Michael L. Draney

Epigeal Spider (Araneae) Communities in Moist Acidic and Dry Heath Tundra at Toolik Lake, Alaska

Abstract For the 2004–2006 growing seasons, we trapped a total of 6980 spiders (5066 adults, 1914 immatures) using pitfall traps at the Arctic Long Term Experimental Research (LTER) site in Toolik Lake, Alaska. We found 10 families and 51 putative species, with 45 completely identified, in two distinct habitats: Moist Acidic Tundra (MAT) and Dry Heath (DH) Tundra. We captured spiders belonging to the following families (number of species captured): Araneidae (1), Clubionidae (1), Dictynidae (1), Gnaphosidae (4), Linyphiidae (26), Lycosidae (11), Philodromidae (2), Salticidae (1), Theridiidae (1), and Thomisidae (3). Statistical comparisons of families captured at MAT and DH Tundra indicate that the habitats have significantly different spider communities (Chi Square Test: p < 0.0001, and Fishers Exact Test: p  =  0.0018). This finding is further supported by differences in similarity, diversity, evenness, and species richness between the two habitats. In this report, we present eight new state records and five extensions of previously described ranges for spider species. The following species are new state records for Alaska: Emblyna borealis (O.P.-Cambridge 1877), Horcotes strandi (Sytschevskaja 1935), Mecynargus monticola (Holm 1943), Mecynargus tungusicus (Eskov 1981), Metopobactrus prominulus (O.P. -Cambridge 1872), Poeciloneta theridiformis Emerton 1911, and Poeciloneta vakkhanka (Tanasevitch 1989). The following five species have been reported previously in Alaska, but not near Toolik Lake: Hypsosinga groenlandica Simon 1889, Gnaphosa borea Kulczynski 1908, Gnaphosa microps Holm 1939, Haplodrassus hiemalis (Emerton 1909), and Islandiana cristata Eskov 1987. Pairwise similarity indices were calculated across 13 other arctic and subarctic spider communities and statistical tests show that all sites are dissimilar (p  =  0.25). These results fit the general pattern of both the patchiness and habitat specificity of arctic spider fauna.

Spider Fauna of Semiarid Eastern Colorado Agroecosystems: Diversity, Abundance, and Effects of Crop Intensification

ABSTRACT Spiders are critical predators in agroecosystems. Crop management practices can influence predator density and diversity, which, in turn, can influence pest management strategies. Crop intensification is a sustainable agricultural technique that can enhance crop production although optimizing soil moisture. To date, there is no information on how crop intensification affects natural enemy populations, particularly spiders. This study had two objectives: to characterize the abundance and diversity of spiders in eastern Colorado agroecosystems, and to test the hypothesis that spider diversity and density would be higher in wheat (Triticum aestivum L.) in crop-intensified rotations compared with wheat in conventional rotations. We collected spiders through pitfall, vacuum, and lookdown sampling from 2002 to 2007 to test these objectives. Over 11,000 spiders in 19 families from 119 species were captured from all sampling techniques. Interestingly, the hunting spider guild represented 89% of the spider fauna captured from all sites with the families Gnaphosidae and Lycosidae representing 75% of these spiders. Compared with European agroecosystems, these agroecosystems had greater diversity, which can be beneficial for the biological control of pests. Overall, spider densities were low in these semiarid cropping systems, and crop intensification effects on spider densities were not evident at this scale.

Ceraticelus vesperus Chamberlin & Ivie, 1939 is a Synonym of C. fissiceps (O. Pickard-Cambridge, 1874) (Araneae: Linyphiidae)

Summary Examined specimens of Ceraticelus fissiceps (O. Pickard-Cambridge, 1874) and C. vesperus Chamberlin & Ivie, 1939 were indistinguishable in diagnostic characters, apart from some variation in clypeal slope. Statistical analysis shows no geographic cline between putative species, but rather greater variability of this character in the western spiders. There was also variation among specimens within each putative species in degree of development of the tooth of the apophysis of the male palpal tibia. Ceraticelus vesperus is therefore synonymized with C. fissiceps, Ceraticelus fissiceps is redescribed, and a lectotype is designated. The role of online tools that allow curators to identify and compare their holdings is noted.