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J. ENTOMOL. SOC. BRIT. COLUMBIA 103, DECEMBER 2006 61 A survey of the spiders (Arachnida, Araneae) of Chichagof Island, Alaska, USA JOZEF SLOWIK1 ABSTRACT A spider survey was conducted over the summer of 2003 on Chichagof Island, Alaska, USA. Based on this, as well as on data from a preliminary survey in 2002, and two sub- sequent visits, a preliminary list of 95 spider species is presented for the island. This survey resulted in 10 new species records for Alaska and 8 species not known to occur in British Columbia. The data were tested for completeness using Chao 1, Chao 2, bootstrap, and Michaelis-Menten species richness equations. The number of species observed fell within the variance for both Chao indicators but was below the other two estimators indicating that more species may still be found. Twenty-two micro and three macro habitats were defined in the survey. All data were submitted to the Nearctic Spi- der Database and cataloged on the Denver Museum of Nature & Science’s website. Key Words: Southeast Alaska, species richness estimators, species list, species diversity INTRODUCTION Spiders are a diverse but poorly under- ders may play roles in the control of de- stood animal group in the Pacific North- structive insects (Jennings & Pase 1986; west of North America (Bennett 2001). Maloney et al. 2003). Little spider research has been completed Southeast Alaska provides important in southeast Alaska (Mann & Gara 1980). resources for three major industries: log- Species lists are available for British Co- ging, fishing, and tourism. Biodiversity lumbia (Thorn 1967; West et al. 1984, surveys provide important baseline infor- 1988; Bennett et al. 2006) and Yukon Ter- mation to help land resource managers ritory (Dondale et al. 1997) but there are understand and monitor environments util- none for the southeast Alaskan archipel- ized by these industries. Spiders may pro- ago. vide a useful survey option because of the Spider surveys may provide an effec- relative ease with which they can be col- tive means for measuring the impact of lected, preserved, and identified. habitat degradation or land use change on The objective of this study was to docu- biodiversity. Baseline studies involving ment the spider fauna of northern spiders as biological indicators have been Chichagof Island, Alaska in a manner that conducted elsewhere; e.g. Allred (1969) can be replicated on other islands in the and Allred & Gertsch (1976) documented southeast Alaskan archipelago in an at- spider diversity in Arizona and Utah after tempt to assemble a comprehensive spider new power plant installations and in Ne- fauna list for the area. The preliminary vada at the Nevada Nuclear Test Site. The spider species list and other information need for spider species lists for use in con- provided here are meant to be resources for servation decision making has also been future surveys in the area and relevant bio- expressed (Skerl 1999). In addition, spi- geographic and taxonomic studies. 1 Department of Zoology, Denver Museum of Nature and Science, 2001 Colorado Blvd., Denver CO 80205, (303) 370-6354, [email protected] 62 J. ENTOMOL. SOC. BRIT. COLUMBIA 103, DECEMBER 2006 MATERIALS AND METHODS Study Site. The study site is located at canopy. 58.10° N 135.42° W in southeast Alaska There are no protected areas within the on the northeast corner of Chichagof Is- study site and substantial clear-cut logging land, approximately 100 km west of Jun- on blocks ranging from 0.08 to 40.00 ha eau (Fig. 1). The study area is located occurred on the island from the early within the Tongass National Forest, 1980’s until 2004. During the survey pe- Sealaska Corporation land, Huna Totem riod, the resulting second growth areas Corporation land and Alaska State lands. were relatively young and differed little in The study site consisted of an area of structure from the naturally occurring roughly 86,765 ha located around the town shrubby skree areas. of Hoonah, Alaska (Fig. 1), and is charac- Data Collection. All specimens were terized as northern temperate rainforest collected by the author during the period dominated by western hemlock (Tsuga 22 April to 24 August 2003 using one of hetrophylla (Raf.) Sarg.). The area around six methods: beat sheeting, sweep netting, Hoonah and northward to Gustavus is in a sifting moss, head-lamping, pitfall trapping slight rain shadow for southeast Alaska and casual collection. Because of the den- with an average annual rainfall of 130 cm sity and thickness of the forests and clear- (versus Juneau at 250 cm). The area is cut areas an alternative method of sweep- dominated by steep, abruptly ascending ing/beating was used in those areas. This mountains and narrow valleys left by re- method consisted of grabbing either cent glacial activity with elevations from branches or the top of a tree and stuffing it sea level to over 1,180 m. into the sweep net, then beating the branch In 2002 a preliminary survey was con- or treetop in the net. This method was also ducted and three general macro-habitats used in shrubby areas where the vegetation and 22 micro-habitats were defined (Table was too dense to sweep or beat. The head- 1). The micro-habitats were used for com- lamping method consisted of using a head- paring similar sites in the study area and lamp or other light source and looking both for expanding search areas if few or only up and down for eye shine and webs after immature spiders were found at a given dark. Specimens were deposited directly site. Each of the 22 micro-habitats is in- into 75% ethanol for preservation. Each cluded in one of the three macro-habitats: collection occurrence consisted of one shrubby skree or logged areas, open mus- method and was conducted for one half keg meadows, and densely treed old hour, although multiple collection occur- growth forests. The shrubby areas are rences may have occurred in a day or at a dominated by several species of Vaccinium site. L. and Rubus L. and devil’s club Pitfall traps were sets of 230 ml plastic (Oplopanax horridum (Smith)) growing to cups placed in the ground with the lip of over 2 m in height. The muskeg areas con- each cup level with the ground surface. sist of low shrubs under 0.5 m tall (Kalmia Each set consisted of 10 cups placed 1 m microphylla (Hook.) Heller) and Andro- apart in a line. The traps were filled with meda polifolia L.) and grasses, with pools 30-60 ml of propylene glycol as a pre- or slow moving streams. The old growth servative. Traps were covered only if rain areas consist mainly of hemlocks (Tsuga was imminent. Pitfall trap specimens were hetrophylla and T. mertensiana (Bong.) collected every two days to one week Carr.) with some Sitka spruce (Picea (dependant upon rainfall) then sorted, sitchensis (Bong.) Carr.) and yellow cedar washed and stored in 75% alcohol. (Chamaecyparis nootkatensis (D. Don) Because of the difficulty of identifying Spach) intermixed and usually have few juvenile spiders only adults were identified shrubs in the understory and a closed and used for the analyses. Linyphiidae J. ENTOMOL. SOC. BRIT. COLUMBIA 103, DECEMBER 2006 63 Figure 1. Spider collections sites on Chichagof Island, Alaska, USA, 2002-2005. Each point may represent more than one habitat or collection occurrence. were identified by D. J. Buckle Three of the richness equations, Chao (Saskatoon, Saskatchewan), Philodromidae 1, Chao 2, and bootstrapping require col- and Thomisidae were identified by F. X. lection occurrence data, which is defined Haas (Denver, Colorado). All other spiders as each separate occurrence in which spi- were identified by the author using Roth ders were collected. For the sampling ef- (1993) or Ubick et al. (2005) and included fort aspect of the Michaelis-Menten equa- references. Voucher specimens were de- tion each collection occurrence (other than posited at the Denver Museum of Nature & casual and pitfall trapping) consisted of Science. Nomenclature follows Platnick one-half hour (as described above). Be- (2006). See discussions in Crawford cause the movements of spiders are not (1988), Buckle et al. (2001) and Ubick et well understood, statistical analysis of each al. (2005) regarding linyphiid nomencla- pitfall trap occurrence was arbitrarily at- ture. tributed one hour of sampling effort fol- Statistical analysis. Species richness lowing Coddington et al. (1996) (although was estimated using Chao 1 (Chao 1984), Coddington used leaf litter samples and a Chao 2 (Chao 1984, 1987), bootstrap Tullgren-funnel). Specimens collected with (Smith & van Belle 1984), and Michaelis- methods other than those described above Menten (Raaijmakers 1987) estimators were considered to be casual occurrences following Coddington et al. (1996). The and were each attributed five minutes of Chao 1 estimator is a non-parametric equa- time. tion using relative abundance data; the Specimen data were submitted to the Chao 2 estimator is also non-parametric Nearctic Spider Database (http:// but uses presence-absence data. The boot- canadianarachnology.webhop.net) and strap estimator uses incidence data and the catalogued on the Denver Museum of Na- Michaelis-Menten model contrasts sam- ture & Science website (www.dmns.org/ pling effort data and number of species spiders/default.aspx). observed. See Magurran (2004) for discus- Habitat and collection method were sion of the various usage and accuracy used to determine general species habitat issues associated with these estimators. associations: arboreal, ground-dwelling, or Species accumulation curves were plotted other. These determinations are speculative using EstimateS (Version 7.5, Colwell but may be helpful in locating species in 2005). similar environments. 64 J. ENTOMOL. SOC. BRIT. COLUMBIA 103, DECEMBER 2006 Table 1. Habitats sampled for spiders on Chichagof Island, Alaska, 2002-2005.

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