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Chapter 6
Grasslands: Biodiversity Hotspots for
Some Arthropods in British Columbia
Geoffrey G. E. Scudder
Department of Zoology, University of British Columbia
Vancouver, British Columbia, Canada V6T 1Z4
Abstract. This chapter reports on research into the potentially rare and endangered terrestrial arthropods in
British Columbia to determine the rarity and richness hotspots for these species as well as those for terrestrial true
bugs (Heteroptera: Prosorrhyncha), butterflies (Lepidoptera), and terrestrial neuropteroids (includes Neuroptera
and Raphidioptera). The results are interpreted in relation to the distribution of natural low-elevation grasslands
in the province. Conservation implications are discussed.
Résumé. Ce chapitre fait état des recherches effectuées sur les arthropodes terrestres qui pourraient être rares ou en
danger de disparition en Colombie-Britannique afin de déterminer la rareté et la richesse des régions névralgiques
de la biodiversité de ces espèces et d’autres espèces d’hémiptères terrestres (Heteroptera : Prosorrhyncha),
de lépidoptères (Lepidoptera) et de neuroptéroïdes terrestres (y compris Neuroptera et Raphidioptera). Nous
interprétons les résultats à l’aune de la répartition des prairies basses naturelles dans la province, et examinons
leur signification du point de vue de la conservation.
Introduction
The term “biodiversity hotspot” was originally coined by Myers (1989, 1990) to indicate
priority conservation areas of the world with a high number of endemic species. However,
the term hotspot is now applied more generally to indicate geographical areas that rank
particularly high in one or more axes of species richness, levels of endemism, number of
rare species, and intensity of threat (Reid 1998).
Such biodiversity hotspots have now been identified in the British Isles (Prendergast,
Quinn et al. 1993; Williams et al. 1996), Europe (Williams, Humphries et al. 2000;
Komonen 2003; Gjerde et al. 2004), Africa (Pomeroy 1993; Williams, Wicz et al. 2000),
the United States (Dodson et al. 1997), and elsewhere (Harcourt 2000; Roberts et al. 2002).
Preliminary results on hotspot analyses in British Columbia have also been published
(Scudder 2005).
Distribution of BC Grasslands
The distribution of the main natural low-elevation grassland areas in British Columbia
is shown in Fig. 1. The most extensive areas are in the southern interior of the province,
with lesser representation on the south coast and the northeast in the Peace River area.
The distribution of grasslands in British Columbia used for this study is based on the
Biogeoclimatic Ecosystem Classification described in Meidinger and Pojar (1991). Within
Scudder, G. G. E. 2010. Grasslands: Biodiversity Hotspots for Some Arthropods in British Columbia.
In Arthropods of Canadian Grasslands (Volume 1): Ecology and Interactions in Grassland Habitats.
Edited by J. D. Shorthouse and K. D. Floate. Biological Survey of Canada. pp. 121-134.
© 2010 Biological Survey of Canada. ISBN 978-0-9689321-4-8
doi:10.3752/9780968932148.ch6
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G. G. E. Scudder
this classification, Nicholson et al. (1991) document the distribution and community
structure of the extensive grasslands of the bunchgrass zone (BG). However, natural lowelevation grasslands occur in other ecozones. Specifically, the Garry oak ecosystem in the
dry areas of the coastal Douglas-fir zone (CDF) (Nuszdorfer et al. 1991) characteristically
contains patches of grasslands. Furthermore, the ponderosa pine zone (PP) is open and parklike with a ponderosa pine (Pinus ponderosa P. and C. Lawson) canopy and an understory
dominated by bluebunch wheat grass (Pseudoroegneria spicata (Pursh) A. Löve). These
grasslands that occur throughout the PP are thought to have developed as a result of a
combination of edaphic and topographic conditions, together with a history of fire (Hope,
Lloyd et al. 1991).
This combination of conditions and fire history has likewise led to the development of
large grassland areas in the interior Douglas-fir zone (IDF) (Hope, Mitchell et al. 1991).
Grasslands also occur on the steep, south-facing slopes above the Peace River in the boreal
white and black spruce zone (BWBS) (DeLong et al. 1991), in part of what Munro and
Cowan (1947) call the Peace River Parklands. In addition, grassland patches occur on the
south-facing slopes of the Stikine River near Telegraph Creek in the BWBS.
The BG, CDF, IDF, and PP were mapped by using data from the BC Ministry of
Sustainable Resource Management website at ftp://ftp.elp.gov.bc.ca/dist/arcwhse/
wildlife/ (now available at the BC Ministry of Forests and Range at FTP://ftp.for.gov.
bc.ca/HRE/external/!publish/becmaps/GISdata/CurrentVersion). The polygons for the
south-facing slopes of the Peace River were mapped by using data from the Grasslands
Conservation Council of BC, and the Stikine River section of the BWBS, as shown in
Fig. 1, was added freehand.
Table 1. Terrestrial arthropod data (as of May 6, 2008)1 imported into WORLDMAP 1:20,000. Abbreviation:
AAFC = Agriculture and Agri-Food Canada.
Data Set
No. of Taxa
No. of Records
Data Source
Arthropods
669
9,514
G.G.E. Scudder (compilation)
Heteroptera
99
3,491
G.G.E. Scudder
Butterflies
60
3,486
A. Jessop (AAFC), C. Guppy,
J. Heron, N. Kondla
Neuropteroids
18
185
G.G.E. Scudder
Heteroptera
623
32,458
G.G.E. Scudder
Butterflies
187
38,787
A. Jessop (AAFC), C. Guppy,
J. Heron, N. Kondla
74
2,911
Rarity Hotspots
2
Richness Hotspots
Neuropteroids
G.G.E. Scudder
1
Alien species excluded.
2
Includes species and subspecies listed on the provincial Red list and Blue list by the BC Conservation Data Centre.
Grasslands: Biodiversity Hotspots for Some Arthropods in British Columbia
123
Fig. 1. Distribution of the main natural low-elevation grassland areas in British Columbia. Many of these areas
are treed savanna or are developed for agriculture, houses, or other human uses.
Georeferenced Distributional Data
Georeferenced distributional data were assembled for the rare species of terrestrial
arthropods listed in Scudder (1994), as well as a few additional species added to this list
since 1994. The distribution data for butterflies were obtained from the Butterflies of
Canada database, supplemented by additional data from local lepidopterists.
The data for terrestrial Heteroptera and terrestrial neuropteroids were assembled by
the author from the recent published literature and from an examination of material in most
of the major entomological collections in Canada. Table 1 lists the number of taxa and
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number of records involved in these databases. ArcView (version 3.2) software was used
to map the location of the records in these taxonomic databases.
Hotspot analyses were undertaken by using WORLDMAP software that was made
available and custom modified by Dr. P. Williams (Natural History Museum, London) for
application in British Columbia. Analysis was done by using a 1:20,000 NTS grid with
7,056 grid cells in the province. ArcView software was then used to map the centroid of the
top 5% of the hotspot grid cells on the grassland map layer.
The locations for the potentially rare and endangered terrestrial arthropods included in
the analysis are shown in Fig. 2. The rarity hotspot analysis is depicted in Fig. 3 and shows
that the majority of the top hotspots are in the southern interior and the southwest parts of the
province. Figs. 4–6 show the separate rarity hotspot analyses for the rare Heteroptera, the
rare butterflies, and the rare neuropteroids, respectively. Table 2 summarizes the distribution
of the top 5% of the hotspots for these taxa, relative to the low-elevation grasslands in the
province. The rare terrestrial Heteroptera have 78%, the rare butterflies 93%, and the rare
neuropteroids 100% of the top 5% of the rarity hotspots in these grasslands. Potentially
rare and endangered terrestrial arthropods have 55% of the top 5% of rarity hotspots in the
grasslands.
The distribution of the full list of localities involved in the terrestrial Heteroptera
database is shown in Fig. 7. Similarly, Figs. 8 and 9 represent the localities involved in the
butterfly and neuropteroid databases, respectively. Figs. 10–12 present the centroid of the
grid square for the top 5% of richness hotspots for the terrestrial Heteroptera, butterflies,
and terrestrial neuropteroids.
Table 2. Top 5% grid cells within and outside of grasslands in British Columbia for terrestrial arthropods.
Results
Grid Cells within
Grasslands
Number
Percentage
Grid Cells outside of
Grasslands
Number
Percentage
Total Grid
Cells Identified
for Top 5%
Richness
Rarity
Hotspots
Arthropods
18
55
15
45
33
Heteroptera
7
78
2
22
9
Butterflies
13
93
1
7
14
2
100
0
0
2
Heteroptera
18
60
12
40
30
Butterflies
26
57
20
43
46
Neuropteroids
10
56
8
44
18
Neuropteroids
Richness
Hotspots
Grasslands: Biodiversity Hotspots for Some Arthropods in British Columbia
Fig. 2. Recorded localities for the rare terrestrial arthropods.
Fig. 3. Top 5% of hotspots for the rare terrestrial arthropods.
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G. G. E. Scudder
Fig. 4. Top 5% of hotspots for the rare terrestrial Heteroptera.
Fig. 5. Top 5% of hotspots for the rare butterflies.
Grasslands: Biodiversity Hotspots for Some Arthropods in British Columbia
Fig. 6. Top 5% of hotspots for the rare terrestrial neuropteroids.
Fig. 7. Recorded localities for the terrestrial Heteroptera.
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G. G. E. Scudder
Fig. 8. Recorded localities for the butterflies.
Fig. 9. Recorded localities for the terrestrial neuropteroids.
Grasslands: Biodiversity Hotspots for Some Arthropods in British Columbia
129
Table 3. Top hotspot grid cell, followed by number of taxa found within grid cell and total number of taxa plotted
for each group.
Top Hotspot
Grid Cell
No. of Taxa
Total No. of
Taxa
Plotted
Percentage
in Top
Hotspot
Rarity Hotspots
Arthropods
082E.003
130
669
19
Heteroptera
082E.003
37
99
37
Butterflies1
082E.003
12
60
20
Neuropteroids
082E.013
6
18
33
Heteroptera
082E.003
302
623
48
Butterflies
082E.003
97
187
52
Neuropteroids
082E.053
31
74
42
Richness Hotspots
See Table 1 for note on taxa included.
1
In the analysis of richness hotspots (Table 2), 60% of the top 5% of the terrestrial
Heteroptera hotspots occur in the low-elevation grasslands, and 57% of the top 5% of
butterfly hotspots occur in these grasslands. For terrestrial neuropteroids, 56% of the top
5% of the richness hotspots are also in these grasslands. The tabulation thus shows that
there is little difference between the richness hotspot percentages for terrestrial Heteroptera,
butterflies, and neuropteroids in the grasslands.
Table 3 lists the top hotspot grid cell for the groups studied in this rarity and richness
analysis. Shown is the number of taxa present in this cell compared with the total number
plotted. Only three cells are involved, namely, 82E.003, 82E.013, and 83E.053, all in the
South Okanagan; cell 82E.003 in the extreme south near Osoyoos dominates. All have lowelevation native grassland as the predominant habitat.
Conclusions
Only a few terrestrial arthropod taxa are involved in this analysis because these are the
only taxa to date for which there is an extensive georeferenced distributional, computerized
database. When data for other taxa become available, additional analyses will show whether
similar results occur.
An examination of Figs. 7–9 shows that collection records are concentrated in the
southern part of the province and that those in the northern half are centred on main roads
and highways. L.D. Warman and G.G.E. Scudder (unpublished) found that 95% of the
records for butterflies in the province are within 3 km of a major road. However, much
of the northern half and western third of the province is mountainous and inaccessible.
The forested areas in these high, inaccessible areas may not contain suitable habitat for
the taxa studied.
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G. G. E. Scudder
Fig. 10. Top 5% of richness hotspots for the terrestrial Heteroptera.
Fig. 11. Top 5% of richness hotspots for the butterflies.
Grasslands: Biodiversity Hotspots for Some Arthropods in British Columbia
131
Fig. 12. Top 5% of richness hotspots for the terrestrial neuropteroids.
Positive relationships found between the species richness of two or more groups may
reflect patterns of sampling effort (Gaston 2000). Unfortunately, the collecting effort cannot
be assessed in a way that has been used in similar analyses elsewhere (Prendergast, Wood
et al. 1993). Nevertheless, main roads and highways in the province pass through all 16
Biogeoclimatic Ecosystem Classification zones, and records show that all of these zones
have been sampled.
The results for butterflies reported herein are consistent with the results presented by
Kerr (2001) in an analysis of patterns of butterfly species richness in Canada. This is not
surprising, because Kerr used the same basic database as is examined herein and did not
rely on range maps, as has been done in similar studies in Canada (Warman et al. 2004).
Kerr (2001) found that butterfly richness in Canada was correlated with average annual
potential evapotranspiration, but the mapping scale used by Kerr was different to that used
in the present study.
Although scale can influence the results in such richness analyses (Willis and Whittaker
2002), the analysis used in the present study was based on an Albers Equal Area projection
and 1:20,000 scales, which gave 7,056 grid cells in the province, with these grid cells
varying from 124.52 km2 in the northeast to 165.16 km2 in the southwest. This is a finer
scale than that used by Kerr (2001).
Natural grasslands occupy less than 1% of British Columbia’s land base (Grasslands
Conservation Council of British Columbia 2004). Gayton (2004) has pointed out that
overgrazing by wild and domestic ungulates, weed invasion, forest ingrowth (encroachment
as a result of fire suppression), and habitat fragmentation all threaten the integrity of the
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grassland ecosystems in the interior of the province. Hence, because these grassland
ecosystems are important rarity and richness hotspots for several arthropods and other
taxa (Scudder 2005), they are prime areas for biodiversity conservation. The high richness
areas detected for the terrestrial arthropods investigated are also high irreplaceability areas
for much of the biota in the province (Warman and Scudder 2007). Meir et al. (2004) have
concluded that when investment has to be staged over a number of years, the best strategy
for biodiversity conservation is probably the protection of sites with the highest species
richness or highest irreplaceability.
Furthermore, because grasslands are likely to be the ecosystems that first show response
to current climate change (Knapp and Smith 2001), grassland arthropods, which typically
have short life cycles, are likely to be among the first biotic elements to demonstrate range
change in these high-priority conservation areas. Indeed, many wild animals and plants
are already showing the fingerprint of global warming (Parmesan and Yohe 2003; Root
et al. 2003). Butterflies in particular are responsive to climate change (Dennis 1993),
and elsewhere in the world they show changes in range correlated with climate change
(Parmesan 1996; Parmesan et al. 1999; Warren et al. 2001; Wilson et al. 2007). In this
context, the butterflies, terrestrial Heteroptera, and terrestrial neuropteroids living in the
richness hotspots in British Columbia’s native grasslands warrant conservation, monitoring,
and further study.
Acknowledgements
Research for this chapter was supported by grants from the Natural Sciences and Engineering
Research Council of Canada and funds from the British Columbia Ministry of Water,
Land and Air Protection (now Ministry of Environment). Dr. P. Williams (Natural History
Museum, London) kindly provided the WORLDMAP software and custom modified it for
application in British Columbia. Richard Doucette (Grasslands Conservation Council of
BC) provided an ArcView shape file for the Peace River grasslands area. I thank Annabelle
Jessop (Agriculture and Agri-Food Canada, Ottawa), C.S. Guppy, J. Heron, and N. Kondla
for providing the butterfly data used in this analysis. I am indebted to Launi Lucas for the
preparation and maintenance of the georeferenced distributional databases, for carrying out
the mapping, and for help in preparation of the figures and manuscript.
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