiods (Table 3.6 and Fig 3.3). When sampled by the stalk and catch technique in the Hoover Meadows Deep Swamp, C. brevipennis also
44 Functional short matrix ruderal ruderal X2 P Group tussock Interstitial
C fasciatus 7.38+1.53 0.12 + 0.12 5.12 + 0.85 1.88 + 1.06 20.80 0.000
C. brevipennis 1.50 + 0.33 0.62 + 0.18 0.25 + 0.25 0.12 + 0.12 12.74 0.003
Table 3.8 Comparison of grasshopper transect counts (mean + SE) (N = 8)by sweep netting in different plant groups on Morrow Meadows Pond in Morrow County, Ohio 1999.
45 Functional group tussock interstitials tussock interstitials ZP (short) (tall)
Sweep Net Samples (8 transects)
C. fasciatus 0.75 + 0.36 0.12 + 0.12 -1.32 0.19 C. brevipennis 2.00 + 0.56 3.56 + 0.56 -1.65 0.09
Stalk and Catch Samples (8 transects)
C. fasciatus 2.87 + 0.93 0.12 + 0.12 -2.66 <0.05 C. brevipennis 9.25+1.37 3.62 + 0.42 -3.04 <0.05
Table 3.9 Comparison of grasshopper transect counts (mean ;^SE)(N = 8)using Mann-WhitneyU tests in different wetland plant species on Hebron Fish Hatchery wetlands, Licking County, Ohio 2000.
46 Species P. pennsylvanicum E. crus-galli B. cernuaZ2 P
C. fasciatus 1.00 + 0.38 5.12 + 0.85 1.12 + 0.48 13.80 0.001 C. brevipennis 0.50 + 0.19 0.25 + 0.25 0.37 + 0.26 1.75 0.417“
“ c. brevipennis counts were not significantly different within ruderals.
Table 3.10 Comparison of grasshopper transect counts (mean± SE) (N = 8) by stalk and catch in ruderals on Morrow Meadows Pond in Morrow County, Ohio 1999.
47 flushed from ruderal patches.
On Morrow Meadows Pond, C.brevipennis occurred in significantly higher
numbers on plants associated with moister habitats especially the short tussock interstitial
L oryzoides and matrix P. arundinacea (%^= 13.74; df = 3; P = 0.003) (Table 3.8 and
Fig. 3.3). Sweep net counts of C.brevipennis were not significantly different among the
plant groups on the Hebron Fish Hatchery = -1.65; P = 0.09) (Table 3.9) though
higher counts were evident in tall tussock interstitials (3.56 + 0.56) compared to lower
counts in the short tussock interstitial community (2.00 + 0.56). Stalk and catch counts
taken in September produced opposite trends from expected: significantly higher counts
of C. brevipennis (%^ = -3.04; P = < 0.05) were present in reed interstitials and short
tussock interstitials on drier sites (9.25 + 1.37) compared to lower counts in tall tussock
interstitials (3.62 + 0.42) on wetter sites. This trend may be explained not necessarily by
increased abundance of C. brevipennis in these plant groups, but by the absence of C. fasciatus which may have migrated to new food or oviposition sites later in the summer
(Capinera 1997). 1 mainly caught C. brevipennis in short tussocks interstitials because C. fasciatus had already departed these plant groups. This dispersal behavior is supported
by (1) higher counts of C.fasciatus (11.67 + 0.88) on mudflat ruderals in the Hoover
Meadows Deep Swamp in July compared to lower counts in reed interstitials (4.67 +2.02)
( Table 3.7), and (2) by much higher counts of C. fasciatus (5.12 + 0.85) on the mudflat ruderal E. crus-galli compared to lower counts of the short-winged C.brevipennis (0.25 +
0.25) on the same plant (Table 3.8). Collections of C.brevipennis were not significantly different within these ruderals (%^ = 1.75; df = 3; P = 0.417).
48 DISCUSSION
Fielding and Bnisven (1995) suggested rangeland grasshopper and plant
community relationships were linked by similar life-history strategies, especially in
response to disturbance gradients and habitat predictabili^. Grasshopper species with
higher densities and wider habitat breadths were more abundant in disturbed areas than
were grasshopper species with lower densities and narrower habitat breadths found in
more predictable environments. This study supported these general observations with
two Tettigoniidae. C.fasciatus was collected in higher densities in a wide range of
habitats including the reed interstitial, tussock interstitial, and matrix communities of
Hoover Nature Preserve and Hebron Fish Hatchery, and the ruderal, short tussock
interstitial, and matrix communities of Morrow Meadows Pond. This long-winged grasshopper frequented plant groups growing in both fluctuating and stable water levels, factors which caused high or low disturbances or stresses on plants. Within each functional plant group, though, C.fasciatm may choose a specific host plant such as preferring the ruderal grass E. crus-galli over the two ruderal forbs, P. pennsylvanicum and B. cemua. Alternately, C. brevipennis occurred in higher densities in the tussock interstitial and matrix communities. This short-winged grasshopper favored sites with either more stable water levels and lesser amounts of disturbance or it favored plant groups such as L. oryzoides which were associated with longer hydroperiods
(Galatowitsch and van der Walk 1998).
In agreement with these findings, Urquhart (1941) reported similar habitat preferences by these two Tettigoniidae on Point Pelee, Ontario. C.fasciatus was
49 abundant in a wide range of habitats, such as short grass pastures, roadsides, marginal
areas of a marsh, and the marsh itself, while C. brevipennis was abundant in a sedge
meadow with the perennials Carexstricta and Carex tribuloides, tussock-like plants able
to tolerate flooding for one to two months in spring (Galatowitsch and van der Walk
1994). Vickery and McE. Kevan (1985) reported C. brevipennis inhabited more moist
locations than C.fasciatus, and Caperina et al.(1997) noted C. fasciatus was abundant in a variety of Florida habitats including pastures, citrus groves, and irrigation ditches.
This research supported the hypothesis that C.fasciatus and C. brevipennis were associated with different functional wetland plants and plant life-history strategies. These associations seemed to fall along well-established light gradients, standing crop gradients, and disturbance or stress gradients (Boutin and Keddy 1993). Wetlands subjected to either greater perturbations or to draw downs experienced increased light availability and increased plant regeneration opportunities, conditions conducive to ruderal or reed interstitial growth. The wide ranging C. fasciatus preferred plant groups that emphasized quick growth and high seed production. A less disturbed environment with more stable water levels favored large perennial plants which maximized vegetative growth as evidenced by their tall heights, large stem diameters, and large root diameters. These competitors displaced other functional groups by creating more shade and decreasing regeneration opportunities (Boutin and Keddy 1993). Tall tussock interstitials and matrix were preferred by the specialist C. brevipennis.
A life history strategy of many aquatic insects entails annual migration between temporary and permanent aquatic environments (Batzer and Wissinger 1996, Wissinger
50 1997). Cyclic colonization is also prevalent in terrestrial insects (as cited in
Wissinger 1997) that travel between annual crop fields and more permanent réfugia.
These migrations were associated with catastrophic but predictable breakdown of crop
structure each year. Similar to crop systems, ruderals colonized mudflats on shallow
emergent wetlands in late summer on Hoover Nature Preserve and these plants
catastrophically brake down with the onset of winter flooding (Galatowitsch and van der
Walk 1994). The late-seasonal movements of Cfasciatus firom wet prairies with reed
interstitials and short tussock interstitials to mudflat ruderals in small ponds and shallow
emergent marshes appears to be another example of cyclic colonization. Catastrophic
plant breakdowns also occur with floodplain ruderals (Menges and Waller 1983) and with
riverbank herbaceous vegetation (Weaver 1960). In Saskatchewan, Canada, small
exposures of soil regularly occurred in shallow marsh basins, resulting in germination by
disturbance species such as Polygonum coccineum (Millar 1973).
Grasshoppers migrating in heterogeneous wetland landscapes may find new food sources, moister conditions, and shelter, which, in turn, may lead to populations with more rapid growth rates, higher feeding rates, and higher survival rates (Wissinger 1997).
In Florida, higher numbers of nymphal C. fasciatus were present in pastures in June while relatively lower numbers of adults were present in these same pastures in October
(Capinera et al. 1997). Possible explanations for this trend included: (1) pastures were more or less suitable for growth and reproduction of tettigonids; (2) birds ate the large visible adults in pastures; (3) and adults dispersed to more preferred feeding or oviposition sites.
51 Wetland grasshoppers ^ may be well i—=----- suited1------:to------=------wetland— -T—vegetation . - -■ dynamics. -fc— .. , For
example, Amctional plant groups change in response to above-normal or below-normal
precipitation on semi-permanent and permanent prairie potholes (Galatowitsch and van
der Walk 1994). Severe droughts occur in the prairie pothole region every ten years or so,
starting a cycle of marsh stages: dry marsh with ruderals, regenerating marsh with
emergents, degenerating marsh stage with fewer emergents, and lake marsh stages with
loss of emergents. C.fasciatus, with its long wings and ability to exploit a range of
functional plant groups, may be well adapted to these marsh stages. In times of drought, it
migrates among reed interstitial, tussock interstitial, matrix, and mudflat ruderals.
Alternately, C. brevipennis with its shorter wings may prefer (1) more predictable
hydrologie regimes, especially shallow emergent cycles that dry up annually creating
niches for tussock interstitials (Galatowitsch and van der Walk 1994) or (2) semi permanent cycles with longer hydroperiods and matrix plants. Pre-settlement landscapes in central and northern Iowa contained four to nine acres of wet prairie and sedge meadow wetland to every one acre of shallow emergent or semi-permanent wetland
(Galatowitsch and van der Walk 1994). Just the large size of these wetlands complexes alone may have fostered niche partitioning that benefited both habitat restricted species and migratory species. A life-history classification scheme emphasizing habitat predictability and adversity (Fielding and Brusven 1995) may be useful in predicting grasshopper habitat distributions and density responses in different wetland habitats.
52 CHAPTER 4
RELATIONSHIPS AMONG FUNCTIONAL
WETLAND PLANTS, HYDROPERIODS, ANQ NEOPLEA STMOLA
(HEMIPTERA: PLEIDAE)
Abstract: This study investigated the response of the pygmy backswimmer {Neoplea striola) and functional plant groups to hydroperiods in Central Ohio wetlands.N. striola preferred wetlands with longer hydroperiods and plant groups such as tall tussock interstitials and clonal dominant matrix compared to wetlands with shorter hydroperiods supporting reed and short tussock interstitials. Sites with longer hydroperiods selected for tall, competetive plants with perennial life spans, large biomasses, deep root depths, and flowering at the end of the season. This seasonal pond template also selected forN. striola life history characteristics such as long-lived adults, predictable, seasonal growth rates, slow larval growth, predation, and adults overwintering in water or moist litter.
Conversely, the temporary pool template selected for plants which either grew and reproduced quickly between flooding periods, or, developed stress tolerance to flooding and grew slowly, strategies closely allied with invertebrate characteristics such as differential development, short-lived adults, and fast larval growth but not found in
53 pygmy backswimmers. The response of ûmctionsd plant groins and aquatic invertebrates
to different hydroperiods may be useful in predicting their distribution and abundance in
natural and mitigated wetlands. For example, wetland sites with longer hydroperiods may
be colonized by (1) matrix species such as Typha angustifolia (2) predators such as N.
striola (3) and pygmy backswimmer prey species such as Cladocera and Amphipoda.
Biotic interactions become increasingly important in wetland sites with low disturbance
regimes and longer hydroperiods.
INTRODUCTION
Life-history theory coupled with the quality and predictability of the environment may provide a framework for understanding patterns in insect-plant communities
(Southwood 1977,1988). In a large Minnesota prairie marsh (Olson et al. 1995), abundances in nine of 16 aquatic invertebrate orders were significantly different among vegetative communities; T. angustifolia supported the most diverse populations of macroinvertebrates, compared with less diverse populations in Scirpus actus and
Potamogeton sp.. Water level fluctuations also contributed to differences among invertebrate orders in different years.
Temporary pools may have been extremely stable features in our terrain
(Collinson et al. 1995) as they filled up slowly with sediments, were oxidized during the dry phase, and regularly dried out, leading to re-mineralization of nutrients. Compared to concentrations in more permanent waters, detritus in temporary pools decomposed faster
54 when exposed to air, which in turn, promoted higher protein contents during spring
floods (Wiggins et ai. 1980). Decay rates depended upon both aquatic invertebrate life
cycles and the dynamics of flooding regimes (Magee 1993). Decomposition of litter
began with leaching of nutrients such as calcium, potassium, and magnesium, followed
by mechanical ôagmentation due to wind or ice, and finally biological fiagmentation by
microbes and invertebrates. Coarse particulate organic matter (CPOM, diameter > 1 mm)
was eventually converted into fine particulate organic matter (FPOM, diameter < 1 mm).
The pygmy back swimmer Neoplea striola was abundant in Chara beds firom both
slow running streams and pools in Michigan (Rice 1954). Life history traits included: egg incubation for 8 - 21 days, hatching to the adult stage in 56 days, and a total development time o f64-77 days. Bare (1926) collected N. striola in Kansas ponds with sedges {Carex spp.) and reported a total development time o f64-73 days, adult emergence in April, 188 day adult longevity, and overwintering in ponds beneath ice.
Eggs, inserted into Chara and Elodea, hatched in 10 days. In a Connecticut study,
Gittelman (1974) noted pygmy back swimmers preferred clear, permanent, static waters, especially shallows (< 0.3 m) with high nutrient sources fi-om sedges, plants with thin stems, narrow leaves, and tussock forms. Marginal habitat contained deeper water, broad- leaf floating plants, and thick stemmed emergent plants such as Typha and Phragmites.
Blatchley (1926) foimd N. striola in the muck of a dried up wet weather pond, and Ellis
(1965) collected them firom dense mats of willow roots in the Mississippi River. In
Illinois, pygmy back swimmers were univoltine; adults overwintered in mud or flooded detritus and emerged in early March (McPherson 1986). The first instars were collected
55 by the middle o f May and new adults appeared in November.
N. striola became active at water temperatures greater than 10° C, though temperatures between 8° and 12°C were critical in determining spring emergence and fall dormancy (Gittleman 1975). In conjunction with an obligate diapause, successful reproduction was induced after exposure of adults to 4.5°C with a short photoperiod
(Takahashi et al. 1979).
The life history ofN. striola does not neatly classify it into a Wiggins et al. (1980) temporary water strategy. Similar to Group II members, oviposition is dependent on water, but unlike Group H members, flightless adults probably (1) only passively disperse and (2) overwinter in moist pool basins, not dry ones. In common with Group IV strategies, N. striola is predatory, oviposits in water, and overwinters in permanent wetlands. Unlike Group IV invertebrates, N. stroila does not actively migrate to temporary pools in spring.
Pygmy back swimmers feed on ostracods (Sanderson 1982), mosquito larvae
(Bare 1926), Daphnia and amphipods (Gittleman 1974). Blatchley (1926) noted they feed on Entomostraca in tine leaved plants and algae.
This study investigated relationships among N. striola, hydroperiods, and functional wetland plant groups. 1 hypothesized that pygmy back swimmers’ life history traits were well suited to wetlands with longer, more stable hydroperiods that supported clonal matrix or tall tussock interstitials.
56 METHODS - STUDY SITES, HYDROPERIODS, WETLAND PLANTS
Research was conducted at two study areas in central Ohio. The first area.
Hoover Nature Preserve near Hoover Reservoir, Delaware County, was sampled for plant
and hydroperiod data in 1998 and 1999 and consisted of three temporary wetlands (Table
3.2). The second area, Hebron Fish Hatchery in Licking County, was sampled in 2000,
and consisted of two marshes and a complex of temporary pools (Table 3.2). Refer to
Chapter 3 for a description of the study sites, hydroperiods, and wetland plants on these
two study areas.
METHODS - INVERTEBRATE AND ORGANIC MATTER SAMPLING
The pygmy back swimmer, N. striola, was collected over a six-week period from
March to late April in 1998 at Hoover Preserve and from March to early May 2000 at the
Hebron Fish Hatchery using a nine cm diameter cylindrical water column sampler
(Swanson 1978). Five samples were taken weekly from randomly chosen points within major vegetative groups. At each sampling point, the cylinder was inserted through the water column and the top five cm of the basin substrate which formed a plug with a tight seal. After field collecting, samples were immediately transported to the lab, washed, and decanted to remove both animals and detritus from soil sediments. Detritus was first filtered through nested sieves (0.5 mm and 0.1 mm) which separated CPOM from FPOM, then sugar floated to collect the live pygmy back swimmers (Anderson 1959). Organic matter fractions were re-washed to remove sugar residue, oven dried at 65°C to a constant mass, and weighed with a triple beam balance to nearest 0.1 gram. Means (+SEM) were
57 compared with ANOVA tests after log (x + 1) transfprmatigns.
At the Hebron Fish Hatchery, N. striola was also collected fromTypha stands on
both marshes (one with fish predators, one without fish predators) during March and
April at the rate o f five samples per week. I swept a horizontal length of 1.0 meter along
the bottom of the basin twice with a standard D frame dip net at each random point.
Samples were taken immediately to lab, filtered through 0.5 mm and 0.10 mm nested
sieves, and visually inspected for pygmy back swimmers. Counts of N. striola within the
plant groups were analyzed with non-parametric Friedman tests.
Pygmy back swimmers were identified to genus with Merritt and Cummins’s
(1996) keys and to species level using Sanderson (1982). Steve Chordas at the Museum of Biological Diversity, The Ohio State University, verified species identification.
Vouchers were maintained at The Ohio State University Entomology Department.
RESULTS Based on plant associations, the Hoover Meadows Upland site was classified as a wet prairie/sedge meadow mix with species such as Solidago gramniflora, Carex tribuloides, and J. effitsus (Table 3.2). The Hoover Meadows Deep Swamp with S. cyperinus and the Hoover Meadows Shallow Swamp with C.htpulifarmis supported sedge meadow plants though hydroperiods were longer in the Hoover Meadows Deep
Swamp. T. angustifolia stands on both Hebron Fish Hatchery Marshes were classified as deep emergents while shallower areas or inlets withS. cyperinus were sedge meadows.
Wet prairie/sedge meadow species grew on the temporary pool complex especially C. vulpinoidea and J. effiisus. The aggressive P. arundinacea invaded the edge of the Hole
58 Marsh inlet.
Mean FPOM weights within each Hoover Nature Preserve site were not
significantly different (P > 0.05) except for the Hoover Nature Preserve Wet Upland site
which contained lesser amounts than the Hoover Meadows Shallow Swamp and Hoover
Meadows Deep Swamp (F = 15.63; df = 2; P = 0.00) (Table 4.1 and Fig 4.1). Mean
CPOM weights in the Hoover Nature Preserve wetlands (F = 45.10; df == 2; P = 0.00),
Hebron Highway Marsh (F = 7.99; df = 2; P = 0.00), and Hebron Hole Marsh (F = 4.09;
df = 2; P = 0.02) were significantly different among plant groups with higher weights
occurring in deeper water sites with T. angustifolia ox S. cyperinus (Table 4.1 and Fig
4.1) and lower weights occurring in shallower water sites or in wet prairies.
Four different functional plant groups and their corresponding hydroperiods were
present on these sites: (1) reed interstitials, (2) tussock interstitials, (3) clonal dominant matrix and (4) clonal stress tolerator matrix with competitive-like traits (Table 4.2 and
Fig 4.2). The reed interstitial J. effusus and short tussock interstitials C. lupulifomis and
C. vulpinoidea grew in waters with short or medium duration hydroperiods while the matrix, T. angustifolia, colonized wetlands with both medium to long duration hydroperiods and with varying or unvarying fluctuations. The invasive, P. arundinacea, another matrix, not only grew in waters with short, varying hydroperiods but it also tolerated shallow flooding into midsummer (Galatowitsch and van der Walk 1994).
Height, shoot number, stem diameter, root diameter, and root depth were significantly different among Hoover Nature Preserve plants (P < 0.05) (Table 4.3).
Compared to the tall tussock interstitialS. cyperinus, both the reed interstitial J. effusus
59 FPOM CPOM Site Mean (+SE) F df P Mean (+SE) F df P
Hoover Nature Preserve
Wet Upland 2.75+025a 15.63 2 0.00 3.33+0.22a 45.10 2 0.00
Shallow Swamp 5.43+0.45b 5.27+034b
Deep Swamp 5.43+0.52b 8.26+0.53C
Hebron Highway Marsh
Wet Prairie 1.85+0.19a 2.81 2 0.07 3.21+0.39a 7.99 2 0.00
Shallow Water 2.20+023a 4.17+0.43a
Deep Water 2.5I+0.l9a 5.20+0.40b
Hebron Hole Marsh
Inlet Edge 2.62+0.29a 2.22 2 0.12 3.26+0.35a 4.09 2 0.02
Inlet Shallows 3.06+0.27a 3.l0+0.36a
Deep Water 3.32+0.30a 4.50+0.38b
Results for both comparisons horn one-way ANOVA after log (x+1) transformations. Means within columns for a given wetland area followed by the same letter are not significantly different (Tukey with Harmonic Mean Size: P = 0.05)
Table 4.1 Mean organic matter comparisons (+SE) on wetlands in Central Ohio (N = 40).
6 0 Figure 4.1
Comparison of FPOM and CPOM weights in different functional plant groups on the
Hebron Fish Hatchery Highway Marsh. Clonal dominant plants and tall tussocks produced more FPOM and CPOM than reed interstitials and short tussocks.
61 Ueb(on.U(ghway^MaRh-2000- Hne Particulate Organic Matter
clonal dominant matrix otI tall tussock interstitial short tussock interstitial I i
Functional Plant Groups
Hebron Highway Marsh 2000 Coarse Particulate Organic Matter
I clonal dominant matrix I tall tussock interstitial short tussock interstitial I5 3 3
1
0 Functional Plant Groups
Figure 4.1
62 Site Species Functional Group Hydroperiod Description
Hoover Nature Juncus reed interstitial short, highly variable Preserve effusus
Hoover Nature Carex short tussock interstitial medium, some Preserve lupuliformis variability
Hoover Nature Scirpus tall tussock interstitial long, little variability Preserve cyperinus
Hebron Highway Carex short tussock interstitial short, highly variable Marsh vulpinoidea
Hebron Highway Scirpus tall tussock interstitial short, highly variable Marsh cyperinus
Hebron Highway Typha clonal dominant matrix long, little variability Marsh angustifolia
Hebron Hole Phalaris clonal stress tolerator short, highly variable Marsh anmdinacea matrix
Hebron Hole Scirpus tall tussock interstitial long, little variability Marsh cyperinus
Hebron Hole Typha clonal dominant matrix medium, some Marsh angustifolia variability
Table 4.2. Classification of plants into functional groups and their association with hydroperiods in Central Ohio. See Fig 4.2 for hydroperiods.
63 Figure 4.2
Hydroperiods of basins with certain plant groups in Central Ohio. In most instances, longer hydroperiods were associated with tall tussock interstitials and clonal dominant matrix while shorter hydroperiods were associated with reed interstitials and short tussock interstitials.
64 Hoover Nature Presewe.l998_ Hebron-Higbway^Mafsh- 2000- reed interstitial short tussock interstitial tall tussock interstitial
§
I — short tussock interstitial i — tall tussock interstitial — donal dominant matrix
Apr Jul Apr May June Jul
Hebron Hole Marsh 2000
/ %
clonal stress tolerator matrix I tall tussock interstitial S clonal dominant matrix I
Apr May June Jul Aug
Figure 4.2 65 Trait reed tussock tussock P-Value
interstitial interstitial interstitial
"short"' “tall”*
Height 33.22+3.42 74.56+4.02 187.30+3.81 0.000
Shoot 21.08+2.09 3.08+0.20 3.84+0.26 0.000 Number
Stem 0.36+0.02 0.60+0.02 0.91+0.04 0.000 Diameter (cm)
Root 0.40+0.02 0.33+0.01 2.68+0.21 0.000 Diameter (cm)
Root 1.35+0.09 2.81+0.21 2.68+0.21 0.000 Depth (cm)
° Trait comparisons between reed interstitials and short tussock interstitials by Mann Whitney U: Height (Z = -3.94; P < 0.05), Shoot Number (Z = -6.09; P < 0.05), Stem Diameter (Z = -5.97; P < 0.05), Root Diameter (-2.90; P < 0.05) Root Depth (Z = -4.61; P < 0.05).
Table 4.3 Mean trait (+SEM) (N = 25) values for difierent functional plant groups iir Hoover Nature Preserve wetland*.
66 and the short tussock_ interstitial— - . ,C. . . lupuliformis ^ - - were ■ - . _ shorter, — produced smaller root — .... diameters, and more shoots. In the Hebron Fish Hatchery, the same general trends
existed with shorter heights, larger number of shoots, smaller stem diameters, smaller
root diameters, and shorter rooting depths in the short tussock interstitial C.vulpinoidea
compared with the taller tussock interstitial S. cyperinus and the matrix T. angustifolia
(Table 4,4). The variables height, shoot number, and root diameter (steps 1-3) contributed
most to the discrimination between Hoover Nature Preserve functional groups while
height, root diameter, and root depth (steps 1-3) discriminated most at the Hebron Fish
Hatchery (Table 4.5) The first canonical function with Hoover Nature Preserve plants
accounted for 84.3% of the variance among scores with a high correlation (0.962) between the scores and groups, and a high correct classification rate (93%) (Table 4.6).
High positive loadings were present on the variables height (0.813) and root diameter
(0.402). The first canonical function at the Hebron Hatchery also accounted for most of the variance between points (95.7%) with a high canonical correlation (0.975) and 100% correct classification rate (Table 4.6). High positive loadings were calculated for height
(0.762) and root diameter (0.695). On Hoover Nature Preserve (Fig 4.3), reed interstitials were associated with negative scores (small heights and small root diameters) while tall tussock interstitials were associated with positive scores (taller heights and greater root diameters); short tussock interstitial scores occurred between these two groups. Hebron
Fish Hatchery short tussock and tall tussock interstitials were associated with negative or small positive scores (smaller heights and shorter root diameters) while corresponding
67 Trait Tussock Clonal Tussock Clonal P Interstitial Stress-Tolerator Interstitial Dominant “short” Matrix “tall” Matrix
C P. S. T. vulpinoideaanmdinacea cyperinus^ angidstifolia'’
Height 59.46+2.03 136.58+4.37 130.32+3.00 173.02+2.65 0.000
Shoot 8.2+1.01 3.36+0.336 2.84+0.49 1.00+0.00 0.000 Number
Stem 0.38+0.01 0.49+0.03 0.70+0.19 2.92+0.19 0.000 Diameter
Root 0.35+0.21 0.65+0.04 1.10+0.05 3.86+0.21 0.000 Diameter
Root 2.17+0.21 5.28+0.44 2.44+0.12 5.35+0.34 0.000 Depth
“ Plants associated with N. striola presence. *^rait comparisons between short tussock interstitials and tall tussock interstitials were tested by Mann Whitney U: Height (Z = -6.06; P < 0.01), Shoot No. (Z = -4.71; P < 0.01), Stem Diam. (Z = -6.08; P < 0.01), Root Diam. (Z = -6.80; P < 0.01), Root Depth (Z =-1.350; P = 0.18).
Table 4.4. Mean trait (+SE1V^ (N » 25^ values for different functionaf plant groups in Hebron Fish Hatchery wetlands.
68 Site Step Variable Wilk’s Function #1 Function #2
Lambda Standardized Standardized
CoefBcients CoefBcients
Hoover 1 Height 0.087 0.813 0.311
Nature 2 Shoot Num. 0.038 -0.174 0.806
Preserve 3 Root Diam. 0.028 0.402 0.376
4 Stem Diam. 0.022 0.293 -0.0395
5 Root Depth 0.020 0.162 -0.373
Hebron 1 Height 0.122 0.762 0.591
Fish 2 Root Diam. 0.0279 0.695 -0.768
Hatchery 3 Root Depth 0.018 0.007 0.508
For stepwise statistics, F to enter 3.84, F to remove 2.71.
Table 4.5 Stepwise statistics and standardized canonical function coefGcients from the discriminant functional analysis on plant traits from the Hoover Nature
Preserve and Hebron Fish Hatchery wetlands in Central Ohio (N=2S on each wetland).
69 Site Function Eigen % Variance Canonical Wilks Sig. Correct
Number Value Correlation Lambda Class.
Rate
Hoover 1 12.47 84.3 0.96 0.01 0.00 93%
Nature 2 1.96 18.3 0.81
Preserve
Hebron 1 19.15 95.7 0.98 0.03 0.00 100%
Fish 2 0.86 4.3 0.68
Hatchery
Table 4.6 Discriminant functional analysis summary statistics on plant traits from the Hoover Nature Preserve and Hebron Fish Hatchery wetlands in Central Ohio (N
= 25 on each wetland).
70 Figure 4.3
Discriminant function scores separating plant groups in Hoover Nature Preserve and
Hebron Fish Hatchery. In both wetland sites, tall tussock interstitials and clonal dominant matrix were associated with taller heights and increased diameters compared with reed interstitials and short tussock interstitials.
71 Hoover Nature Preserve Plants 1999 7.0 r
4.4 reed interstitial tall tussock interstitial i 1-8 Ig -0.8 y - ^'1 .a -3.4 short tussock interstitial - 6.0 I_____ ± -7 -2 3 Discriminant Function 1
Hebron Fish Hatchery Plants 2000 7.0 r
4.4 IN clonal strep tolerator
1.8 tall tussock I interstitial
J - 0.8
clonal dominant of -3.4 ~ short tussock interstitial
- 6.0 1 1 -7 -2 3 Discriminant Function 1
Figure 4.3 72 matrix species received more positive scores (taller plants with larger root diameters)
(Fig. 4.3).
N. striola counts were significantly higher in tall tussock interstitials (0.840 +
0.189) on Hoover Nature Preserve compared with lower counts in the short tussock
interstitials (0.080+ 0.080) and no counts in the reed interstitials (Table 4.7) (Mann-
Whitney U Test; Z = -3.627, n = 25, P < 0.001). Only the zone with clonal dominant
matrix (Typha) plants produced counts ofN. striola (1.090 + 0.360) on the Hebron
Highway Marsh; no individuals were collected in tall tussock or short tussock interstitials
probably due to the lack of standing water. On Hebron Hole Marsh, pygmy back
swimmers occurred in significantly higher numbers (Mann-Whimey U Test; Z = -2.739,
n = 25, P = 0.006) in clonal dominant matrix (0.680 + 0.236) compared with lower
numbers in tall tussock interstitials (0.080 + 0.080) and no counts in clonal stress
tolerator matrix.
DISCUSSION
The pygmy backswimmer N. striola preferred wetlands with S. cyperinus and T.
angustifolia, plants classified as tall tussock interstitials or clonal dominant matrix found
normally in temporary autumnal pools or semi-permanent waters. Environmental
conditions which increased productivity and decreased disturbances such as stable water
levels may have favored growth of these strong competitors which, in turn, reduced light availability and regeneration opportunities of other plants. Conversely, wetlands
73 Reed Short Tall Clonal Clonal P
Interstitial Tussock Tussock Dominant Stress Tolerator
Interstitial Interstitial Matrix Matrix
Hoover Nature Preserve
0.00 + 0.00 0.08+0.08 0.84 + 0.19 < 0.05"
Hebron Fish Hatchery Highway Marsh
0.00 + 0.00 0.0 + 0.00 1.090 + 0.360 <0.05'*
Hebron Fish Hatchery Hole Marsh
0.08 + 0.08 0.68 + 0.24 0.00 + 0.00 <0.05®
^Wilcoxson signed ranks test between short and tall tussocks, Z = -3.00 Friedman test among different groups. Chi-square = 18.00, df = 2 ® Friedman test among different groups. Chi-square - 16.22, df = 2
Table 4.7 Comparison ofN . s tr io la counts (mean +SE> (N — 30> wetland functional plant groups on the Hoover Nature Preserve and the Hebron Fish Hatchery.
74 subjected to fluctuating water levels or shorter hydroperiods such as wet grairie
communities with reed interstitials and short tussock interstitials were not preferred by N.
striola. These results generally agreed with observations from Bare (1926) and
Gittleman (1974), who reported higher N. striola presence in more permanent waters with
thick stemmed or thin stemmed emergent plants. Beds of Chara used as oviposition sites
also grew in deeper, more stable water levels with less salinity and less disturbance
compared to water levels in wet prairies (Rader 1999) or mesosaline lakes (Lowora et al
1999), P. arundinacea occurred in a variety of moisture conditions and did not serve as
reliable predictor of pygmy back swimmer presence.
Hydroperiods acted as a template for shaping life histories of plants and animals
(Anderson et al. 1999). For example, deep pools contained more predictable water levels, smaller temperature fluctuations, smaller water fluctuations, more predation, and more interspecific competition, an environment well suited to Æstriola (Table 4.8). The life history strategy of pygmy back swimmers fits this template: sustained oviposition, short incubation times, slow larval growth rates, predictable growth rates, non-diapausing larvae, longer lived adults (188 days), and a high association between life history stages and environmental factors. Trophically, it was a predator which hatched when maximum prey was available. Matrix clonal dominants and tall tussock interstitials were also found in more permanent, predictable waters, conditions conducive for storing nutrient capital and increased competition (Table 4.8). In temporary autumnal waters or semi-permanent waters, natural selection processes favored more competitive plant traits such as tallness, fewer numbers o f shoots, large stem and root diameters, deep roots, large biomass, and
75 Plants (a) Animais (b)
Temporary Vemal Pool (Wet Prairie)
facultative annual or perennial short lived adults, highly vagile
seeds not viable for long periods (d) long term diapausing adults
rapid or slow growth, flowers differential development, fast growth throughout the season
places resources into reproductive tissue high fecundity
high % flowering the first year staggered hatching, opportunistic feeding seeds germinate in moist soil (e) immature stages resistant to dehydration
Temporary Autumnal Pool (Deep Emergents)
perennial long lived adults, semelparous seeds long-lived short term diapausing eggs completes reproduction at end of season predictable, seasonal growth rate emphasizes vegetative spread intermediate fecundity low % flowering the first year hatch time with prey reappearance seeds germinate submerged or irr moist soil penultimate instar witlr desiccation resistance a Most plant references firom Boutin and Keddy (1993) d van der Walk (1978) b Invertebrate references from Williams (1996) e Smith and Kadlec (1985) c See introduction for references
Table 4.8 The habitat template and life history strategies of aquatic plants and invertebrates in Central Ohio wetlands 1998 and 2000.
76 large litter accumulations. These process^ also favored plants with slow growth rates,
perennial life spans, flowering after maximum productivity, low percent flowering the
first year, and small annual production devoted to sexual reproduction (Table 4.8).
Conversely, the temporary vemal pool template selected for plants which either grew and
reproduced quickly between flooding periods, or developed stress tolerance and grew
slowly, strategies closely allied with invertebrate differential development and fast
growth but not found in pygmy back swimmers.
This study has examined relationships between life history strategies and one important environmental variable - hydroperiods. Environmental cues for invertebrate oviposition, hatch, and development depend upon flooding times and depths (Neckles et al. 1990). Wetlands with deeper water levels and clonal dominant matrix probably contained more consistent and reliable temperature cues, which initiated pygmy back swimmer winter dormancy or spring emergence at 10-11°C. For example, cattails growing on the Hebron Fish Hatchery in March were frequently trapped in a thick ice crust, while small sedges growing in wet prairies were ice free, less shaded, and more exposed to solar radiation, probably resulting in greater water temperature fluctuations.
This study also suggested that hydroperiods may more accurately predict N. striola presence rather than their associations with different functional plant groups. Though strands of T. angustifolia and S. cyperinus were found in both stable and variable water levels, pygmy back swimmers were mainly collected in plant communities associated with stable water levels.
77 Copious litter produced by matrix groups may insulate invertebrates from
moisture and temperature changes, especially during autumn draw downs, cold winters,
or droughts. Litter creates a stable substrate for a clinging N. striola, which hunts and
hides in its structure (Gittelman 1974 and 1975) (Table 4.9). Unlike other hemipterans,
the pygmy back swimmer’s large gill surface-body volume ratio permits longer
submergence times and longer dive times in dense emergent stands, an adaptation that
may help it survive anoxic waters and fish predators (Euliss et al. 1999, Murkin et al.
1992, and Rose and Crumptom 1996). Fish foraging efiBciency may be reduced in dense emergents (Murkin et al.l992) and in waters with low oxygen concentration (Gillinsky
1984).
The presence of fimctional plant groups may help researchers predict not onlyN. striola abundances in certain types of wetlands, but also predict abundances of other aquatic invertebrates.
78 Influence of T. angustifolia Adaptations ofN. striola
Increases submerged structure Large forelegs and mid-legs for clinging which decomposes relatively to submerged structure; a deep, slowly due to tough structural rounded ball-like ^pearance adapted materials such as lignin, for clinging but not swimming cellulose, and hemicellulose (Gittleman 1974) (Rose and Crumpton 1996) Hind legs used for crawling and Alters dissolved oxygen not exclusively for swimming, concentrations (causes anoxia) by: unlike other Notonectidae (1) reducing photosynthesis (Sanderson 1982) (light is intercepted by emergent canopy) A most efficient physical gill (2) reducing wind velocity permitting longer submergence and blocking water movement times and longer dive duration into the column with living or than other back swimmers dead macrophyte shoots and leaves (Gittelman 1975) (3) generating high microbial oxygen demand because of higher litter inputs Less oxygen consumption than other Notonectid adults (Gittelman 1975) Provides a substrate for periphyton, which is a preferred food of Cladocera A predator of Cladocera, Amphipoda, (Euliss et ai. 1999) (Rose and and other small crustaceans (Gittelman Crumpton 1996) 1974)
Creates cover for Amphipoda and Cladocera (Murkin et ai. 1992)
Table 4.9 Conceptual framework relating influences of dense emergent macrophytes to adaptations ofiV.strio la
79 CHAPTERS
RELATIONSHIPS AMONG AQUATIC COLEPTERA,
FUNCTIONAL PLANT GROUPS, AND HYDROPERIODS:
FIELD COLLECTION RESULTS AND A CONCEPTUAL FRAMEWORK
Abstract; This study investigated relationships among aquatic coleopterans, functional plant groups, and hydroperiods at the Hebron Fish Hatchery in Licking County, Ohio.
The dytiscid, Hydrovatus pustulatus, was collected in the waters of a semi-permanent marsh with clonal dominant matrix plants while another dytiscid, Copelatus glyphicus, was found in temporary pools with ruderals and short tussock interstitials. Finally, the hydrophilid, Paracmns subcuprem, was collected in both temporary pools and semi permanent marshes; such wetlands support either short tussock interstitial or clonal dominant matrix groups.
Conceptually, H. pustulatus exploits spring nutrient pulses in clonal dominant matrix stands; this beetle avoids desiccation in late summer by remaining in wetlands with deeper, more stable water levels. Using a different strategy, C. glyphicus exploits nutrient pulses in temporary pools as they fill up during both spring and summer rains. This dytiscid avoids desiccation by burrowing into moist soils during draw downs.
Finally, P. subcupreus, is not as restricted in its hydroperiod choice as larvae develop in
80 riparian_ zones at the water/moist . ...soil — boundary — - and -adults ; live in terrestrial .... environments. - -
An understanding of the relationships between hydroperiods and life history strategies may be a valuable tool for predicting how perturbations will affect joint plant and animal communities in wetlands. Environmental factors which increase productivity or decrease disturbance may cause a shift from ruderals to matrix species and a shift from temporary pool invertebrates to more seasonal permanent invertebrates.
81 INTRODUCTION
Nelson and Kadlec (1984) suggested optimal conditions formaximiTing
invertebrate production occurred in both newly flooded litter accumulations and in
submerged macrophytes found in openings fringed by emergent vegetation. These
habitats were structurally complex, received high inputs of fine particulate organic
matter, and supported productive assemblages of algal epiphytes. Higher numbers of
invertebrates were also found in submerged vegetation interspersed with emergent
vegetation by Murkin et al. (1992), though Voights (1976) reported that invertebrate
diversity and abundance were more probably related to a mixture of habitat types than to
the amount of vegetation-open water interface. Macrophytes not only increased habitat
structure within the water column, but also served as oviposition, emergence, respiration, attachment, and pupation sites (Euliss et al. 1999). Dense emergent stands in summer produced abundant litter, restricted water circulation, and increased shading which caused anoxic conditions not tolerated by some invertebrate predators (Murkin et al. 1992, Rose and Crumpton 1996).
Invertebrates benefited greatly from recharged ponds in spring or after summer rains, which resulted in nutrient pulses and nucrobial blooms (Higgins and Merritt 1999).
During aerobic draw down phases, bacteria, protozoans, and terrestrial fungi colonized leaf surfaces and produced large amounts of microbial biomass. Upon re-flooding, this enriched detritus released dissolved organic carbon and nitrogen for use by planktonic bacteria, aquatic heterotrophic bacteria, and algae, which, in turn, nourished filter-
82 feeders, gathering collectors, and detritivorousjJ^ddj^. Eventually^ these goups
became prey for opportunistic migrant predators (Group 4 of Wiggins et al. 1980) or
cyclic colonizers (Batzer and Wissinger 1996, Wissinger 1997).
The distribution of aquatic and semi-aquatic Coleoptera in Wisconsin wetlands
was influenced by water depths, water permanence, and floral and faunal composition
(Lillie 1991). Dytiscids such as Liodessus flavicollis and Hydrovatus pustulatus were
restricted to large, deep, lake-like wetlands, while the curculionids, Tanysphyrus lemnae
and Lixellus hubbardi, were found in small, shallow, acidic wetlands or temporarily
flooded basins.
I hypothesized (1) that different species of aquatic Coleoptera would use different
wetland functional plant groups and hydroperiods and (2) that the life history strategies of
adult Coleoptera could be related to the life history strategies of their associated
functional plant groups. This investigation also presents a conceptual framework for understanding associations between some aquatic insects and aquatic plants based on life history strategies.
METHODS - STUDY SITES, HYDROPERIODS, AND WETLAND PLANTS
Research was conducted from March to September 2000 on three different wetlands in the Ohio Division of Wildlife’s Hebron Fish Hatchery, Licking County,
Ohio. Refer to Chapter 3 for a description of the study sites, hydroperiods, and wetland plants.
83 INVERTEBRATE SAMPLING METHODS
Aquatic Coleoptera at the Hebron Fish Hatchery have been collected in a variety
of wetland habitats (Chapman 1989, Hanson and Swanson 1989, Hilsenhoff 1992,1993,
1994, 1995, and Hilsenhoff and Brigham 1978) (Table 5.1). Hydrovatus pustulatus,
Hydrocanthus iricolor, and Enochrus perplexus preferred more permanent wetlands
while Copelatus glyphicus was found in temporary pools.Haliplus immaculicollis,
Enochrus ochraceus, and Paracymus subcupreus were more generally distributed.
Except for Enochrus perplexus, which was found in temporary waters in central Ohio, all
other species at the Hebron Fish Hatchery were collected in habitats similar to those
reported by past researchers.
Ten samples of aquatic Coleoptera were collected monthly, April to August, from randomly chosen sites in the dominant functional plant groups of each wetland. Using a standard A frame dip net (#20 mesh), 1 swept a horizontal length of one meter, twice, along the bottom of the pool or basin at each sample site. As sweeping through dense vegetation may result in bias (Murkin et al. 1983), collections were also taken with a 9 cm diameter shallow water column sampler (Swanson 1978) by inserting the cylinder through the top 5.0 cm of each basin. This technique, however, was only used in dry temporary basins because few aquatic beetles were captured in permanent water samples.
Adult Dytiscidae and Hydrophilidae adults are generally good swimmers (Merritt and
Cummings 1996) and probably easily avoided the sampler opening.
Additionally, forty sweep net samples were taken in late March and early April from sites in the different functional plant groups on Hole Marsh, and forty sweep
84 Family Species Central Northeasten Wisconsin Ohio Ohio
Haliplidae ^Halipus shorelines of temporary and wide variety immaculicollispermanent ponds permanent ponds of lotie and lentic habitats
Dytiscidae ^Copelatus temporary temporary pools shallow water glyphicus pools and apparently habitats permanent ponds
Hydrovatus permanent open ponds, open ponds, pustulatus ponds swamps, marshes larger marshes
Noteridae Hydrocanthuspermanent permanent ponds cattails, iricolor ponds swamps, tamarack burreeds, bog
Hydrophilidae Enochrus temporary wide range of ponds, ochraceus pools and lentic habitats margins of permanent ponds streams
Enochrus temporary woodland swamps ponds, perplexus ponds, marshes ponds, marshes marshes, margins of streams, bogs
Paracymus temporary and temporary and shallow lentic subcupreus permanent permanent habitats, edges ponds ponds, streams of streams
I ... A burrower in flocculent organic debris and seepage (Young 1963)
Table 5.1 Habitat descriptions of aquatic Coleoptera in central Ohio, northeastern
Ohio (Chapman 1998), and Wisconsin (Hilsenhoff 1992,1993,1994,1995).
85 net samples were taken in late September from sites in recently flooded ruderals on the
shorelines of Highway Marsh and in Typha stands.
Field samples were immediately transported to lab, filtered through 0.5 mm and
0.1 mm nested sieves, and visually inspected for aquatic beetles. Cylinder samples were
also flooded to expose burrowing individuals. Adult Coleoptera were preserved in 70%
ethanol and identified to species level with keys from Gundersen and Otremba (1988),
Hilsenhoff (1992,1993,1994, and 1995), Hilsenhoff and Brigham (1978), and Merritt
and Cummins (1996). Eric Chapman, Kent State University, confirmed species
identifications. Voucher specimens were retained at The Ohio State University
Entomology Department.
RESULTS
HYDROPERIODS, WETLAND PLANTS, AND INVERTEBRATES
Wetland plants were assigned to these functional groups: T. angustifolia - clonal dominant matrix (CDM); S. cyperinus- tall tussock interstitial (TTl), C. vulpinoidea - short tussock interstitial (TI),P. arundinacea - clonal stress tolerator matrix (CSTM),J. effusus — reed interstitial (RI), and P. hydropiperoides - obligate annual (OA) or ruderal
(Table 5.2).
Clonal dominant matrix was foimd in wetlands with both stable and somewhat variable water levels though they generally occurred in deeper marsh waters (Table 5.2 and Fig 5.1). Tall tussock interstitials were also found in both stable and variable hydroperiods, but were most prevalent in shallow water zones. Short tussock interstitials,
86 Site Species Functional Group Hydroperiod
Highway Carex short tussock interstitial. short, highly variable Marsh vulpinoidea
Scirpus tall tussock interstitial short, highly variable cyperinus
Typha clonal dominant matrix long, lesser variability angustifolia
Hole Phalaris clonal stress tolerator short, highly variable Marsh antndinacea matrix
Juncus reed interstitial short, highly variable effusus
Scirpus tall tussock interstitial long, lesser variability cyperinus
Typha clonal dominant matrix medium, some angustifolia variability
Temporary Carex short tussock interstitial short, highly variable Pools vulpinoidea
Polygonum obligate annual short, highly variable hydropiperoides ruderal
Table 5.2 Assignment of Hebron Fish Hatchery plants into functional groups based on the Boutin and Keddy (1993) and Menges and Waller (1983) classification schemes. Also listed are comparative hydroperiod descriptions.
87 Figure 5.1
Spring and summer hydroperiods of functional wetland groups at the Hebron Fish
Hatchery in central Ohio, 2000. Clonal dominant matrix preferred more stable water levels while ruderals, short tussock interstitials, and reed interstitials preferred temporary pools.
88 a) Highway Marsh 30 - clonal dominant matrix - tall tussock interstitial .. short tussock interstitial 20
001 1 10
0 Mar Apr May Jun Jul Aug
b) Hole Marsh 25
20
1 clonal dominant matrix IS tall tussock interstitial I clonal stress tolerator matrix 10 i 5
0 Mar Apr May JunJul Aug
c) Temporary Pools 15 pool #3 pool #2 pool#1 10 o 5 n i
0 Apr May JunJul Aug
Figure 5.1 89 reed interstitials, and ruderals colonized . temporary ■ —pools -——^ with --- shorter, more -- variable hydroperiods.
In a comparison of functional plant traits, short tussock interstitial measurements
were significantly different firom tall tussock interstitial and matrix measurements
(Kruskal-Wallace Test, P < 0.05) (Table 5.3). Short tussock interstitials produced higher
numbers of shoots (8.2 +1.01), smaller root diameters (0.35 + 0.21), shorter heights
(59.46 + 2.03), and smaller stem diameters (0.38 + 0.01) than tall tussock interstitials and
matrix. The clonal dominant matrix, T. angustiolia, a strong competitor, was the tallest
and largest plant. Root diameter (step 1) contributed most to the discrimination among
three Hole Marsh plant groups followed by root depth and height (Table 5.4). The first
discriminant function accounted for 90.1% of the variability among groups, while the
second function accounted for 9.9% resulting in an overall 92% correct classified rate
(Table 5.4). High loadings were evident for root diameter and height on the first function, and for root depth on the second function. Clonal stress tolerator matrix and tall tussock interstitials received high negative scores on the first function indicating smaller root diameters and smaller heights compared to the more positive scores of clonal dominant matrix with larger root diameters and taller heights (Fig 5.2).
Height and root diameter contributed most to the discrimination between short tussock interstitials and clonal dominant matrix plants on the Highway Marsh (Table 5.4).
This one function accounted for 100% of the variance with high loadings on height and root diameter (Table 5.5). Short tussock interstitial scores were associated with shorter heights and smaller root diameters compared to clonal dominant matrix (Fig 5.3).
90 Trait Short Tussock Tall Tussock Clonal Stress Clonal Dom P Interstitial Interstitial Tolerator Matrix Matrix (STl) (TTI)“ (CSTM)* (CDM)
height 59.46+2.03 136.35+4.37 130.32+3.00 173.02+2.65 <0.05 (cm)
shoot 8.2+1.01 3.36+0.34 2.48+0.49 1.00+0.00 <0.05 number
stem 0.38+0.01 0.49+0.03 0.70+0.19 2.92+0.19 <0.05 diameter (cm) root 0.35+0.21 0.65+0.04 1.10+0.05 3.86+0.21 <0.05 diameter (cm) root 2.17+0.21 5.28+0.44 2.44+0.12 5.35+0.34 <0.05 depth (cm)
' Trait comparisons between short tussock interstitials and tall tussock interstitials were tested by Mann Whitney U: Height (Z = -6.06; P < 0.01), Shoot No. (Z = -4.71; P < 0.01), Stem Diam. (Z = -6.08; P < 0.01), Root Diam. (Z = -6.80; P < 0.01), Root Depth (Z =-1.350; P = 0.18)
Table 5.3 Trait measurements among four functional plant groups. Mean (+SE) values of measurements are reported for each plant group (N = 25) on Hebron Fish
Hatchery, Licking County, Ohio.
91 Sites Step Variable Wilk’s Function #1 Function #2
Entered Lambda Standardized Standardized
Coefficients Coefficients
Hole 1 root diameter 0.160 0.935 -0.316
Marsh 2 root depth 0.097 -0.125 0.987
3 height 0.076 0.437 0.351
Highway I height 0.040 0.909 ------
Marsh 2 root diameter 0.030 0.510 and Pools
Table 5.4 Stepwise statistics and standardized canonical function coefficients, from the discriminant functional analysis on plant groups from Hebron Fish Hatchery,
Licking County, Ohio (N = 25 for each functional group). For stepwise statistics, F to enter 3.84, F to remove 2.71.
92 Figure 5.2
Discriminant functional analysis of three plant groups using five plant traits firom the
Hole Marsh, Hebron, Ohio, 2000. Function 1, firom left to right, is a gradient with increasing root diameters and increasing heights (root diameter coefficient 0.935, height coefficient 0.437). Function 2, fiom top to bottom, is a gradient with decreasing root depths (coefficient 0.987)
93 4.0
■ ■ clonal stress tolerator matrix 2.8 ■ ■ ■ clonal dominant matrix e § 1.6 • ■ • # ■ ■ .1 • • • ^ E 0.4 1 L : . • ■ o ° • -0.8 o • # # 1 tall tusscjck interstitial # -2.0 1 1 -4.0 -1.8 0.4 2.6 4.8 7.
Discriminant Function 1
Figure 5.2
94 Site Function Eigen % Variance Canonical Wilks Sig. Correct
Number Value Correlation Lambda Class.
Hole I 6.62 90.1 0.932 0.076 <0.05 92%
Marsh 2 0.73 9.9 0.649
Highway I 32.42 100.0 0.985 0.03 <0.05 100%
Marsh and Pools
Table 5.5 Summary statistics from the discriminant functional analysis on plant groups from the Hebron Fish Hatchery, Licking County, Ohio.
95 Figure 5.3
Discriminant analysis between short tussock interstitial and clonal dominant matrix functional plant groups at the Hebron Fish Hatchery, Hebron, Ohio, 2000. Five traits were measured from each plant. From left to right is a gradient with increasing height and root diameter (height coefficient 0.909, root diameter coefficient 0.510)
96 short tussock clonal dominant Interstitial matrix o e oo oo oo oo O 0 oooo o o oooooo oo e
I------1------1------1------1 -8 -4 0 4 8 Function 1
Figure 5.3
97 H. pustulatus and H. immaculosus = = were :. -- «fc.—.present . . - — only .— in clonal ' dominant - - - matrix — — -
samples on the Highway Marsh (Table 5.6). E.perplexus, C. glyphicus, and P.
subcupreus counts were significantly higher in temporary pools compared to lower
counts in deeper marsh waters with clonal dominant matrix (Mann Whitney U Test, P <
0.05). Higher densities of E. ochreus were found in the clonal dominant communities
compared to lower densities in temporary pool communities (Mann Whitney U Test, P <
0.05).
H. pustulatus counts varied significantly in the different types of Hole Marsh plants, as they preferred clonal dominant matrix to stress tolerator matrix and tall tussock interstitials (Kruskal-Wallace Test, P < 0.05) (Table 5.7). Conversely, the crawling water beetle, P. muticus, preferred clonal stress tolerator matrix and tall tussock interstitials over clonal dominant matrix (Kruskal-Wallace Test, P < 0.05) while the predaceous diving beetle, H. iricolor, was rather evenly distributed among these three plant groups
(Kruskal-Wallace Test, P = 0.72). In late summer, counts of both E. ochreus and B. fratem us were significantly higher in flooded ruderals compared to counts in clonal dominant matrix (Kruskal-Wallace Test, P < 0.05) (Table 5.8). Higher densities of P. ochrus were present in Polygonum communities while higher densities ofB. fratem us were present in dense strands of E. crusgalli. The dytsicid, C. glyphicus, burrowed into temporary pool sediments during dry periods (total of 13 in 40 samples) withE. plexus
(total of 4) and E. oechrus (total of 3) (Table 5.9).
98 Temporary Pools with Highway Marsh with
Ruderals and Short Clonal Dominants
Tussock Interstitials
Species Mean (+SE) Sum Mean (+SE) Sum pa
H. pustulatus 0 +.0.00 0.0 1.46 + 0.52 73 <0.05
H. immaculosus 0 +.0.00 0.0 0.34 + 0.141 17 <0.05
E. perplexus 0.86+.0.21 43 0.02 +.0.02 01 <0.05
E. ochreus 0.34+.0.19 17 0.74+.0.16 37 <0.05
C. glyphicus 0.42+.0.10 21 0.00 +.0.00 0.0 <0.05
P. subcupreus 0.70 + 0.14 35 0.28 +.0.07 14 <0.05
® Results of the Maim-Whitney U Test
Table 5.6 Coleoptera counts collected by sweep netting temporary pools and the deep water zone of the Highway Marsh from March to August (N=50) Hebron Fish
Hatchery, Ohio. Fish were not present in this wetland.
99 Clonal Stress Tall Tussock Clonal P
Tolerator Interstitial Dominant Value
Matrix Matrix
Species Mean (+SE) Sum Mean (+SE) Sum Mean (+SE) Sum
H. pustulatus 0.67+0.20 27 0.18+0.09 7 1.82+0.53 73 < 0.05“
P. muticus 0.47+0.16 19 0.62+0.17 25 0.33+0.18 13 0.38'*
H. iricolor 0.20+0.07 8 0.27+0.09 11 0.37+0.19 15 0.87*=
“ Friedman Test, Chi-Square = 10.19, df = 2 Friedman Test, Chi-Square = 1.95, df = 2 ® Friedman Test, Chi-Square = 0.25, df = 2
Table 5.7 Coleopteran counts in the different vegetative zones of the Hole Marsh,
Hebron Fish Hatchery, Ohio. Samples were collected with aquatic nets in March and April (N = 40). Fish were present in this wetland.
100 Species Ruderals Ruderals Clonal Dominant Matrix P
(Polygonum spp) (E. crus-galli) (T. latifolia)
mean (+SE) mean (+SE) mean (+SE)
E. ochreus 7.84+0.69 1.42 + 0.17 0.27 + 0.12 <0.05*
B. fratem us 1.20+0.35 3.25 + 0.58 0.02 + 0.02 <0.05'’
“ Friedman Test, Chi-Square = 65.35, df = 2 ** ** Friedman Test, Chi-Square = 49.18, df = 2
Table 5.8B. fratemus and E. oechrus counts (N = 40) in clonal dominants and flooded ruderals at Highway Marsh, Hebron Fish Hatchery, Ohio.
101 Species Total Number Collected mean (+SE)
C. glyphicus 13 0.32 + 0.10
E. plexus 4 0.10 + 0.04
E. ochraceus 3 0.07 + 0.04
Table 5.9 Summary counts of three Coleoptera species taken from Hebron Fish
Hatchery dry temporary pool basins with a cylinder water column sampler in late
September (N = 40).
102 DISCUSSION
Aquatic Coleoptera were associated with a variety of wetland functional plant
groups and hydroperiods during the growing season. H. immaculosus, H pustulatus, and
E. ochraceus preferred clonal dominant matrix stands with stable hydroperiods, while C.
glypicus, E. perplexus and P. subcupreus preferred temporary pools with ruderals, short
tussocks, and reed interstitials. The predaceous diving beetle, H. iricolor, was collected
in both the shallow and deeper waters of semi-permanent marshes, sites with clonal
stress tolerator matrix, tall tussock interstitials, and clonal dominant matrix. The
hydrophilid, E. ochraceus, migrated from clonal dominant matrix to flooded ruderals
after late summer rains.
Aquatic insects and emergent plants have adapted to different water cycles by a
variety of mechanisms such as physiological tolerance, migration (insects) or seed and vegetative spread (plants), and unique life history strategies. For example, the predaceous diving beetle, C. glyphicus, may take advantage of spring nutrient pulses in temporary pools, a strategy which probably emphasizes greater reproductive effort, rapid egg maturation, and high fecundity in short flooding periods (Table 5.10). During natural draw downs, they avoided desiccation by burrowing into moist soils, which conserved resources and delayed reproduction. Adults found in flooded pools immediately after summer rains may bet-hedge, a strategy supported by the presence of tenerals in October
(Hilsenhofif 1993). Ruderals in temporary pools avoided flooding by growing quickly and producing high seed yields, a strategy that also emphasizes greater reproductive effort but in short drying periods. The other temporary pool groups, reed interstitials and
103 Strategy Strategy Strategy
Plants Ruderals - Smartweeds Reed Interstitials - Soft rush (P. hydropiperoides) (J. ejffusus) generally avoid flooding; Short Tussock Interstitials - complete life cycle by Sedges (Carex) growing quickly in moist stress tolerant; survive soils; invest resources periodic flooding and short into photosynthetic and spring inundation periods; reproductive tissues, short grow slowly; low reproductive life span; high seed effort throughout the growing production season
C. glyphicus^ Adults Adults Adults (1) in spring, exploit (2) during summer draw (3) exploit temporarily flooded pools downs, burrow in moist flooded pools with high nutrient piUses, soils to avoid high after summer high algae concentrations. temperatures and rains which and abundant prey; desiccation; emphasize trigger nutrient emphasize high conservation of resources pulses and reproductive effort with periods of short renewed especially rapid egg reproduction invertebrate maturation and high cycles; use a fecimdity; avoid bet-hedging desiccation; avoid fish strategy predation
* Life history by Hilsenhoff (1993): univoltine, cyclic colonizer between temporary and more permanent waters, larvae and teneral adults found in shallow, rain flooded habitats July t^ u g h October, adults apparently ever winter inlentie habitats.
Table 5.10 Conceptualized life history strategies ofglyphicus C (Dytiscidae) and its associated functional plant groups during spring and summer months at the Hebron
Fish Hatchery, Hebron, Ohio. This predaceous diving beetle prefers ruderals, reed interstitials, and short tussock interstitials in temporary pools.
104 short tussock interstitials, tolerated flooding^stress by growing slowly and reproducing in
low numbers throughout the growing season.
In a different type of strategy, H. pustulatus avoided desiccation by preferring
marshes with stable water levels and dense stands of clonal dominant matrix (Table
5.11). They exploited nutrient pulses in deeper waters with abundant litter, an
environment well suited for its later hatch dates compared to other Dytiscidae (Hilsenhofif
1993). Predator/prey interactions became increasingly important to this semi-permanent
resident. Similarly, clonal dominant matrix preferred stable water levels, flowered at the
end of the growing season, and were greatly influenced by biotic factors, especially
competition. H. pustulatus was also present in flooded ruderals in late September, a time
of delayed reproduction and allocation of resources for dispersal, storage, and
overwintering survival.
The ubiquitous P. subcupreus was collected in both temporary pools with flooded
ruderals and short tussock interstitials, and in semi-permanent marshes with clonal
dominant matrix. Both of these sites experienced spring nutrient pulses conducive to rapid egg maturation and high fecundity (Table 5.12). Because larvae developed in adjacent riparian zones and adults wintered in terrestrial environments (Hilsenhofif 1995),
P. subcupreus was probably not as restricted in hydroperiod choice as are other species which required standing water for egg, larval, and adult stages. Though I analyzed invertebrate and plant functional groups in very specific wetland zones, there was much overlap in habitat use. For example, mderals and short tussock interstitials germinated on both the exposed mudflats of semi-permanent marshes during dry marsh stages and on
105 Strategy Strategy Strategy
Plants Clonal Dominant Matrix Clonal Stress Tolerator Ruderals Cattails (T. angustifolia)’, Matrix Barnyard Grass flood tolerant competitive Reed Canary Grass (£. crus-galli)’, plants which allocate {P. arundinacea); avoid flooding; resources into storage aggressive invader; grow complete life structures; grow quickly, quickly in moist soils, cycle between increase reproductive tolerate shallow flooding;floods by efforts at the end of the exhibit a mix of ruderal growing quickly growing season; exploit and clonal dominant in moist soils, wetlands with longer traits; colonize steep invest resources hydroperiods; rhizomatic shorelines with into reproduction, spread fluctuating water levels short life span
H. pustulatus^ Adults Adults (1) in spring, they exploit (2) after late September the nutrient pulse in clonal rains, they exploit flooded dominant plants; emphasize shoreline openings with reproductive efforts later ruderals, sites with in the season; avoid nutrient pulses and high desiccation by preferring prey abundance; allocate more permanent waters; resources for dispersal as a small Dytiscid, they flights, overwintering avoid larger predators survival, and delayed by finding shelter in reproduction; avoid matrix structures desiccation stress and anoxic cattail stands
Life history by Hilsenhoff (t99T)ruravoltme, resident of deeper lentic waters, teneral adult counts peaked in August, reproduction occurred later in the season compared to other Dytiscids, adults over wintered in more open waters and in larger marshes.
Table 5.11 Conceptualized life history strategiesofH, pustulatus (Dytiscidae) and its associated functional plant groups during spring and summer months at the Hebron Fish Hatchery, Hebron, Ohio. This predaceous diving beetle prefers (1) clonal dominant matrix in deeper, more permanent pond waters, (2) clonal stress tolerator matrix on pond shorelines, and (3) flooded ruderals in late summer. 106 Strategy Strategy Strategy
Plants Ruderals - Smartweeds Reed Interstitials Clonal Dominant Short Tussocks Matrix generally avoid flooding; stress tolerant; flood tolerant complete life cycles survive periodic competitive plants between floods by flooding and which allocate growing quickly in short spring resources into moist soils; invest inundations; grow storage structures; resources into slowly; low constant grow quickly; photosynthetic and reproductive efforts reproduce reproductive tissues; throughout the at the end of the short life span with high growing season growing season seed production exploit wetlands with longer hydroperiods; rhizomatic spread
P. subcupreus^ Adults Adults (1) in spring, exploit (2) exploit flooded pools nutrient pulses in after late summer rains; temporary pools and allocate resources for semi-permanent ponds; dispersal flights. emphasize high overwintering survival; reproductive efforts. delay reproduction; rapid egg maturation avoid anoxic cattail and high fecundity; conditions ubiquitous distribution
® Life history by Hilsenhoff (1995): univoltine, cyclic colonizer betweett shallow water sites and terrestrial habitats, larvae complete development in riparian habitats, teneral adult abundance peaks in August, prefers a variety of lentic habitats.
Table 5.12 Conceptual life history strategies ofsubcupreus P. (Hydrophillidae) and its associated functional plant groups during spring and summer at the Hebron Fish Hatchery, Hebron, Ohio. This beetle prefered both (1) ruderals, short tussocks, and reed interstitials in temporary pools, and (2) clonal dominants in permanent ponds.
107 the basins of temporary pools (Galataowitsch and derJValk 1994). TheAedes sp.
mosquito was present on both short and long duration ponds, though higher abundances
were found on shorter duration ponds (Schneider and Frost 1996).
A conceptual framework relating life strategies of some aquatic plants and aquatic
insects is presented in Table 5.13. The temporary pool template selected for emergent
plants that (1) emphasized fast growth and reproduction, thereby avoiding flooding
disturbance or (2) tolerated flooding stress, grew slowly, and reproduced with low,
constant efforts. Ruderals, reed interstitials, and short tussock interstitials favored this
template. Aquatic insects in temporary pools generally synchronized life styles with
water occurrence, grew quickly in flooding phases, and either adapted to drought conditions or migrated out of these conditions. Wiggins et al.(1980) Groups 1-4,
Williams (1996) non-seasonal aquatic insects, and cyclic colonizers favored this template. Adaptive traits in unpredictable waters included short-life spans, high dispersal abilities, high fecundity, long-diapause eggs, staggered hatching, and poorly defined cohorts with differential development The semi-permanent pond template selected for competitive emergent plants that (1) allocated resources for vegetative spread and storage, (2) tolerated flooding, and (3) were well adapted to biotic factors. Aquatic insects in semi-permanent ponds included all of Wiggins et al. (1980) Groups 1-4,
Williams (1996) seasonal and aseasonal aquatic types, cyclic colonizers, and permanent water residents. Traits favoring seasonal aquatic insects and permanent residents were longer life spans, semelparity, intermediate fecundity, shorter-term diapausing eggs that hatched with the historically optimum time water reappeared, and predictable growth
108 Temporary Pool Template (-Temporary Pool and Semi-permanent Pond Template Life History Strategies Semi-permanent Pond Life History Strategies Template
short and variable see adjacent filters for longer hydroperiods; hydroperiods; increased each appropriate wetland decreased disturbance; disturbance frequency; habitat listed above decreased light availability; high light availability; more ambient spring water elevated spring water temperatures; short dry periods temperatures; long dry periods
ruderals avoid flooding (temporary pools) ruderals, matrix species grow quickly; phases and grow quickly reed interstitials, and short allocate resources to in dry phases; allocate tussock interstitials which vegetative and storage resources to reproduction; either (1) avoid floods and structures; flood tolerant; short life cycle; annuals; grow quickly in the dry well adapted to biotic factors seeds require moist soil phase or (2) tolerate (competition); emphasize germination; high response flooding and grow reproduces at end of growing to abiotic factors slowly season; vigorous lateral spread short tussocks tolerate short (semi-permanent wetlands) flooding periods and grow clonal dominant matrix slowly; emphasize low grow quickly and allocate constant reproduction most resources to vegetative and storage structures; flood tolerant competitors well adapted to biotic factors
Wiggins et al (1980) Wiggins et al (1980) Wiggins et al (1980) temporary water temporary water temporary water Groups 1-3; Williams Group 4 or cyclic colonizersGroups 1-4; Williams (1996) (1996) non-seasonal Wissinger (1997); seasonal species; permanent species; synchronize “establishment generations” water residents (Schneider life cycles with water in temporary pools are and Frost 1996) that (1) lack occurrence; grow quickly sedentary, grow quickly; desiccation resistance, (2)
Table 5.13 Conceptual life history strategies of aquatic plants and aquatic insects in temporary pools and semi-permanent ponds. (CONTINUED) 109 Tabic 5.13: CONTINUED in flooding phases; well reproduce at an early age, have longer aquatic life adapted to drying conditions are highly fecund; stages; more influenced by by diapause and desiccation “overwintering generations” biotic factors especially resistance; mainly allocate in semi-permanent ponds complex food webs and resources for survival and are adapted for dispersal, predation; intermediate reproduction in response delayed reproduction, and fecundity; shorter term to abiotic factors; short winter survival diapausing eggs lived; high fecundity
110 rates with well defined cohorts. Permanent residents lacked desiccation resistant stages,
developed over longer time intervals, and survived increased predation and competition.
The life history strategy of a cyclic colonizer, such as a water strider (Hemiptera:
Gerridae), exemplified similar plant and animal strategies. These skaters exhibited wing-
length polymorphism and developmental flexibility (Wissinger 1997). In spring, long
winged adults migrated firom permanent ponds or terrestrial habitats to temporary ponds.
Upon arrival, female wing musculature histolyzed thus expanding thoracic space for developing ovaries. Similar to ruderals, these females emphasized greater reproductive efforts in shorter time periods. One or more short-winged generations completed their life cycles in temporary flooded ponds, but with autumn drying, long-winged individuals developed with immature gonads. These individuals migrated back to permanent ponds, which probably supported matrix functional groups. In wetlands with more permanent water levels, both plant and animal groups delayed reproduction and emphasized energy storage. In summary, reproductive development (faster egg maturation and higher fecundities) and sedentary behavior in “establishment generations” of cyclic colonizers were associated with (1) ruderals that also emphasized reproduction and with (2) short tussocks that grew slowly. Correspondingly, delayed reproduction, higher survival, energy storage, and dispersal in “overwintering generations” of cyclic colonizers were associated with matrix plants that also delayed reproduction, stored energy, and lived longer.
Aquatic plants and aquatic insects have evolved unique life-history solutions to disturbances and stresses, especially different hydroperiods. Joint plant and animal guild
111 studies may be valuable tools for predicting how perturbations will affect wetland communities. As noted by Boutin and Keddy (1993), environmental factors which increased productivity or decreased disturbance may cause a shift ftom ruderals to clonal dominant matrix; these same factors may shift aquatic insect assemblages from Wiggins et al (1980) Groups 1-4 to more seasonal, permanent residents.
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