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A Checklist of Manitoba Spiders (Araneae)

with notes on geographic relationships

Discussion: Distribution Patterns of Manitoba Spiders

Many species in the province that were previously known from only one or a few scattered localities are now seen to have definable patterns of distribution. For example, some 30 species of eastern Canada and the northeastern United States apparently find their western limits within the borders of Manitoba, e.g., Cybaeopsis tibialis, Centromerus denticulatus, Eperigone tridentata, Islandiana longisetosa, Scotinotylus exsectoides, Walckenaeria pallida, Pirata montanus, Geolycosa wrightii, Ozyptila curvata, Clubiona obesa, Sergiolus decoratus, Habrocestum pulex and Phidippus whitmanii. Similarly species of western Canada find their eastern limits in Manitoba, e.g., Titanoeca nigrella, Lathys alberta, Sciastes hastatus, Pardosa ontariensis, Ebo bucklei, Xysticus acquiescens, Neon ellamae, Sitticus fasciger, and Habronattus altanus. Many of these are characteristically found in the boreal forest. Those species with more southerly ranges may have expanded northward into Manitoba at about 6000 B.P., when the prairie extended to approximately 54°N and mixed woods to approximately 55°N (Lehmkuhl. 1980; Shay, 1984). A number of arctic or subarctic species extend southward into the tundra zone bordering Hudson Bay, e.g., Alopecosa hirtipes and Pardosa podhorskii. Hence Manitoba is seen as an area of major overlap for North American spiders, this overlap reflecting the province's central location and broad range of biotic communities.

One hundred forty-one (29%) of the species of Manitoba spiders are indicated as holarctic. Four of these, namely, Argiope trifasciata, Achaearanea tepidariorum, Tegenaria domestica, and Salticus scenicus, are cosmopolitan in range; the last three are associated with buildings and are generally regarded as introductions from Europe. Other introduced species, but with more limited occurrence in Manitoba, are Steatoda castanea and Lepthyphantes nebulosus. The remaining holarctic species are believed to have occupied Manitoba since the retreat of the Pleistocene glaciers, e.g., Neriene clathrata, Pityohyphantes phrygianus, Baryphyma kulczynskii, Maso sundevalli, Araneus marmoreus, Tetragnatha extensa, Arctosa alpigena, Pardosa hyperborea, Misumena vatia, Philodromus cespitum, and Sitticus finschii.

For many spider species, the major habitat is still unknown, but for those species for which it is known, 10 are mainly arctic or subarctic, 84 are mainly boreal, 58 are mainly boreoalpine, and 28 mainly grassland. Having about two-thirds of its land surface covered by boreal forest, Manitoba is occupied mainly by spiders characteristic of that biome. Peatland litter is the main habitat for many of the Linyphiidae, Erigonidae, Amaurobiidae, Hahniidae, Gnaphosidae, Clubionidae, Lycosidae, and Thomisidae. Coniferous tree foliage is the primary habitat for such species as Hyptiotes gertschi, Theridion glaucescens, Pityohyphantes costatus, Grammonota angusta, and Xysticus punctatus. Tall grass and shrubs are primary habitats for such spiders as Tibellus oblongus and Sitticus palustris, and tree bark is the main habitat for the species of Coriarachne.

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