Grasslands and Grassland Arthropods of Canada1

1 Chapter 1 Grasslands and Grassland Arthropods of Canada1 Joseph D. Shorthouse Department of Biology, Laurentian University Sudbury, Ontario, Canada P3E 2C6 David J. Larson Box 56, Maple Creek, Saskatchewan, Canada S0N 1N0 Abstract. Grasslands are areas dominated by grasses and herbaceous vegetation and with few or no trees. They are generally open and contiguous and are widely distributed across Canada from the Yukon to eastern Ontario. The largest grasslands are those of the Prairies Ecozone, which extends from the Canada–United States border in a triangle from the western edge of Alberta to the eastern edge of Manitoba. This ecozone comprises the northern extension of the Great Plains of North America. This chapter provides an overview of the geography and biota of the Canadian Prairies Ecozone. Canada’s prairies were covered by several continental glaciations that resculptured the surface topography and kept biotic communities in a state of flux. Thus, the current grasslands of the Canadian prairies are the product of environmental stresses, including a varied continental climate, low and variable precipitation, fire, and biotic pressures such as grazing by herbivores. The arthropods that developed here are mostly species that are tolerant of environmental changes. The first humans to arrive on the Central Plains about 10,000 years ago were low-impact hunter-gatherers. Europeans arrived about 150 years ago with technological agriculture and quickly settled throughout the prairies. The once extensive native grasslands were reduced to small fragments, and alien species now dominate or occur in most regions. Most of the arthropod fauna seems to have survived these radical changes, probably due to its members being widely distributed and adapted to unstable and stressful environments. Insects, spiders, and mites are the most diverse and abundant animals in native grasslands, are important in the functioning of grassland ecosystems, and occupy a wide array of niches. Grassland insects in Canada are adapted to cold winter temperatures, a short summer growing season, drought, and strong winds. Grasshoppers are particularly well adapted to grasslands. Résumé. Les prairies sont des zones dominées par les graminées et d’autres plantes herbacées, et où les arbres sont rares ou absents. Elles sont généralement dégagées et contigües, et sont largement réparties au Canada, du Yukon à l’est de l’Ontario. Les plus vastes se trouvent dans l’écozone des prairies qui s’étend en triangle au nord de la frontière américaine, de la limite occidentale de l’Alberta à la limite orientale du Manitoba. Cette écozone est un prolongement vers le nord des prairies herbagères des grandes plaines d’Amérique du Nord. Ce chapitre présente un aperçu de la géographie et des biotes de cette écozone. Les prairies canadiennes ont traversé plusieurs périodes de glaciation continentale qui ont modifié leur topographie et stimulé l’évolution des communautés biotiques. Leur état actuel est le produit de divers facteurs de stress environnemental, y compris un climat continental varié, un régime de précipitations faibles et variables, les incendies et des pressions biotiques comme le broutage par les herbivores. La faune d’arthropodes qui caractértise la région sont surtout des espèces tolérantes de changements environnementaux. Les premiers humains qui sont arrivés dans les plaines centrales il y a environ 10 000 ans étaient des chasseurs-cueilleurs dont l’empreinte sur le milieu naturel était faible. Les Européens sont arrivés il y a environ 150 ans et ont rapidement colonisé l’ensemble de la région en y pratiquant une agriculture technologique. Les 1 This introductory chapter is dedicated to Dr. Ruby I. Larson, who introduced both authors to the world of prairie insects in the late 1950s when we were in our early teens and members of her Junior Science Club of Lethbridge. Her mentorship and enthusiasm led to us both developing careers in entomology. Shorthouse, J. D. and D. J. Larson. 2010. Grasslands and Grassland Arthropods of Canada. 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. 1-24. © 2010 Biological Survey of Canada. ISBN 978-0-9689321-4-8 doi:10.3752/9780968932148.ch1 2 J. D. Shorthouse and D. J. Larson vastes prairies naturelles ont été fragmentées en petites parcelles, et la plupart des régions sont désormais peuplées d’espèces végétales exotiques parfois dominantes. La plupart des arthropodes ont semble-t-il survécu à ces changements radicaux parce qu’ils étaient probablement déjà largement répandus et adaptés à des environnements instables et rigoureux. Les insectes, arachnides et acariens sont les animaux les plus diversifiés et les plus abondants des prairies naturelles; ils jouent un rôle important dans le fonctionnement des écosystèmes des prairies et occupent une grande variété de niches. Les insectes des prairies canadiennes sont adaptés aux hivers froids, aux saisons de croissance estivale courtes, aux sécheresses et aux vents forts. Les criquets sont particulièrement bien adaptés à ce genre de milieu. Introduction Grassland ecosystems cover approximately 25% (33 million km2) of the planet’s surface, a larger portion of the Earth’s land surface than any other vegetation type (Shantz 1954; Brown 1989; Meyer and Turner 1992). They represent one of the Earth’s major biomes and are one of the most productive and diverse terrestrial ecosystems. Common features found among grasslands include climates with periodic droughts, frequent fires, occurrence on landscapes that are level to gently rolling, low temperatures for part of the year, and an abundance of grazing animals (Anderson 2006). Grasslands contain few trees or shrubs and are dominated by grasses (members of the family Poaceae), which escape the deleterious impact of these features by having growing tips beneath the soil surface such that they are not exposed to desiccation and cannot be damaged by surface-feeding herbivores. Non- graminoid herbaceous species called forbs, many of which are found in the sunflower (Asteraceae) and pea (Fabaceae) families, are also common in grasslands (Anderson 2006). Thus grasslands are restricted to areas where water availability falls below the requirement for trees but is sufficient to support grasses. In many of Canada’s grasslands, shrubs provide the only woody plant component. Native grasslands are the largest vegetation biome in North America, and before the continent was settled by Europeans, grasslands covered about 162 million ha (Samson and Knopf 1994). They constitute a relatively continuous and roughly triangular area that extends from southern Alberta, Saskatchewan, and Manitoba south through the northern, central, midwest, and southern states of the United States to northeastern and central Mexico (Gauthier et al. 2003). This area is the widest latitudinal range of any North American ecological region, with North American grasslands representing about 7–10% of the world’s grasslands (Gauthier et al. 2003). A variety of conditions affect the extent, permanence, and vegetation composition of grasslands in Canada. They merge into northern forested sites through a continuum of vegetation types that include increased proportions of broad-leafed and woody plants and are described by such terms as parkland and open forest. Grasslands also merge into arctic and alpine, marsh, fen and bog, and desert-like habitats. Grassy habitats may occur and persist over long periods in an early successional stage, usually maintained by a disrupting factor, or in a climax-like stage with a stable assemblage of flora and fauna. Many abiotic and biotic factors have been responsible for the history and sustainability of the grasslands in various parts of Canada. However, this introductory chapter is mainly devoted to the history of the grasslands of the three prairie provinces. We also provide a brief overview of prairie insects and describe some of their habits and adaptations. The term “prairie” is the most frequently used to describe grasslands in Canada, whereas the term “steppe” is commonly used for similar habitats in eastern Europe and Grasslands and Grassland Arthropods of Canada 3 western Asia. The prairies of Canada and the adjoining United States support rich and highly specialized communities of plants and animals in their native state that evolved in response to a variety of stresses, including drought, grazing, fire, erosion, deposition, soil disturbance, and decomposition (Anderson 2006). Classification of Canada’s Grassland Ecosystems Ecologists have traditionally divided grasslands in North America into three sectors based on the height of the native grasses, which is a function of annual precipitation. According to Anderson (2006), these sectors are western shortgrass prairie (260–375 mm precipitation), eastern tallgrass prairie (625–1,200 mm precipitation), and mid- or mixedgrass prairie (375–625 between the two). Shortgrass prairie is dominated by grasses that are 0.3–0.5 m tall, mixedgrass prairie is dominated by species that are 0.8–1.2 m tall, and tallgrass prairie is dominated by grasses that are 1.8–2.4 m tall. However, in the 1970s and 1980s, the Canada Committee on Ecological Land Classification established a different system to classify and map terrestrial ecosystems. This system delineated and described ecologically distinct areas of the country’s surface at different levels of generalization by various abiotic

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