Diversity of forest upland arachnid communities in Manitoba taiga (Araneae, Opiliones)

The diversity of taiga upland arachnid communities, collected mainly in pit fall or pan traps, is compared among forested habitats in two Manitoba regi ons, one southern and one northern. In the south, where collections were ta ken both in summer and in winter under the snow cover. the dominant spider families were Erigonidae, Linyphiidae, Lycosidae, and Gnaphosidae. The diur nal and nocturnal pursuit guilds dominated across habitats. In the north, w ith summer collecting only, dominant families were Lycosidae, Gnaphosidae a nd Erigonidae of the diurnal pursuit guild. The southern taiga uplands had YS, species of spiders, northern uplands 49 species with 19 species common to both regions. The five most dominant species from these families are Agr oeca ornata Banks. Gnaphosa microps Helm. Pardosa xerampelina (Keyserling), P. mackenziana (Keyserling), and Agelenopsis utahana (Chamberlin and Ivie) . Three opilionid species occur in the south and one species, Odiellus pict us Wood. occurs in both regions. In this region of the taiga, we found the most species-rich habitats to be undisturbed forest types, i.e., alder-tama rack ecotone in winter, which produced 34 winter-active species (n=233), wi th 27 species collected only during winter months. Among-habitat difference s in species richness, species dominance and guild composition suggests tha t maintenance of habitat heterogeneity is needed at all scales to preserve the diversity of forest floor arachnid communities in managed taiga forests .