Southeastern Naturalist C.M. Smith, A.R. Diamond, and C.H. Ray 2018 Vol. 17, No. 1 32 2018 SOUTHEASTERN NATURALIST 17(1):32–42 A Comparison of Spider (Arachnida: Araneae) Diversity from Adjacent Mesic and Xeric Habitats Within the Pocosin Nature Preserve, Pike County, Alabama Chelsea M. Smith1,*, Alvin R. Diamond1, and Charles H. Ray2 Abstract - Knowledge of Alabama’s Araneae fauna is limited, with estimates ranging from 580 to 1000 species within the state. Until now, the most recent surveys were conducted in the 1940s and focused on 3 families. Studies elsewhere indicate that spider diversity is correlated to habitat and plant diversity. Alabama’s diversity of ecoregions and flora should therefore support a highly diverse spider fauna. This study focused on spiders inhabiting a xeric upland and a mesic ravine area in Pike County, AL. The xeric area is a fire-maintained Pinus palustris (Longleaf Pine) plantation dominated by herbaceous vegetation. The ravine is relatively undisturbed and is dominated by hardwoods with little herbaceous growth. We employed a variety of techniques to collect a total of 1224 spiders from October 2015 until May 2016. Mature individuals represented 82 species in 24 families. About 16% of these species are new records for Alabama. Over half of the spiders collected were from the xeric area, and 61.0% of all specimens were male. Abundant prey and a varied understory in the xeric area appears to support a more diverse spider fauna compared to that found in the ravine. Introduction Spiders (Arachnida: Araneae) function in many important ecological and economic roles. They serve as important predators and prey in grazing and decompositional communities (Mallis and Hurd 2005, Ovtcharenko et al. 2014). As predators, spiders act as a highly effective mechanism of population control by eating an estimated 400–800 million tons of prey annually (Hoefler et al. 2006, Nyffeler and Birkhofer 2017). As prey, spiders provide an abundant source of food. A significant number of bird species consume spiders as a major portion of their diet, acting as a form of top-down population control (Rogers et al. 2012). Knowledge about the use of spiders as biological control agents and environmental monitoring tools has increased. Hendawy et al. (2009) and Jeyaparvathi et al. (2013) found that spiders can effectively limit pest-insect populations in crops. Furthermore, spiders have been used successfully as bioindicators of environmental conditions and heavy metal pollution (Ghione et al. 2013, Otter et al. 2013). Several studies have found that spider webs accumulate airborne toxins and heavy metals, such as polycyclic aromatic hydrocarbons (PAHs), lead, and cadmium (Rybak and Olejniczak 2014, Xiao-li et al. 2006). 1Department of Biological and Environmental Sciences, Troy University, Troy, AL 36081. 2Department of Entomology and Plant Pathology, Auburn University, Auburn, AL 36849. *Corresponding author - csmith101919@troy.edu. Manuscript Editor: Jason Cryan Southeastern Naturalist 33 C.M. Smith, A.R. Diamond, and C.H. Ray 2018 Vol. 17, No. 1 Unfortunately, knowledge of Alabama’s Araneae fauna is severely lacking. Before our study, about 390 species had been recorded in the state. However, many of the voucher specimens have been lost or destroyed. Estimates of the total number of taxa vary from 580 to 1000 species (Folkerts 2006, Oliver 2013). Approximately ⅓ of these estimated species lack vouchers from Alabama and were included on the list because their known ranges approach Alabama (Folkerts 2006). The most recent surveys of Alabama’s spider fauna were conducted in the 1940s and were focused on the superfamily Araneoidea and the families Theridiidae, and Mimetidae. These studies documented 122 species from a handful of counties within the state (Archer 1940, 1941, 1947). Species-diversity data collected during surveys of Black Rock Forest Preserve in New York, Ash Meadows National Wildlife Refugein Nevada, and Őrség National Park in Hungary have indicated that an area’s spider diversity is strongly connected to the diversity of its habitats and flora (Crews and Stevens 2009, Ovtcharenko et al. 2014, Samu et al. 2014). This trend may occur because higher plant diversity provides a wider range of food and habitat for herbivorous invertebrates and their spider predators (Malumbres-Olarte et al. 2013). Alabama’s geographic and floral diversity is relatively high, with 6 level-III ecoregions and over 4000 vascular plant species (Alabama Plant Atlas Editorial Committee 2017, Griffith et al. 2001). Furthermore, Alabama’s sub-tropical climate is also likely promotes high spiderspecies diversity (Cardoso et al. 2011, Chaney 2013). We chose the Pike County Pocosin Nature Preserve (PNP) as the study area because it contains rare flora and an unusual arrangement of a xeric upland area, which is dominated by Pinus palustris Mill. (Longleaf Pine) in a sandhills habitat adjacent to mesic ravines (Diamond 2002). Although no previous studies have focused on sandhills spider species in the state of Alabama, some have been carried out in neighboring Florida and present an opportunity to document previously unrecorded species. Corey et al. (1998) studied the spider species inhabiting 12 sandhills ecosystems in north and central Florida. The plant communities of their sampling sites closely resembled the plant community of the upland area of the PNP. Corey et al. (1998) used pitfall traps to sample spiders and collected 154 species. The primary objective of our study was to conduct a similar survey of the spider species found in a sandhill ecosystem and compare them to the spider species found in adjacent mesic ravines. The secondary objective of the study was to provide details on the species that are new state records. Study Area Pike County, AL, lies within the Gulf Coastal Plain ecoregion and is ~1740 km2 in area. The Conecuh River watershed drains most of the county, with tributaries of the Choctawhatchee River watershed draining the southeastern area. Much of Pike County is dominated by pine stands, mixed forests, and agricultural areas. The PNP represents a protected xeric upland habitat and adjacent mesic ravines (Diamond et al. 2002, Siebenthaler 2013). The PNP is a 135-ha tract that has been maintained by the Alabama Department of Conservation and Natural Resource’s Forever Wild Southeastern Naturalist C.M. Smith, A.R. Diamond, and C.H. Ray 2018 Vol. 17, No. 1 34 Program since 1999 (Forever Wild 2014). It contains ecosystems conjoining xeric upland areas and steep mesic ravines, each of which possess a vastly different flora. Several rare plant species, such as Apteria aphylla (Nuttall) Barnhart ex Small (Nodding Nixie) and Gentiana catesbaei (Walter) (Elliott’s Gentian), have been found at the PNP, which suggests that other rare floral and faunal species may be present (Diamond et al. 2002). Much of the upland area is a sandhills ecosystem and has soils in the Troup-Alaga complex that are well drained, contain low levels of natural fertility, and have low organic content (Neal 1997). Sandhills ecosystems are distributed throughout the southeastern US as narrow patches dominated by flora and fauna adapted to xeric, low-nutrient soils (Elliot 201 4). The PNP’s sandhills plant community was heavily logged, and the trees were subsequently replaced with a Longleaf Pine plantation in the 1970s (Diamond 2002). Quercus laevis (Walter) (Turkey Oak) and Cladonia spp. (reindeer lichens) are also commonly found, and Pteridium aquilinum (L.) Kuhn (Common Bracken Fern) is one of the most abundant understory plants, covering much of the ground in and around the pine plantation. The pine plantation has been maintained with controlled fires since 2000, with the burns usually taking place every 1–2 y (D. Hopper, Alabama Department of Conservation and Natural Resources, Montgomery, AL, and E. Soehren, Wehle Land Conservation Center, Midway, AL, unpubl. data). These fires are necessary to prevent hardwood tree species from becoming dominant and creating a closed canopy, which is detrimental to the understory plants adapted to living in Longleaf Pine stands (Clewell 2013). The ravines of the PNP are heavily shaded by a thick canopy and contain small streams fed by underground seepage. The steep walls of the ravines prevented access for the logging experienced by the upland areas; however, they were used as dumps, and metal scrap is still present in some ravine bottoms (Diamond 2002). The ravines contain a Troup loamy-sand soil that is very similar to the soil found in the upland areas, but this soil is very susceptible to erosion. The bottoms of the ravine slopes have clayey subsoil (Neal 1997). These ravines are dominated by hardwoods, such as Magnolia grandiflora (L.) (Southern Magnolia) and Fagus grandifolia (Ehrhart) (American Beech), as well as mosses and ferns (Diamond et al. 2002, Forever Wild 2014). Materials and Methods Site selection and sample collection We selected 3 sites within each of the ravine and upland areas to conduct transect sampling from October 2015 to May 2016. We chose this sampling time-frame to avoid interference from the controlled burns used to clear the underbrush of the pine plantation as well as to study the changes in spider community structure after such fires had taken place. Sites were 25 m from each other. We installed 10 pitfall traps at 1-m intervals along each transect, for a total of 60 traps. These traps consisted of a white outer container with holes for drainage, a funnel, and attachments for a raised green lid. We placed a plastic cup filled with Prestone Low-Tox anti-freeze to a depth of about 5 cm inside each trap. The anti-freeze prevented the trapped spiders from escaping and preserved them until collected. We left the Southeastern Naturalist 35 C.M. Smith, A.R. Diamond, and C.H. Ray 2018 Vol. 17, No. 1 traps open for 1 week, sampled for spiders, and then closed them for the following week. After the closed week, we reopened the traps; this pattern was repeated for the entire course of the study. We carried out additional sampling with a sweep net, aspirator, handheld vacuum, and beating sheet. Use of the sweep net and vacuum was restricted to the xeric and ravine areas, respectively. We conducted the additional sampling for ~1-h intervals 3 times weekly and alternated between the xeric and ravine sites on a weekly basis. These sampling areas were located at least 10 m away from the pitfall traps. We stored the collected organisms inside a lidded container and froze them for later sorting. We preserved in 75% ethanol, identified, labeled, and placed in separate vials for storage all spider specimens. We installed a rain gauge and 2 Hobo® temperature loggers (Onset Computer Corporation, Bourne, MA) at each site to record rainfall throughout the entire sampling period and record temperature between the months of December 2015 and May 2016, respectively. Statistical analysis We conducted statistical analysis in SPSS statistical analysis software (IBM Corp 2013). We employed ANOVA to examine rainfall and temperature data. We ran a chi-square test to discern collection-method success by family, and conducted tests for correlation to search for possible connections between collection method, average rainfall, average temperature, and date collected. We calculated Shannon– Weiner diversity index and Sørenson’s coefficient of community values to analyze the differences in spider species diversity between the 2 sites. Taxonomic identification of spiders We referred to Ubick et al. (2005) to identify the collected spiders. Additional resources include keys by Levi (2002), Dondale and Redner (1982), and Platnick (1974), as well as Iowa State University’s Bugguide.net (https://bugguide.net/). We identified specimens to the lowest taxonomic level possible. These specimens will be deposited at the Auburn University Museum of Natural History (AUMNH) in Auburn, AL. Results Habitat preference and diversity We collected a total of 1224 spiders over the course of the study. The xeric site had the greatest number of individual specimens and genera—718 and 44, respectively. The ravine site had 506 individuals in 42 genera. About 600 specimens were mature, representing 82 species and 77 genera within 24 families. The families and their percent abundance between areas are presented in Table 1. The most abundant families within the mature specimens were Linyphiidae (28.5%), Hahniidae (13.5%), and Lycosidae (11.4%). The most commonly collected species was the Theridiid Euryopis funebris (Hentz), with 14 individuals. Furthermore, male spiders made up 61.0% of the mature specimens. We collected males mainly during the winter months, whereas female spiders had a broader temporal distribution. Southeastern Naturalist C.M. Smith, A.R. Diamond, and C.H. Ray 2018 Vol. 17, No. 1 36 Of the remaining spiders, 558 were immature and 45 had damaged abdomens or lacked pedipalps. Overall, the highest abundances of collected immature spiders were in the families Lycosidae (23.1%), Oxyopidae (16.1%), and Salticidae (10.4%). We collected over 3800 arthropods as bycatch during the study—2384 specimens from the xeric area and 1427 from the ravines. Spiders made up ~23% of the xeric area’s collection and ~26% of the ravine’s; the remaining specimens were non-spider species. Comparison of sites Our collections of mature spiders suggest that genera exhibit site preferences. Only 13 of the 77 species were common to both areas, and based on Sørenson’s coefficient of community, the xeric and ravine areas are only 24.0% similar in diversity among adult spiders. Further calculations of species richness using the Shannon–Weiner diversity index revealed that the xeric site was more diverse, with a score of H = 3.3 (EH = 0.87) compared to the ravine’s score of H = 2.9 (EH = 0.76). Table 1. A comparison of the percent abundance for each family found in the xeric and ravine areas of the PNP. Family Percent xeric Percent ravine Unknown 7.9 3.2 Agelenidae 0.1 0.4 Amaurobiidae 0.6 0.0 Amphinectidae 2.6 0.0 Anyphaenidae 1.2 7.3 Araneidae 3.1 1.6 Clubionidae 0.7 1.8 Corinnidae 2.6 0.0 Ctenidae 0.0 5.7 Cyrtaucheniidae 0.0 0.8 Dictynidae 1.4 2.8 Eutichuridae 1.4 0.0 Gnaphosidae 7.7 2.2 Hahniidae 1.4 15.4 Linyphiidae 22.3 9.3 Liocranidae 0.0 0.2 Lycosidae 9.6 26.9 Mimetidae 0.3 0.0 Miturgidae 0.0 0.4 Mysmenidae 0.3 0.0 Oxyopidae 13.1 0.4 Phrurolithidae 3.9 3.9 Pisauridae 0.0 0.2 Salticidae 6.3 7.9 Tetragnathidae 0.1 1.4 Theridiidae 3.2 2.2 Theridiosomatidae 0.0 0.2 Thomisidae 8.8 7.1 Titanoecidae 1.2 0.0 Trachelidae 0.0 0.2 Southeastern Naturalist 37 C.M. Smith, A.R. Diamond, and C.H. Ray 2018 Vol. 17, No. 1 Fifty-six percent of all individuals were mature, and we collected the majority of these specimens from the xeric area. Some of the genera unique to the xeric area include Linyphiidae: Erigone, Araneidae: Mangora, and Gnaphosidae: Zelotes. Genera unique to the ravine area include Euctenizidae: Myrmekiaphila, Linyphiidae: Ceratinops, and Dictynidae: Cicurina. Regardless of maturity, the most commonly collected species in the xeric area was Peucetia viridans (Hentz) (Green Lynx Spider), and the most abundant species in the ravine was Anyphaenid Wulfila albens (Hentz). New records and notable species The checklist created by Folkerts (2006) lacks several species collected over the course of this study, which are new records for the state of Alabama (Table 2). Folkerts’ list has not been updated since 2006; thus, we also carried out further literature searches to confirm each species’ status as a new record. Collection-method results There were major differences between the efficacy of each collection method. Pitfall traps accounted for about 87.7% of all mature specimens. There was a significant difference in the average temperature between sites (F = 34.7, P = 0.018). The average temperature was 15.4 °C at the xeric site and 14.3 °C at the ravine site. Throughout the study, higher daytime and lower nighttime temperatures occurred in the xeric site relative to the ravine. For most of the collection methods, the greatest number of specimens were from the fall and spring months. The pitfall traps did not follow this trend. Instead, there was a steady increase in success throughout the coldest months, from a low of 4 mature individuals in October to a maximum number of 134 in April. The exception Table 2. New state records and other notable species collected from the xeric and ravine areas of the PNP. S = a new state record, C = a new county record, I = that the species has been introduced, and CC = conservation concern. Family Species Status Amphinectidae Metaltella simoni (Keyserling) S, I Corinnidae Castianeira descripta (Hentz) S Falconina gracilis (Keyserling) S, I Ctenidae Anahita punctulata (Hentz) C, CC Gnaphosidae Urozelotes rusticus (L. Koch) C, I Camillina pulchra (Keyserling) C, I Linyphiidae Ceratinops crenatus (Emerton) S Origanates rostratus (Emerton) S Pelecopsidis frontalis (Banks) S Theridiidae Rhomphaea projiciens (O. Pickard-Cambridge) S Theonoe stridula (Crosby) S Titanoecidae Titanoeca brunnea (Emerton) S Salticidae Anasaitis canosa (Walckenaer) S Sassacus vitis (Cockerell) S Tutelina harti (Emerton) S Zygoballus nervosus (Peckham & Peckham) S Southeastern Naturalist C.M. Smith, A.R. Diamond, and C.H. Ray 2018 Vol. 17, No. 1 38 to this pattern was the month of January, which experienced the highest average rainfall, lowest average temperature, and a lower capture rate than either December or February. There was also a significant and moderately positive correlation (r = 0.518, P ≤ 0.01) between temperature and frequency of collection. Correlation between abundance and average rainfall was neither statistically significant nor did it follow a noticeable trend (r = -0.005, P = 0.889). Sixteen of the 24 families from which we collected specimens came primarily from pitfall traps. For some families, 100% of specimens were captured in pitfall traps, such as Corinnidae, Amphinectidae, Ctenidae, and Hahniidae, which are primarily ground dwellers. Plant-dwelling spiders in the families Oxyopidae, Tetragnathidae, Trachelidae, and Eutichuridae were all primarily collected by sweep net and beating sheet. Discussion The results of this study suggest that most of the spider species that inhabit the PNP have clear habitat preferences, with 47 out of 82 species choosing the xeric area. When choosing habitats, the stability of temperature and availability of water characteristic of the ravines was likely outweighed by the upland site’s larger number of prey items. As discussed by Ovtcharenko et al. (2014), plant diversity’s influence on prey species also affects the diversity of the area’s spider assemblage. The open canopy of the upland site allows for a greater number of plants to colonize the area after controlled burns, while the closed canopy and lack of human intervention in the ravines have led to an environment dominated by taller, older trees and less ground-level vegetation (Diamond 2002). This interaction between the PNP’s plants, the arthropods that consume them, and the spiders that consume the arthropods may explain why the xeric area had a larger spider population as well as higher spider diversity. During their study of Florida’s sandhill ecosystems, Corey et al. (1998) also collected 31 species from 20 families found over the course of this study. The Florida study sampled 12 sites across the northern and central parts of the state. We calculated Sørenson’s coefficient of community to determine the similarity between these 12 sites and the present study’s 2 sites and found a commonality of only 26%. We also compared Corey et al.’s (1998) 2 Florida locations closest to Alabama, Suwannee River State Park and O’leno State Park, with our sites and found a 27% similarity. Approximately 75% of the spiders collected in the Florida study were Lycosidae. However, the Linyphiidae family had a species diversity of 16%—the highest value for that study. For the present study, the Linyphiidae family had the highest abundance, with 28.5% of all mature specimens. Lycosids made up a much smaller proportion of our project’s collection at 11.4%. Salticidae was the most diverse at 13 species, while Linyphiidae was the second most diverse with 12 species. Lycosidae was represented by 8 species. Past studies have found that some spiders are able to survive fires by seeking refuge beneath rocks and woody debris (Underwood and Quinn 2010). The xeric Southeastern Naturalist 39 C.M. Smith, A.R. Diamond, and C.H. Ray 2018 Vol. 17, No. 1 upland area lacks rocky soil and has little in the way of the downed woody material to offer as a haven during a fire. It appears possible that ground-dwelling spiders in the xeric study area would have to seek safety by climbing trees or entering burrows, such as those created by the area’s Gopherus polyphemus (Daudin) (Gopher Tortoise) population. Spiders unable to reach such places were likely killed when the controlled burn took place in the months prior to this study. Afterwards, the individuals in refuges or living on the fringe of the burned plot would have been able to colonize the area. Hahnia and Pelegrina, from the Hahniidae and Salticidae families, respectively, were among the first of the mature specimens collected in the xeric area that are shared genera between habitats. However, we did not document these taxa at the xeric site for the remainder of the study. A possible explanation for their early occurrence and subsequent absence is that they were among the first to colonize the burned area, only to be displaced by the later arrival of species better adapted to the xeric environment. Underwood and Quinn (2010) found that fire had a noticeable, but brief and delayed, effect on the affected arthropod populations. They also found that members of the Thomisidae family were slowest to repopulate the burned areas. While the xeric area’s pre-fire population of Thomisidae is unknown, their rate of collection throughout this 7-month study period was fairly uniform. The pitfall traps we used throughout the course of this study were the most productive of the sampling methods. Even though many spider species spend the majority of their time on vegetation, the males’ search for mates can lead them down to the ground, where they may seek shelter under the cover of the pitfall traps. This behavior likely explains why males made up the bulk of specimens collected. Despite the success of pitfall traps, sampling methods targeting vegetation and crevice-dwelling spiders are needed to get a better representation of the species that inhabit an area. We collected all 78 Green Lynx Spider individuals with the beating sheet and sweep net. This abundant species would have been missed if pitfall traps had been our sole collection method. Female spiders made up most the mature specimens collected through the bug vacuum, sweep net, and beating sheet. These other forms of sampling are important when seeking web-building female spiders because their lifestyles keep them off the ground and away from pitfall traps (Harwood et al. 2003). Thus, several sampling methods are required in order to fully examine the spider species diversity within an area. We collected 138 spider species and 108 genera from 24 families throughout the course of this study. The vast majority of these species were new records for Pike County. However, we were able to confidently identify only 82 mature species beyond the family level. Our collections represent a tiny portion of the 500–1000 species estimated to live within the state of Alabama (Folkerts 2006, Oliver 2013). Alabama’s position between the Appalachian Mountains and the Gulf of Mexico provides a diverse mixture of ecosystems likely to host an equally diverse assemblage of spider species. Additional surveys are needed to find and classify the spiders that live in Alabama in order to formulate conservation strategies as the natural world is rapidly altered by anthropogenic disturbance and climate change. Much like the Pocosin Nature Preserve, many other areas have undergone rapid change Southeastern Naturalist C.M. Smith, A.R. Diamond, and C.H. Ray 2018 Vol. 17, No. 1 40 due to land development, pollution, and shifts in temperature and precipitation. Gaining knowledge on the biotic and abiotic components of vulnerable ecosystems is essential to making preparations for their protection and rehabilitation. Thus, it is increasingly important that surveys focused on understudied taxa and locations are conducted in the near future. Acknowledgments We thank Dr. Stephen Landers and Dr. Michael Stewart for their assistance and advice in writing this report as well as with statistical help. Thanks also to Priya Bhattacharya for help carrying out sampling efforts. We appreciate Dr. Neil Billington’s and Jonathan Miller’s additional efforts in completing this report. Literature Cited Alabama Plant Atlas Editorial Committee. 2017. Alabama Plant Atlas. University of West Alabama, Livingston, AL. Available online at http://www.floraofalabama.org. Accessed 5 March 2015. Archer, A.F. 1940. The Argiopidae or orb-weaving spiders of Alabama. Geological Survey of Alabama, Alabama Museum of Natural History Museum Paper 14:1–77. Archer, A.F. 1941. 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