Bennett Et Al., Abundance, Rarity and Invasion Debt Among Exotic Species in a Patchy Ecosystem
Bennett et al., Abundance, rarity and invasion debt among exotic species in a patchy ecosystem
Electronic Supplementary Material 1. Study patches, sampling protocol and patch sizes
Fig. ES1: Map showing location of study patches with respect to Vancouver Island, BC (inset, top), and detail of the northern (inset, A) and southern (B) study patch locations. Patch sizes are given in Table S1 below.
Quadrat Sampling Protocol
Quadrats for intra-patch surveys were established using a stratified-random sampling protocol, in which the number of quadrats was scaled by area. Patches were divided a priori into grids based on UTM coordinates in site maps. Patches <1 ha were divided into 25-m grids; patches 1-5 ha were divided into 50-m grids; and patches >5 ha were divided into 100-m grids. In the field, sample points were navigated to using a handheld GPS. As soon as the UTM coordinates for an exact grid intersection point were displayed on the GPS (e.g. UTM northing ending in “00”, easting ending in “00”), a plot was established. Spatial error on the initial GPS readings (±~10m) and navigation to the first GPS reading showing specific grid points introduced randomness, while ensuring adequate spatial coverage. Quadrats were placed on as many grid intersections as possible within sites. Locations that had >50% cover rock, had slope >45 degrees, or were obscured by shrub cover >1.5 m high were rejected.
Table ES1: Patch numbers and sizes. Italicized sites were included in the subset of 22 isolated/least disturbed small-island patches.
Site Number / Area (ha) / Site Number / Area (ha)1 / 0.32 / 35 / 0.77
2 / 6.52 / 36 / 1.22
3 / 1.84 / 37 / 1.07
4 / 5.03 / 38 / 0.62
5 / 0.39 / 39 / 0.64
6 / 0.3 / 40 / 0.63
7 / 5.89 / 41 / 1.1
8 / 1.17 / 42 / 0.57
9 / 3.48 / 43 / 0.34
10 / 1.2 / 44 / 0.26
11 / 1.35 / 45 / 0.34
12 / 1.27 / 46 / 0.59
13 / 3.19 / 47 / 1.96
14 / 5.88 / 48 / 1.62
15 / 2.03 / 49 / 1.26
16 / 1.31 / 50 / 0.56
17 / 1.15 / 51 / 0.68
18 / 1.48 / 52 / 3.37
19 / 16.38 / 53 / 3.83
20 / 0.18 / 54 / 0.17
21 / 0.6 / 55 / 4.02
22 / 2.77 / 56 / 1.93
23 / 8.72 / 57 / 0.42
24 / 17.68 / 58 / 0.59
25 / 8.82 / 59 / 0.84
26 / 1.22 / 60 / 3.72
27 / 1.73 / 61 / 2.84
28 / 1.11 / 62 / 3.81
29 / 4.43 / 63 / 3.83
30 / 4.48 / 64 / 1.07
31 / 2.15 / 65 / 3.01
32 / 1.55 / 66 / 11.54
33 / 0.49 / 67 / 3.66
34 / 0.72
Bennett et al., Abundance, rarity and invasion debt among exotic species in a patchy ecosystem
Electronic Supplementary Material 2. Phylogenetic Analyses
Creation of Phylogenetic Tree
We created a phylogenetic tree of our species using the Angiosperm Phylogeny Group III (2009) phylogeny. Where there was no sub-family phylogenetic information, species within genera were assumed to be more closely related than genera within families. Internal nodes were dated using fossil evidence where available (Wikstrom et al. 2001), and the branch lengths for the tree were scaled to the dated nodes and made ultrametric via Bladj software (Webb 2000). Phylogenetic distances among species were subsequently used to test intra- versus inter-group distances and to test for a phylogenetic signal in abundance differences.
Tests for Phylogenetic Relatedness Within and Among Groups
We tested for significant differences in intra- versus inter-group phylogenetic distances using permutation tests (permuting group identities 10 000 times) of mean within-group distances versus means of all other distances. Apart from native long dispersers, selected groups exhibited lower intra-group than inter-group phylogenetic distances (Table S3). As reported in the main article, we also tested for a phylogenetic signal in abundance differences at both scales, using Mantel tests.
Table ES2: Permutation test results for intra- versus inter-group phylogenetic distances
Group / Intra-Group vs. Inter-Group Difference (%) / Z / PExotic Long Dispersers / -3.1 / -7.82 / <0.0001
Exotic Short Dispersers / -5.9 / -8.55 / <0.0001
Native Long Dispersers / 0.2 / 0.53 / 0.60
Native Short Dispersers / -1.0 / -3.01 / 0.0032
References
Angiosperm Phylogeny Group III phylogeny (2009) An update of the Angiosperm Phylogeny Group classification for the orders and families of flowering plants: APG III. Bot J Linn Soc 161:105–21
Wikstrom, N, Savolainen V, Chase, MW (2001) Evolution of the angiosperms: calibrating the family tree. Proc R Soc Lond Ser B 268:2211–2220
Webb, CO (2000) Exploring the phylogenetic structure of ecological communities: an example for rain forest trees. Am Nat 156:145-155
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Bennett et al., Abundance, rarity and invasion debt among exotic species in a patchy ecosystem
Electronic Supplementary Material 3. Tests for all variables from most parsimonious models
Table ES3: Significant and non-significant coefficients from the most parsimonious models for numbers of occurrences and forms of rarity/commonness. P<0.1 are italicized; P<0.05 are bolded and italicized.
Response Variable / Predictor Variables / Final Model / Coefficient / CoefficientValue / Standard Error / T / PNumber of Occurrences in Patches / O, D, Gf / O × D / EL / 0.364 / 0.169 / 2.161 / 0.0342
ES / -0.756 / 0.192 / 3.948 / 0.0003
NL / -0.010 / 0.143 / 0.070 / 0.9443
NS / 0.081 / 0.254 / 0.321 / 0.7491
Number of Occurrences in Quadrats / O, D, Gf / O × D / EL / 0.626 / 0.368 / 1.698 / 0.0940
ES / -1.109 / 0.418 / 2.654 / 0.0114
NL / -0.202 / 0.312 / 0.649 / 0.5176
NS / 0.271 / 0.553 / 0.490 / 0.6256
Commonness on Both Inter- and Intra-Patch Scales / O, D, Gf / O × D / EL / 0.510 / 0.397 / 1.283 / 0.2037
ES / -1.626 / 0.472 / 3.443 / 0.0014
NL / -0.047 / 0.362 / 0.129 / 0.8979
NS / 0.434 / 0.649 / 0.669 / 0.5053
Rarity on Both Inter- and Intra-Patch Scales / O, D, Gf / O × D / EL / -1.008 / 0.365 / 2.765 / 0.0073
ES / 0.334 / 0.411 / 0.812 / 0.4216
NL / 0.385 / 0.302 / 1.276 / 0.2047
NS / 0.211 / 0.518 / 0.407 / 0.6853
Number of Occurrences in Full Surveys (Exotic spp. only; including estim. time since arrival) / D, Gf, Ta / D + Ta / Ta / -0.453 / 0.103 / 4.399 / <0.0001
Number of Occurrences in Quadrats (Exotic spp. only; including estim. time since arrival) / D, Gf, Ta / D + Ta / Ta / -1.479 / 0.280 / 5.275 / <0.0001
Minimum Convex Polygon Size (Exotic spp. only; including estim. time since arrival) / D, Gf, Ta / D + Ta / Ta / -0.210 / 0.095 / 2.218 / 0.0292
Number of Occurrences on Patches (22 Small-Island Patches Only) / O, D, Gf / O × D / EL / 0.326 / 0.225 / 1.448 / 0.1522
ES / -1.500 / 0.259 / 5.798 / <0.0001
NL / 0.207 / 0.194 / 1.066 / 0.2888
NS / 0.217 / 0.346 / 0.629 / 0.5312
Number of Occurrences in Quadrats (22 Small-Island Patches Only / O, D, Gf / O × D / EL / 0.385 / 0.425 / 0.906 / 0.3682
ES / -2.003 / 0.484 / 4.135 / 0.0002
NL / 0.223 / 0.362 / 0.616 / 0.5391
NS / 0.398 / 0.644 / 0.618 / 0.5383
Notes:
-Predictor variables: O = origin (native or exotic); D = dispersal ability (short or long); Gf = growth form (forb, grass, shrub, tree); Ta = estimated time since arrival
-Predictor variable categories: E = exotic; N = Native; S = short dispersers; L = long dispersers (i.e., EL = coefficient for exotic long dispersers in O×D interaction term)
Bennett et al., Abundance, rarity and invasion debt among exotic species in a patchy ecosystem
Electronic Supplementary Material 4. Patch-level analysis using mean proportion of quadrats occupied per patch.
Table ES4: Significant and non-significant coefficients from the most parsimonious models for numbers of occurrences and forms of rarity/commonness. P<0.1 are italicized; P<0.05 are bolded and italicized.
Response Variable / Predictor Variables / Final Model / Coefficient / Coefficient Value / Standard Error / T / PCommonness / O, D, Gf / O × D + Gf / EL / 0.015 / 0.012 / 1.212 / 0.229
ES / -0.023 / 0.014 / 1.690 / 0.099
NL / -0.009 / 0.010 / 0.907 / 0.367
NS / 0.010 / 0.018 / 0.582 / 0.562
F / -0.005 / 0.003 / 1.628 / 0.105
G / 0.047 / 0.013 / 3.721 / 0.001
S / -0.012 / 0.014 / 0.860 / 0.396
T / -0.020 / 0.020 / 0.979 / 0.344
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Bennett et al., Abundance, rarity and invasion debt among exotic species in a patchy ecosystem
Electronic Supplementary Material 5. Alternate forms of rarity/commonness
Conservative estimate (fewer common, more rare):
Common (patch-level) = 20 or more patches
Rare (patch-level) = 4 or fewer patches
Common (quadrat-level) = greater than one occurrence in quadrats from at least one patch
Rare (quadrat-level) = never found in more than one quadrat per patch
Liberal estimate (more common, fewer rare):
Common (patch-level) = 10 or more patches
Rare (patch-level) = 1 or 0 patches
Common (quadrat-level) = greater than one occurrence in quadrats from at least one patch
Rare (quadrat-level) = never found in more than one quadrat per patch
Table ES5a: Coefficients from most parsimonious models for rarity/commonness (conservative estimate)
Response Variable / Predictor Variables / Final Model / Coefficient / Coefficient Value / Standard Error / T / PCommonness / O, D, Gf / O × D + Gf / EL / 0.389 / 0.414 / 0.940 / 0.3507
ES / -1.330 / 0.490 / 2.714 / 0.0098
NL / -0.066 / 0.374 / 0.177 / 0.8601
NS / 0.413 / 0.669 / 0.617 / 0.5393
F / -0.198 / 0.095 / 2.080 / 0.0388
G / 0.760 / 0.324 / 2.343 / 0.0244
S / 0.563 / 0.374 / 1.504 / 0.1432
T / -0.375 / 0.642 / 0.584 / 0.5686
Rarity / O, D, Gf / O × D / EL / -0.803 / 0.311 / 2.580 / 0.0120
ES / 0.448 / 0.352 / 1.274 / 0.2099
NL / 0.334 / 0.260 / 1.281 / 0.2032
NS / 0.045 / 0.456 / 0.098 / 0.9221
Table ES5b: Most parsimonious models for rarity/commonness (liberal estimate)
Response Variable / Predictor Variables / Final Model / Coefficient / Coefficient Value / Standard Error / T / PCommonness / O, D, Gf / O × D + Gf / EL / 0.433 / 0.380 / 1.141 / 0.2576
ES / -1.342 / 0.446 / 3.009 / 0.0045
NL / -0.163 / 0.339 / 0.481 / 0.6316
NS / 0.499 / 0.605 / 0.825 / 0.4115
F / -0.180 / 0.093 / 1.943 / 0.0534
G / 0.757 / 0.321 / 2.355 / 0.0238
S / 0.567 / 0.365 / 1.554 / 0.1307
T / -0.605 / 0.638 / 0.948 / 0.3590
Rarity / O, D, Gf / O / E / -0.536 / 0.207 / 2.587 / 0.0110
N / 0.322 / 0.124 / 2.587 / 0.0105
Notes:
-Predictor variables: O = origin (native or exotic); D = dispersal ability (short or long); Gf = growth form (forb, graminoid, shrub, tree)
-Predictor variable categories: E = exotic; N = native; S = short dispersers; L = long dispersers; F = forb; G = graminoid; S = shrub; T = tree
Bennett et al., Abundance, rarity and invasion debt among exotic species in a patchy ecosystem
Electronic Supplementary Material 6. Patterns on small-island patches.
Fig. ES1. Frequencies of long- and short-dispersing exotic and native species in the subset of 22 small-island patches. a) number of patches per species in full patch surveys; b) number of quadrats per species in quadrat-level surveys. Error bars indicate ±1 standard error.
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