Newsletter of the Biological Survey of Canada (Terrestrial Arthropods)

Volume 17 No. 2, Fall 1998

 

 

Project Update:
Arthropods of Canadian Grasslands

General information and editorial notes

News and Notes
Update on the BSC Web Page
Insects of Canada on the Web
Summary of the Scientific committee meeting
Membership of the Scientific Committee

The Carmanah Canopy Project: Conservation of Arthropod Biodiversity in Coastal Sitka Spruce Forests

Project Update: Arthropods of Canadian Grasslands
Aculeate Wasps from CFB Suffield

The Quiz Page

Recent Publications associated with the Biological Survey

Selected Future Conferences

Quips and Quotes

Requests for Material or Information Invited

Request for Cooperation

The grasslands project was developed some years ago to catalyze and coordinate relevant work on the faunas of “undisturbed” grassland habitats in Canada, and for comparison with the faunas of modified range and crop habitats. In this way, it was hoped that the deficient knowledge of the arthropods of grasslands would be improved, and with it our understanding of the origin and setting of those faunas.

The project developed slowly, partly because many of the potential cooperators were heavily occupied in the Survey’s Yukon project (recently published). However, several grasslands newsletters were produced, and over the past few years specific subprojects have developed at some Canadian sites. The article below presents the first detailed results from one of them, Suffield, Alberta, giving instructive lessons about both the nature of grassland faunas and the methods available to characterize them.

RESULTS FROM GRASSLANDS:
ACULEATE WASPS FROM CANADIAN FORCES BASE SUFFIELD
(Hymenoptera: Chrysidoidea, Vespoidea, and Apoidea: Sphecidae)

Albert T. Finnamore
Provincial Museum of Alberta, 12845 102 Avenue, Edmonton, Alberta, Canada T5N 0M6

Introduction

Canadian Forces Base Suffield comprises a 2,690 km2 area northwest of Medicine Hat in the arid grasslands of the Prairies Ecozone in Alberta. It remains relatively unmodified by European settlement and currently supports high proportions of native vegetation. The Suffield National Wildlife Area (SNWA) was proposed in 1992 to protect the sensitive eastern sections of the Base. The site offered an opportunity to document arthropod species assemblages that occur in relatively unmodified grasslands.

Canadian Forces Base Suffield contains over 1,500 documented archaeological sites representing occupation by native cultures over at least the last 6,000 years (Brumley and Dau 1985). Native peoples on the Base were entirely big game hunters subsisting on abundant populations of Bison, Bison bison (Linnaeus). Dau (1983) estimated the grasslands of CFB Suffield could have supported between 9,000 and 50,000 bison in any one year. Several sites termed Bison Kills provide evidence of communal hunts where natives would assemble into large groups and coordinate hunting to bring considerable numbers of Bison to a single location for slaughter.

Indigenous societies in most of southern Alberta were largely supplanted by European settlement around the turn of the century. Excerpts from the Base Brief (Anonymous 1993) indicate that by 1900 there were 12 outfits ranging cattle on the area now occupied by the base. Federal government policy supported a prairie settlement plan which resulted in 2,283 registered farmers on the area in 1919; only 645 remained by 1924 due to unsuitability of the land for cultivation. Only 15% of the land was broken for cultivation. Wawaskesy Park was established in 1922 on the Middle Sand Hills in the northeastern sections of the Base in response to concerns that Pronghorn, Antilocapra americana (Ord), were in danger of extirpation. The park was closed in 1938 when Pronghorn populations stabilized. In 1941 the land now comprising CFB Suffield was expropriated by the Federal Government; about 125 families were affected. The Base was operated by the Defence Research Board until 1971 when it came under control of the Department of National Defence and began to serve as a training base for the British Army. The Department of National Defence recognized the sensitive nature of the ecosystems in the eastern portion of the base and since 1971 placed it out of bounds to all military training. Those sections now comprise the proposed Suffield National Wildlife Area to include 458.7km2 encompassing the Middle Sand Hills, some mixed grassland, and the riparian zone along the South Saskatchewan River.

About 1,200 feral Horses, Equus caballus Linnaeus, were removed from the base in 1993 because of damage caused to ecosystems in the National Wildlife Area. CFB Suffield at that time supported about 4,000 Pronghorn, 1,500 Mule Deer (Odocoileus hemionus (Rafinesque)), and 1,000 White-tailed Deer (Odocoileus virginianus (Zimmermann)). In all 25 species of mammals, 42 birds, 7 herptiles, 14 fish, and 426 vascular plants are known from the base. Finnamore (1992) estimated that between 6,000 and 8,000 species of arthropods could occur in the region.

It is no longer possible to find pristine examples of arid grasslands. CFB Suffield contains the largest contiguous area of surviving native grassland (> 50% native vegetation remaining) in western Canada (Patriquin and Skinner 1992) and probably North America. Its potential role for sustaining and restoring ecosystem dynamics, and acting as a refugium for native grassland species is invaluable, and potentially a resource of national significance.

Objectives

The objectives of this study were to document the structure of arthropod species assemblages in the grassland ecosystem at the SNWA, and to demonstrate any shifts in species assemblages associated with soil type or hydrological gradient.

Methods

Sampling methodology was designed to extract a broad range of biota representative of size classes and trophic levels in the above-ground terrestrial ecosystem. For arthropod meso- and macrofauna, triple replicate, passive samplers (pan and pitfall traps) were used to obtain quantitative information on species assemblages. Pan traps and pitfall traps provide quantitative data on species abundance in the form of relative trapability. Malaise traps and occasional sweep samples were also employed to obtain additional qualitative information on species richness.

Traps were placed in each of four vegetation zones, based on the maximum canopy height of vegetation (approximately 8cm, 15cm, 30cm, and 60cm), that crossed the surficial hydrological gradient on chernozem and eolian soil types. Each trap was assigned a unique identification number based on soil, vegetation height, and replicate. Traps were operated continuously from May to September with sampling intervals initially of about 15 days, and 30 days toward the end of the season. Water, soap and salt were used as the collecting medium during the initial year but were substituted with propylene glycol in the second year to solve problems with sample desiccation in the traps. Samples were washed on site, placed in plastic bags, labelled, and preserved with 95% denatured ethyl alcohol. Samples were then sorted, labelled, and sent to specialists for identification.

Sites selected for sampling included a transect on chernozem soil containing four mixed grassland species assemblages with different vegetation structures, a reflection of the underlying hydrological gradient; and four sites on eolian soils including a site on fine sandy soil (stabilized dune), a second stabilized dune site characterized by the presence of bushes in the community, a destabilized dune site or dune blowout, and the nearly unvegetated shoreline of a saline lake. Another site was established in the riparian community adjacent to the South Saskatchewan River but was destroyed by flooding early in the season. Detailed site descriptions can be found in the Arthropod Component Report for Canadian Forces Base Suffield, prepared for the Canadian Wildlife Service (Finnamore and Buckle in press). The protocols for pitfall traps, pan traps and Malaise traps followed that of Finnamore et al. (1998) except as follows: for pitfall traps no covers were used, and propylene glycol was used as a preservative; and pan traps were made from aluminum roasting pans (32 x 25.5 x 6 cm) coated with yellow enamel (Safety Yellow) on the inner surface.

Data analysis

Data were analyzed from a number of aspects including species richness estimation, geographic affiliation, complimentarity, and dominance distribution. Species richness estimation was performed using EstimateS version 5, species estimation program (Colwell 1997). The Abundance-based Coverage Estimator (ACE) and the Incidence-based Coverage Estimator (ICE), available on the EstimateS package, were used to calculate an estimate of species richness at each site. The ACE measure uses species with 10 or fewer individuals to calculate an estimate of species richness. The corresponding ICE measure uses species that occur at 10 or fewer sites to calculate species richness. The ACE and ICE measures were then used to calculate the proportion of common species to infrequent species at the regional level.

Complimentarity measures were calculated using BIODIV 5.1 (Baev and Penev 1995) for analysis of species assemblages across soil and hydrological gradients. The Czekanovski-Dice-S°rensen index of association was used in all comparisons. In its quantitative forms the Czekanovski-Dice-S°rensen index of association a simple and direct measure of overlap (Baev and Penev 1995). The form of the equation used in this analysis is as follows:

equat.gif (5274 bytes)
Where nij is the relative trapability (abundance) of the i-th species in the j-th site, and nik is the relative trapability of the i-th species in the k-th site. The results were clustered using the single linkage or nearest neighbour algorithm available on BIODIV.

Distribution of dominance in arthropod communities was based on a paper by Hňgvar (1994) which demonstrated that the dominance structure of soil microarthropod communities shifts in response to stress. The primary naturally occurring stress at the SNWA was water (surficial hydrology). Changes in arthropod dominance structure were examined over the surficial hydrological gradient.

Results

The duration of the sampling program at the SNWA spanned two years and produced about 3 million arthropod specimens. These included 237 species of aculeate Hymenoptera collectively represented by 3,006 specimens. A synopsis of the families of aculeate wasps collected in the SNWA is presented in Table 1. The 237 species found in the SNWA represent 26% of the aculeate wasp fauna known from Canada (902 species). The high level of species richness of aculeate wasp fauna in the SNWA is underscored by comparison with the aculeate wasp fauna for the entire Yukon Territory where 153 species have recently been reported (Finnamore 1997); the aculeate wasp fauna of the McIntyre Ranch, a fescue/mixed grass prairie near Magrath, Alberta, where 93 species were recently reported (Finnamore 1996); and the fauna of the Wagner Natural Area, an extreme rich fen in central Alberta near Edmonton from which 81 species have been reported (Finnamore 1994). About 58% (137 species) of the 237 species found in the SNWA are here reported for the first time from Alberta, and 15% (35 species) are reported for the first time in Canada.

The presence of several species of aculeate wasps in the SNWA is particularly noteworthy. Among these is Pseudisobrachium persimile Evans (Bethylidae) known from California and suspected from British Columbia. The single specimen collected in the SNWA represents the first confirmed record of the species in Canada. A single specimen of Pseudogonatopus autoxenobius R.C.L. Perkins (Dryinidae) was collected from the SNWA. It is known from Arizona and New Jersey, its presence in the SNWA represents a substantial extension of its known range. Similar range extensions have been demonstrated for several other species collected in the SNWA. These include Hedychridium frugale Bohart (Chrysididae) previously known from California and Arizona; Priocnemis nigriceps (Ashmead) (Pompilidae) a brachypterous (flightless) spider wasp previously known from a dozen specimens between Texas and Iowa; Ammoplanops moenkopi Pate (Sphecidae) previously known from the southwestern United States north to Wyoming and Utah; Pisonopsis triangularis Ashmead (Sphecidae) previously known from California to Colorado; Didineis dilata Malloch and Rohwer (Sphecidae) previously known from Wisconsin to Nebraska; Bembix sayi Cresson (Sphecidae) previously known as far north as South Dakota; Cerceris deserta Say (Sphecidae) previously known from eastern Canada and eastern United States; and Cerceris wyomingensis Scullen (Sphecidae) previously known from the central United States. One species of Methocha (Tiphiidae), appears to be undescribed; its small size and mesosomal microsculpture differing from that of any of the 4 species of Methocha known in the Nearctic Region.

Table 1. Synopsis of the aculeate wasps (Hymenoptera) collected in the SNWA.

Family Species Specimens
Bethylidae 5 33
Dryinidae 12 54
Chrysididae 19 150
Tiphiidae 8 63
Sapygidae 1 1
Mutillidae 11 100
Bradynobaenidae 1 1
Formicidae 37 516
Vespidae 15 208
Pompilidae 33 369
Sphecidae 95 1511
Total 237 3006

Species richness of aculeate wasps at the various sampling sites is presented in Table 2. The richest sites for aculeate wasps in the SNWA were the stabilized dune sites (mean richness of 56 species), and the Malaise trap site which was also on a stabilized dune. The chernozem sites demonstrated substantially less richness with a mean of 39 species in the wet sites and a mean of 34 species in the dry sites.

The aculeate wasp data from the traps were used in a quantitative analysis of species assemblages of the sites sampled in the SNWA. Samples were pooled for two seasons. Formicidae (ants) were excluded from the analysis because of a sampling bias associated with proximity of traps to a colony of eusocial insects. Analysis of wasp species assemblages was performed using the Czekanovski-Dice-S°rensen index of association. The results were clustered using the single linkage or nearest neighbour algorithm available on BIODIV software. The resulting dendrogram is presented in Figure 1.

In this spatial analysis the results obtained from the Czekanovski-Dice-S°rensen index of association demonstrated a strong relationship between soil type (chernozem and eolian) and species assemblages of aculeate wasps. In other words, a change in soil from chernozem to eolian types is accompanied by a substantial shift in aculeate wasp species assemblages. Moreover, within the chernozem sites aculeate wasp species assemblages also shifted with respect to vegetation structure (vegetation height is used as a proxy for structure), although not to the degree demonstrated by spider species assemblages (Finnamore and Buckle in press). The aculeate wasp assemblages in the chernozem sites clustered more or less sequentially along the transition from wet sites through increasingly arid sites, mirroring a response by vegetation to the surficial hydrological gradient in this grassland system. Again, the clustering along the hydrological gradient was not as pronounced as that found with the spider data from the same sites but nonetheless is readily evident. The surficial hydrological gradient reflected by vegetation structure in this grassland is the gradient most likely to demonstrate the greatest biotic shifts in climate change scenarios that hypothesize increasing aridity. In the eolian soil sites there is a shift in aculeate species assemblages with respect to vegetation cover. The stabilized or vegetated dune sites (3.1.) differed in species assemblages with respect to the relatively vegetation free destabilized dune blowout sites (4.1.). The transition from stabilized dunes to active dunes is another gradient likely to demonstrate a great deal of biotic shift in climate change scenarios that hypothesize increasing aridity. Aculeate wasp assemblages in both the chernozem and eolian grassland systems in the SNWA could prove valuable in assessing biotic shifts resulting from climate or human induced changes that affect surficial hydrology (increasing aridity) or affect vegetation structure (grazing and fire).

Table 2. Species richness of aculeate wasps at the SNWA sampling sites.  

Chernozem Soil Sites
Soil Moisture High Soil Moisture Medium-high Soil Moisture Medium-low Soil Moisture Low Soil Moisture
Plant Height

60 cm▒ canopy height

30 cm▒ canopy height 15 cm▒ canopy height 8 cm▒ canopy height
 

(1.1)

(1.2) (1.3) (1.4)
# species
37  43  37
38  35  46
34  30  37
34  29  39
Eolian Soil Sites
Soil Moisture High Soil Surface Moisture Medium Soil Surface Low Soil Surface Moisture Malaise Trap
Plant Height No vegetation MoistureStabilized dune Active dune blowout  
  (2.1) (3.1) (4.1) (5.1)
# species
14  26  20
43  58  67
18  34  32
108 

Sites

Differences between the aculeate wasp species assemblages on eolian and chernozem soils are presented in Table 3 which enumerates the species restricted to grasslands which developed on eolian and chernozem soils. There are almost 1.7 times as many species restricted to the eolian grassland ecosystems as there are species restricted to the chernozem grassland ecosystems. Only about 27% (62 species) of species were present in both grassland ecosystems.

Table 3. Species richness of aculeate wasps (232 species) restricted to soil types sampled in the SNWA (species collected in the riparian zone were excluded).

  Chernozem soil sites Eolian soil sites Species found in both soil types
# species 63 107 62

Species richness can also be considered from perspective of vegetation height classes as illustrated in Table 4. The stabilized dune sites (3.1, 5.1) with 96 and 108 species respectively, were substantially richer in aculeate wasp species than any other sites sampled in the SNWA. Among the chernozem sites, the relatively wetter sites with vegetation canopy greater than 30 cm and the relatively dryer sites with vegetation canopy up to 8 cm were about equal in richness and slightly richer in species than the moderately dry sites. Of the 227 species represented in Table 4, 54% (122 species) were found only within single vegetation height classes in the sites sampled in the SNWA. These are presented in Table 5. The stabilized dune sites again demonstrate the greatest richness in species apparently restricted to that habitat. Among the chernozem sites the relatively wet and the driest sites show the greatest richness in species apparently restricted to a single vegetation canopy height class. The species represented in Table 5 are of particular interest should these vegetation structures be altered through climate change or ecosystem management. For instance, will these species readily shift to other vegetation structures should change occur, and if so, will such shifts result in species compaction or species displacement.

Table 4. Species richness of aculeate wasps occurring within common vegetation canopy heights.

Chernozem Soil Sites
Soil Moisture High Soil Moisture Medium-high Soil Moisture Medium-low Soil Moisture Low Soil Moisture
Plant Height

60 cm▒ canopy height

30 cm▒ canopy height 15 cm▒ canopy height 8 cm▒ canopy height
 

(1.1)

(1.2) (1.3) (1.4)
# species
70
70
59
67
Eolian Soil Sites
Moisture High Soil Surface Moisture Medium Soil Surface Moisture Low Soil Surface Moisture Malaise Trap
Stability No vegetation
(shoreline\0
Stabilized dune Active dune blowout  
  (2.1) (3.1) (4.1) (5.1)
# species
41
96
57
108 

Table 5. Species richness of aculeate wasps (122 species) restricted to single vegetation canopy height classes

Chernozem Soil Sites
Soil Moisture High Soil Moisture Medium-high Soil Moisture Medium-low Soil Moisture Low Soil Moisture
Plant Height

60 cm▒ canopy height

30 cm▒ canopy height 15 cm▒ canopy height 8 cm▒ canopy height
 

(1.1)

(1.2) (1.3) (1.4)
# species
10
9
5
13
Eolian Soil Sites
Moisture High Soil Surface Moisture Medium Soil Surface Moisture Low Soil Surface Moisture Malaise Trap
Stability No vegetation
(shoreline\0
Stabilized dune Active dune blowout  
  (2.1) (3.1) (4.1) (5.1)
# species
8
34
16
27 

 

Figure 1. Cluster analysis of aculeate wasp species assemblages from the SNWA.

Cluster analysis of results obtained using the Czekanovski-Dice-Sorensen index of association with 190 species and 2,739 specimens of aculeate wasps (Hymenoptera) collected from the SNWA during the spring and summer of 1994 and 1995. Sites correspond to those characterized in the section on Methods. First number in the site designation corresponds to major soil type; 1 = chernozem, 2 = unvegetated margin of saline water basin, 3 = eolian with vegetation cover, and 4 = eolian sparse vegetation, if any (dune blowout). Middle number in the site designation corresponds to vegetation height; 1 = 60cm ▒, 2 = 30cm ▒, 3 = 15cm ▒, and 4 = 8cm ▒. The last number in the site designation is the replicate within the vegetation height class

 fig1.gif (86551 bytes)

Species Abundance and Dominance Distribution

A series of recently published papers provide evidence that higher biodiversity enhances ecosystem productivity, sustainability, and reliability (Kareiva 1996, Moffat 1966, Naeem and Li 1997, Tilman et al. 1996, and review article Culotta 1996). To briefly summarize; the higher the number of species in an ecosystem the greater the resiliency an ecosystem has to change. Most species in an ecosystem are infrequent, that is they normally occur at relatively low abundance or are sampled at relatively few sites. Relatively few species are common or dominant in most ecosystems, that is they normally occur at high populations or are sampled at a large number of sites. Changing conditions enable some of the infrequent species to replace common species as populations shift in response to change. The more infrequent species an ecosystem supports, the greater its ability to function under changing conditions. A loss or a gain of infrequent species in an ecosystem implies a reduction or increase, respectively, in the ability of an ecosystem to function under changing conditions. The ratio of dominant to infrequent species can be used as a measure of vulnerability to change, used to assess change over time, and used to assess the impact of stress on an ecosystem.

The ratio of dominant to infrequent species was calculated using 10 specimens as the cut off point for infrequent species. Dominant species had 11 or more specimens. Table 6 presents the results at the site scale and also at the regional scale. Species richness at the regional scale was estimated using the EstimateS program (Colwell 1997) with pan trap and pitfall trap data (Figure 2) to determine the number of infrequent species at that scale. The program estimated species richness at 216 species, which when combined with Malaise trap data (28 species were collected only in Malaise traps at Suffield) brings the estimated species for the region to 244 species. Although the eolian sites demonstrated greater species richness, they had the lowest ratios of dominant to infrequent species and are therefore more vulnerable to changing conditions.

Figure 2. Species estimation of aculeate wasps at the Suffield SNWA

fig2.jpg (15131 bytes)

Ecosystem disturbance or stress can also be measured by following change in the distribution of species dominance. Hňgvar (1994) demonstrated that the dominance structure of soil microarthropod communities shifts in response to stress. Using pan and pitfall trap data, distribution of individuals among species is presented for each site in Figures 3,5,7,9,11, and 13. The same data were transformed to a logarithmic scale representing size classes and presented in the corresponding figures, Figures 4,6,8,10,12, and 14. As surficial aridity increases across sites in chernozem soils there is a clear shift in dominance classes from a high percentage of species in the class containing 0.25-0.5% of individuals in the wetter sites to a high percentage of species in the class containing 0.5-1.0% of individuals in the relatively dryer sites. A similar shift is evident in the eolian sites. The shift in dominance classes across sites is presented in Figure 15. The use of shifts in dominance classes may prove a valuable tool in demonstrating the effects of stress induced by natural or anthropogenic activity.

Table 6. The ratio of dominant species to infrequent species. Based on 165 species collected by pan and pitfall traps.

Chernozem Soil Sites
Soil Moisture High Soil Moisture Medium-high Soil Moisture Medium-low Soil Moisture Low Soil Moisture
Plant Height 60 cm▒ canopy height 30 cm▒ canopy height 15 cm▒ canopy height 8 cm▒ canopy height
  (1.1) (1.2) (1.3) (1.4)
Dominant: infrequent 1:12.5 1:13.25 1:16 1:24
Eolian Soil Sites
Moisture Medium Soil Surface Moisture Low Soil Surface Moisture Chernozem Eolian Regional
Stability Stabilized Dune Active Dune Blowout     All Sites
  (3.1) (4.1) (1.1-1.4) (3.1-4.1) (5.1)
Dominant: infrequent 1:6.27 1:5.85 1:9.42 1:8.39 1:5.8

Geographic Affiliations

The aculeate wasps of the SNWA can also be viewed in terms of components based on the distribution of the individual species found at the sampling sites. Seven faunal components were identified in the aculeate wasp species collected in the SNWA (Table 7). The Holarctic faunal component includes species that are circumpolar in distribution; they are generally northern species with ranges that dip southward in the mountains but the SNWA records represent the southern limits of many of these species in the central part of the continent. Transcontinental species are generally distributed from Alaska and California to Newfoundland and Florida. Transcontinental boreal species range from coast to coast in the ecozones spanned by the boreal forest and also dip southward in the mountains. Transcontinental boreal species collected in the SNWA usually represent the southern limits of these species in the central parts of the continent. Transcontinental southern species range from coast to coast south of the boreal forest. Collections of these species in the SNWA represent the northern limits known for many of these species. Eastern species range from the Atlantic Coast westward to the mountains. In many cases the SNWA collections represent the western limits of the range of eastern species. Western species range west of the 100th meridian to the Pacific Coast and include many grassland endemic species. Great Basin species occur in the grassland ecosystems occupying the central part of the continent and includes mostly grassland endemic species.

The numbers of aculeate wasps belonging to the different faunal components are shown in Table 7. Not surprising is the low number of Holarctic species, 2.5% of the fauna in the SNWA. In comparison, the Holarctic component of the Yukon fauna was 15% of species (Finnamore 1997). That study also found 70% of the Yukon fauna to be composed of generally distributed species. The generally distributed faunal component of the species in the SNWA is 38%, about half of that found in the Yukon. The western and Great Basin faunal components at the SNWA, which contain the grassland endemic species, comprised nearly half (47%) of the aculeate wasp fauna as compared with 26% for the same component of the Yukon fauna. The high level of probable grassland endemic species in the SNWA is an indication of the relatively undisturbed nature of the grassland ecosystems contained therein.

Table 7. Faunal components of aculeate Hymenoptera collected from the SNWA (species that could not be identified beyond the generic level were excluded).

Range Number of species
1. Holarctic 6
2. Transcontinental 24
3. Transcontinental, boreal 19
4. Transcontinental, southern 41
Total of generally distributed species (1-4) 90
5. Eastern 25
6. Western 73
7. Great Basin 38
Total of probable grassland endemic species (6-7) 111

Figure 3 fig3.jpg (21485 bytes)

Figure 4fig4.jpg (21883 bytes)

Figure 5fig5.jpg (22215 bytes)

Figure 6fig6.jpg (22824 bytes)

Figure 7fig7.jpg (23289 bytes)

Figure 8fig8.jpg (23230 bytes)

Figure 9fig9.jpg (21262 bytes)

Figure 10fig10.jpg (21824 bytes)

Figure 11fig11.jpg (22885 bytes)

Figure 12fig12.jpg (21090 bytes)

Figure 13fig13.jpg (18342 bytes)

Figure 14fig14.jpg (22286 bytes)

 

Figure 15.

Shift in dominance classes across soil type and hydrological gradients of aculeate wasp sepcies at CFB Suffield.fig15.jpg (82240 bytes)

The species richness of the probable grassland endemic species at each sampling site is presented in Table 8. The stabilized dune sites (3.1, 5.1) demonstrate the greatest richness of probable grassland endemic aculeate wasps. The chernozem sites show maximum richness of these species in sites at the extremes of the surficial hydrological gradient, the wettest and the driest sites.

Species of probable grassland endemics that appear to be restricted to specific vegetation canopy heights are of particular interest because these species will most likely be affected by management practices that alter vegetation in the SNWA. This study found 46 species of probable grassland endemic species that appear to be restricted to a single vegetation height class (Table 9). Again, the stabilized dune sites were by far the richest with 27 (60%) of these species found only at those sites. Either destabilization of the dune systems in the SNWA or increasing vegetation density would almost certainly affect populations of these species.

Table 8. Species richness of probable grassland endemics (western and Great Basin) of aculeate wasps found in the SNWA sampling sites (111 species). Species that could not be identified beyond generic level were excluded, as were species collected at sites other than those indicated below.

Chernozem Soil Sites
Soil Moisture High Soil Moisture Medium-high Soil Moisture Medium-low Soil Moisture Low Soil Moisture
Plant Height

60 cm▒ canopy height

30 cm▒ canopy height 15 cm▒ canopy height 8 cm▒ canopy height
 

(1.1)

(1.2) (1.3) (1.4)
# species
29
24
23
293
Eolian Soil Sites
Moisture High Soil Surface Moisture Medium Soil Surface Moisture Low Soil Surface Moisture Malaise Trap
Stability No vegetation
(shoreline\0
Stabilized dune Active dune blowout  
  (2.1) (3.1) (4.1) (5.1)
# species
15
39
26
 55

Table 9. Species richness of probable grassland endemic aculeate wasps that are restricted to specific vegetation canopy heights in the sites sampled in the SNWA (46 species).

Chernozem Soil Sites
Soil Moisture High Soil Moisture Medium-high Soil Moisture Medium-low Soil Moisture Low Soil Moisture
Plant Height

60 cm▒ canopy height

30 cm▒ canopy height 15 cm▒ canopy height 8 cm▒ canopy height
 

(1.1)

(1.2) (1.3) (1.4)
# species
4
3
1
6
Eolian Soil Sites
Moisture High Soil Surface Moisture Medium Soil Surface Moisture Low Soil Surface Moisture Malaise Trap
Stability No vegetation
(shoreline\0
Stabilized dune Active dune blowout  
  (2.1) (3.1) (4.1) (5.1)
# species
0
12
5
15

The SNWA is the extreme northern locality known for a large number of species found there. Table 10 includes 107 species occurring in the SNWA that are at or near the northern limits of their known ranges. They are composed almost entirely of western and transcontinental southern faunal components. These are species that comprise the faunal component most likely in danger of extirpation from Alberta should the grassland ecosystems be altered, especially so if those species occupy limited habitats within the grassland ecosystems. The high proportion of species at the northern limits of their known ranges (45% of species) is a result of the location of the SNWA near the northern limit of the central continental grassland ecosystems. As a result the SNWA is almost certainly acting as a northern refugium (from agriculture) for these species and therefore functioning as a reserve of national significance. The stabilized dune sites again demonstrate the greatest species richness of species at their northern limits in the SNWA.

Species at the northern limits of their ranges that appear to be restricted to specific vegetation canopy heights are of particular interest because some of these species will most likely be in danger of extirpation in Alberta should management practice or climate change alter vegetation in the SNWA. There are 52 species at the northern limits of their known ranges that appear to be restricted to specific vegetation classes in the SNWA. These are presented in Table 11. Of the 52 species listed in table 11 only a small proportion would likely be affected in the most likely climate change or management scenarios. Either increasingly arid climate patterns or grazing the SNWA to the extent where a xeric shift in vegetation occurs could affect those species that appear to be restricted to the wettest sites. Those 8 species occur in the relatively wet chernozem sites (1.1, 1.2). However, the greatest effects would likely be observed with destabilization of the vegetated dune systems which could affect 27 species that appear to be restricted to the stabilized dune habitat.

Table 10. Species richness of aculeate wasps at the northern limit of their ranges that occur at sites sampled in the SNWA (107 species)

Chernozem Soil Sites
Soil Moisture High Soil Moisture Medium-high Soil Moisture Medium-low Soil Moisture Low Soil Moisture
Plant Height

60 cm▒ canopy height

30 cm▒ canopy height 15 cm▒ canopy height 8 cm▒ canopy height
 

(1.1)

(1.2) (1.3) (1.4)
# species
27
24
22
32
Eolian Soil Sites
Moisture High Soil Surface Moisture Medium Soil Surface Moisture Low Soil Surface Moisture Malaise Trap
Stability No vegetation
(shoreline\0
Stabilized dune Active dune blowout  
  (2.1) (3.1) (4.1) (5.1)
# species
14
43
30
53

Table 11. Species richness of aculeate wasps potentially subject to extirpation that are restricted to specific vegetation canopy heights in the sites sampled in the SNWA (52 species).

Chernozem Soil Sites
Soil Moisture High Soil Moisture Medium-high Soil Moisture Medium-low Soil Moisture Low Soil Moisture
Plant Height

60 cm▒ canopy height

30 cm▒ canopy height 15 cm▒ canopy height 8 cm▒ canopy height
 

(1.1)

(1.2) (1.3) (1.4)
# species
4
4
2
7
Eolian Soil Sites
Moisture High Soil Surface Moisture Medium Soil Surface Moisture Low Soil Surface Moisture Malaise Trap
Stability No vegetation
(shoreline\0
Stabilized dune Active dune blowout  
  (2.1) (3.1) (4.1) (5.1)
# species
1
13
7
14

Conclusion and Management Considerations

The SNWA contains 237 species of aculeate wasps, the most species-rich assemblage of aculeate Hymenoptera known from Canada. That status is largely a consequence of three factors: its location near the northern limits of the midcontinental grasslands; the eolian grasslands contained therein; and its relatively unaltered vegetation. Species at the northern limit of their known ranges constitute 45% of the aculeate wasp fauna known from the SNWA. As a result the SNWA is almost certainly acting as a northern refugium (from agriculture) for these species and therefore functioning as a reserve of national significance. Eight species from chernozem soil sites have been identified as potentially in danger of extirpation should climate or management practice force a xeric shift in vegetation structure. A further 27 species may be adversely affected through destabilization of the dune systems at the eolian sites.

Analysis of aculeate wasp data of species assemblages in the sites sampled in the SNWA demonstrates these assemblages are structured with respect to soil type and vegetation canopy height (a  proxy for structure). Results show that 54% of species (122 species) were found within single vegetation height classes. These species are of particular interest should these vegetation structures be altered through climate change or ecosystem management. For instance, will these species readily shift to other vegetation structures should change occur, and if so, will such shifts result in species compaction or species displacement? The management implications for the SNWA are such that the reduction of vegetation canopy diversity to fewer levels than present may adversely affect species diversity, particularly for those species associated with specific vegetation canopy heights. Management practice or climate changes that destabilize the dune systems would almost certainly have the greatest impact on the aculeate wasp fauna in the SNWA. Should destabilization occur species apparently restricted to the stabilized (vegetated) dune systems should be monitored and used to assess the efficacy of establishing corridors to allow biota unobstructed movement out of the SNWA.

References

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Acknowledgements

Thanks to Canadian Forces Base Suffield, Department of National Defence; the Canadian Wildlife Service, Environment Canada, Prairie and Northern Region, for supporting arthropod inventories as part of the wildlife inventory of the National Wildlife Area on the proposed SNWA; thanks to the following people for identification of material: James Carpenter, American Museum of Natural History (several Vespidae); Lynn Kimsey, University of California (several Chrysididae); Rob Longair, University of Calgary (several eumenine Vespidae); Marius Wasbauer, Brookings, Oregon (several Pompilidae). Thanks are also due to Darren Pollock for sorting specimens and servicing the traps at the SNWA sites; to Jim Tansey for assistance in sorting specimens; and to Robert Gerlock for field assistance.

 

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