DOI: 10.5061/dryad.3tx95x6cf
title: Local and landscape-scale environmental filters drive the functional diversity and taxonomic composition of spiders across urban greenspaces

description: 1. Urban patch colonization and species establishment within cities are
 restricted by the behavioral, life history, and physiological attributes
 of colonizing species, in conjunction with environmental filtering
 processes at small and large spatial scales. To enhance local biodiversity
 in urban greenspaces, these filtering processes need to be assessed so
 that greenspace design and management can guide establishment of local
 species pools. 2. We investigated the relative importance of local and
 landscape-scale features on spider community assembly using a functional
 and taxonomic approach. Within the shrinking city of Cleveland Ohio, we
 established a field experiment wherein control vacant lots, urban meadows,
 and low- & high-diversity pocket prairies were established across
 eight neighborhoods (N = 32). Spiders were sampled in June-August of 2015
 and 2016 using pitfall traps and vacuums. Spider functional diversity was
 assessed using null models, while local and landscape drivers were
 analyzed via canonical partial least squares and clustered image maps. 3.
 Increased mowing strongly influenced spider communities leading to
 lower-than-expected spider functional alpha and beta diversity in 2015.
 Patch isolation and percentage impervious surface increased the functional
 dissimilarity and taxonomic diversity of spiders in 2016, resulting in
 higher-than-expected overall functional alpha diversity. We also found
 that increasing plant height and biomass favored spiders with large
 body-size and decreased the abundance of small web-weavers. 4. Synthesis
 and applications. Our findings suggest that impervious surface is a strong
 environmental filter that influences the colonization and establishment of
 spider communities in cities. Additionally, while periodic mowing in
 vacant lots benefits some spider taxa, it has a negative impact on the
 establishment of several species, mainly larger spiders and those most
 sensitive to disturbance. To conserve spiders and the biota depended upon
 them, investment in managed greenspaces such as pocket prairies that
 require infrequent mowing is warranted. In so doing, cities can enhance
 urban biodiversity and beautify local neighborhoods.31-Mar-2020
description: Our study was conducted in the city of Cleveland,
 Ohio, USA. In 2014, we established the Cleveland Pocket Prairie Project
 across eight inner-city neighborhoods and selected 32 vacant lots (15 x 30
 m on average) wherein four experimental treatments were established:
 Control Vacant Lots, Urban Meadows, Low-Diversity Pocket Prairies and
 High-Diversity Pocket Prairies. Pocket prairies were mown to a height of
 20 cm monthly in 2015 to reduce weed competition and facilitate the
 establishment of flowering species. All data collection occurred within a
 7 x 15 m grid of 105 quadrats (1 m<sup>2</sup> each), placed
 within the center of each site.
   To account for both active and
 less-mobile spiders, specimens were collected in each site using four
 pitfall traps and four vacuum samples three times per year in 2015 (12-22
 June, 8-20 July, 11-18 August), and in 2016 (1-9 June, 6-14 July, 3-11
 August). Within each site, four quadrats were randomly selected, and
 pitfall traps were set up for seven consecutive days. Pitfall traps
 consisted of 1 L plastic cups (12 cm diameter x 14 cm depth) filled
 halfway with water containing a small amount of dish soap
 (Dawn<sup>®</sup> Ultra, original scent). While pitfall traps
 were active, we vacuumed an area of 0.25 m<sup>2</sup> (30-50
 cm away from each trap in any direction) for 45 seconds using a modified
 leaf vacuum (12 cm diameter). Specimens were stored in 80% ethanol and
 transported to the laboratory for sorting and identification. Due to
 weather and issues with landscaping contractors, vacuum sampling did not
 occur in July 2015.  
 Lycosidae and Linyphiidae adult spiders were
 identified to species and other adult and sub-adult spiders were
 identified to genus. Spider functional traits and groups were classified
 following Cardoso et al. (2011). Functional traits comprised foraging
 activity (web type or hunting method), prey range (stenophagous or
 euryphagous), vertical stratification (ground or vegetation), circadian
 activity (diurnal or nocturnal), and mean body size measured as the
 community-weighted mean. Voucher specimens were deposited in the Museum of
 Biological Diversity at The Ohio State University.
   Local habitat variables were
 measured within 20 randomly selected quadrats. Using a 0.5
 m<sup>2</sup> sub-quadrat, vegetation was sampled twice in
 2015 (16 June - 3 July and 22 July - 13 August) and three times in 2016
 (13-24 June, 11-22 July, and 4-16 August). We recorded the three most
 dominant plant species per quadrat and diversity was calculated per site
 using the Shannon-Wiener index. Plant biomass was estimated with a
 comparative-yield method and the dry-weight-rank method from the 20
 selected quadrats. First, five quadrats were ranked (1 = lowest biomass
 density, 5 = highest biomass density, and 2-4 in between) and established
 as the ‘standard yields’ reflecting the range of biomass within each site.
 In each of our 20 quadrats, we estimated the biomass yield, on a scale of
 1 to 5, in comparison to our five standard yields. Only the five standard
 yields were harvested, oven-dried at 75 °C for 48 hours and weighted.
 Finally, we plotted our standard yields, obtained an equation from the
 trendline, and inserted our 20 ranked comparative yields from each site
 into this equation to estimate biomass in each quadrat. Average site-wide
 biomass was then calculated as the mean of these 20 comparative yield
 estimates.  
 Mean bloom abundance, bloom area, and plant height
 were also calculated at each site from an additional six randomly selected
 quadrats. Average plant height was derived from three height measurements
 (cm) taken in each quadrat. Likewise, bloom abundances were counted per
 each flowering species present in the six quadrats. For each flowering
 species present, we recorded five bloom area measurements
 (mm<sup>2</sup>) and then multiplied the average bloom size by
 the number of blooms present at a site to derive an average bloom area.
 Additionally, twenty soil cores were randomly sampled and pooled per site
 in April 2014 to measure the concentration of heavy metals. The
 Contamination Factor of aluminum, antimony, arsenic, barium, cadmium,
 chromium, cobalt, copper, iron, lead, manganese, nickel, vanadium, and
 zinc was calculated using regional background levels from eastern United
 States, and from these values Pollution Load Indices were calculated per
 site.  
 Landscape information was obtained from the Cuyahoga
 County Planning Commission using remotely sensed images at 1-2 m
 resolution, captured in 2011. Following previous studies that reported
 spider communities patterns across the landscape we selected buffer zones
 at 200 m and 1500 m radii from each site. Landscape cover was classified
 into percentage: grass/shrubs, bare soil, water, buildings,
 roads/railroads, other paved surfaces, tree canopy (TC) over vegetation,
 TC over buildings, TC over roads/railroads, and TC over other paved
 surfaces. We limited the landscape covers to those directly affecting
 ground-dwelling spiders. To assess landscape composition, percentage
 grass/shrubs, percentage buildings, percentage flat impervious surface
 (roads/railroads & other paved), and Shannon landscape diversity
 were included in the analysis. For landscape configuration, we
 re-classified our categories into either ‘greenspace’ (grass/shrubs
 & TC over vegetation) or ‘other’ based on the importance of patch
 connectivity on our spider functional groups, and calculated the
 <i>class</i>-metrics patch size (m<sup>2</sup>)
 and patch isolation (m). Shannon landscape diversity, patch size, and
 patch isolation were computed at 200 m and 1500 m radii using Fragstats
 v4.2.