Supporting Information
Gotzek et al.
Global Invasion History of the Tropical Fire Ant: A Stowaway on the First Global Trade
Routes
SI Figure Legends
Figure S1: A) Number of clusters inferred for the complete dataset. Left: BIC scores for K = 1-15
using K-means clustering. Right: Posterior probabilities using the DPP implemented in
Structurama. B) Number of clusters for inferred for Old World samples only. CAS6 from
Reunion is excluded, since it always forms its own cluster. Left: BIC scores for K = 1-8 using Kmeans clustering. Right: Posterior probabilities using the DPP implemented in Structurama.
Figure S2: Stability of group membership probabilities for maximal clustering (K = 8) of the
complete dataset. Using clusters derived from clustering methods, reassignment proportions are
always high (>80%), whereas reassignment proportions with random clusters never exceed 50%.
Figure S3A: Three scenarios compared in ABC analyses A – C to identify the source population.
The invasive Old World cluster is always Pop 3, the two alternate New World source populations
are Pop 1 and Pop 2 (see SI Figure S3B).
Figure S3B: Posterior probabilities of competing scenarios (see SI Figure S3A) of ABC.
Analysis A: Pop 1 = South America, Pop 2 = (TexMex,Meso1,Meso2,Caribbean); Analysis B:
Pop 1 = (TexMex,Meso2), Pop 2 = (Meso1,Caribbean); Analysis C: Pop 1 = TexMex, Pop 2 =
Meso2.
Figure S4A: Scenarios and posterior probabilities (with 95% CI) used in analyses D based on
logistic regression estimates. Scenario 1: serial invasion, scenario 2: independent invasion,
scenario 3: serial invasion from a ghost population, scenario 4: independent invasion from a
ghost population. Pop1: Meso2 cluster, Pop2: Indo-Pacific cluster, Pop3: Australian cluster, Nu:
unsampled ghost population, Nxb: bottlenecked populations.
Figure S4B: Prior and posterior density distributions of demographic parameters for scenario 3
(serial invasion from unsampled ghost population) of analysis D. Priors are shown in red,
posteriors are in green, and median estimates are indicated. N1: Meso2 cluster, N2: Australian
cluster, N3: Indo-Pacific cluster, Nu: ghost population, Nxb: bottlenecked founding populations,
db: bottleneck duration, ty: divergence time. Time (t and db) is given in generations.
1
Table S2: Estimates of genetic diversity (and standard error for microsatellites and standard
deviation for mtDNA in brackets) within clusters for nuclear and cytoplasmic genomes. Cluster
(sample) size (N), mean number of alleles (Na), number of effective alleles (Ne), observed
heterozygosity (Ho), (unbiased) expected heterozygosity (He), fixation index (F), number of
haplotypes (h), gene diversity (Hd), nucleotide diversity (Pi), and average within group
evolutionary distance. Calculations are conducted over all loci for each cluster as defined by
clustering methods.
microsatellites
Cluster
South Am.
TexMex
Caribbean
Meso1
Meso2
Australia
Indo-Pac1
Indo-Pac2
Total
mtDNA
N
Na
Ne
Ho
He
F
h
Hd
Pi
within
group
mean
27.311
7.378
4.431
0.368
0.552
0.338
34
0.937
0.018
0.067
[0.258]
[0.882]
[0.570]
[0.041]
[0.051]
[0.033]
[0.019]
[0.003]
[0.030]
11.000
3.556
2.497
0.327
0.376
0.087
[0.000]
[0.450]
[0.320]
[0.050]
[0.052]
[0.035]
11.311
3.800
2.520
0.250
0.448
0.401
[0.171]
[0.377]
[0.242]
[0.032]
[0.049]
[0.041]
7.800
4.667
3.590
0.411
0.540
0.221
[0.068]
[0.502]
[0.376]
[0.053]
[0.058]
[0.047]
8.667
5.267
3.912
0.358
0.587
0.345
[0.105]
[0.470]
[0.384]
[0.040]
[0.053]
[0.039]
21.844
2.289
1.511
0.169
0.208
0.104
[0.078]
[0.237]
[0.128]
[0.033]
[0.040]
[0.031]
22.756
2.489
1.472
0.161
0.209
0.135
[0.072]
[0.289]
[0.114]
[0.029]
[0.038]
[0.039]
30.533
2.667
1.716
0.223
0.266
0.218
[0.144]
[0.288]
[0.159]
[0.037]
[0.043]
[0.048]
17.769
4.022
2.712
0.282
0.398
0.247
0.442
[0.188]
[0.126]
[0.015]
[0.019]
[0.015]
8
5
6
5
2
2
3
59
0.924
0.009
0.010
[0.057]
[0.003]
[0.004]
0.833
0.036
0.203
[0.098]
[0.009]
[0.112]
1.000
0.014
0.028
[0.096]
[0.002]
[0.013]
0.893
0.035
0.167
[0.086]
[0.007]
[0.078]
0.100
0.000
0.000
[0.088]
[0.000]
[0.000]
0.087
0.000
0.000
[0.078]
[0.000]
[0.000]
0.127
0.000
0.000
[0.080]
[0.000]
[0.000]
0.823
0.040
0.540
[0.028]
[0.001]
[0.298]
2
Table S3: Degree of genetic differentiation between clusters (FST, Jost’s Dest, Hedrick’s G”ST).
All pairwise differences are statistically different after Bonferroni correction (Gerlach et al.
2010).
South
America
TexMex
Caribb.
Meso1
Meso2
Australia
IndoPacific2
IndoPacific1
FST
South Am.
TexMex
Caribbean
Meso1
Meso2
Australia
Indo-Pac2
Indo-Pac1
----0.305
0.242
0.156
0.181
0.422
0.403
0.423
----0.346
0.309
0.175
0.538
0.469
0.526
----0.206
0.182
0.546
0.508
0.546
----0.150
0.529
0.479
0.523
----0.404
0.363
0.406
----0.223
0.212
----0.122
-----
G”ST
South Am.
TexMex
Caribbean
Meso1
Meso2
Australia
Indo-Pac2
Indo-Pac1
----0.608
0.505
0.350
0.417
0.703
0.675
0.702
----0.596
0.559
0.330
0.725
0.659
0.707
----0.406
0.375
0.774
0.745
0.771
----0.352
0.744
0.702
0.732
----0.571
0.531
0.571
----0.297
0.268
----0.163
-----
Jost’s Dest
South Am.
TexMex
Caribbean
Meso1
Meso2
Australia
Indo-Pac2
Indo-Pac1
----0.421
0.341
0.229
0.293
0.475
0.460
0.474
----0.382
0.369
0.194
0.435
0.383
0.414
----0.256
0.241
0.532
0.512
0.528
----0.239
0.521
0.486
0.506
----0.347
0.326
0.348
----0.091
0.071
----0.044
-----
3