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Litter-dwelling Ground Beetles (Coleoptera: Carabidae) and Ground Spiders (Araneae: Gnaphosidae) of the Ozark Highlands, USA
Fredericka B. Hamilton, Robert N. Wiedenmann, Michael J. Skvarla, Raghu Sathyamurthy, Danielle M. Fisher, Jon Ray Fisher, and Ashley P.G. Dowling

Southeastern Naturalist, Volume 17, Issue 1 (2018): 54–73

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Southeastern Naturalist 55 F.B. Hamilton, et al. 22001188 SOUTHEASTERN NATURALIST Vo1l7.( 117):,5 N5–o7. 31 Litter-dwelling Ground Beetles (Coleoptera: Carabidae) and Ground Spiders (Araneae: Gnaphosidae) of the Ozark Highlands, USA Fredericka B. Hamilton1,*, Robert N. Wiedenmann1, Michael J. Skvarla1, Raghu Sathyamurthy2, Danielle M. Fisher1, Jon Ray Fisher1, and Ashley P.G. Dowling1 Abstract - Each year, temperate deciduous forests produce a layer of litter comprised primarily of leaves. Two common and diverse taxa found in the litter layer are ground beetles (Coleoptera: Carabidae) and ground spiders (Araneae: Gnaphosidae). We collected and identified these groups on a monthly basis from April 2014 to March 2015 at 4 sites in Northwest Arkansas to determine their abundance and diversity across the following 3 variables: season, litter depth, and site location. A total of 480 litter samples and 208 pitfall-trap samples were collected and processed. These samples resulted in 645 carabids representing 47 species and 421 gnaphosids representing 15 species. Statistical analyses detected significant differences in species richness, average number of individuals, and species diversity of gnaphosids among sites. In contrast, leaf-litter depth had no significant effect on the number of individuals collected, species richness (except at one site), or species diversity of carabids and gnaphosids. Both carabids and gnaphosids were most abundant and diverse during the spring. Introduction The Interior Highlands is a mountainous region primarily comprising the Ozark Mountains of northern Arkansas and southern Missouri, and the Ouachita Mountains of southern Arkansas and eastern Oklahoma. Due to the unique geologic and geographic history of the region, the Interior Highlands are home to many endemic species and considered a biodiversity hotspot (Costa et al. 2008; Frazer et al. 1991; Mayden 1985, 1988; Skvarla et al. 2015). This region is dominated by Quercus (oak)–Carya (hickory) forests, which drop leaves annually and accumulate a thick litter layer each year. The litter layer is dynamic, with periodic additions of leaves resting on top of organic material in various stages of decay. The litter layer constitutes an important habitat for a variety of animal species and provides resources such as food, shelter from adverse environmental conditions, and protection from predators. Arthropods are a dominant and diverse group that inhabits the leaf-litter layer of temperate deciduous forests. Several factors influence the arthropod litter community, including plant species (Elfaki et al. 2013), litter depth (Bultman and Uetz 1982, 1984; Koivula et al. 1999; Uetz 1979), and the physical structure of the layer 1Department of Entomology, University of Arkansas, Fayetteville, AR 72701. 2CSIRO Health and Biosecurity, and USDA-ARS Australian Biological Control Laboratory, PO Box 2583, Brisbane, Queensland, Australia 4001. *Corresponding author - Manuscript Editor: Robert Jetton Southeastern Naturalist F.B. Hamilton, et al. 2018 Vol. 17, No. 1 56 (Bultman and Uetz 1982). Two abundant and diverse taxa found in leaf litter are ground beetles (Coleoptera: Carabidae) and ground spiders (Araneae: Gnaphosidae), which are the focus of the present study. Carabidae comprise ~40,000 described species (Lovei and Sunderland 1996). They have worldwide distribution and can be found in nearly every terrestrial habitat (Erwin 1985) and include an array of feeding guilds including predators, herbivores, granivores, and omnivores (Lovei and Sunderland 1996, Luff 1987, Thiele 1977). In temperate regions, photoperiod and temperature are 2 main factors that contribute to carabid seasonality (Thiele 1977). Their activity is generally highest during the spring and fall for reproduction and lowest during the winter (diapause) and summer (aestivation) (Lovei and Sunderland 1996, Makarov 1994). Ground beetles are sensitive to environmental changes and are often used as bioindicators of habitat conditions (Fuller et al. 2008, Pearce and Venier 2006, Willand and McCravy 2006). Litter extraction and pitfall traps are common collection methods used to capture carabids (Carlton and Robison 1998, Lovei and Sunderland 1996). Gnaphosidae comprise 2134 described species in 118 genera (Platnick 2013). They have a worldwide distribution with ~250 species in North America (Bennett et al. 2006, Guarisco and Kinman 1990, Ubick et al. 2005). Gnaphosids are active, wandering predators that capture prey while moving through litter (Guarisco and Kinman 1990). Uetz (1975) found gnaphosid species richness to increase in midsummer and decrease in autumn, which he correlated with prey abundance rather than weather because annual fluctuations in prey abundance could act as a regulating factor. Sampling gnaphosids is usually done via litter extraction and pitfall trapping (Bultman and Uetz 1982; Dorris et al. 1995; Uetz 1975, 1977). Uetz and Unzicker (1976) found that pitfall trapping was superior to litter extraction for estimating the densities of gnaphosids and other wandering spiders. Terrestrial arthropods have been the focus of extensive survey and study of other diverse areas, such as the Great Smoky Mountains (Carlton and Bayless 2007). Despite the high biodiversity of the Interior Highlands, however, deciduous leaf-litter communities of the area have received little attention (though see Carlton and Robison [1998] and Dorris et al. [1995]). During this study, we examined the diversity, presence, and seasonality of ground beetles and ground spiders collected during a year-long survey of 4 sites in the Ozark Mountains. We selected these taxa as the focus of this study because (1) the University of Arkansas Arthropod Museum (UAAM) has voucher specimens of carabids identified to species level that we could refer to when identifying the beetles, and (2) gnaphosids can be readily identified to species level by non-specialists with user-friendly keys (Ubick et al. 2005). Field-Site Description Four sites in Northwest Arkansas at 3 locations in Washington and Madison counties were selected for this study, which was conducted from April 2014 until March 2015. We chose these sites on the basis that they were primarily oak–hickory forests and were also easily accessible during a 12-month study in Southeastern Naturalist 57 F.B. Hamilton, et al. 2018 Vol. 17, No. 1 various weather conditions. Sites were located at Lake Wilson (Fayetteville city park, 109 ha; 35°59'53.39"N, 94°8'13.52"W; elevation 410 m), Lake Wedington (Ozark National Forest, 485,600 ha; 36°6'8.03"N, 94°23'29.94"W; elevation 416 m), and 2 different sites at Withrow Springs State Park (Withrow 1 and Withrow 2; total park area = 318 ha; 36°9'52.31"N, 93°43'21.31"W and 36°9'57.33"N, 93°43'26.57"W, respectively; elevations 421 m and 441 m, respectively). The distances between the collection sites are as follows: Lake Wilson to Lake Wedington = 40.4 km (21.5 mi), Lake Wilson to Withrow 1 = 57.1 km (35.5 mi), Lake Wilson to Withrow 2 = 57.5 km (35.7 mi), Lake Wedington to Withrow 1 = 74.4 km (46.2 mi), Lake Wedington to Withrow 2 = 74.7 km (46.4 mi), and Withrow 1 to Withrow 2 = 0.3 km (0.2 mi). The dominant canopy species at Lake Wedington are Quercus velutina Lam (Black Oak), Q. stellata Wangenh (Post Oak), Q. alba L. (White Oak), Ulmus spp. (elms), and Carya tomentosa (Lam. ex. Poir.) Nutt. (Mockernut Hickory), with the understory being composed of the same tree species and Prunus serotina Ehrh. (Black Cherry). At Lake Wilson, the dominant canopy tree species are Mockernut Hickory, Q. rubra L. (Northern Red Oak), Post Oak, and White Oak, with the understory trees being mainly composed of Black Cherry, Cornus spp. (dogwoods), Fraxinus pennsylvanica Marsh. (Green Ash), Mockernut Hickory, Morus spp. (mulberries), and White Oak. The main canopy trees at Withrow Springs consist of Platanus occidentalis L. (American Sycamore), Carya spp. (hickories), Northern Red Oak, Q. falcata Michx. (Southern Red Oak), and White Oak, with the understory trees being primarily dogwoods, Acer rubrum L. (Red Maple), and Sassafras albidum (Nutt.) Nees (Sassafras). Withrow 1 is gently sloping with understory, and Withrow 2 is edged by a ravine and with little understory. Each of the 4 collection sites had been recently disturbed. The Withrow Springs sites were logged in the 1940s, and a water line was routed through to a nearby camping area in 2004. At Wedington, disturbance was experienced when the area directly across from the collection site was logged in 2014. Lake Wilson, Lake Wedington, and Withrow Springs are frequently used as recreational areas and experience disturbance from human foot traffic throughout the year . Methods Litter collection and Berlese extraction We collected litter on a north-facing slope at each of the 4 locations once per month from April 2014 until March 2015 along 100-m transects from the same starting points at each site. The direction of the transect away from the starting points was decided randomly by rolling a 6-sided die, with each number on the die corresponding to a 30° angle measured from perpendicular to the right (i.e., 1 = 30°, 2 = 60°, 3 = 90°; 90° corresponded to straight ahead). We took 10 samples ~10 m apart. At each 10-m mark, we placed a 1-m2 frame on the ground in a randomly generated spot that was determined by throwing a flag up into the air and placing the frame where it fell. We measured leaf-litter depth with Southeastern Naturalist F.B. Hamilton, et al. 2018 Vol. 17, No. 1 58 a ruler for each sample by taking 4 measurements within the frame and then averaging those measurements. All leaf litter was removed from within the frame and processed in the field using a litter reducer (Paradox Company, Cracow, Poland), which had a metal screen with 10 mm x 10 mm openings that allowed arthropods, small leaf fragments, and soil to fall into a 3.7-l storage bag. Each litter sample was stored in a separate bag. We processed leaf-litter samples individually in Berlese- Tullgren funnels for 3 to 5 days until the litter was thoroughly dry and collected all arthropods from the litter in plastic cups that contained 70% ethanol. Samples were strained through a 63-μm sieve in order to remove the arthropods from the alcohol and soil and stored in 59.15-ml Whirl-Pak® (Nasco, Fort Atkinson,WI) bags in 70% ethanol until later processing. Pitfall-trap sampling We were successful in making pitfall-trap collections at only Lake Wilson and Lake Wedington due to continued animal disturbance of pitfall traps at Withrow Springs. At both sites, ten 0.95-l, round, plastic containers with a top diameter of 11.4 cm and a depth of 14 cm were placed on the same north-facing slopes where leaf litter was collected. We arranged the pitfall traps at Lake Wilson in a transect with the starting point adjacent to the litter-sample starting point, and those at the Lake Wedington site in a transect that was located ~200 m upslope from the starting point of the leaf-litter transect. We spaced the pitfall traps ~5–10 m apart at each site. We covered each container with a plastic lid and cut out 3 openings (8 cm wide x 2 cm tall, approximately equidistantly spaced around the perimeter of the container) on the sides of the containers. Containers were placed in the soil deep enough so the openings were level with the ground surface to allow arthropods to fall in. We added a 50:50 mixture of propylene glycol and water to each trap to a depth of 9 cm below the openings, and processed samples in the field by pouring the liquid through a 63-μm sieve. We stored strained specimens in 59.15-ml Whirl-Pak® bags that contained 70% ethanol and discarded used pitfall preservative after straining. We serviced the pitfall traps every 2 weeks (14 ± 2 days). There was one exception: the pitfall traps placed in mid-February 2015 were not collected until mid-March, due to inclement weather; thus, those traps were in place for nearly 1 month. We included in the analysis pitfall samples collected on the same dates as the leaf-litter samples, but not samples from off dates because those traps were set a month prior to leaf-litter collection. Identification We sorted all carabid and gnaphosid specimens from bulk samples and preserved the bycatch from each sample in individual glass jars that contained 70% ethanol. For identification, carabids were individually pinned, whereas gnaphosids were stored in ethanol. We identified carabids to genus using Arnett and Thomas (2001) and then to species using keys in Freitag (1969) and Ciegler and Morse (2000). We identified gnaphosids to genus level using Ubick et al. (2005) and then to species level using a series of keys for each genus (Platnick 1975; Platnick and Shadab 1975, 1976, 1977, 1980a, 1980b, 1982, 1983). Voucher specimens were Southeastern Naturalist 59 F.B. Hamilton, et al. 2018 Vol. 17, No. 1 deposited in the UAAM, and 1–5 exemplars of each species were deposited in the Dowling Lab Collection at the University of Arkansas. Data analysis We calculated species richness as: (# of species) / (month-site-method). We calculated species diversity as the Shannon-Wiener index, using the formula: '’= -Σ(pi *ln[pi]) (Shannon 1948). Data were analyzed using Excel 2013 and JMP Pro 11. We conducted similar analyses for both the carabids and gnaphosids, and determined the appropriate statistical methods based on examination of the data. We performed repeated-measures analysis of variance (rm-ANOVA) tests in order to examine data from all 4 sites over 12 months and included the following variables: number of individuals collected per month, species richness, species diversity, and litter depth. We used a Tukey Kramer HSD test to separate the means when significance was detected. We employed regression analyses to examine Berlese data in order to determine if litter depth had a significant effect on the number of individuals collected per month, species richness, and species diversity at each site. For all analyses, a significance level of 0.05 was used. Results Leaf litter Average monthly leaf-litter depths varied from a low of 1.35 cm at Withrow 2 to 7.03 cm at Wedington (Fig. 1). Overall litter depth did significantly differ among sites (F = 12.412, df = 11, 33, P= 0.0001). Figure 1. Average depth (cm) of leaf litter collected monthly at 4 sites in Washington and Madison counties, AR, from April 2014 to March 2015. Error bars above each of the means represent the standard deviation. Southeastern Naturalist F.B. Hamilton, et al. 2018 Vol. 17, No. 1 60 Carabidae A total of 645 individual carabids from 47 species, 24 genera, and 15 tribes were collected (Table 1). The Wedington site produced 37 species and 214 individuals. Table 1. Numbers of species of Carabidae collected by Berlese and pitfall sampling at Lake Wedington, Lake Wilson, and Withrow Springs sites 1 and 2, Washington and Madison counties, AR, from April 2014 to March 2015. New county records are indicated by an asterisk (*). Also shown are the tribe of each species and the appropriate feeding guild (O = omnivore, P = predator) of each species. Superscripts correspond to the references (below) used to assign species to guilds. † indicates that information from a congeneric species was used for guild assignment. Sites: Wed = Wedington, Wil = Wilson, Wit 1 = Withrow 1, and Wit 2 = Withrow 2. [Table continued on following page.] Feeding Sites Carabidae taxa Tribe guild Wed Wil Wit 1 Wit 2 Total Agonoleptus conjunctus (Say) Harpalini P13 1 0 1 0 2 Agonum octopunctatum (Fabricius) Platynini O11 7 0 0 0 7 Agonum punctiforme (Say)* Platynini O7,12 2 0 1 0 3 Agonum sp. 3 Bonelli Platynini O7,11,12† 2 0 1 0 3 Amara aenea (De Geer) Zabrini O7,12 2 0 0 0 2 Amara musculis (Say) Zabrini O13 1 1 0 1 3 Amara sp. 3 Bonelli Zabrini O7,12,13† 3 0 0 1 4 Amara sp. 4 Bonelli Zabrini O7,12,13† 0 0 0 1 1 Anisodactylus rusticus (Say) Harpalini O7,12 1 0 0 0 1 Apenes sinuata (Say) Lebiini P5 6 2 2 1 11 Bembidion rapidum (LeConte) Bembidiini P4 1 0 0 0 1 Calathus opaculus LeConte Sphodrini O7 7 0 2 2 11 Calosoma scrutator (Fabricius) (Fiery Carabini P7 1 0 0 0 1 Searcher) Carabus sylvosus Say Carabini P9 11 0 0 0 11 Chlaenius aestivus Say Chlaeniini P1 0 1 0 0 1 Chlaenius emarginatus Say Chlaeniini P1,4† 1 0 0 0 1 Chlaenius laticollis Say Chlaeniini P1,4† 0 1 0 0 1 Chlaenius platyderus Chaudoir Chlaeniini P4 0 3 0 0 3 Cicindela sexguttata Fabricius Cicindelini P15 2 6 0 0 8 (Six-Spotted Tiger Beetle) Cyclotrachelus incisus (LeConte) Pterostichini P4,12† 11 0 0 3 14 Cyclotrachelus parasodalis (Freitag) Pterostichini P12† 52 213 0 0 265 Cyclotrachelus seximpressus (LeConte) Pterostichini P4 15 0 1 1 17 Cyclotrachelus sodalis (LeConte) Pterostichini P4 7 0 0 0 7 Cyclotrachelus whitcombi (Freitag)* Pterostichini P4,12† 1 0 0 0 1 Cymindis limbata (DeJean) Lebiini P3† 0 0 3 1 4 Cymindis platicollis (Say) Lebiini P3† 1 0 0 0 1 Dicaelus ambiguus Laferte-Senectere Licinini P4,7† 1 1 0 0 2 Dicaelus elongatus Bonelli Licinini P4,7 3 7 0 0 10 Dicaelus sculptilis Say Licinini P4,7† 1 0 0 0 1 Galerita atripes LeConte Galeritini P8† 1 0 0 0 1 Galerita bicolor (Drury) Galeritini P8 2 0 0 0 2 Harpalus erythropus (Dejean) Harpalini P13 0 0 1 0 1 Harpalus pensylvanicus (De Geer) Harpalini O7,12 1 0 0 0 1 Lebia collaris (Dejean)* Lebiini P4,6,16† 2 1 0 0 3 Lebia fuscata Dejean Lebiini P4 1 0 0 0 1 Lebia grandis Hentz Lebiini P16 1 0 0 0 1 Lebia solea Hentz Lebiini P4,6,16† 4 0 0 0 4 Southeastern Naturalist 61 F.B. Hamilton, et al. 2018 Vol. 17, No. 1 The Wilson site yielded 16 species and 317 individuals, of which 213 (67%) were Cyclotrachelus parasodalis (see Fig. S1 in Supplemental File 1, available online at, and, for BioOne subscribers, at Withrow 1 and 2 each produced 13 species, with a total of 56 and 58 individuals, respectively. Fifteen species were represented by single individuals. At individual sites, singletons comprised 16 of the 37 (43%) species at Wedington, 6 of the 16 (38%) species at Wilson, 8 of the 13 species (62%) at Withrow 1, and 7 of the 13 species (54%) at Withrow 2. Across all sites and sampling methods, the 4 most abundant carabid species collected were C. parasodalis, Trichotichnus autumnalis, Notiophilus novemstriatus, and Pterostichus permundus. The average number of carabid individuals varied from 0 to 3.0 per sample across the 12 sampling dates and 4 sites (Fig. 2a). We constructed species-accumulation curves to show the addition of species with subsequent monthly Berlese and pitfall sampling from April until the following March (Fig. 2b). At 3 sites (Wilson, Wedington, and Withrow 1), new species were added throughout the year. On the other hand, no new species were added at Withrow 2 after September. Our analyses for carabids indicated no significant differences among the sites for average number of individuals, species diversity, or species richness (Fig. 3). Results of rm-ANOVA indicated no significant differences among the 4 sites for the average number of individuals (F = 1.771; df = 11, 33; P = 0.101) or species diversity (F = 1.514; df = 11, 33; P = 0.173), but suggested potential significant differences for species richness among the sites (F = 2.659; df = 11, 33; P = 0.015). However, the Tukey-Kramer HSD test did not produce any significant P-values for pairwise comparisons of the species richness means among the sites, indicating that species richness did not differ among the sites. Table 1, continued. Feeding Sites Carabidae taxa Tribe guild Wed Wil Wit 1 Wit 2 Total Lebia viridis Say Lebiini P6 0 1 1 0 2 Notiophilus novemstriatus LeConte Notiophilini P7 1 25 10 18 54 Pterostichus permundus (Say) Pterostichini P2 1 44 0 2 47 Pterostichus punctiventris (Chaudoir) Pterostichini P2† 30 0 1 2 33 Scaphinotus sp. Dejean Cychrini P14† 0 2 0 0 2 Scarites subterraneus Fabricius Scaritini P7,12 0 6 0 0 6 Synuchus impunctatus (Say)* Sphodrini P4† 0 0 1 1 2 Tachys columbiensis Hayward* Bembidiini P7† 2 0 0 0 2 Trichotichnus autumnalis (Say)* Harpalini O1,10† 26 3 31 24 84 Trichotichnus fulgens (Csiki) Harpalini O1,10† 2 0 0 0 2 Number of individuals per site 214 317 56 58 645 Number of species per site 37 16 13 13 47 1Ball and Bousquet (2001), 2Brunke et al. (2009), 3Cutler et al. (2012), 4Gardiner et al. (2010), 5Greenberg and Thomas (1995), 6Hoffman (1987), 7Larochelle (1990), 8Larochelle and Lariviere (2003), 9Latty et al. (2006), 10Loreau (1988), 11Losey and Denno (1999), 12Lundgren (2009), 13Nemec et al. (2014), 14Pakarinen (1994), 15Schultz (1998), and16Weber et al. (2006). Southeastern Naturalist F.B. Hamilton, et al. 2018 Vol. 17, No. 1 62 For carabids at all 4 sites, regression analyses showed no significant effect of the depth of leaf litter on the number of individuals (Wedington: F = 0.036; df = 1,10; P = 0.853; Wilson: F = 1.911; df = 1,10; P = 0.197; Withrow 1: F = 0.968; df = 1,10; P = 0.348; and Withrow 2: F = 0.974; df = 1,10; P = 0.347) and species diversity Figure 2. Collections of Carabidae by month in Berlese and pitfall trap samples: (a) average numbers of carabid individuals collected, and (b) numbers of carabid species accumulated monthly. Error bars above each of the means represent the standard deviation. Southeastern Naturalist 63 F.B. Hamilton, et al. 2018 Vol. 17, No. 1 Figure 3. Carabidae collected in Berlese and pitfall-trap samples: (a) average numbers of carabid individuals, (b) species diversity, and (c) species richness. Error bars above each of the means represent the standard deviation. Southeastern Naturalist F.B. Hamilton, et al. 2018 Vol. 17, No. 1 64 (Wedington: F = 0.066; df = 1,10; P = 0.802; Wilson: F = 0.294; df = 1,10; P = 0.600; Withrow 1: F = 2.724; df = 1,10; P = 0.130; and Withrow 2: F = 0.045; df = 1,10; P = 0.837). Regression analyses showed no significant effect of the depth of leaf litter on species richness at 3 of the sites: Wedington (F = 0.245; df = 1,10; P = 0.631), Wilson (F = 2.399; df = 1,10; P = 0.152), and Withrow 2 (F = 2.398; df = 1,10; P = 0.153). However, litter depth significantly affected the species richness at Withrow 1 (F = 5.513; df = 1,10; P = 0.041) with the negative slope of the regression having a value of -0.144. The 47 carabid species collected by Berlese and pitfall sampling were assigned to either predator or omnivore feeding guilds (Table 1). Thirty-five species (74%) were categorized as predators, and 12 species (26%) were categorized as omnivores. We compared trap catches for predator and omnivore guilds at Wedington and Wilson because the 2 sites had both Berlese and pitfall samples (see Table S1 in Supplemental File 1, available online at suppl-files/s17-1-S2370-Hamilton-s1, and, for BioOne subscribers, at https:// The 2 sites yielded 14 species of predators found in Berlese samples and 23 species of predators found in pitfall samples; 5 of those species were found in both trap types. All 4 Chlaenius spp., 2 Galerita spp., and 5 Cyclotrachelus spp. were collected in pitfall traps. In contrast, all 5 Lebia spp. were collected only in Berlese samples at those sites. The 11 species of omnivores at the Wilson and Wedington sites represented 6 genera. Of these, 1 genus (Harpalus) was found only in pitfalls, 1 genus (Anisodactylus) was found only in Berlese samples, and the other 4 genera were collected in both trap types. Although 47 species of carabids were collected, none represent new state records. However, there are 8 new county records including: Cyclotrachelus whitcombi, Lebia collaris, and Tachys columbiensis in Washington County; Synuchus impunctatus in Madison County; and Agonum punctiforme and T. autumnalis in Washington and Madison counties. Cyclotrachelus whitcombi is a rare species that has been recorded 15 times from eastern Oklahoma and southern Arkansas (Freitag 1969). It was collected once in a pitfall trap at Lake Wedington in August 2015 which may indicate a range extension. Prior to this study, only 4 specimens of T. columbiensis have been collected in the Ozark Mountain Region of Arkansas (Skvarla et al. 2015). Similarly, only 3 specimens of S. impunctatus have been collected in Arkansas before this study (Skvarla et al. 2015). Gnaphosidae A total of 421 individual gnaphosids consisting of 11 genera and 15 species was collected (Table 2). The Wilson site yielded 15 species (100%) and 201 individuals, and the Wedington site produced 12 species (80%) and 164 individuals. Five species (33%) and 33 individuals were collected at Withrow 1, whereas 6 species (40%) and 23 individuals were collected at Withrow 2. Two species (13%) were represented by only 1 individual, and both were found at Wilson. Across all sites and both sampling methods, the 4 most abundant gnaphosid species collected were Zelotes duplex, Talanites echinus, Drassyllus aprilinus, and Gnaphosa fontinalis. Southeastern Naturalist 65 F.B. Hamilton, et al. 2018 Vol. 17, No. 1 An average of 0 to 5 individual gnaphosids per sample were collected across 12 months from the 4 sites (Fig. 4a). We constructed species-accumulation curves to show the addition of species with subsequent monthly leaf-litter and pitfall-trap sampling from April until the following March (Fig. 4b). At Wilson and Withrow 2, all species had been collected by November. No new species were added at Withrow 1 after June and at Wedington after August. Significant differences were detected among the 4 sites using rm-ANOVA for the average number of individuals (F = 3.084; df = 11, 33; P = 0.006; Fig. 5a), species richness (F = 4.363; df = 11, 33; P = 0.001; Fig. 5b), and species diversity (F = 4.486; df = 11, 33; P = 0.0004; Fig. 5c). For gnaphosids at all 4 sites, regression analyses showed no significant effect of the depth of leaf litter on the average number of individuals captured (Wedington: F = 0.942; df = 1,10; P = 0.355; Wilson: F = 0.014; df = 1,10; P = 0.909; Withrow 1: F = 0.175; df = 1,10; P = 0.684; and Withrow 2: F = 0.920; df = 1,10; P = 0.360), species richness (Wedington: F = 0.985; df = 1,10; P = 0.344; Wilson: F = 0.083; df = 1,10; P = 0.779; Withrow 1: F = 0.033; df = 1,10; P = 0.859; and Withrow 2: F = 2.189; df = 1,10; P = 0.170), and species diversity (Wedington: F = 0.335; df = 1,10; P = 0.575; Wilson: F = 0.645; df = 1,10; P = 0.441; Withrow 1:F = 1.175; df = 1,10; P = 0.304; and Withrow 2: F = 1.774; df = 1,10; P = 0.212). The 15 species of Gnaphosidae collected during this study do not represent any new state records. However, 10 of the 15 species (67%) represent new county records including: Cesonia bilineata, Sergiolus capulatus, Sosticus insularis, and Talanites exlineae in Washington County; and Drassyllus aprilinus, D. covensis, Gnaphosa fontinalis, Litopyllus temporarius, Zelotes duplex, and Z. hentzi in Table 2. Numbers of species of Gnaphosidae captured by Berlese and pitfall sampling at 4 sites (Lake Wedington, Lake Wilson, and Withrow Springs 1 and 2) in Washington and Madison counties, AR, from April 2014 to March 2015. New county records are indicated by a n asterisk (*). Sites Gnaphosidae taxa Wedington Wilson Withrow 1 Withrow 2 Total Callilepis imbecilla (Keyserling) 1 18 0 0 19 Cesonia bilineata (Hentz)* 3 22 0 0 25 Drassodes sp. Westring 0 1 0 0 1 Drassyllus aprilinus (Banks)* 22 23 19 8 72 Drassyllus covensis Exline* 4 1 2 4 11 Drassyllus dixinus Chamberlin 1 1 0 0 2 Gnaphosa fontinalis Keyserling* 51 3 4 5 63 Herpyllus ecclesiasticus Hentz 1 1 0 0 2 Litopyllus temporarius Chamberlin* 0 2 0 1 3 Sergiolus capulatus (Walckenaer)* 1 3 0 0 4 Sosticus insularis (Banks)* 0 1 0 0 1 Talanites echinus (Chamberlin) 2 78 0 0 80 Talanites exlineae (Platnick and Shadab)* 24 2 0 0 26 Zelotes duplex Chamberlin* 49 39 4 2 94 Zelotes hentzi Barrows* 5 6 4 3 18 Number of individuals per site 164 201 33 23 421 Number of species per site 12 15 5 6 15 Southeastern Naturalist F.B. Hamilton, et al. 2018 Vol. 17, No. 1 66 Madison County. Sosticus insularis has been recorded throughout the south-central US, Midwest, and parts of the East Coast, but has only been recorded in Arkansas once (in Newton County) prior to this study (Heiss 1977). Figure 4. Collections of Gnaphosidae by month in Berlese and pitfall-trap samples: (A) average numbers of gnaphosid individuals collected, and (B) numbers of gnaphosid species accumulated monthly. Error bars above each of the means represent the standard deviation. Southeastern Naturalist 67 F.B. Hamilton, et al. 2018 Vol. 17, No. 1 Figure 5. Gnaphosidae collected in Berlese and pitfall-trap samples: (a) average numbers of gnaphosid individuals, (b) species richness; and (c) species diversity. Error bars above each of the means represent the standard deviation. Southeastern Naturalist F.B. Hamilton, et al. 2018 Vol. 17, No. 1 68 Discussion The use of both Berlese sampling and pitfall trapping at Wedington and Wilson proved to be advantageous in capturing a greater number of carabid and gnaphosid species. Lake Wedington was the most diverse site, with 79% of carabid and 80% of gnaphosid species collected there. Lake Wilson was the second most diverse site, with 34% of carabid and 100% of gnaphosid species. The 2 Withrow Springs sites were the least diverse, with 28% of carabids collected at each site and 33% of gnaphosid species captured at Withrow 1 and 40% of gnaphosid species captured at Withrow 2. Since many species were collected only in 1 trap type, sampling consisting of only 1 trapping method would have yielded fewer species—a factor that might have played a role in the lower diversity measured at the 2 Withrow Springs sites. Although Lake Wilson is a city park and smaller in area (109 ha) than the other 2 locations, many taxa were collected there. The site is dominated by many large canopy trees and located amid an expanse of large trees in an urban forest. The fact that the park was a remnant of an earlier forested habitat might at least partly explain the high species diveristy found there. The diversity of species collected at this site also points out the importance of its inclusion in sampling the arthropod diversity of urban locations—high levels of species diversity are not exclusive to “natural” areas. Pitfall traps are the most frequently used collection method for active predators, such as carabids (Lovei and Sunderland 1996), but design and installation can influence the species caught. If openings in the trap are not flush with the ground, small carabid species may be prevented from falling in the traps and thus be underrepresented in the collection. Similarly, if the opening is too small, the trap can discriminate against larger species. The design and installation of our pitfall traps was effective in capturing both small (e.g., Bembidion rapidum and N. novemstriatus) and large (Calosoma scrutator, Carabus sylvosus, and C. parasodalis) carabid species. Cyclotrachelus parasodalis was the dominant species captured in pitfall traps at Wedington and Wilson, and all 265 individuals were collected in pitfall traps. The July sample contained 160 of the 213 (75%) individuals collected at Wilson and 35 of the 52 (67%) individuals collected at Wedington. These numbers were much greater than the number of individuals found the other months—fewer than 10 at each site, except in November when 22 were found at Wilson. Heavy rains in July (amounts not recorded) flooded the traps and diluted the propylene glycol, diminishing its ability to preserve collected arthropod specimens. The diluted fluid with decomposing individuals may have acted as an attractant for C. parasodalis. However, because this species is classified as predatory, it is also possible that the beetles were not attracted to decomposing arthropods, but to other species (e.g., carrion beetles [Coleoptera: Silphidae]) that responded to the decomposing specimens. If a dilute mixture of propylene glycol and water leads to decomposing arthropods, then it may be the most effective method for collecting C. parasodalis. It is also possible that C. parasodalis increased its activity during heavy rains. Southeastern Naturalist 69 F.B. Hamilton, et al. 2018 Vol. 17, No. 1 Pitfall traps appeared to be the most effective method in collecting gnaphosids, which are fast-moving predators that can move quickly through the litter and escape collection. Uetz (1977) abandoned leaf-litter collection during his study due to many wandering spiders moving out of the sampling area, and he noted that pitfall trapping was the more effective method to measure their diversity and abundance. However, while we also found that pitfall traps collected more gnaphosids compared to leaf-litter sampling, the latter method did result in the capture of significant numbers of individuals. For example, at Wedington and Wilson, 261 gnaphosids were collected by pitfall traps and 104 individuals were collected in Berlese samples (see Table S2 in Supplemental File 1, available online at Hamilton-s1, and, for BioOne subscribers, at s1). Gnaphosids were more commonly collected in leaf litter that contained woody debris or large rocks, possibly because the spiders could use these surfaces to attach their silken sacs during the day. Finding more gnaphosids near substrates was similar to the results of Ulyshen and Hanula (2009), who found that Araneae were significantly more abundant near logs. Carabids were more abundant during the spring and fall, whereas gnaphosids were more abundant during the spring and summer months. Upon examination of the most abundant carabid and gnaphosid species collected, there were some prevalent patterns in their seasonal activity. Cyclotrachelus parasodalis was most abundant in the summer and fall months, whereas the carabids N. novemstriatus, and T. autumnalis were active throughout the year. Hamilton et al. (2016) found that the rarely collected carabid Pterostichus punctiventris was a winter-active species, and we collected the majority of specimens of that species between November and April. On the other hand, 3 of the most commonly collected gnaphosid species, Z. duplex, T. echinus, and G. fontinalis, were more abundant during the spring and summer months. Similar to N. novemstriatus and T. autumnalis, the gnaphosid D. aprilinus was also collected throughout the year. The diversity of carabids and gnaphosids collected in leaf litter during this study helps to illustrate the biodiversity that can be found in the understudied Ozark Highlands. Compared to Carlton and Robison’s (1998) study over 12 months in leaf litter of the Ouachita Highlands of Arkansas, we collected many more carabid species and individuals in the Ozark Mountain Region of Arkansas. We collected 47 carabid species and 645 carabid individuals whereas they collected 21 carabid species and 91 carabid individuals. On the other hand, 286 carabid species were collected during a survey of the Great Smoky Mountains National Park, which also represents an area of high biodiversity (Carlton and Bayless 2007). Similar to this study, Heiss (1977) collected 16 species of Gnaphosidae in Newton County, AR, which is also located in the Ozark Mountain Region. In contrast, Dorris et al. (1995) collected a lower number of gnaphosid species (8) in leaf litter of the Ouachita Mountains of Arkansas. This study represents a small snapshot of the biodiversity of arthropod groups found in leaf litter from the Ozark Mountain Region of Arkansas and provides a starting point upon which other similar studies may be based. Southeastern Naturalist F.B. Hamilton, et al. 2018 Vol. 17, No. 1 70 Acknowledgments We thank John Rosenfeld for his assistance with identification of the gnaphosids; Earl Minton of Withrow Springs State Park, who provided tree species identifications; Dennis Spear and Kevin Hickie of Arkansas Forestry Commission, who also provided tree species identifications; and the US Forest Service and Withrow Springs State Park for issuance of collection permits to allow for the collection of arthropods for this study. We also thank the 2 anonymous reviewers for their helpful comments and suggestions to improve this manuscript. 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