<p> 1 SUPPLEMENTARY ONLINE MATERIAL</p><p>2</p><p>3 Assessing trophic position from nitrogen isotope ratios: effective</p><p>4 calibration against spatially varying baselines </p><p>5</p><p>1 1 2 1 6 Paul Woodcock , David P. Edwards , Rob J. Newton , Felicity A. Edwards , </p><p>3 2 1 7 Chey Vun Khen , Simon H. Bottrell , Keith C. Hamer</p><p>8</p><p>9 1Institute of Integrative and Comparative Biology, University of Leeds, Leeds, LS2 9JT, UK</p><p>10 2School of Earth and Environment, University of Leeds, Leeds, LS2 9JT, UK.</p><p>11 3Sepilok Forest Research Centre, Sandakan, Sabah, Malaysia</p><p>12</p><p>13 Corresponding author: Paul Woodcock; email: [email protected]</p><p>14</p><p>15 Table S1: Details of approaches to baseline correction in 34 recent stable isotope studies</p><p>16 conducted in terrestrial ecosystems.</p><p>17 Table S2: Mean and standard deviation for repeated isotope analyses of ant and plant</p><p>18 samples.</p><p>19 Table S3: Standard deviations of random effects in linear mixed models.</p><p>20 Figure S1: Variation in plant δ15N values between transects, with and without samples of</p><p>21 the Fabaceae. 2 22 Table S1: Approaches to baseline correction in recent stable isotope studies conducted in terrestrial ecosystems Study # distinct consumer # spatially Max. distance between Baseline # Question, study taxa and sampling sites distinct baselines sampling locations material Sa ecosystem recognised used to interpret assumed to have a mp data constant baselinea les pe r ba seli ne Duyck et al. ? - but total sampling area is N/ Examine effects of cover crops on N 4 0 and 2b N/A (2011) 920m2 A arthropod food web structure o Pisanu et al. N/ Determine trophic positions of 2 b 4km N/A (2011) 0 and 1 A rats on a Subantarctic island δ15N used as a trait to assess B Bihn et al. N/ 12 0 ? – Not given N/A changes in ant functional diversity (2010) A a along a successional gradient O’Grady et ? – but sampling area is 4 x N/ Trophic ecology of ants in s 1 0 N/A al. (2010) 2km A temperate grassland. e Compare trophic positions of 4 Prochazka et N/ l 1 0 120m N/A understorey bird species across a al. (2010) A i forest-savannah ecotone Divergence in resource use Vidal and N/ n 5 0 and 2b 100km N/A amongst mainland and island Sabat (2010) A e lizard populations Investigate intra- and inter- Smith et al. N/ 4 0 c N/A colonial variation in diet of (2008) Several km A harvester ant castes Tillberg et al. N/ Inter and intra-colonial variation 2 0 ? – Not given N/A (2006) A in trophic position of ants Yi et al. N/ Describe food web in alpine 1 0 and 1b ? – Not given N/A (2006) A meadow 23</p><p>1 a No baseline means that the study effectively assumes that all sampling locations have a constant baseline of zero. 2 b A combination of uncorrected and corrected data were presented/analysed 3 c Principal conclusions on caste determination unaffected, because all castes are collected from all nests (thereby averaging out baseline variation), but cannot be 4 confident on whether intercolonial variation is genuine. Study # distinct # spatially Max. distance between Baseline # Question, study taxa and consumer distinct baselines sampling locations material Sam ecosystem sampling sites used to interpret assumed to have a ples recognised data constant baselinea per base line Pisanu et al. Leaf litter, grass Determine trophic positions of S 2 0 and 1b 4km ? (2011) and top soil rats on a Subantarctic island i Describe tropical forest food Hyodo et al. Leaves, litter, dead 1 1 ?- Not given ? web, including birds, mammals n (2010) wood and soil g and invertebrates Pollierer et ? – Not given, but sampling area Leaf litter and Describe soil food web in 6 1 15 l al. (2009) is 2000m2 roots temperate forest Traugott et Trophic positions of wireworm e 29 1 Several km Soil, plants 382 al. (2008) species in European farmland Sanders and Intraguild interactions between Moss, herbs and B Platner 5 1 ? – Not given 18 predatory arthropods in grass a (2007) grassland and meadow. Kupfer et al. Describe tropical forest food 1 1 < 50m Termites 11 s (2006) web. Yi et al. Describe alpine meadow food e 1 0 and 1b ? - Not given Herbivores ? l (2006) web. Describe soil invertebrate food Halaj et al. Plants, litter and i 5 1 ? - Not given 10 web in coniferous forest and (2005) soil n examine effects of thinning Schmidt et ? – Not given, but sampling area e 4 1 Plants and stubble 19 Soil food web in arable field al. (2004) is 2000m2 Tooker and Investigate trophic position of 15- Hanks 10 d >50 km Plants flower beetle on 2 plant species 1 29 (2004) in Illinois and Indiana prairies Omnivory and food web Blüthgen et ≈3km. Within-site sampling area 2 1 Leaves 37 structure in arboreal rainforest al. (2003) not givene ants 24</p><p>5 d Study presents data separately for beetles on 2 different plant species, with each plant species used as a separate baseline 6 e Models investigating interspecific variation in ant δ15N values included the δ15N value of the plant from which the ant was collected as a covariate. Study # distinct # spatially Max. distance between Baseline # Question, study taxa and consumer distinct baselines sampling locations material Sam ecosystem sampling sites used to interpret assumed to have a ples recognised data constant baselinea per base line Duyck et al. ? - but each baseline applies Examine effects of cover crops M 4 b Plants ? (2011) 0 and 2 to an area of 460m2 on arthropod food web structure u 3 hom l Gibb and Leaf litter, grass, ogeni Comparing ant community t Cunningham 12 12 <6m top soil sed across regenerating pastures (2011) i samp p les Hom l ogeni e sed samp Hawke and le Describe arthropod food web in 2 2 <5m Soil B Clark (2010) analy penguin burrows a sed in s dupli e cate 4-5 l Examine spatial variation in Menke et al. ? – Not given, but may be plant 4 4 Plants trophic position of i (2010) >100m speci chaparral/scrub ants n es e 1 hom s Smith and ogeni Trophic position of harvester ant 8 8 0m Seeds Suarez (2010) sed castes samp le Divergence in resource use Vidal and Sabat 5 0 and 2f 50km Seeds & fruits ? amongst mainland and island (2010) lizard populations El-Wakeil 2 2 30m Plants, soil and 25 Description of soil food web in (2009) litter coniferous forest 7 f 2 mainland sites and 3 island sites examined, each separated by ≈50-100km. Correction carried out at mainland and island levels. Within site distances not given. Kozhu et al. 5m in some analyses, 60- Description of arthropod and 10 g Plants ? (2009) 2 and 10 1000m in other analyses mammal food web on grasslands 3 repli cates of 3 McGlynn et al. Determining predictors of ant 7 7 <10m? Leaf litter hom (2009) d15n values ogeni sed samp les 1-7 per York and samp Compare trophic level within 5 5 ? – Not given Plants Billings (2009) ling and between fruit bat species locati on 25</p><p>8 g Data sometimes interpreted at the site level (= 2 distinct baselines) and sometimes at each of 5 sampling locations within each site (= 10 distinct baselines) Study # distinct # spatially distinct Max. Baseline # Samples Question, study taxa and consumer baselines used to distance material per ecosystem sampling sites interpret data between baseline recognised sampling locations assumed to have a constant baselinea Effect of humification on termite M Hyodo et al. Soil, leaf litter 6 2 1kmh 4-5 & earthworm δ15N values in (2008) & grass u forest & savannah Effect of disturbance on food l Takimoto et al. 36 36 <20m Leaves 5-10 chain length, focusing on lizards t (2008) & spiders i Daugherty and Trophic structure of arthropod 4 4 0m Leaves 10-31 p Briggs (2007) community in pear orchards Spatial variation in trophic Tillberg et al. l 6 6 ? – Not given Plants 6-21 position of invasive ant species (2007) e in woodland/pasture ? – Not Plants, leaf Effect on arthropod food web of Gratton and 36 4 given, but litter & soil 5-10 removing an invasive plant from Denno (2006) B >10m core salt marshes Mooney and a Spatial variation in ant omnivory Tillberg 6 6 0m Pine needles 5 s in pine forest (2005) e Schneider et Leaf litter and Niche differentiation in orbatid 4 4 5m 8 l al. (2004) bark mites in temperate forest. Davidson et al. 3 3 ? – Not given Leaves ? 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J Mammal, 90 90:1469-1477 15 91 Table S2: Mean and standard deviation (SD) of δ Nair values for repeated isotope analyses of</p><p>92 ants collected from within single sampling points: Lophomyrmex bedoti (Ant1),</p><p>93 Pachycondyla obscurans (Ant2 and Ant3), Paratrechina sp3 (Ant4) and Pseudolasius sp1</p><p>94 (Ant5) and sp2 (Ant6). The standard deviation for repeats of a homogeneous leaf sample</p><p>95 (EUP) run in several columns is also shown. Numbers of repeats analysed per sample are</p><p>96 shown in brackets. </p><p>97</p><p>Ants Plant</p><p>Sample Sample Sample Sample Sample Sample EUP</p><p>1 (5) 2 (3) 3 (3) 4 (3) 5 (3) 6 (3) (38) Mea n 5.77 6.89 7.54 6.03 5.64 5.46 0.00 (‰) SD 0.18 0.20 0.21 0.07 0.36 0.36 0.25 (‰)</p><p>98 99 Table S3: Standard deviation of random effects in linear mixed models of corrected ant δ15N</p><p>100 values versus local baseline for overall ant community, ant subfamily, and ant species</p><p>101 analyses within unlogged and logged forests. The greater the standard deviation, the more</p><p>102 variation is attributable to the random effect.</p><p>Overall Subfamily Species Unlogged Logged Unlogged Logged Unlogged Logged subfamily 1.85 1.58 - - 0.20 0.32 species (within subfamily) 0.96 0.86 - - - - species - - 1.01 0.87 - - 104 Figure S1: Mean plant δ15N values (‰) + for the entire dataset (n=160 plants; ALL) and for</p><p>105 each transect (n = 20 plants per transect) in (a) unlogged forest and (b) logged forest. Shaded</p><p>106 columns have Fabaceae samples removed for comparison. Transects are presented in rank</p><p>107 order, from highest plant δ15N value to lowest. </p><p>(a) 3.5 All leaf samples 3 Excluding Fabaceae samples 2.5 N 5 1</p><p>δ 2</p><p> t n a</p><p> l 1.5 p</p><p> n 1 a e</p><p>M 0.5</p><p>0 ALL 1 2 3 4 5 6 7 8 -0.5 Sampling location in rank order 108</p><p>(b) Sampling location in rank order ALL 1 2 3 4 5 6 7 8</p><p>0</p><p>-0.5 N 5 1 δ</p><p> t -1 n a l p -1.5 n a e M -2 All leaf samples</p><p>Excluding Fabaceae samples 109 -2.5</p>