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Title. Opportunistic predator prefers habitat complexity that exposes prey while reducing cannibalism and intraguild encounters

List of Authors. Jason M. Schmidt, Department of Zoology, Miami University, Oxford, OH 45056, U.S.A.and Ann L. Rypstra, Department of Zoology,Miami University, Hamilton, OH 45011, U.S.A.

Correspondence author. Email:

Jason M. Schmidt, Department of Zoology, Miami University, 212 Pearson Hall, 700 E. High Street, Oxford, OH 45056, USA.

Online Resource 1 Aerial photograph of the experimental agroecosystem at Miami University’s Ecology Research Center, Butler County, Oxford, OH.

Online Resource 2 Size and body condition of Pardosa milvina assigned to treatments before the 24 hour period of foraging in laboratory enclosures.

Online Resource 3Habitat complexity andmicroclimate measurements of experimental field plots.

Online Resource 4 Mean abundance of other spiders sampled in experimental plots at the ERC. Spiders in bold are either known or potential competitors with Pardosa milvina as they utilize similar foraging tactics and live on the soil surface.

Online Resource 1 Aerial photograph of the experimental soybean agroecosystem at Miami University’s Ecology Research Center, Butler County, Oxford, OH.

Our field site contains 12 soybean fields measuring 60 x 70 m (a). Photographs of the habitat islands containing (b) natural and (c) artificial treatments containing both plant structure and soil surface structure additions.

(a)

(b)(c)

Online Resource 2 Mean size (carapace width) and abdomen width of Pardosa milvina before treatments. Treatments represent density and in parentheses the habitat that spiders were assigned to for the experiments. These data were used to confirm that spiders were similar in size and condition prior to treatment using ANCOVA with the carapace width as the covariate of abdomen.

Treatment / Carapace width before (mm) / Abdomen width before (mm)
Experiment 1
One (Bare soil) / 2.21±0.17 / 1.94±0.31
One (Soybean plants) / 2.18±0.19 / 1.97±0.24
One (Thatch) / 2.19±0.18 / 1.97±0.23
One (Soy + Thatch) / 2.18±0.22 / 1.96±0.26
One (Fiber) / 2.11±0.11 / 1.99±0.24
One (Polyvinyl plants + fiber) / 2.20±0.14 / 1.98±0.15
One (Bare soil) / 2.23±0.17 / 2.01±0.32
Five (Soybean plants) / 2.24±0.20 / 2.03±0.27
Five (Thatch) / 2.22±0.19 / 2.03±0.34
Five (Soy + Thatch) / 2.18±0.21 / 2.05±0.31
Five (Fiber) / 2.25±0.13 / 2.01±0.21
Five (Polyvinyl plants + Fiber) / 2.26±0.11 / 2.00±0.22
Experiment 2
Two (Bare soil) / 2.16±0.19 / 1.89±0.20
Two (Fiber) / 2.29±0.12 / 2.11±0.19
Two (Thatch) / 2.18±0.14 / 1.92±0.29

Online Resource 3 Habitat structure andmicroclimate measurements of experimental field plots.

Measurements represent the quantity of habitat structure of each plot including: plant size, depth of substrate and leaf area index (LAI). Temperature and relative humidity data are daily averages, where we calculated the daily mean temperature and humidity measured by our data loggers within plots over a 25-day period. Coefficient of variation (CV) represents the daily fluctuation in temperature and humidity. Superscripts represent Tukey pair-wise comparisons with dissimilar letters representing significant treatment differences (p<0.05).

Measurements / Natural treatments / Artificial treatments
Bare soil / Soybean plants (Soy) / Wheat straw (Thatch) / Soy + Thatch / Fiber / Plastic plants + fiber
Habitat structure
Plants per plot / 60.4±2.3 / 52.8±6.9 / 50
Plant height (cm) / 69.3±5.8a / 72.7±8.7a / 39.2±2.8b
Plant width (cm) / 49.2±3.6a / 49.2±5.4a / 24.4±3.3a
Substrate depth (cm) / 7.52±1.9ns / 7.08±1.8ns / 7.87±2.8ns / 7.88±1.4ns
Leaf area index / 1.56±0.7b / 2.44±0.6a / 1.15±0.3b / 2.78±0.4a / 1.30±0.4b / 1.48±0.3b
Microclimate
Mean daily temperature (°C) / 25.26b / 23.94a / 24.62ab
CV of temperature / 10.13 / 8.28 / 8.93
Mean daily absolute humidity (g/m3) / 15.92b / 18.29a / 17.56a
CV of absolute humidity / 32.29 / 16.13 / 23.99

Online Resource 4 Mean abundance of other spiders sampled in experimental plots at the ERC. Spiders in bold are either known or potential competitors with Pardosa milvina as they utilize similar foraging tactics and live on the soil surface*.

Habitat treatment
Genus / Family / Feeding guild* / Bare soil / Soy / Thatch / Soy + Thatch / Fiber / Plastic plants+ Fiber
Hogna helluo / Lycosidae / Hunting ground runner / 0 / 0 / 15 / 13 / 4 / 3
Pirata sp. / Lycosidae / Hunting ground runner / 0 / 0 / 4 / 18 / 0 / 0
Rabidosa sp. / Lycosidae / Hunting ground runner / 0 / 0 / 0 / 2 / 0 / 2
Schizocosa sp. / Lycosidae / Hunting ground runner / 0 / 0 / 0 / 0 / 1 / 0
Xysticus sp. / Thomisidae / Hunting ambush / 0 / 1 / 0 / 0 / 0 / 1
*Spider guilds proposed by Uetz et al. (1999) through use of hierarchical cluster analysis to differentiate groups based on web use, foraging mode, web type, and microhabitat use.

Uetz GW, Halaj J, Cady AB (1999) Guild structure of spiders in major crops. J Arachnol 27:270-280

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