75 Chapter 4 Spiders (Arachnida: Araneae) of the Canadian Prairies Héctor Cárcamo Lethbridge Research Centre, Agriculture and Agri-Food Canada, Lethbridge, AB Jaime Pinzón Department of Renewable Resources, Faculty of Agricultural, Life and Environmental Sciences, University of Alberta, Edmonton Robin Leech 10534, 139 St NW, Edmonton AB John Spence Department of Renewable Resources, Faculty of Agricultural, Life and Environmental Sciences, University of Alberta, Edmonton Abstract. Spiders are the seventh most diverse order of arthropods globally and are prominent predators in all prairie habitats. In this chapter, a checklist for the spiders of the Prairie Provinces (767 recorded species and 44 possible species) is presented along with an overview of all 26 families that occur in the region. Eighteen of the species from the region are adventive. Linyphiidae is by far the dominant family, representing 39% of all species in the three provinces. Gnaphosidae and Lycosidae each represent 8% and three other families (Salticidae, Dictynidae, and Theridiidae) each account for 7%. A summary of biodiversity studies conducted in the Prairies Ecozone and from transition ecoregions is also provided. The Mixed Grassland Ecoregion has the most distinctive assemblage; Schizocosa mccooki and Zelotes lasalanus are common only in this ecoregion. Other ecoregions appear to harbour less distinctive assemblages, but most have been poorly studied. Lack of professional opportunities for spider systematists in Canada remains a major barrier to the advancement of the taxonomy and ecology of spiders. Résumé. Les aranéides forment le septième ordre le plus diversifi é d’arthropodes dans le monde; ce sont des prédateurs très présents dans tous les habitats des Prairies. Ce chapitre présente une liste des espèces d’araignées des provinces des Prairies (767 espèces connues et 44 prévues) ainsi qu’une vue d’ensemble des 26 familles présentes dans la région. Dix-huit des espèces de la région sont adventices. La famille des linyphiidés domine de très loin, représentant 39 % de toutes les espèces présentes dans les trois provinces. Deux autres familles (gnaphosidés et lycosidés) représentent chacune 8 % des espèces, et trois autres (salticidés, dictynidés et théridiidés) représentent chacune 7 % des espèces. Le chapitre présente également un résumé des études portant sur la biodiversité réalisées dans l’écozone des prairies et dans les écorégions de transition. L’écorégion de la prairie mixte présente l’assemblage le plus distinctif; Schizocosa mccooki et Zelotes lasalanus ne sont communs que dans cette écorégion. D’autres écorégions semblent abriter des assemblages moins distinctifs, mais la plupart restent mal connues. La pénurie de débouchés professionnels pour les systématiciens qui s’intéressent aux araignées au Canada continue de faire obstacle aux progrès de la taxonomie et de l’écologie de cette classe d’arthropodes. Introduction Spiders are among the most ubiquitous predatory invertebrates in terrestrial ecosystems and have been able to colonize nearly all habitats on Earth, except for Antarctica (Turnbull 1973; Foelix 2011), including freshwater (Seymour and Hetz 2011), semi-aquatic (Graham Cárcamo H., J. Pinzón, R. Leech, and J. Spence. 2014. Spiders (Arachnida: Araneae) of the Canadian Prairies. In Arthropods of Canadian Grasslands (Volume 3): Biodiversity and Systematics Part 1. Edited by H. A. Cárcamo and D. J. Giberson. Biological Survey of Canada. pp. 75-137. © 2014 Biological Survey of Canada. ISBN 978-0-9689321-6-2 doi: http://dx.doi.org/10.3752/9780968932162.ch4 Species checklist available at http://dx.doi.org/10.5886/qwco8c3a 76 H. Cárcamo, J. Pinzón, R. Leech, and J. Spence et al. 2003), and marine intertidal (Roth 1967) habitats. In temperate terrestrial zones, spiders are among the most diverse and abundant groups of ground-dwelling predators (Gertsch 1979). Spiders are mainly generalist predators (Wise 1995) of invertebrates and, occasionally, of vertebrates (McCormick and Polis 1982), although a few species may also feed on pollen (Smith and Mommsen 1984; Ludy and Lang 2006). Spiders play an important functional role in ecosystems, affecting plant productivity through predation on herbivorous insects (Snyder and Wise 1999) and infl uencing litter decomposition by feeding on detritivores (Clarke and Grant 1968). In addition, spiders are important in the diet of various invertebrates and vertebrates (Wise 1995). Spiders are often useful as bioindicators in environmental studies because of their diversity, abundance, and ease of capture, as well as our ability to assign families effectively into functional guilds (e.g., Cárcamo 1997; Pinzón 2011). Despite the importance of spiders, their ecology remains poorly studied in the Prairies Ecozone. Many species, particularly in the Linyphiidae and Theridiidae, are undescribed, and we lack well-developed diagnostic keys for these and other families. Here we provide a short overview of spider phylogeny and taxonomic status in Canada, followed by a checklist of the spiders in the Prairie Provinces, a review of faunistic studies from the Prairies Ecozone and adjacent transition ecoregions, and an outline of areas for future research. Phylogenetic Placement The order Araneae belongs to the class Arachnida, which includes a number of groups of eight-legged arthropods. Among other groups that are more common in warmer climates, common orders include Acari (mites and ticks), the most diverse of the class, and the scorpions (order Scorpiones), pseudoscorpions (order Pseudoscorpiones), and harvestmen or daddy-long-legs (order Opiliones). The tail-less whip scorpions (order Amblypygi), the whip scorpions (order Thelyphonida), and the short-tailed whip scorpions (order Schizomida) are the closest relatives to spiders (Shultz 1990; Coddington and Levi 1991; Shultz 2007; Penney and Selden 2011; Fig. 1). Two monophyletic suborders are recognized within the order Araneae: Mesothelae and Opisthothelae (Fig. 2) (Platnick and Gertsch 1976; Penney and Selden 2011). These two suborders have existed since at least the Carboniferous period (ca. 350 million years before present (mbp)) (Shultz 1990, 2007). The Mesothelae is considered the most primitive and basal lineage and is represented mostly from Paleozoic fossils (>250 mbp) (Penney and Selden 2006; Selden and Penney 2010). It contains a single extant family, the Liphistiidae (three genera, 90 species), distributed only in China, Japan, Southeast Asia, and Sumatra (Platnick and Sedgwick 1984). The Opisthothelae is subdivided into the infraorders Mygalomorphae and Araneomorphae. The members of these two infraorders radiated at least during the Triassic (200–250 mbp). The Mygalomorphae (16 families, 328 genera, 2,775 species) includes the tarantulas and several other groups of primitive spiders, while the Araneomorphae (regarded as “true” spiders) is the most diversifi ed and evolved lineage, with 95 families, 3,574 genera, and 41,167 species described to date (Platnick 2013; Platnick and Raven 2013). These two infraorders are distributed in all continents except for Antarctica. Spiders are among the most diverse arthropod orders, ranking seventh after Coleoptera, Diptera, Hymenoptera, Lepidoptera, Hemiptera, and Acari in numbers of described species (Coddington and Levi 1991). Worldwide estimates of spider richness range from 76,000 (Platnick 1999) to 170,000 (Coddington and Levi 1991), although only 44,032 species have been described (Platnick 2013). Thus, only about 35% of the world’s species have Spiders (Arachnida: Araneae) of the Canadian Prairies 77 been described on the basis of a conservative estimate of diversity from the average of the two extremes (Agnarsson et al. 2013). Currently, mygalomorphs are represented in Canada by only four families and six species; fi ve are reported only from British Columbia and one from Ontario (Paquin et al. 2010). The remaining 1,407 species and 39 families are included Fig. 1. Phylogeny of the class Arachnida with spiders and their closer relatives shown in bold (modifi ed from Dunlop and Penney 2012). Fig. 2. Higher phylogeny of the order Araneae (modifi ed from Dunlop and Penney 2012). 78 H. Cárcamo, J. Pinzón, R. Leech, and J. Spence within the Araneomorphae and are widely distributed in the Nearctic region (Paquin et al. 2010), with many having Holarctic distributions. The Canadian fauna includes only about 3% of the world’s species. Signifi cant progress has been made recently in understanding the evolution and phylogeny of spiders (Selden and Penney 2010; Penney and Selden 2011). Although the fossil record for spiders is not as extensive as that for insects, almost 1,200 valid species are known from fossils (Dunlop et al. 2013). Currently, 70 extant spider families are represented in the fossil record (Penney et al. 2012; Dunlop et al. 2013) and 27 families are recognized strictly from fossils (Penney and Selden 2006, 2011). The earliest known true spider fossil belongs to Palaeothele montceauensis Selden, 1996, from the late Carboniferous (295 mbp) (Selden 1996a, 1996b). This species is closely related to species in the Liphistiidae (Mesothelae), a family that is considered a living fossil. Ancestors to the spiders and their relatives were some of the fi rst animals colonizing terrestrial habitats over 400 million years ago. The fi rst spiders likely played an important role as predators. Penney (2004) has suggested that there is a relationship between the evolutionary radiations of spiders and their insect prey.